Fiber-Supported AcidâBase Bifunctional Catalysts ... - ACS Publications

Subscriber access provided by the University of Exeter

Article

Fiber-supported acid-base bifunctional catalysts for efficient nucleophilic addition in water Jianguo Du, Minli Tao, and Wenqin Zhang ACS Sustainable Chem. Eng., Just Accepted Manuscript • DOI: 10.1021/acssuschemeng.6b00785 • Publication Date (Web): 12 Jul 2016 Downloaded from http://pubs.acs.org on July 17, 2016

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 free 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 accessible to all readers and 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.

ACS Sustainable Chemistry & Engineering 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 33

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 Sustainable Chemistry & Engineering

Fiber-supported acid-base bifunctional catalysts for efficient nucleophilic addition in water Jianguo Du, Minli Tao*, Wenqin Zhang* Department of Chemistry, School of Science Tianjin University, Collaborative Innovation Center of ChemicalScience and Engineering (Tianjin), Weijin Road, Tianjin 300072 (P. R. China). Corresponding Author

E-mail: [email protected],

KEYWORDS: polypropylene fiber (PPF) • heterogeneous catalyst • bifunctional catalyst • aqueous catalysis • nucleophilic addition ABSTRACT: A series of fiber supported acid-base bifunctional catalysts (FABCs) were developed by successive grafting of acrylic acid and 4-vinylpyridine onto the polypropylene fiber (PPF). The FABCs can efficiently catalyze a number of reactions whose key steps involve in nucleophilic addition. The obviously enhanced activities of the bifunctional catalysts compared with that of the individual fiber supported acid or base upon the nitro-aldol and Knoevenagel reactions indicate that the FABCs perform in a cooperative catalyzing model and their activities can be easily tuned by controlling the acid-base ratio. An optimized bifunctional catalyst was successfully applied to the aqueous Gewald, tandem Michael-Henry reaction and one three-component reaction with excellent catalytic performances. In addition, this newly developed bifunctional fiber catalyst also exhibits excellent recyclability and reusability with simple treatment.

ACS Paragon Plus Environment

1


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 33

INTRODUCTION Heterogeneous catalysts possess inherent advantages of simple operation and high efficiency in catalysis owing to their unique catalytic abilities.1-8 Recently, anchoring catalytically active species on insoluble matrices via covalent bonds become a current area of interest in the design and preparation of heterogeneous catalysts, which not only generates recoverable and reusable heterogeneous catalysts but also enhances catalytic performances.9-14 Many positive effects of immobilization have been reported.15-20 Among them, cooperative catalysis on the support surfaces with multifunctions which have been designed following the way of enzymatic catalysis21-25 is a particularly important advantage of the use of immobilized catalyst.10,

26, 27

Especially, acid–base dual-activation catalysts have received much attention for activation of both electrophile and nucleophile, respectively. In consideration of the appropriate surface acidity, high porosity and large surface area of inorganic materials,28-30 most bifunctional catalysts were developed based on inorganic materials.31-43 In 2005, Katz and co-workers reported a cooperative acid–base catalyst of amine and silanol groups in silica matrix for Knoevenagel condensation and nitro–aldol reaction.42 Lin and co-workers then reported silica-supported hydrogen-bonding urea and amine bifunctional catalyst for aldol reaction and cyanosilylation.31 In 2012, Wang and co-workers reported a Schiff base structured acid–base cooperative catalyst for Knoevenagel condensation in an ionic solid phosphotungstate.36 However, tedious preparation procedures, easy deactivation of the catalysts and low selectivity for the products are still issues that need to be improved. Recently, porous organic frameworks have received much attention.44-48 In 2007, Toy and co-workers reported cooperative acid–base catalyst of DMAP, triphenylphosphane, alkyl alcohol or phenol groups in non-crosslinked polystyrene for Morita–Baylis–Hillman reactions.46 In 2014, Ma and co-workers


2

Page 3 of 33

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


reported dual functionalization of porous aromatic frameworks as a new platform for heterogeneous cascade catalysis.45 However, organic solvents are often applied to swell the polymers. Therefore, it is necessary to develop more effective materials for immobilizing organic multifunctional groups to investigate the cooperative effect in greener solvents. Polypropylene fiber (PPF), one of the synthetic fiber, has been widely utilized in many fields due to its plenty advantages of low cost, high tensile strength, and high resistance to chemicals.49 Besides, many other chemical applications50-52 of modified PPF are explored, which benefits from the synthesis and modification technologies of this fiber.53-55 For the practical application, the fibrous shape of PPF makes it easily to be woven into desired shapