Cooperative Multi-Functional Organocatalysts for Ambient Conversion

Sep 14, 2018 - Each and every day, ACS ... Women in Bioconjugate Chemistry: Celebrating Women Scientists ... Biochemistry provides an international fo...
1 downloads 0 Views 735KB Size
Subscriber access provided by Kaohsiung Medical University

Article

Cooperative Multi-Functional Organocatalysts for Ambient Conversion of Carbon Dioxide into Cyclic Carbonates Ning Liu, Ya-Fei Xie, Chuan Wang, Shi-Jun Li, Dong-Hui Wei, Min Li, and Bin Dai ACS Catal., Just Accepted Manuscript • Publication Date (Web): 14 Sep 2018 Downloaded from http://pubs.acs.org on September 14, 2018

Just Accepted “Just Accepted” manuscripts have been peer-reviewed and accepted for publication. They are posted online prior to technical editing, formatting for publication and author proofing. The American Chemical Society provides “Just Accepted” as a service to the research community to expedite the dissemination of scientific material as soon as possible after acceptance. “Just Accepted” manuscripts appear in full in PDF format accompanied by an HTML abstract. “Just Accepted” manuscripts have been fully peer reviewed, but should not be considered the official version of record. They are citable by the Digital Object Identifier (DOI®). “Just Accepted” is an optional service offered to authors. Therefore, the “Just Accepted” Web site may not include all articles that will be published in the journal. After a manuscript is technically edited and formatted, it will be removed from the “Just Accepted” Web site and published as an ASAP article. Note that technical editing may introduce minor changes to the manuscript text and/or graphics which could affect content, and all legal disclaimers and ethical guidelines that apply to the journal pertain. ACS cannot be held responsible for errors or consequences arising from the use of information contained in these “Just Accepted” manuscripts.

is published by the American Chemical Society. 1155 Sixteenth Street N.W., Washington, DC 20036 Published by American Chemical Society. Copyright © American Chemical Society. However, no copyright claim is made to original U.S. Government works, or works produced by employees of any Commonwealth realm Crown government in the course of their duties.

Page 1 of 39 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

ACS Catalysis

Cooperative Multi-Functional Organocatalysts for Ambient Conversion of Carbon Dioxide into Cyclic Carbonates †



Ning Liu,*, Ya-Fei Xie, Chuan Wang,‡ Shi-Jun Li,§ Donghui Wei,*,§ Min Li,† Bin Dai,*,† †

School of Chemistry and Chemical Engineering, Key Laboratory for

Green Processing of Chemical Engineering of Xinjiang Bingtuan, Shihezi University, North Fourth Road, Shihezi, Xinjiang, 832003, People’s Republic of China ‡

Department of Chemistry, University of Science and Technology of

China, 96 Jinzhai Road, Hefei, Anhui 230026, People’s Republic of China §

College of Chemistry and Molecular Engineering, Center of

Computational Chemistry, Zhengzhou University, 100 Science Avenue, Zhengzhou, Henan Province, 450001, People’s Republic of China

1 ACS Paragon Plus Environment

ACS Catalysis 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Page 2 of 39

ABSTRACT: A series of pincer-type compounds possessing an N-heterocyclic carbene precursor and a carboxyl group as proton transfer agent were synthesized and used as organocatalysts for the cycloaddition of epoxides with CO2. In this context, we have demonstrated the high activity of these one-component organocatalysts in the CO2 transformation to cyclic carbonates under ambient conditions (room temperature, 1 bar of CO2). The catalytic potential of these multi-functional organocatalysts on challenging internal epoxides is particularly deserved to be mentioned because organocatalysts being able to mediate the cycloaddition reaction of internal epoxides with CO2 under mild conditions remain scarce. The intramolecular synergistic activation mechanism was elucidated by control experiments and DFT calculations.

KEYWORDS: carbon dioxide, cyclic carbonate, multi-functional organocatalyst, metal-free, cycloaddition

ACS Paragon Plus Environment

2

Page 3 of 39 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

ACS Catalysis

Introduction Carbon dioxide utilized as an abundant, inexpensive, and renewable C1 building block for the synthesis of cyclic carbonates represents a much more sustainable alternative to the use of phosgene.1 Cyclic carbonates are an important class of compounds that can be utilized as intermediates for preparation of fine chemicals,2 as electrolytes in lithium ion batteries,3 and raw materials for polymers.4 Given the importance of cyclic carbonates, many catalytic systems for this transformation have been developed over the past decade to achieve this type of compounds.5 Among these methods of organocatalyzed cycloadditons between CO2 and epoxides represents an attractive approach to cyclic carbonates, because organocatalysts are usually low-cost, readily available, and free of metal contaminants.6 To date, a wide range of organocatalysts for this transformation have been developed, such as imidazolium salts,7 organic amines,8 phosphonium salts,9 ammonium salts,10 and phenols,11 have been developed. Despite the growing number of organocatalysts, organocatalytic systems aforementioned still suffer from some disadvantages in the synthetic point of view: low activity, high catalyst loading, poor substrate scope, and harsh reaction conditions.12 Recent developments in the area of cyclic carbonates synthesis have demonstrated that careful design of catalysts plays a significant role for tuning the catalytic activity. For instance, Shirakawa et al. demonstrated that triethylamine hydroiodide is an

ACS Paragon Plus Environment

3

ACS Catalysis 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Page 4 of 39

effective one-component catalyst for the coupling of terminal epoxides with CO2 at 40 °C under ambient pressure.13 D’Elia et al. discovered an environmentally benign binary system of ascorbic acid with TBAI (tetrabutylammonium iodide). This work reported the successful conversion of terminal epoxides with CO2 to cyclic carbonates under ambient conditions.14 Another contribution by Lu and co-workers was described that the phosphorus ylide CO2 adducts are able to effectively catalyze the conversion of terminal epoxides and CO2 into cyclic carbonates under ambient conditions.15 More recently, Kleij and co-workers developed binary organocatalytic systems based on squaramide scaffold that are highly active catalysts for the cycloaddition reaction between internal epoxides and CO2 at 80 °C under 30 bar of CO2.16 Therefore, the development of a one-component catalyst that can be effective for the conversion of internal epoxides under mild conditions is a still a challenging task. Recent reports have demonstrated that bifunctional imidazolium halides or quaternary phosphonium salts possessing a hydroxyl17 or carboxyl groups,18 play an imperative role in activating of epoxides by the hydrogen-bonding donor group. Meanwhile, He and co-workers have proved that the amino acid salts are capable of capturing one equivalent of CO2 through the insertion of CO2 into N-H bond.19 Bowen et al. found that CO2 can bind to the quinoline N atom to form the (quinoline-CO2) anionic complex.20 In addition, previously reported catalysts and

ACS Paragon Plus Environment

4

Page 5 of 39 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

ACS Catalysis

catalytic systems showed that NHC (N-heterocyclic carbenes) can react with CO2 to form NHC-CO2 adducts.18b,f These recent advances promoted our interest in the design of effective multi-functional catalysts which allow the simultaneous activation of CO2 and the epoxide. Since the pyridine ring is a typical electronic transfer structure, it is an alternative bridge for the design of multi-functional catalysts through varying functional groups attached. Recently, we reported pyridine-bridged benzimidazolium salt and pincer-type iron(II) complexes that show interesting potential toward epoxide/CO2 couplings.21 Amino acids are readily available and environmentally benign natural products,22 which consist of a combination of a carboxyl group as a Brønsted acid and an amino group as CO2 activating agent. It is highly desired to design and synthesize a multi-functional catalyst, which is composed of a Brønsted acidic site, a nucleophilic site, and CO2 absorbent and activating sites through introduction of a benzimidazolium salt and an amino acid to a pyridine ring (Figure 1). In this work, we demonstrate that one-component, neat, and highly active multi-functional catalysts can offer a competitive alternative to metal catalysis in the conversion of terminal and internal epoxide under mild conditions.

ACS Paragon Plus Environment

5

ACS Catalysis 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Page 6 of 39

Figure 1. Design and active sites of catalyst. Results and Discussion

Seven multi-functional organocatalysts 1a−g (Scheme 1) were prepared according to procedures reported previously.23 We first report a series of organocatalysts with multi-active sites: amino groups, pyridine N atom and pre-NHC (NHC, N-heterocyclic carbenes precursor) for CO2 capture and activation, carboxyl groups for epoxides activation and halide anion for nucleophilic ring opening.

Scheme 1. Synthesis of multi-functional organocatalysts.

ACS Paragon Plus Environment

6

Page 7 of 39 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

ACS Catalysis

The catalytic performance of all the resultant multi-functional catalysts 1a−g was investigated, and the coupling between PO (propylene epoxide) and CO2 was chosen as a benchmark reaction at 80 °C with CO2 pressure of 5 bar. The obtained results indicated that the catalyst 1e containing phenolic hydroxyl group (Table 1, entry 5) was catalytically more active than other catalysts (Table 1, entries 1-4). The function of carboxyl group and phenolic hydroxyl group in this reaction is generally used as a hydrogen bond donor. To investigate the hydrogen bonding interaction between PO and two hydrogen bond donors, in situ FTIR studies were carried out (see the Supporting Information for details). When PO was added into the catalysts, the characteristic FTIR band at 1725 cm-1 reduced continuously which corresponds to the v(C=O) stretching vibration of carboxyl group (Figure S1). However, the v(OH) bending vibration of phenolic hydroxyl group in the range of 700-800 cm-1 has not significant change during the addition of PO into the catalyst system (Figure S2). Qualitative NMR titration methods were also used to investigate the function of two hydrogen bond donors. Upon addition of PO to the catalyst 1e, shifting of the resonance of COOH proton and OH proton was not observed (Figure S5). However, gradual weakening of the resonance of COOH proton was observed (Figure S5), which was consistent with what observed in the in situ FTIR analysis. In order to exclude the H-D exchange between COOH proton and deuterium reagents, a 1H NMR detection of catalyst 1e in deuterium

ACS Paragon Plus Environment

7

ACS Catalysis 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Page 8 of 39

reagents without adding PO for overnight was performed. The result indicated that the chemical signal of COOH proton was unchanged. The resonance of carbon of COOH shifted downfield from δ = 174.60 to 175.17 ppm, however, shifting of the resonance of aromatic carbon attaching OH was not observed (Figure S6). These results indicated that COOH reacted with PO through a proton transfer process rather than remaining at the stage of the hydrogen bonding interactions. We have additionally considered the pathway where the epoxide is activated by the phenol via transition state TS2’’ (Figure S8). The energy barrier via transition state TS2’’ is 25.0 kcal/mol, which is higher than that via transition state TS2 (21.2 kcal/mol), so we can safely exclude the pathway using phenol as the Brønsted acid. The effect of the counter-anions on the catalytic performance was also studied. The catalytic activity of 1e, 1f, and 1g, which bear I−, Br−, and Cl− ions, respectively, increased in the order 1e > 1f > 1g (I−, Br−, and Cl−; Table 1, entries 5, 6, and 7). Subsequently, we investigated the performance of catalyst under various reaction conditions (Table 1, entries 8–14). When the reaction temperature was lowered from 80 °C to room temperature, we were delighted to observe a 26% yield of 3a in 4 h (Table 1, entry 10) and a slightly higher yield (37%) could be obtained by a prolonged reaction time to 24 h (Table 1, entry 11). Furthermore, the influence of the CO2 pressures on the outcome of the reaction was also evaluated. When the CO2 pressure was decreased from 5 bar to 1 bar, the yield was reduced

ACS Paragon Plus Environment

8

Page 9 of 39 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

ACS Catalysis

from 37% to 29% (Table 1, entries 11 and 12). To our delight, the catalyst loading has an evident effect on catalytic performance. When the catalyst loading of 1e was increased from 1 mol% to 4 mol%, the yield of 3a reached 96% at ambient condition (Table 1, entry 14). Table 1. Optimization of PC Synthesisa

entry catalyst (mol%) temperature (°C) CO2 (bar) time (h) yield (%) 1 1a (1.0) 80 5 4 77 2 1b (1.0) 80 5 4 68 3 1c (1.0) 80 5 4 52 4 1d (1.0) 80 5 4 57 5 1e (1.0) 80 5 4 99 6 1f (1.0) 80 5 4 79 7 1g (1.0) 80 5 4 61 8 1e (1.0) 60 5 4 79 9 1e (1.0) 40 5 4 53 10 1e (1.0) r.t. 5 4 26 11 1e (1.0) r.t. 5 24 37 b 12 1e (1.0) r.t. 1 24 29 13 1e (2.0) r.t. 1b 24 75 b 14 1e (4.0) r.t. 1 24 96 a Reaction conditions unless specified otherwise: PO (10.0 mmol), catalyst (as indicated in this table), neat, the reactions involving a CO2 pressure higher than 1 bar were carried out in a 25 mL stainless steel autoclave, yield was determined by GC using biphenyl as an internal standard. b CO2 balloon.

Under the optimized reaction conditions, the terminal epoxides scope was then evaluated, and the results are demonstrated in Table 2. This protocol can tolerate the presence of various aliphatic substituents of the terminal epoxides and give cyclic carbonate products 3a−3j in 73%−95% yield under ambient (room

ACS Paragon Plus Environment

9

ACS Catalysis 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Page 10 of 39

temperature, one bar of CO2), solvent-free and additive-free conditions. The electronic effect of the substituents of terminal epoxides is significant. The terminal epoxides bearing aliphatic groups had relatively high reactivity than those with aryl groups (3a−3j vs 3l). The terminal epoxides 2l required an increased the reaction temperature to 40 °C, to achieve 89% yield (3l in Table 2). Upon increasing the temperature to 40 °C while still maintaining a bar of CO2, substrate 2m reacted smoothly to obtain 87% yield (3m in Table 2). Moreover, substrate 2k also required a higher reaction temperature (40°C) due to its high melting point (3k in Table 2). Table 2. Scope of terminal epoxidesa

ACS Paragon Plus Environment

10

Page 11 of 39 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

ACS Catalysis

a

Conditions: PO (10.0 mmol), 1e (0.4 mmol, 4 mol%), room temperature, 1 bar of CO2 (balloon), 24 h, neat. isolated yield. b40 °C.

Internal epoxides are challenging substrates in cycloaddition reaction with CO2 owing to their high steric hindrance (Table 3). These were also evaluated in our catalytic system. Increased reaction temperature were required to achieve the high yields of desired products. For example, when 1,2-dimethyloxirane was used, the cyclic carbonate product 4a was obtained with 83% yield at 80 °C with a CO2 of 1 bar. Next, several bicyclic epoxides were examined and could be converted into their cyclic carbonates 4b-d in good yields and chemoselectivities. In addition to

ACS Paragon Plus Environment

11

ACS Catalysis 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Page 12 of 39

six-membered bicyclic cyclohexene oxide was converted into the corresponding carbonate 4b in an isolated yield of 95%, five-membered bicyclic epoxides could be also converted into their carbonates 4c and 4d in good yields. Oxetanes are particularly challenging substrates because of their lower ring strain. When an unsubstituted oxetane was employed as substrate only yield of 37% was obtained (4e in Table 3). The conversion of internal epoxides such as epoxidized fatty acid esters is challenging because of highly steric hindrance.24 Subsequently, the scope of our protocol for the synthesis of fatty acid based bio-carbonates was investigated (Table 3). Under the reaction conditions of 100 °C and 5 bar of CO2, carbonate 4f was isolated in a yield of 51%. The epoxidized ethyl oleate was also converted and the corresponding carbonate 4g was obtained in a moderate yield. The cyclic carbonate 4h originating from erucic acid was also isolated in a yield of 48%. Two epoxide-functionalized carbonate 4i was obtained in an isolated yield of 43%, although the reaction time had to be prolonged to 48 h. Table 3. Scope of internal epoxidesa

ACS Paragon Plus Environment

12

Page 13 of 39 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

ACS Catalysis

a

Conditions: PO (10.0 mmol), 1e (0.4 mmol, 4 mol%), 80 °C, 1 bar of CO2 (balloon), 24 h, neat. isolated yield. b100 °C, 5 bar of CO2, 24 h. c100 °C, 5 bar of CO2, TBAI (12 mol%), 48 h.

Table 4 lists several reported organocatalytic systems employed under ambient conditions. D’Elia and co-workers reported ascorbic acid/TBAI catalytic system.14 Under ambient conditions, a TON of 16 and a TOF of 0.7 were achieved using PO as model substrate (Table 4, entry 1). The TON = 18 and TOF = 3 was reported by Lu et al. using the phosphorus-ylide-CO2 adducts as catalysts (Table 4, entry 2).15 To the best of our knowledge, this is the highest TON and/or TOF for the literatures reported organocatalysts under ambient conditions. When 4 mol% catalyst loading was employed, a TON of 24 and a TOF of 1.0 were achieved in our developed catalytic system (Table 4, entry 3). Lowing catalyst loading to 2

ACS Paragon Plus Environment

13

ACS Catalysis 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Page 14 of 39

mol% could increase slightly TON and TOF value (Table 4, entry 4). These results indicated that this work also are proved to be highly active catalysts, which are commensurate with the catalysts reported by Lu et al.15 Table 4. Comparison of Catalytic Activity of Catalysts

entry ref. yield (%) TON TOF (h-1) a 1 64 16 0.70 Ref. 14 2 90 18 3.0 Ref. 15b c 3 96 24 1.0 this work 4 75 38 1.6 this workd a Conditions: PO (25.0 mmol), ascorbic acid (4 mol%), TBAI (8 mol%), r.t., 1 bar of CO2 (balloon), neat, 23 h. bPO (10.0 mmol), P-Ylide-CO2-adducts (5 mol%), r.t., 1 bar of CO2 (balloon), neat, 6 h. cPO (10.0 mmol), 1e (4 mol%), r.t., 1 bar of CO2 (balloon), neat, 24 h. dPO (10.0 mmol), 1e (2 mol%), r.t., 1 bar of CO2 (balloon), neat, 24 h. TON, turnover number; TOF, turnover frequency (TOF = TON/reaction time (h)).

The use of enantiopure terminal epoxides as substrates gave us the opportunity to gain insight into the reaction mechanism. We investigated the mechanism of this multi-functional-catalyzed reaction from the viewpoint of stereochemistry using (R)-2l. As shown in scheme 2, the (R)-2l was converted preferentially into the (R)-3l with the retention of the configuration in a ratio of 85:15. The retention of the configuration in the cyclic carbonate product (R)-3l suggests that (R)-2l attacks preferentially at the methylene carbon (less hindered carbon atom).

ACS Paragon Plus Environment

14

Page 15 of 39 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

ACS Catalysis

Scheme 2. Investigation of the Reaction Mechanism by Using an Optically Pure Epoxide.

To clarify the effect of the counter-anions on the catalysts, we used pure trans-2,3-epoxybutane to reveal some mechanistic insights into reaction pathways (Table 5). When 1f (Br-) and 1g (Cl-) are used as catalysts, trans-3n and cis-3n were obtained in a ratio of 92:8 and 97:3, respectively (Table 5, entries 2 and 3). However, the use of the organocatalyst 1e resulted in some epimerization from the original configuration of the starting epoxides (Table 5, entry 1). This result suggests that the 1e-mediated reaction undergoes different reaction pathway compared with 1f and 1g. Table 5. Possible Reaction Pathways for 1e−g Catalyzed the Conversion of trans-2,3-Epoxybutane into cis- and trans-Cyclic Carbonate.a

entry catalyst cis-4a (%)b trans-4a (%)b total yield (%)c 1 57 43 83 1e 2 8 92 58 1f 3 3 97 12 1g a Conditions: trans-2,3-epoxybutane (10.0 mmol), catalyst (0.4 mmol, 4 mol%), 80 °C, 1 bar of CO2 (balloon), 24 h, neat, isolated yield. bDetermined by 1H and 13C NMR (CDCl3) from the raw reaction mixture.5d,25 cIsolated yield.

ACS Paragon Plus Environment

15

ACS Catalysis 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Page 16 of 39

In order to prove the synergistic action between the imidazolium and amino acid moieties whether occurs in intramolecular interactions or in intermolecular interactions. A control experiment was carried out using a binary catalyst system combining a pyridine-substituted benzimidazolium salt (1h in Scheme 3, eqn. 1) with a pyridine-substituted tyrosine (1i in Scheme 3, eqn. 1). Previous literatures reported that phenol is an active organocatalytic moiety for the cycloaddition of CO2 to epoxides. So the 1h/phenol binary system was also tested for the cycloaddition of CO2 to PO under ambient conditions. However, only 5% yield of product was obtained (Scheme 3, eqn. 2). The results showed that two-component catalytic system was proved to be difficult to trigger this reaction at ambient condition (Scheme 3, eqns. 1 and 2), suggesting that the unique pincer-type structures of our developed catalysts provide CO2 and epoxides a chance for intramolecular interactions. To explore the effect of carboxyl group on this reaction, a catalyst was synthesized by the esterification of carboxylic acid (1j in Scheme 3, eqn. 3). In the absence of carboxyl proton, only 9% of yield was obtained (Scheme 3, eqn. 3). The results showed that the existence of carboxyl group is essential for the highly catalytic performance.

ACS Paragon Plus Environment

16

Page 17 of 39 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

ACS Catalysis

The effect of amino group were also investigated (Scheme 3, eqn. 4). When amino group being protected by methyl group (1k in Scheme 3, eqn. 4), the catalytic activity of catalyst 1k is almost not affected and a slightly lower yields (93% yield in Scheme 3, eqn. 4) was obtained compared with the catalyst 1e (96% yield in Table 1, entry 14). We also investigated possible process of CO2 binding to amino group by DFT calculations. However, this process is impossible due to the high Gibbs free energy barrier, and more details can be found in the Supporting Information. The results suggest that the effect of amino group is negligible in this reaction.

ACS Paragon Plus Environment

17

ACS Catalysis 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Page 18 of 39

Scheme 3. Study on Active Sites of Catalysts.

To determine whether CO2 preferentially binds to the C2 position of the benzimidazolium ring, a catalyst was designed by introducing the methyl group to the C2 position of the benzimidazolium ring (1l in Scheme 3, eqn. 5). The result showed that the alkylation of the C2 position leads to a significant decrease of product yield, which might be caused by the lack of interaction between CO2 and the C2 position of catalyst. In addition, we have considered and investigated the two possible activation processes of CO2 catalyzed by both of the two different nitrogen atoms (i.e. the N atoms of amino group and pyridine) using DFT calculations (Scheme S1). The calculated results indicated that the free energy changes and Gibbs free energy barrier of the possible pathways would be too high to overcome, so we think the pyridine N atom cannot directly work as catalyst to activate the CO2 molecule. This was also confirmed by in situ FTIR. The C-C bond and C-H bond stretching vibration of the pyridine ring in the range of 700-1100 cm-1 have no change in wavelengths during the addition of CO2 into the catalyst system (Figures S3-4). More details can be found in the Supporting Information. In order to clarify the detailed mechanisms, we have additionally carried out theoretical calculations by using DFT method, which has been widely applied in

ACS Paragon Plus Environment

18

Page 19 of 39 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

ACS Catalysis

the mechanistic studies.26 As shown in Scheme 4, pre-NHC can be transferred to NHC (N-heterocyclic carbene) by the release of a molecule of HX (X=I, Br, and Cl), so the efficiency of catalyst would be the best when X=I, which is in agreement with the experimental observation that the yield is the highest when X is I. Firstly, the carbene carbon of NHC catalyst would nucleophilically attack on the carbon atom of CO2 to generate zwitterionic intermediate M1 via transition state TS1. Secondly, the negatively charged oxygen nucleophilically attacks on the epoxy carbon of reactant trans-R1, which is accompanied with the three-membered ring opening and a proton transfer process for the formation of intermediate M2 via transition state TS2. Then, the intermediate M2 can be structurally transformed to intermediate M3 by the C−C single bond rotation. Subsequently, it is the five-membered ring closure process coupled with the other proton transfer for affording intermediate M4 via transition state TS3. The last process is the dissociation of NHC catalyst with product cis-P via transition state TS4. As shown in Figure 2, the Gibbs free energy barriers via the transition states TS1, TS2, TS3, and TS4 are 1.2, 23.6, 0.2, and 8.1 kcal/mol, so the epoxy ring opening should be the rate-determining step. Interestingly, the organocatalyst has two functions, the one is to work as Lewis base NHC to activate the CO2, and the other is to provide and abstract the proton as Brønsted acid/base.

ACS Paragon Plus Environment

19

ACS Catalysis 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Page 20 of 39

Alternatively, we also considered the possible pathways associated with the product trans-P. As depicted in Scheme 4, the negatively charged oxygen of intermediate M1 can also nucleophilically attack on the epoxy carbon of reactant trans-R1 from the other side, which leads to the formation of intermediate M2′ via transition state TS2′. However, the energy barrier via TS2′ is extremely high (39.5 kcal/mol, Figure 2), so we can safely exclude this pathway. Besides, the intermediate M2 can also react with another molecule of CO2 to form intermediate M5 via transition state TS5, and then the product trans-P can be dissociated with the intermediate M1 through a SN2-type transition state TS6 (Scheme 4). As shown in Figure 2, the process associated with TS6 is the rate-determining step for this pathway leading to the trans-P. It should be mentioned that the energy (without the correction) of intermediate M5 is lower than that of transition state TS5, but the free energy (with the thermal correction) of intermediate M5 (11.1 kcal/mol) is slightly higher than that of transition state TS5 (9.6 kcal/mol). Furthermore, other possible pathway, including the activation processes of CO2 catalyzed by pre-NHC and the epoxy ring opening through nucleophilic attack by I-, was also investigated, and more details can be found in the Supporting Information. When X is I, we think the stereoselectivity is kinetically controlled, and the energy barrier of the whole reaction leading to cis-P via TS2 (23.6 kcal/mol) is

ACS Paragon Plus Environment

20

Page 21 of 39 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

ACS Catalysis

slightly lower than that leading to trans-P via TS6 (24.0 kcal/mol), which aligns well with the experimental observation that the ratio of cis-P:trans-P is 57:43. When X is Br or Cl, the HX would be more difficult to dissociate with the NHC catalyst, we think the efficiency of NHC catalyst would become lower and the stereoselectivity is thermodynamically controlled, and thus the more stable trans-P should be the main product.

ACS Paragon Plus Environment

21

ACS Catalysis

Scheme 4. The Suggested Catalytic Cycles.

39.5 TS2'

Relative Gibbs free energies (kcal/mol)

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Page 22 of 39

21.2 TS2

21.6 TS6

9.6 TS5

trans-R1

0.0

CO2

1.2 TS1

4.9 M3

NHC+CO2 -2.4 M1

11.1 M5 5.1 TS3 -4.9 TS4

-2.1 M2 -13.0 M4

-11.2 -10.3 trans-P cis-P

Reaction Coordinate Figure 2. The Energy Profiles of the Possible Reaction Pathways Leading to the Products cis-P and trans-P.

In summary, we have demonstrated that one-component, neat, and highly active multi-functional catalysts can offer a competitive alternative to metal catalysis in the conversion of epoxide with CO2 under mild conditions. This potential is clearly proven in the conversion of internal epoxides which are generally difficult substrates to activate, especially by the organocatalytic systems. The control experiments and DFT calculations suggest that the reaction was realized by

ACS Paragon Plus Environment

22

Page 23 of 39 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

ACS Catalysis

combining the carbene as catalyst for the activation of CO2 with the carboxyl group as proton transfer agent. In contrast with many organocatalysts in which halide anion is using as the nucleophilic agent for open-ring of epoxide, in our catalytic system halide anion was using as a carbene initiator by the deprotonation. The knowledge obtained through these studies provides insight and new concept into the rational design of highly active catalysts. Experimental Section General Procedure for the Synthesis of organocatalysts 1a−g. A mixture of 2,6-dibromopyridine (5 mmol), amines (10 mmol), CuI (1 mmol), tetramethylethane-1,2-diamine (2 mmol) and K2CO3 (15 mmol) in DMSO (20 mL) was stirred for 30 min at room temperature, and

then

heated

to

90

°C

for

24

h

under

nitrogen

atmosphere.

Thereafter,

2-bromo-6-substituent-pyridine (5 mmol), amino acids (7.5 mmol), CuI (1 mmol), N,N-dimethylethylenediamine (2 mmol) and K2CO3 (15 mmol) in DMSO (20 mL) was allowed to react under nitrogen atmosphere. The resultant 2,6-disubstituent-pyridine (5 mmol), and alkyl halides (10 mL) was heated to the desired temperature and the reaction stirred for 8 h under air atmosphere, and affording a series of multi-functional organocatalysts 1a−g. The solvent was concentrated under vacuum and the product of organocatalysts 1a−g was isolated by flash chromatography. Data for 1a are as follows: Purification by flash chromatography (DCM/MeOH = 20:1): a yellowish solid (1.468 g, 61%), M.P. = 159.1–159.6 °C; 1H NMR (400 MHz, DMSO-d6): δ 12.68 (br., 1H, COOH), 10.29 (s, 1H, NCHN), 8.39 (d, J = 8.0 Hz, 1H), 8.20 (d, J = 7.2 Hz, 1H), 7.81-7.71 (m, 3H), 7.47 (d, J = 8.0 Hz, NH), 7.08 (d, J = 7.2 Hz, 1H), 6.96 (d, J = 7.6 Hz, 1H), 4.55 (t, J = 6.8 Hz, 2H), 4.33 (t, J = 5.6 Hz, 1H), 2.23 (sext, J = 6.8 Hz, 1H), 2.02 (sext, J = 7.2 Hz, 2H), 1.05-0.98 (m, 9H), ppm;

13

C NMR (100 MHz, DMSO-d6): δ 174.49, 158.93, 146.05,

142.14, 140.17, 132.09, 129.95, 127.80, 127.43, 116.44, 114.39, 103.92, 59.74, 49.04, 30.33, 22.50, 19.80, 18.85, 11.26, ppm; HRMS (MALDI) calcd for C20H25N4O2I [M-I]+ 353.1972, found 353.1969.

ACS Paragon Plus Environment

23

ACS Catalysis 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Page 24 of 39

Data for 1b are as follows: Purification by flash chromatography (DCM/MeOH = 25:1): a yellowish solid (1.227 g, 49%), M.P. = 113.2–114.3 °C; 1H NMR (400 MHz, DMSO-d6): δ 12.66 (br., 1H, COOH), 10.27 (s, 1H, NCHN), 8.37 (d, J = 8.0 Hz, 1H), 8.19 (d, J = 7.6 Hz, 1H), 7.80-7.70 (m, 3H), 7.62 (d, J = 8.0 Hz, NH), 7.06 (d, J = 7.2 Hz, 1H), 6.83 (d, J = 7.6 Hz, 1H), 4.53 (t, J = 7.6 Hz, 2H), 4.41-4.35 (m, 1H), 2.02 (sext, J = 7.6 Hz, 2H), 1.75-1.60 (m, 2H), 1.01-0.95 (m, 6H), 0.88 (d, J = 6.4 Hz, 3H), ppm;

13

C NMR (100 MHz, DMSO-d6): δ 175.72,

158.67, 146.27, 142.17, 140.25, 132.09, 130.01, 127.72, 127.43, 116.46, 114.38, 103.98, 52.65, 49.04, 24.98, 23.36, 22.47, 21.81, 11.27, ppm; HRMS (MALDI) calcd for C21H27N4O2I [M-I]+ 367.2129, found 367.2125. Data for 1c are as follows: Purification by flash chromatography (DCM/MeOH = 15:1): a yellowish solid (0.905 g, 35%), M.P. = 93.5–93.9 °C; 1H NMR (400 MHz, DMSO-d6): δ 12.75 (br., 1H, COOH), 10.29 (s, 1H, NCHN), 8.40 (d, J = 8.0 Hz, 1H), 8.20 (d, J = 8.0 Hz, 1H), 7.82-7.68 (m, 3H), 7.67 (d, J = 8.0 Hz, NH), 7.09 (d, J = 8.0 Hz, 1H), 6.84 (d, J = 8.0 Hz, 1H), 4.59-4.52 (m, 3H), 2.67-2.61 (m, 2H), 2.07-2.00 (m, 6H), 1.00 (t, J = 7.6 Hz, 3H), ppm;

13

C

NMR (100 MHz, DMSO-d6): δ 175.00, 158.65, 146.24, 142.18, 140.33, 132.09, 129.99, 127.76, 127.44, 116.55, 114.37, 104.15, 53.06, 49.05, 31.18, 30.38, 22.48, 14.97, 11.27, ppm; HRMS (MALDI) calcd for C20H25N4O2SI [M-I]+ 385.1693, found 385.1699. Data for 1d are as follows: Purification by flash chromatography (DCM/MeOH = 10:1): a yellowish solid (1.309 g, 49%), M.P. = 115.6–116.3 °C; 1H NMR (400 MHz, DMSO-d6): δ 12.90 (br., 1H, COOH), 10.25 (s, 1H, NCHN), 8.28 (d, J = 8.0 Hz, 1H), 8.19 (d, J = 8.0 Hz, 1H), 7.77-7.73 (m, 3H), 7.71 (d, J = 8.0 Hz, NH), 7.32-7.25 (m, 4H), 7.18 (t, J = 7.6 Hz, 1H), 7.04 (d, J = 7.2 Hz, 1H), 6.82 (d, J = 8.4 Hz, 1H), 4.70-4.66 (m, 1H), 4.52 (t, J = 7.6 Hz, 2H), 3.22 (dd, J = 14.0 Hz, 4.8 Hz, 1H), 3.02 (dd, J = 14.0 Hz, 4.8 Hz, 1H), 2.01 (sext, J = 7.6 Hz, 2H), 0.99 (t, J = 7.6 Hz, 3H), ppm; 13C NMR (100 MHz, DMSO-d6): δ 174.52, 158.45, 146.08, 142.16, 140.32, 138.41, 132.07, 129.96, 129.58, 128.66, 127.78, 127.42, 126.91, 116.35, 114.39, 104.14, 55.91, 49.02, 37.53, 22.49, 11.25, ppm; HRMS (MALDI) calcd for C24H25N4O2I [M-I]+ 401.1972, found 401.1970. Data for 1e are as follows: Purification by flash chromatography (DCM/MeOH = 40:1): a yellowish solid (1.671 g, 61%), M.P. = 136.5–137.2 °C; 1H NMR (400 MHz, DMSO-d6): δ 12.80 (br., 1H, COOH), 10.28 (s, 1H, NCHN), 9.19 (s, 1H, OH), 8.28 (d, J = 8.0 Hz, 1H), 8.20 (d, J = 8.0 Hz, 1H), 7.78-7.66 (m, 3H), 7.65 (d, J = 8.0 Hz, NH), 7.11 (d, J = 8.0 Hz, 2H), 7.06

ACS Paragon Plus Environment

24

Page 25 of 39 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

ACS Catalysis

(d, J = 8.0 Hz, 1H), 6.84 (d, J = 8.0 Hz, 1H), 6.66 (d, J = 8.0 Hz, 2H), 4.61-4.52 (m, 3H), 3.09 (dd, J = 14.0 Hz, 4.8 Hz, 1H), 2.94-2.88 (m, 1H), 2.02 (sext, J = 7.6 Hz, 2H), 0.99 (t, J = 7.6 Hz, 3H), ppm; 13C NMR (100 MHz, DMSO-d6): δ 174.94, 158.51, 156.32, 146.09, 142.04, 140.21, 132.04, 130.53, 129.91, 128.58, 127.79, 127.39, 116.46, 115.41, 114.38, 103.87, 56.55, 49.05, 36.89, 22.50, 11.25, ppm; HRMS (MALDI) calcd for C24H25N4O3I [M-I]+ 417.1921, found 417.1911. Data for 1f are as follows: Purification by flash chromatography (DCM/MeOH = 25:1): a yellowish solid (1.056 g, 50%), M.P. = 141.0–141.5 °C; 1H NMR (400 MHz, DMSO-d6): δ 10.29 (s, 1H, NCHN), 9.20 (s, 1H, OH), 8.30 (d, J = 8.0 Hz, 1H), 8.19 (d, J = 8.0 Hz, 1H), 7.77-7.70 (m, 3H), 7.61 (d, J = 8.0 Hz, NH), 7.10 (d, J = 8.0 Hz, 2H), 7.03 (d, J = 8.0 Hz, 1H), 6.82 (d, J = 8.0 Hz, 1H), 6.64 (d, J = 8.0 Hz, 2H), 4.58-4.51 (m, 3H), 3.10 (dd, J = 14.0 Hz, 4.8 Hz, 1H), 2.93-2.87 (m, 1H), 2.01 (sext, J = 7.6 Hz, 2H), 0.99 (t, J = 7.6 Hz, 3H), ppm; 13C NMR (100 MHz, DMSO-d6): δ 174.70, 158.51, 156.36, 146.11, 142.15, 140.21, 132.07, 130.51, 129.96, 128.51, 127.78, 127.39, 116.46, 115.40, 114.36, 103.87, 56.42, 49.00, 36.87, 22.49, 11.24, ppm; HRMS (MALDI) calcd for C24H25N4O3Br [M-Br]+ 417.1921, found 417.1917. Data for 1g are as follows: Purification by flash chromatography (DCM/MeOH = 20:1): a yellowish solid (0.972 g, 46%), M.P. = 112.3–112.9 °C; 1H NMR (400 MHz, DMSO-d6): δ 10.38 (s, 1H, NCHN), 8.37 (d, J = 8.0 Hz, 1H), 8.14 (d, J = 8.0 Hz, 1H), 7.70-7.65 (m, 3H), 7.47 (s, NH), 7.06 (d, J = 8.0 Hz, 2H), 7.00 (d, J = 8.0 Hz, 1H), 6.77 (d, J = 8.0 Hz, 1H), 6.61 (d, J = 8.0 Hz, 2H), 4.52 (t, J = 7.6 Hz, 3H), 3.10 (dd, J = 14.0 Hz, 4.8 Hz, 1H), 2.89-2.82 (m, 1H), 1.98 (sext, J = 7.6 Hz, 2H), 0.99 (t, J = 7.6 Hz, 3H), ppm; 13C NMR (100 MHz, DMSO-d6): δ 175.19, 158.72, 156.23, 146.13, 142.10, 139.87, 132.03, 130.50, 129.90, 129.24, 127.82, 127.26, 116.71, 115.27, 114.22, 102.97, 57.49, 48.92, 37.20, 22.51, 11.21, ppm; HRMS (MALDI) calcd for C24H25N4O3Cl [M-Cl]+ 417.1921, found 417.1913. Data for 1h are as follows: Purification by flash chromatography (DCM/MeOH = 20:1): a yellowish solid (1.366 g, 72%), M.P. = 157.2–157.7 °C; 1H NMR (400 MHz, DMSO-d6): δ 10.62 (s, 1H), 8.77 (d, J = 4.8 Hz, 1H), 8.47-8.44 (m, 1H), 8.33-8.25 (m, 2H), 8.16 (d, J = 8.0 Hz, 1H), 7.76-7.70 (m, 3H), 4.62 (d, J = 8.0 Hz, 2H), 2.06 (sext, J = 7.2 Hz, 1H), 1.01 (t, J = 7.2 Hz, 3H), ppm;

13

C NMR (100 MHz, DMSO-d6): δ 149.77, 147.84, 142.52, 140.96, 132.08,

129.88, 128.15, 127.55, 125.47, 117.54, 116.46, 114.62, 49.29, 22.51, 11.32, ppm; HRMS (MALDI) calcd for C15H16N3I [M-I]+ 238.1339, found 238.1329.

ACS Paragon Plus Environment

25

ACS Catalysis 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Page 26 of 39

Data for 1i are as follows: Purification by flash chromatography (DCM/MeOH = 20:1): a yellowish solid (1.224 g, 65%), M.P. = 117.9–118.3 °C; 1H NMR (400 MHz, DMSO-d6): δ 8.77 (S, 1H), 8.14 (d, J = 8.0 Hz, 1H), 7.74 (d, J = 7.2 Hz, 1H), 7.60 (t, J = 8.0 Hz, 1H), 7.36-7.28 (m, 3H), 7.12 (d, J = 8.0 Hz, 2H), 6.94 (d, J = 8.0 Hz, 1H), 6.67 (d, J = 8.0 Hz, 2H), 6.60 (d, J = 8.0 Hz, 1H), 4.61-4.56 (m, 1H), 3.08 (dd, J = 14.0 Hz, 4.8 Hz, 1H), 2.90 (dd, J = 14.0 Hz, 9.6 Hz, 1H), ppm; 13C NMR (100 MHz, DMSO-d6): δ 175.07, 158.31, 156.33, 148.38, 144.62, 142.60, 139.84, 132.31, 130.51, 128.58, 124.05, 123.10, 120.19, 115.43, 114.19, 101.58, 56.55, 49.07, 36.92, ppm; HRMS (MALDI) calcd for C21H18N4O3 [M]+ 374.1373, found 374.1376. Data for 1j are as follows: Purification by flash chromatography (DCM/MeOH = 15:1): a yellowish solid (1.681 g, 61%), M.P. = 109.3–109.9 °C; 1H NMR (400 MHz, DMSO-d6): δ 10.31 (s, 1H, NH), 8.22-8.19 (m, 2H), 7.81-7.72 (m, 4H), 7.12-7.09 (m, 3H), 6.87 (d, J = 8.0 Hz, 1H), 6.68 (d, J = 8.0 Hz, 2H), 4.71-4.66 (m, 1H), 4.56 (t, J = 7.2 Hz, 2H), 3.63 (s, 3H), 3.09-2.93 (m, 2H), 2.01 (sext, J = 7.2 Hz, 2H), 0.99 (t, J = 7.2 Hz, 3H), ppm;

13

C NMR (100 MHz,

DMSO-d6): δ 173.65, 163.56, 158.20, 156.48, 146.05, 142.12, 140.47, 132.08, 130.53, 129.92, 127.88, 127.70, 127.42, 116.13, 115.52, 114.51, 104.45, 56.28, 52.41, 49.09, 36.97, 22.48, 11.25, ppm; HRMS (MALDI) calcd for C25H27N4O3I [M-I]+ 431.2078, found 431.2072. Data for 1k are as follows: Purification by flash chromatography (DCM/MeOH = 15:1): a yellowish solid (0.791 g, 31%), M.P. = 112.3–112.9 °C; 1H NMR (400 MHz, DMSO-d6): δ 10.24 (s, 1H), 8.16 (d, J = 8.0 Hz, 1H), 8.05-7.98 (m, 1H), 7.82 (t, J = 8.0 Hz, 1H), 7.75-7.67 (m, 2H), 7.06 (d, J = 8.0 Hz, 1H), 7.00 (d, J = 8.0 Hz, 2H), 6.82 (d, J = 8.0 Hz, 1H), 6.56 (d, J = 8.0 Hz, 2H), 5.41 (s, 1H), 4.50 (t, J = 7.2 Hz, 2H), 3.22-3.04 (m, 2H), 2.96 (s, 3H), 1.98 (sextet, J = 7.2 Hz, 2H), 0.96 (t, J = 7.2 Hz, 3H), ppm; 13C NMR (100 MHz, DMSO-d6): δ 173.26, 158.71, 156.10, 145.37, 142.25, 141.32, 132.07, 130.18, 129.82, 128.73, 127.84, 127.37, 115.91, 115.39, 114.47, 107.50, 104.04, 60.45, 49.01, 33.95, 22.45, 11.22, ppm; HRMS (MALDI) calcd for C25H27N4O3I [M-I]+ 431.2078, found 431.2075. Data for 1l are as follows: Purification by flash chromatography (DCM/MeOH = 15:1): a yellowish solid (0.763 g, 27%), M.P. = 125.3–125.7 °C; 1H NMR (400 MHz, DMSO-d6): δ 8.20 (d, J = 8.0 Hz, 1H), 7.84-7.60 (m, 4H), 7.12 (d, J = 8.0 Hz, 2H), 6.95 (d, J = 8.0 Hz, 2H), 6.69 (d, J = 8.0 Hz, 2H), 4.58 (t, J = 7.6 Hz, 2H), 4.51-4.46 (m, 1H), 3.08 (dd, J = 14.0 Hz, 4.4 Hz, 2H), 2.89 (s, 3H), 1.95 (sextet, J = 7.2 Hz, 2H), 1.07 (t, J = 7.2 Hz, 3H), ppm; 13C NMR (100 MHz, DMSO-d6): δ 174.74, 159.12, 156.34, 151.78, 144.23, 140.06, 131.26, 130.98, 130.52,

ACS Paragon Plus Environment

26

Page 27 of 39 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

ACS Catalysis

128.58, 127.19, 126.90, 115.38, 113.98, 113.72, 108.81, 56.36, 47.19, 36.88, 22.32, 12.16, 11.38, ppm; HRMS (MALDI) calcd for C25H27N4O3I [M-I]+ 431.2078, found 431.2075. General Procedure for the Synthesis of Cyclic Carbonates. Epoxides (10.0 mmol), and organocatalyst 1e (0.4 mmol) were successively put into a 25 mL Schlenk flask. The reaction mixture was stirred at room temperature for 24 h under a CO2 atmosphere (1 atm, using a balloon). The reaction mixtures were added to brine (50 mL) and extracted three times with dichloromethane (3×50 mL). The solvent was removed under reduced pressure, and the products were isolated by flash chromatography. 4-Methyl-1,3-dioxolan-2-one (3a).5d Purification by flash chromatography (petroleum ether/EtOAc = 2:1) gave a colorless oil (949.2 mg, 93%). 1H NMR (400 MHz, CDCl3) δ 4.90-4.82 (m, 1H), 4.56 (t, J = 8.0 Hz, 1H), 4.03 (t, J = 8.0 Hz, 1H), 1.50 (t, J = 6.4 Hz, 3H), ppm; 13C NMR (100 MHz, CDCl3): δ 155.16, 73.76, 70.68, 19.03, ppm. 4-Ethyl-1,3-dioxolan-2-one

(3b).15

Purification

by

flash

chromatography

(petroleum

ether/EtOAc = 2:1) gave a yellow oil (1.003 g, 87%). 1H NMR (400 MHz, CDCl3) δ 4.70-4.63 (m, 1H), 4.53 (t, J = 8.0 Hz, 1H), 4.09 (t, J = 8.0 Hz, 1H), 1.87-1.72 (m, 2H), 1.04 (t, J = 8.0 Hz, 3H), ppm; 13C NMR (100 MHz, CDCl3) δ 155.21, 78.11, 69.06, 26.79, 8.38, ppm. 4-Hexyl-1,3-dioxolan-2-one (3c).18b

Purification

by flash chromatography (petroleum

ether/EtOAc = 5:1) gave a colorless oil (1.537 g, 89%). 1H NMR (400 MHz, CDCl3) δ 4.73-4.66 (m, 1H), 4.52 (t, J = 8.0 Hz, 1H), 4.06 (t, J = 8.0 Hz, 1H), 1.83-1.63 (m, 2H), 1.49-1.28 (m, 8H), 0.87 (t, J = 7.2 Hz, 3H), ppm; 13C NMR (100 MHz, CDCl3) δ 155.15, 77.15, 69.43, 33.76, 31.46, 28.73, 24.26, 22.39, 13.91, ppm. 4-Butyl-1,3-dioxolan-2-one

(3d).5d

Purification

by

flash

chromatography

(petroleum

ether/EtOAc = 5:1) gave a colorless oil (1.299 g, 90%). 1H NMR (400 MHz, CDCl3) δ 4.74-4.67 (m, 1H), 4.53 (t, J = 8.0 Hz, 1H), 4.07 (t, J = 8.0 Hz, 1H), 1.86-1.65 (m, 2H), 1.49-1.34 (m, 4H), 0.93 (t, J = 8.0 Hz, 3H), ppm; 13C NMR (101 MHz, CDCl3) δ 155.2, 77.2, 69.5, 33.6, 26.5, 22.3, 13.8, ppm. 4-(Chloromethyl)-1,3-dioxolan-2-one (3e).5d Purification by flash chromatography (petroleum ether/EtOAc = 2:1) gave a yellow oil (1.272 g, 93%). 1H NMR (400 MHz, CDCl3) δ 5.02-4.96 (m, 1H), 4.61(t, J = 8.0 Hz, 1H), 4.42 (dd, J = 8.8 Hz, J = 5.6 Hz, 1H), 3.83-3.73 (m, 2H), ppm; 13

C NMR (100 MHz, CDCl3) δ 154.54, 74.54, 66.99, 44.20, ppm.

ACS Paragon Plus Environment

27

ACS Catalysis 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Page 28 of 39

4-(Chloromethyl)-4-methyl-1,3-dioxolan-2-one (3f).21b Purification by flash chromatography (petroleum ether/EtOAc = 2:1) gave a yellow oil (1.426 g, 95%). 1H NMR (400 MHz, CDCl3) δ 4.54 (d, J = 8.4 Hz, 1H), 4.11 (d, J = 8.4 Hz, 1H), 3.77 (d, J = 12.4 Hz, 1H), 3.53 (d, J = 12.4 Hz, 1H), 1.45 (s, 3H), ppm; 13C NMR (100 MHz, CDCl3) δ 155.48, 84.04, 71.50, 65.80, 21.29, ppm. 4-(but-3-en-1-yl)-1,3-dioxolan-2-one (3g).13 Purification by flash chromatography (petroleum ether/EtOAc = 5:1) gave a colorless oil (1.115 g, 78%). 1H NMR (400 MHz, CDCl3) δ 5.84-5.74 (m, 1H), 5.12-5.05 (m, 2H), 4.77-4.70 (m, 1H), 4.54 (t, J = 8.0 Hz, 1H), 4.09 (t, J = 8.0 Hz, 1H), 2.31-2.15 (m, 2H), 1.99-1.90 (m, 1H), 1.83-1.75 (m, 1H), ppm; 13C NMR (100 MHz, CDCl3) δ 154.96, 136.08, 116.43, 69.33, 33.07, 28.66, ppm. 4-(butoxymethyl)-1,3-dioxolan-2-one (3h).15 Purification by flash chromatography (petroleum ether/EtOAc = 5:1) gave a colorless oil (1.271 g, 73%). 1H NMR (400 MHz, CDCl3) δ 4.84-4.78 (m, 1H), 4.50 (t, J = 8.0 Hz, 1H), 4.39 (dd, J = 8.0 Hz, 6.0 Hz, 1H), 3.70-3.59 (m, 2H), 3.51 (t, J = 6.4 Hz, 2H), 1.56 (quint, J = 6.4 Hz, 2H), 1.36 (sext, J = 8.0 Hz, 2H), 0.92 (t, J = 8.0 Hz, 3H), ppm;

13

C NMR (100 MHz, CDCl3) δ 154.98, 75.10, 71.91, 69.64, 66.32, 31.52, 19.15, 13.83,

ppm. 4-((allyloxy)methyl)-1,3-dioxolan-2-one

(3i).15

Purification

by

flash

chromatography

(petroleum ether/EtOAc = 5:1) gave a colorless oil (1.279 g, 81%). 1H NMR (400 MHz, CDCl3) δ 5.92-5.83 (m, 1H), 5.31-5.21 (m, 2H), 4.86-4.81 (m, 1H), 4.51 (t, J = 8.0 Hz, 1H), 4.41 (dd, J = 8.0 Hz, 6.0 Hz, 1H), 4.07-4.04 (m, 2H), 3.70 (dd, J = 10.8 Hz, J = 3.6 Hz, 1H), 3.62 (dd, J = 10.8 Hz, J = 3.6 Hz, 1H), ppm; 13C NMR (100 MHz, CDCl3) δ 154.95, 133.67, 117.94, 75.04, 72.61, 68.85, 66.29, ppm. 4-(Phenoxymethyl)-1,3-dioxolan-2-one (3j).15 Purification by flash chromatography (petroleum ether/EtOAc = 2:1) gave a white solid (1.648 g, 85%), M.P. = 100.9-101.2°C. 1H NMR (400 MHz, CDCl3) δ 7.33 (t, J = 8.0 Hz, 2H), 7.04 (t, J = 8.0 Hz, 1H), 6.94 (d, J = 8.0 Hz, 2H), 5.08-5.02 (m, 1H), 4.64 (t, J = 8.4 Hz, 1H), 4.56 (dd, J = 8.8 Hz, J = 6.0 Hz, 1H), 4.26 (dd, J = 10.4 Hz, J = 4.4 Hz, 1H), 4.17 (dd, J = 10.8 Hz, J = 3.6 Hz, 1H), ppm;

13

C NMR (100 MHz,

CDCl3) δ 157.77, 154.71, 129.71, 121.99, 114.63, 74.18, 66.90, 66.25, ppm. 4-(((9H-Carbazol-4-yl)oxy)methyl)-1,3-dioxolan-2-one

(3k).21b

Purification

by

flash

chromatography (DCM) gave a white solid (2.153 g, 76%), M.P. = 215.7-216.2°C. 1H NMR (400 MHz, DMSO-d6) δ 11.33 (s, 1H), 8.13 (d, J = 8.0 Hz, 1H), 7.48 (d, J = 8.0 Hz, 1H), 7.38-7.31 (m, 2H), 7.16-7.13 (m, 2H), 6.72 (d, J = 8.0 Hz, 1H), 5.35 (s, 1H), 4.78 (t, J = 8.4 Hz,

ACS Paragon Plus Environment

28

Page 29 of 39 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

ACS Catalysis

1H), 4.65-4.41 (m, 3H), ppm; 13C NMR (100 MHz, DMSO-d6) δ 155.51, 154.54, 141.64, 139.44, 126.89, 125.22, 122.55, 121.88, 119.21, 111.85, 110.96, 105.04, 100.98, 75.41, 67.82, 66.67, ppm. 4-Phenyl-1,3-dioxolan-2-one (3l).5d

Purification

by flash chromatography

(petroleum

ether/EtOAc = 10:1) gave a yellow solid (1.459 g, 89%), M.P. = 50.0-51.4°C. 1H NMR (400 MHz, CDCl3) δ 7.48-7.43 (m, 3H), 7.38-7.36 (m, 2H), 5.69 (t, J = 8.0 Hz, 1H), 4.81 (t, J = 8.0 Hz, 1H), 4.34 (t, J = 8.0 Hz, 1H), ppm; 13C NMR (100 MHz, CDCl3) δ 154.95, 135.87, 129.72, 129.23, 125.94, 78.05, 71.21, ppm. 4,4-Dimethyl-1,3-dioxolan-2-one (3m).5d Purification by flash chromatography (petroleum ether/EtOAc = 5:1) gave a colorless oil (1.010 g, 87%). 1H NMR (400 MHz, CDCl3) δ 4.13 (s, 2H), 1.50 (s, 6H), ppm; 13C NMR (100 MHz, CDCl3) δ 154.64, 81.81, 75.37, 25.95, ppm. (4R,5S)-4,5-dimethyl-1,3-dioxolan-2-one (4a).21b Purification by flash chromatography (petroleum ether/EtOAc = 2:1) gave a colorless oil (963.1 mg, 83%). trans-4a: 1H NMR (400 13

MHz, CDCl3) δ 4.33-4.26 (m, 2H), 1.41-1.39 (m, 6H), ppm;

C NMR (100 MHz, CDCl3) δ

154.54, 79.93, 18.27, ppm. Hexahydrobenzo[d][1,3]dioxol-2-one (4b).15 Purification by flash chromatography (petroleum ether/EtOAc = 5:1) gave a colorless oil (1.337 g, 95%). 1H NMR (400 MHz, CDCl3): δ 4.67-4.62 (m, 2H), 1.88-1.74 (m, 4H), 1.57-1.48 (m, 2H), 1.41-1.31 (m, 2H), ppm;

13

C NMR (100 MHz,

CDCl3) δ 155.38, 75.78, 26.62, 19.03, ppm. (3aR,6aS)-Tetrahydro-4H-cyclopenta[d][1,3]dioxol-2-one

(4c).16

Purification

by

flash

1

chromatography (petroleum ether/EtOAc = 5:1) gave a white solid (998.7 mg, 78%). H NMR (400 MHz, CDCl3): δ 5.14-5.10 (m, 2H), 2.18-2.13 (m, 2H), 1.85-1.63 (m, 4H), ppm; 13C NMR (100 MHz, CDCl3) δ 155.47, 81.85, 33.19, 21.57, ppm. (3aR,6aS)-Tetrahydrofuro[3,4-d][1,3]dioxol-2-one

(4d).16

Purification

by

flash

chromatography (petroleum ether/EtOAc = 5:1) gave a white solid (976.3 mg, 75%). 1H NMR (400 MHz, CDCl3): δ 5.22-5.21 (m, 2H), 4.28-4.25 (m, 2H), 3.59-3.55 (m, 2H), ppm; 13C NMR (100 MHz, CDCl3) δ 154.39, 80.04, 73.02, ppm. 1,3-Dioxan-2-one (4e).21a Purification by flash chromatography (petroleum ether/EtOAc = 5:1) gave a colorless oil (378.5 mg, 37%). 1H NMR (400 MHz, CDCl3) δ 4.40-4.32 (m, 4H), 2.11-2.00 (m, 2H), ppm; 13C NMR (100 MHz, CDCl3) δ 148.62, 68.09, 21.62, ppm.

ACS Paragon Plus Environment

29

ACS Catalysis 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Methyl

Page 30 of 39

8-(5-octyl-2-oxo-1,3-dioxolan-4-yl)octanoate

(4f).24c

Purification

by

flash

chromatography (petroleum ether/EtOAc = 10:1) gave a colorless oil (1.817 g, 51%, cis:trans=19:81). trans-4g: 1H NMR (400 MHz, CDCl3) δ 4.25-4.20 (m, 2H), 3.67 (s, 3H), 2.31 (t, J = 8.0 Hz, 2H), 1.62-1.28 (m, 26H), 0.88 (t, J = 6.8 Hz, 3H), ppm;

13

C NMR (100 MHz,

CDCl3) δ 174.17, 154.71, 82.02, 81.98, 51.46, 33.99, 33.82, 33.80, 31.78, 29.30, 29.17, 29.12, 28.96, 28.91, 24.81, 24.64, 24.60, 22.62, 14.07, ppm. Ethyl

(4g).24c

8-(5-octyl-2-oxo-1,3-dioxolan-4-yl)octanoate

Purification

by

flash

chromatography (petroleum ether/EtOAc = 10:1) gave a colorless oil (2.083 g, 56%). as a mixture of two diastereoisomers (cis:trans=17:83); trans-4h: 1H NMR (400 MHz, CDCl3) δ 4.25-4.19 (m, 2H), 4.03 (q, J = 6.8 Hz, 2H), 2.29 (t, J = 7.6 Hz, 2H), 1.72-1.24 (m, 28H), 0.88 (t, J = 6.8 Hz, 3H), ppm; 13C NMR (100 MHz, CDCl3) δ 173.73, 154.67, 81.98, 81.94, 60.17, 34.24, 33.78, 31.75, 29.14, 29.08, 28.94, 28.88, 24.80, 24.60, 24.57, 22.59, 14.22, 14.04, ppm. Methyl 12-(5-octyl-2-oxo-1,3-dioxolan-4-yl)dodecanoate (4h).24c Purification by flash chromatography (petroleum ether/EtOAc = 20:1) gave a colorless oil (1.979 g, 48%). trans-4i: 1

H NMR (400 MHz, CDCl3) δ 4.25-4.20 (m, 2H), 3.67 (s, 3H), 2.30 (t, J = 7.6 Hz, 2H),

1.74-1.27 (m, 36H), 0.88 (t, J = 6.8 Hz, 3H), ppm;

13

C NMR (100 MHz, CDCl3) δ 174.30,

154.74, 82.02, 51.43, 34.09, 33.83, 31.78, 29.47, 29.41, 29.37, 29.32, 29.30, 29.22, 29.17, 29.12, 24.93, 24.64, 22.62, 14.07, ppm. Methyl

8-(2-oxo-5-((2-oxo-5-pentyl-1,3-dioxolan-4-yl)methyl)-1,3-dioxolan-4-yl)octanoate

(4i).24c Purification by flash chromatography (petroleum ether/EtOAc = 2:1) gave a colorless oil (1.783 g, 43%). A mixture of four diastereroisomers dr=53:21:10:16; 1H NMR (400 MHz, CDCl3) δ 4.79-4.67 (m, 2H, isomer 1), 4.56-4.47 (m, 2H, isomer 2), 4.44-4.36 (m, 2H, isomer 3), 4.30-4.25 (m, 2H, isomer 4), 3.63 (s, 3H), 2.29-2.24 (m, 2H), 2.18-1.96 (m, 2H), 1.81-1.48 (m, 8H), 1.39-1.22 (m, 12H), 0.89-0.85 (m, 3H), ppm;

13

C NMR (100 MHz, CDCl3) δ 174.20,

154.68, 154.57, 153.66, 153.63, 82.54, 82.48, 82.08, 81.98, 79.44, 79.33, 79.26, 75.71, 74.50, 74.43, 51.46, 34.03, 33.91, 33.51, 33.29, 31.72, 31.25, 28.93, 28.80, 28.50, 25.38, 25.14, 24.71, 24.45, 24.26, 22.52, 22.35, 13.85, ppm. Computational Details All the theoretical calculations in the study were performed using Gaussian16 program package.27 All the geometries were optimized at the M06-2X28/6-31G** level in gas phase, and

ACS Paragon Plus Environment

30

Page 31 of 39 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

ACS Catalysis

the harmonic vibrational frequency calculations were performed at the same level to confirm the local minima and transition state. ASSOCIATED CONTENT Supporting Information. The Supporting Information is available free of charge on the ACS Publications website. NMR spectra of the organocatalysts and prepared cyclic carbonates. AUTHOR INFORMATION Corresponding Author *E-mail for N.L.: [email protected]; [email protected]. Fax: (+0086)-0993-205-7270; phone: (+0086)-0993-205-7277. *E-mail for D.W.: [email protected]. Author Contributions The manuscript was written through contributions of all authors. All authors have given approval to the final version of the manuscript. Funding Sources Support was provided by the National Natural Science Foundation of China. Notes The authors declare no competing financial interest. ACKNOWLEDGMENT

ACS Paragon Plus Environment

31

ACS Catalysis 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Page 32 of 39

We are grateful for the support from the National Natural Science Foundation of China (Grant Nos. U1603103 and 21466033). REFERENCES (1) (a) Artz, J.; Müller, T. E.; Thenert, K.; Kleinekorte, J.; Meys, R.; Sternberg, A.; Bardow, A.; Leitner, W., Sustainable Conversion of Carbon Dioxide: An Integrated Review of Catalysis and Life Cycle Assessment. Chem. Rev. 2018, 118, 434–504. (b) Shaikh, R. R.; Pornpraprom, S.; D’Elia, V., Catalytic Strategies for the Cycloaddition of Pure, Diluted, and Waste CO2 to Epoxides under Ambient Conditions. ACS Catal. 2017, 8, 419-450. (c) Büttner, H.; Longwitz, L.; Steinbauer, J.; Wulf, C.; Werner, T., Recent Developments in the Synthesis of Cyclic Carbonates from Epoxides and CO2. Top. Curr. Chem. 2017, 375, 50. (d) Song, Q.-W.; Zhou, Z.-H.; He, L.-N., Efficient, selective and sustainable catalysis of carbon dioxide. Green Chem. 2017, 19, 3707-3728. (e) Martín, C.; Fiorani, G.; Kleij, A. W., Recent Advances in the Catalytic Preparation of Cyclic Organic Carbonates. ACS Catal. 2015, 5, 1353-1370. (f) Cokoja, M.; Bruckmeier, C.; Rieger, B.; Herrmann, W. A.; Kühn, F. E., Transformation of Carbon Dioxide with Homogeneous Transition‐Metal Catalysts: A Molecular Solution to a Global Challenge? Angew. Chem., Int. Ed. 2011, 50, 8510-8537. (g) Decortes, A.; Castilla, A. M.; Kleij, A. W., Salen-Complex-Mediated Formation of Cyclic Carbonates by Cycloaddition of CO2 to Epoxides. Angew. Chem., Int. Ed. 2010, 49, 9822-9837. (h) Kleij, A.; Rintjema, J., Substrate-Assisted Carbon Dioxide Activation as a Versatile Approach for Heterocyclic Synthesis. Synthesis 2016, 48, 3863-3878. (i) Sanz-Pérez, E. S.; Murdock, C. R.; Didas, S. A.; Jones, C. W., Direct Capture of CO2 from Ambient Air. Chem. Rev. 2016, 116, 11840-11876. (j) Lang, X.-D.; He, L.-N., Green Catalytic Process for Cyclic Carbonate Synthesis from Carbon Dioxide under Mild Conditions. Chem. Rec. 2016, 16, 1337-1352. (k) Bobbink, F. D.; Dyson, P. J., Synthesis of carbonates and related compounds incorporating CO2 using ionic liquid-type catalysts: State-of-the-art and beyond. J. Catal. 2016, 343, 52-61. (l) North, M.; Pasquale, R.; Young, C., Synthesis of cyclic carbonates from epoxides and CO2. Green Chem. 2010, 12, 1514-1539. (2) (a) Cai, A.; Guo, W.; Martínez-Rodríguez, L.; Kleij, A. W., Palladium-Catalyzed Regioand Enantioselective Synthesis of Allylic Amines Featuring Tetrasubstituted Tertiary Carbons. J. Am. Chem. Soc. 2016, 138, 14194-14197. (b) Xie, J.; Guo, W.; Cai, A.; Escudero-Adán, E. C.; Kleij, A. W., Pd-Catalyzed Enantio- and Regioselective Formation of Allylic Aryl Ethers. Org. Lett. 2017, 19, 6388-6391. (c) Gómez, J. E.; Guo, W.; Kleij, A. W., Palladium-Catalyzed Stereoselective Formation of Substituted Allylic Thioethers and Sulfones. Org. Lett. 2016, 18, 6042-6045. (3) (a) Matsumoto, K.; Kakehashi, M.; Ouchi, H.; Yuasa, M.; Endo, T., Synthesis and Properties of Polycarbosilanes Having 5-Membered Cyclic Carbonate Groups as Solid Polymer Electrolytes. Macromolecules 2016, 49, 9441-9448. (b) Chai, J.; Liu, Z.; Zhang, J.; Sun, J.; Tian, Z.; Ji, Y.; Tang, K.; Zhou, X.; Cui, G., A Superior Polymer Electrolyte with Rigid Cyclic Carbonate Backbone for Rechargeable Lithium Ion Batteries. ACS Appl. Mater. Interfaces 2017, 9, 17897-17905. (4) (a) Guillaume, S. M.; Carpentier, J.-F., Recent advances in metallo/organo-catalyzed immortal ring-opening polymerization of cyclic carbonates. Catal. Sci. Technol. 2012, 2, 898-906. (b) Darensbourg, D. J., Making Plastics from Carbon Dioxide:  Salen Metal Complexes

ACS Paragon Plus Environment

32

Page 33 of 39 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

ACS Catalysis

as Catalysts for the Production of Polycarbonates from Epoxides and CO2. Chem. Rev. 2007, 107, 2388-2410. (c) Darensbourg, D. J.; Wilson, S. J., What's new with CO2? Recent advances in its copolymerization with oxiranes. Green Chem. 2012, 14, 2665-2671. (d) Venkataraman, S.; Ng, V. W. L.; Coady, D. J.; Horn, H. W.; Jones, G. O.; Fung, T. S.; Sardon, H.; Waymouth, R. M.; Hedrick, J. L.; Yang, Y. Y., A Simple and Facile Approach to Aliphatic N-Substituted Functional Eight-Membered Cyclic Carbonates and Their Organocatalytic Polymerization. J. Am. Chem. Soc. 2015, 137, 13851-13860. (5) (a) North, M.; Styring, P., Perspectives and visions on CO2 capture and utilisation. Faraday Discuss. 2015, 183, 489-502. (b) Comerford, J. W.; Ingram, I. D. V.; North, M.; Wu, X., Sustainable metal-based catalysts for the synthesis of cyclic carbonates containing five-membered rings. Green Chem. 2015, 17, 1966-1987. (c) Riduan, S. N.; Zhang, Y., Recent developments in carbon dioxide utilization under mild conditions. Dalton Trans. 2010, 39, 3347-3357. (d) Whiteoak, C. J.; Martin, E.; Belmonte, M. M.; Benet-Buchholz, J.; Kleij, A. W., An Efficient Iron Catalyst for the Synthesis of Five- and Six-Membered Organic Carbonates under Mild Conditions. Adv. Synth. Catal. 2012, 354, 469-476. (6) (a) Alves, M.; Grignard, B.; Mereau, R.; Jerome, C.; Tassaing, T.; Detrembleur, C., Organocatalyzed coupling of carbon dioxide with epoxides for the synthesis of cyclic carbonates: catalyst design and mechanistic studies. Catal. Sci. Technol. 2017, 7, 2651-2684. (b) Chaugule, A. A.; Tamboli, A. H.; Kim, H., Ionic liquid as a catalyst for utilization of carbon dioxide to production of linear and cyclic carbonate. Fuel 2017, 200, 316-332. (c) He, Q.; O'Brien, J. W.; Kitselman, K. A.; Tompkins, L. E.; Curtis, G. C. T.; Kerton, F. M., Synthesis of cyclic carbonates from CO2 and epoxides using ionic liquids and related catalysts including choline chloride–metal halide mixtures. Catal. Sci. Technol. 2014, 4, 1513-1528. (d) Xu, B.-H.; Wang, J.-Q.; Sun, J.; Huang, Y.; Zhang, J.-P.; Zhang, X.-P.; Zhang, S.-J., Fixation of CO2 into cyclic carbonates catalyzed by ionic liquids: a multi-scale approach. Green Chem. 2015, 17, 108-122. (7) (a) Büttner, H.; Steinbauer, J.; Werner, T., Synthesis of Cyclic Carbonates from Epoxides and Carbon Dioxide by Using Bifunctional One-Component Phosphorus-Based Organocatalysts. ChemSusChem 2015, 8, 2655-2669. (b) Kuruppathparambil, R. R.; Jose, T.; Babu, R.; Hwang, G.-Y.; Kathalikkattil, A. C.; Kim, D.-W.; Park, D.-W., A room temperature synthesizable and environmental friendly heterogeneous ZIF-67 catalyst for the solvent less and co-catalyst free synthesis of cyclic carbonates. Appl. Catal. B 2016, 182, 562-569. (c) Han, L.; Park, S.-W.; Park, D.-W., Silica grafted imidazolium-based ionic liquids: efficient heterogeneous catalysts for chemical fixation of CO2 to a cyclic carbonate. Energy Environ. Sci. 2009, 2, 1286-1292. (d) Wilhelm, M. E.; Anthofer, M. H.; Reich, R. M.; D'Elia, V.; Basset, J.-M.; Herrmann, W. A.; Cokoja, M.; Kühn, F. E., Niobium(V) chloride and imidazolium bromides as efficient dual catalyst systems for the cycloaddition of carbon dioxide and propylene oxide. Catal. Sci. Technol. 2014, 4, 1638-1643. (e) Li, J.; Jia, D.; Guo, Z.; Liu, Y.; Lyu, Y.; Zhou, Y.; Wang, J., Imidazolinium based porous hypercrosslinked ionic polymers for efficient CO2 capture and fixation with epoxides. Green Chem. 2017, 19, 2675-2686. (f) Buaki-Sogó, M.; Vivian, A.; Bivona, L. A.; García, H.; Gruttadauria, M.; Aprile, C., Imidazolium functionalized carbon nanotubes for the synthesis of cyclic carbonates: reducing the gap between homogeneous and heterogeneous catalysis. Catal. Sci. Technol. 2016, 6, 8418-8427. (g) Calabrese, C.; Liotta, L. F.; Carbonell, E.; Giacalone, F.; Gruttadauria, M.; Aprile, C., Imidazolium-Functionalized Carbon Nanohorns for the Conversion of Carbon Dioxide: Unprecedented Increase of Catalytic Activity after Recycling. ChemSusChem 2016, 10, 1202-1209. (h) Xiao, L.-F.; Li, F.-W.; Peng, J.-J.; Xia, C.-G., Immobilized ionic liquid/zinc chloride: Heterogeneous catalyst for synthesis of cyclic

ACS Paragon Plus Environment

33

ACS Catalysis 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Page 34 of 39

carbonates from carbon dioxide and epoxides. J. Mol. Catal. A: Chem. 2006, 253, 265-269. (i) Zhang, S.; Huang, Y.; Jing, H.; Yao, W.; Yan, P., Chiral ionic liquids improved the asymmetric cycloaddition of CO2 to epoxides. Green Chem. 2009, 11, 935-938. (j) Duan, S.; Jing, X.; Li, D.; Jing, H., Catalytic asymmetric cycloaddition of CO2 to epoxides via chiral bifunctional ionic liquids. J. Mol. Catal. A: Chem. 2016, 411, 34-39. (8) (a) Ema, T.; Yokoyama, M.; Watanabe, S.; Sasaki, S.; Ota, H.; Takaishi, K., Chiral Macrocyclic Organocatalysts for Kinetic Resolution of Disubstituted Epoxides with Carbon Dioxide. Org. Lett. 2017, 19, 4070-4073. (b) Su, Q.; Yao, X.; Cheng, W.; Zhang, S., Boron-doped melamine-derived carbon nitrides tailored by ionic liquids for catalytic conversion of CO2 into cyclic carbonates. Green Chem. 2017, 19, 2957-2965. (c) Liu, F.; Huang, K.; Wu, Q.; Dai, S., Solvent-Free Self-Assembly to the Synthesis of Nitrogen-Doped Ordered Mesoporous Polymers for Highly Selective Capture and Conversion of CO2. Adv. Mater. 2017, 29, 1700445. (d) Zhu, J.; Diao, T.; Wang, W.; Xu, X.; Sun, X.; Carabineiro, S. A. C.; Zhao, Z., Boron doped graphitic carbon nitride with acid-base duality for cycloaddition of carbon dioxide to epoxide under solvent-free condition. Appl. Catal. B 2017, 219, 92-100. (e) Ahmed, M.; Sakthivel, A., Preparation of cyclic carbonate via cycloaddition of CO2 on epoxide using amine-functionalized SAPO-34 as catalyst. J. CO2 Util. 2017, 22, 392-399. (f) Barkakaty, B.; Morino, K.; Sudo, A.; Endo, T., Amidine-mediated delivery of CO2 from gas phase to reaction system for highly efficient synthesis of cyclic carbonates from epoxides. Green Chem. 2010, 12, 42-44. (9) (a) Chatelet, B.; Joucla, L.; Dutasta, J.-P.; Martinez, A.; Szeto, K. C.; Dufaud, V., Azaphosphatranes as Structurally Tunable Organocatalysts for Carbonate Synthesis from CO2 and Epoxides. J. Am. Chem. Soc. 2013, 135, 5348-5351. (b) Steinbauer, J.; Longwitz, L.; Frank, M.; Epping, J.; Kragl, U.; Werner, T., Immobilized bifunctional phosphonium salts as recyclable organocatalysts in the cycloaddition of CO2 and epoxides. Green Chem. 2017, 19, 4435-4445. (c) Wu, Y.; Zhao, Y.; Li, R.; Yu, B.; Chen, Y.; Liu, X.; Wu, C.; Luo, X.; Liu, Z., Tetrabutylphosphonium-Based Ionic Liquid Catalyzed CO2 Transformation at Ambient Conditions: A Case of Synthesis of α-Alkylidene Cyclic Carbonates. ACS Catal. 2017, 7, 6251-6255. (d) Wang, W.; Wang, Y.; Li, C.; Yan, L.; iang, M. J.; Ding, Y., State-of-the-Art Multifunctional Heterogeneous POP Catalyst for Cooperative Transformation of CO2 to Cyclic Carbonates. ACS Sustainable Chem. Eng. 2017, 5, 4523-4528. (e) Yuan, G.; Zhao, Y.; Wu, Y.; Li, R.; Chen, Y.; Xu, D.; Liu, Z., Cooperative effect from cation and anion of pyridine-containing anion-based ionic liquids for catalysing CO2 transformation at ambient conditions. Sci. China Chem. 2017, 60, 958-963. (f) Chatelet, B.; Joucla, L.; Dutasta, J.-P.; Martinez, A.; Dufaud, V., Immobilization of a N-substituted azaphosphatrane in nanopores of SBA-15 silica for the production of cyclic carbonates. J. Mater. Chem. A 2014, 2, 14164-14172. (g) Werner, T.; Büttner, H., Phosphorus-based Bifunctional Organocatalysts for the Addition of Carbon Dioxide and Epoxides. ChemSusChem 2014, 7, 3268-3271. (h) Großeheilmann, J.; Büttner, H.; Kohrt, C.; Kragl, U.; Werner, T., Recycling of Phosphorus-Based Organocatalysts by Organic Solvent Nanofiltration. ACS Sustainable Chem. Eng. 2015, 3, 2817-2822. (i) Sakai, T.; Tsutsumi, Y.; Ema, T., Highly active and robust organic–inorganic hybrid catalyst for the synthesis of cyclic carbonates from carbon dioxide and epoxides. Green Chem. 2008, 10, 337-341. (j) Toda, Y.; Komiyama, Y.; Kikuchi, A.; Suga, H., Tetraarylphosphonium Salt-Catalyzed Carbon Dioxide Fixation at Atmospheric Pressure for the Synthesis of Cyclic Carbonates. ACS Catal. 2016, 6, 6906-6910. (k) Song, Q.-W.; He, L.-N.; Wang, J.-Q.; Yasuda,

ACS Paragon Plus Environment

34

Page 35 of 39 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

ACS Catalysis

H.; Sakakura, T., Catalytic fixation of CO2 to cyclic carbonates by phosphonium chlorides immobilized on fluorous polymer. Green Chem. 2013, 15, 110-115. (10) (a) Tharun, J.; Bhin, K.-M.; Roshan, R.; Kim, D. W.; Kathalikkattil, A. C.; Babu, R.; Ahn, H. Y.; Won, Y. S.; Park, D.-W., Ionic liquid tethered post functionalized ZIF-90 framework for the cycloaddition of propylene oxide and CO2. Green Chem. 2016, 18, 2479-2487. (b) Meng, X.; He, H.; Nie, Y.; Zhang, X.; Zhang, S.; Wang, J., Temperature-Controlled Reaction-Separation for Conversion of CO2 to Carbonates with Functional Ionic Liquids Catalyst. ACS Sustainable Chem. Eng. 2017, 5, 3081-3086. (c) Zhang, Z.; Fan, F.; Xing, H.; Yang, Q.; Bao, Z.; Ren, Q., Efficient Synthesis of Cyclic Carbonates from Atmospheric CO2 Using a Positive Charge Delocalized Ionic Liquid Catalyst. ACS Sustainable Chem. Eng. 2017, 5, 2841-2846. (d) Zakharova, M. V.; Kleitz, F.; Fontaine, F.-G., Carbon Dioxide Oversolubility in Nanoconfined Liquids for the Synthesis of Cyclic Carbonates. ChemCatChem 2017, 9, 1886-1890. (e) Jose, T.; Cañellas, S.; Pericàs, M. A.; Kleij, A. W., Polystyrene-supported bifunctional resorcinarenes as cheap, metal-free and recyclable catalysts for epoxide/CO2 coupling reactions. Green Chem. 2017, 19, 5488-5493. (f) Liu, M.; Li, X.; Liang, L.; Sun, J., Protonated triethanolamine as multi-hydrogen bond donors catalyst for efficient cycloaddition of CO2 to epoxides under mild and cocatalyst-free conditions. J. CO2 Util. 2016, 16, 384-390. (g) Büttner, H.; Lau, K.; Spannenberg, A.; Werner, T., Bifunctional One-Component Catalysts for the Addition of Carbon Dioxide to Epoxides. ChemCatChem 2015, 7, 459-467. (h) Ema, T.; Fukuhara, K.; Sakai, T.; Ohbo, M.; Bai, F.-Q.; Hasegawa, J.-Y., Quaternary ammonium hydroxide as a metal-free and halogen-free catalyst for the synthesis of cyclic carbonates from epoxides and carbon dioxide. Catal. Sci. Technol. 2015, 5, 2314-2321. (i) Tsutsumi, Y.; Yamakawa, K.; Yoshida, M.; Ema, T.; Sakai, T., Bifunctional Organocatalyst for Activation of Carbon Dioxide and Epoxide To Produce Cyclic Carbonate: Betaine as a New Catalytic Motif. Org. Lett. 2010, 12, 5728-5731. (j) Mirabaud, A.; Mulatier, J.-C.; Martinez, A.; Dutasta, J.-P.; Dufaud, V., Investigating Host–Guest Complexes in the Catalytic Synthesis of Cyclic Carbonates from Styrene Oxide and CO2. ACS Catal. 2015, 5, 6748-6752. (k) Cho, W.; Shin, M. S.; Hwang, S.; Kim, H.; Kim, M.; Kim, J. G.; Kim, Y., Tertiary amines: A new class of highly efficient organocatalysts for CO2 fixations. J. Ind. Eng. Chem. 2016, 44, 210-215. (l) Yang, Z.-Z.; Zhao, Y.-N.; He, L.-N.; Gao, J.; Yin, Z.-S., Highly efficient conversion of carbon dioxide catalyzed by polyethylene glycol-functionalized basic ionic liquids. Green Chem. 2012, 14, 519-527. (m) Wang, T.; Zheng, D.; Zhang, J.; Fan, B.; Ma, Y.; Ren, T.; Wang, L.; Zhang, J., Protic Pyrazolium Ionic Liquids: An Efficient Catalyst for Conversion of CO2 in the Absence of Metal and Solvent. ACS Sustainable Chem. Eng. 2018, 6, 2574-2582. (11) (a) Duval, A.; Avérous, L., Cyclic Carbonates as Safe and Versatile Etherifying Reagents for the Functionalization of Lignins and Tannins. ACS Sustainable Chem. Eng. 2017, 5, 7334-7343. (b) Shen, Y.-M.; Duan, W.-L.; Shi, M., Phenol and Organic Bases Co-Catalyzed Chemical Fixation of Carbon Dioxide with Terminal Epoxides to Form Cyclic Carbonates. Adv. Synth. Catal. 2003, 345, 337-340. (c) Liang, S.; Liu, H.; Jiang, T.; Song, J.; Yang, G.; Han, B., Highly efficient synthesis of cyclic carbonates from CO2 and epoxides over cellulose/KI. Chem. Commun. 2011, 47, 2131-2133. (d) Song, J.; Zhang, Z.; Han, B.; Hu, S.; Li, W.; Xie, Y., Synthesis of cyclic carbonates from epoxides and CO2 catalyzed by potassium halide in the presence of β-cyclodextrin. Green Chem. 2008, 10, 1337-1341. (e) Roshan, K. R.; Kim, B. M.; Kathalikkattil, A. C.; Tharun, J.; Won, Y. S.; Park, D. W., The unprecedented catalytic activity of alkanolamine CO2 scrubbers in the cycloaddition of CO2 and oxiranes: a DFT endorsed study. Chem. Commun. 2014, 50, 13664-13667. (f) Martínez-Rodríguez, L.; Otalora Garmilla, J.; Kleij,

ACS Paragon Plus Environment

35

ACS Catalysis 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Page 36 of 39

A. W., Cavitand-Based Polyphenols as Highly Reactive Organocatalysts for the Coupling of Carbon Dioxide and Oxiranes. ChemSusChem 2016, 9, 749-755. (g) Zhi, Y.; Shao, P.; Feng, X.; Xia, H.; Zhang, Y.; Shi, Z.; Mu, Y.; Liu, X., Covalent organic frameworks: efficient, metal-free, heterogeneous organocatalysts for chemical fixation of CO2 under mild conditions. J. Mater. Chem. A 2018, 6, 374-382. (h) Rulev, Y. A.; Gugkaeva, Z. T.; Lokutova, A. V.; Maleev, V. I.; Peregudov, A. S.; Wu, X.; North, M.; Belokon, Y. N., Carbocation/Polyol Systems as Efficient Organic Catalysts for the Preparation of Cyclic Carbonates. ChemSusChem 2017, 10, 1152-1159. (12) Cokoja, M.; Wilhelm, M. E.; Anthofer, M. H.; Herrmann, W. A.; Kühn, F. E., Synthesis of Cyclic Carbonates from Epoxides and Carbon Dioxide by Using Organocatalysts. ChemSusChem 2015, 8, 2436-2454. (13) Kumatabara, Y.; Okada, M.; Shirakawa, S. Triethylamine Hydroiodide as a Simple Yet Effective Bifunctional Catalyst for CO2 Fixation Reactions with Epoxides under Mild Conditions,. ACS Sustainable Chem. Eng. 2017, 5, 7295-7301. (14) Arayachukiat, S.; Kongtes, C.; Barthel, A.; Vummaleti, S. V. C.; Poater, A.; Wannakao, S.; Cavallo, L.; D’Elia, V., Ascorbic Acid as a Bifunctional Hydrogen Bond Donor for the Synthesis of Cyclic Carbonates from CO2 under Ambient Conditions. ACS Sustainable Chem. Eng. 2017, 5, 6392-6397. (15) Zhou, H.; Wang, G.-X.; Zhang, W.-Z.; Lu, X.-B., CO2 Adducts of Phosphorus Ylides: Highly Active Organocatalysts for Carbon Dioxide Transformation. ACS Catal. 2015, 5, 6773-6779. (16) Sopeña, S.; Martin, E.; Escudero-Adán, E. C.; Kleij, A. W., Pushing the Limits with Squaramide-Based Organocatalysts in Cyclic Carbonate Synthesis. ACS Catal. 2017, 7, 3532-3539. (17) (a) Anthofer, M. H.; Wilhelm, M. E.; Cokoja, M.; Drees, M.; Herrmann, W. A.; Kühn, F. E., Hydroxy-Functionalized Imidazolium Bromides as Catalysts for the Cycloaddition of CO2 and Epoxides to Cyclic Carbonates. ChemCatChem 2015, 7, 94-98. (b) Wang, J.; Leong, J.; Zhang, Y., Efficient fixation of CO2 into cyclic carbonates catalysed by silicon-based main chain poly-imidazolium salts. Green Chem. 2014, 16, 4515-4519. (c) Zhong, H.; Su, Y.; Chen, X.; Li, X.; Wang, R., Imidazolium- and Triazine-Based Porous Organic Polymers for Heterogeneous Catalytic Conversion of CO2 into Cyclic Carbonates. ChemSusChem 2017, 10, 4855-4863. (d) Whiteoak, C. J.; Nova, A.; Maseras, F.; Kleij, A. W., Merging Sustainability with Organocatalysis in the Formation of Organic Carbonates by Using CO2 as a Feedstock. ChemSusChem 2012, 5, 2032-2038. (e) Hardman-Baldwin, A. M.; Mattson, A. E., ChemSusChem 2014, 7, 3275-3278. (f) Wu, S.; Wang, B.; Zhang, Y.; Elageed, E. H. M.; Wu, H.; Gao, G., Phenolic hydroxyl-functionalized imidazolium ionic liquids: Highly efficient catalysts for the fixation of CO2 to cyclic carbonates. J. Mol. Catal. A: Chem. 2016, 418-419, 1-8. (18) (a) Sun, J.; Han, L.; Cheng, W.; Wang, J.; Zhang, X.; Zhang, S., Efficient Acid-Base Bifunctional Catalysts for the Fixation of CO2 with Epoxides under Metal- and Solvent-Free Conditions. ChemSusChem 2011, 4, 502-507. (b) Desens, W.; Werner, T., Convergent Activation Concept for CO2 Fixation in Carbonates. Adv. Synth. Catal. 2016, 358, 622-630. (c) Goodrich, P.; Gunaratne, H. Q. N.; Jacquemin, J.; Jin, L.; Lei, Y.; Seddon, K. R., Sustainable Cyclic Carbonate Production, Utilizing Carbon Dioxide and Azolate Ionic Liquids. ACS Sustainable Chem. Eng. 2017, 5, 5635-5641. (d) Wang, Y.-B.; Sun, D.-S.; Zhou, H.; Zhang, W.-Z.; Lu, X.-B., CO2, COS and CS2 adducts of N-heterocyclic olefins and their application as organocatalysts for carbon dioxide fixation. Green Chem. 2015, 17, 4009-4015. (e) Wang, Y.-B.; Wang, Y.-M.; Zhang, W.-Z.; Lu, X.-B., Fast CO2 Sequestration, Activation, and Catalytic

ACS Paragon Plus Environment

36

Page 37 of 39 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

ACS Catalysis

Transformation Using N-Heterocyclic Olefins. J. Am. Chem. Soc. 2013, 135, 11996-12003. (f) Zhou, H.; Zhang, W.-Z.; Liu, C.-H.; Qu, J.-P.; Lu, X.-B., CO2 Adducts of N-Heterocyclic Carbenes: Thermal Stability and Catalytic Activity toward the Coupling of CO2 with Epoxides. J. Org. Chem. 2008, 73, 8039-8044. (19) Liu, A.-H.; Ma, R.; Song, C.; Yang, Z.-Z.; Yu, A.; Cai, Y.; He, L.-N.; Zhao, Y.-N.; Yu, B.; Song, Q.-W., Equimolar CO2 Capture by N‐Substituted Amino Acid Salts and Subsequent Conversion. Angew. Chem., Int. Ed. 2012, 51, 11306-11310. (20) Graham, J. D.; Buytendyk, A. M.; Wang, Y.; Kim, S. K.; Bowen, K. H., CO2 binding in the (quinoline-CO2)- anionic complex. J. Chem. Phys. 2015, 142, 234307. (21) (a) Chen, F.; Liu, N.; Dai, B., Iron(II) Bis-CNN Pincer Complex-Catalyzed Cyclic Carbonate Synthesis at Room Temperature. ACS Sustainable Chem. Eng. 2017, 5, 9065-9075. (b) Chen, F.; Chen, D.; Shi, L.; Liu, N.; Dai, B., “Fiddler crab-type” imidazolium salt as remote substituents tuning organocatalyst for the cycloaddition of epoxides with carbon dioxide. J. CO2 Util. 2016, 16, 391-398. (22) (a) D’Elia, V.; Zwicknagl, H.; Reiser, O., Short α/β-Peptides as Catalysts for Intra- and Intermolecular Aldol Reactions. J. Org. Chem. 2008, 73, 3262-3265. (b) Schmid, M. B.; Fleischmann, M.; D’Elia, V.; Reiser, O.; Gronwald, W.; Gschwind, R. M., Residual Dipolar Couplings in Short Peptidic Foldamers: Combined Analyses of Backbone and Side-Chain Conformations and Evaluation of Structure Coordinates of Rigid Unnatural Amino Acids. ChemBioChem 2009, 10, 440-444. (23) Wang, L.; Liu, N.; Dai, B.; Hu, H., Selective C-N Bond-Forming Reaction of 2,6-Dibromopyridine with Amines. Eur. J. Org. Chem. 2014, 2014, 6493-6500. (24) (a) Longwitz, L.; Steinbauer, J.; Spannenberg, A.; Werner, T., Calcium-Based Catalytic System for the Synthesis of Bio-Derived Cyclic Carbonates under Mild Conditions. ACS Catal. 2018, 8, 665-672. (b) Carrodeguas, L. P.; Cristòfol, A.; Fraile, J. M.; Mayoral, J. A.; Dorado, V.; Herrerías, C. I.; Kleij, A. W., Fatty acid based biocarbonates: Al-mediated stereoselective preparation of mono-, di- and tricarbonates under mild and solvent-less conditions. Green Chem., 2017,19, 3535-3541. (c) Tenhumberg, N.; Büttner, H.; Schäffner, B.; Kruse, D.; Blumenstein, M.; Werner, T., Cooperative catalyst system for the synthesis of oleochemical cyclic carbonates from CO2 and renewables. Green Chem. 2016, 18, 3775-3788. (25) Miao, C.-X.; Wang, J.-Q.; Wu, Y.; Du, Y.; He, L.-N., Bifunctional Metal-Salen Complexes as Efficient Catalysts for the Fixation of CO2 with Epoxides under Solvent-Free Conditions. ChemSusChem 2008, 1, 236-241. (26) (a) Wei, D.; Lei, B.; Tang, M.; Zhan, C., Fundamental Reaction Pathway and Free Energy Profile for Inhibition of Proteasome by Epoxomicin, J. Am. Chem. Soc. 2012, 134, 10436-10450. (b) Guo, X.; Zhang, L.; Wei, D.; Niu, J., Mechanistic insights into cobalt(ii/iii)-catalyzed C-H oxidation: a combined theoretical and experimental study. Chem. Sci. 2015, 6, 7059-7071. (c) Wang, Y.; Wei, D.; Wang, Y.; Zhang, W.; Tang, M., N-Heterocyclic Carbene (NHC)-Catalyzed sp(3) beta-C-H Activation of Saturated Carbonyl Compounds: Mechanism, Role of NHC, and Origin of Stereoselectivity. ACS Catal. 2016, 6, 279-289. (d) Wei, D.; Huang, X.; Qiao, Y.; Rao, J.; Wang, L.; Liao, F.; Zhan, C., Catalytic Mechanisms for Cofactor-Free Oxidase-Catalyzed Reactions: Reaction Pathways of Uricase-Catalyzed Oxidation and Hydration of Uric Acid. ACS Catal. 2017, 7, 4623-4636. (e) Wang, Y.; Wei, D.; Zhang, W., Recent Advances on Computational Investigations of N-Heterocyclic Carbene Catalyzed Cycloaddition/Annulation Reactions: Mechanism and Origin of Selectivities. ChemCatChem 2018, 10, 338-360.

ACS Paragon Plus Environment

37

ACS Catalysis 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Page 38 of 39

(27) Frisch, M. J.; Trucks, G. W.; Schlegel, H. B.; Scuseria, G. E.; Robb, M. A.; Cheeseman, J. R.; Scalmani, G.; Barone, V.; Petersson, G. A.; Nakatsuji, H.; Li, X.; Caricato, M.; Marenich, A. V.; Bloino, J.; Janesko, B. G.; Gomperts, R.; Mennucci, B.; Hratchian, H. P.; Ortiz, J. V.; Izmaylov, A. F.; Sonnenberg, J. L.; Williams-Young, D.; Ding, F.; Lipparini, F.; Egidi, F.; Goings, J.; Peng, B.; Petrone, A.; Henderson, T.; Ranasinghe, D.; Zakrzewski, V. G.; Gao, J.; Rega, N.; Zheng, G.; Liang, W.; Hada, M.; Ehara, M.; Toyota, K.; Fukuda, R.; Hasegawa, J.; Ishida, M.; Nakajima, T.; Honda, Y.; Kitao, O.; Nakai, H.; Vreven, T.; Throssell, K.; Montgomery Jr., J. A.; Peralta, J. E.; Ogliaro, F.; Bearpark, M. J.; Heyd, J. J.; Brothers, E. N.; Kudin, K. N.; Staroverov, V. N.; Keith, T. A.; Kobayashi, R.; Normand, J.; Raghavachari, K.; Rendell, A. P.; Burant, J. C.; Iyengar, S. S.; Tomasi, J.; Cossi, M.; Millam, J. M.; Klene, M.; Adamo, C.; Cammi, R.; Ochterski, J. W.; Martin, R. L.; Morokuma, K.; Farkas, O.; Foresman, J. B.; Fox, D. J., Gaussian16, Gaussian, Inc., Wallingford, CT, 2016. (28) (a) Zhao, Y.; Truhlar, D. G., Exploring the Limit of Accuracy of the Global Hybrid Meta Density Functional for Main-Group Thermochemistry, Kinetics, and Noncovalent Interactions. J. Chem. Theory Comput. 2008, 4, 1849-1868. (b) Zhao, Y.; Truhlar, D. G., Density Functionals with Broad Applicability in Chemistry. Acc. Chem. Res. 2008, 41, 157-167.

ACS Paragon Plus Environment

38

Page 39 of 39 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

ACS Catalysis

The one-component, neat, and highly active multi-functional catalysts have applied successfully for the cycloaddition of terminal epoxides with CO2 under ambient conditions. 169x67mm (300 x 300 DPI)

ACS Paragon Plus Environment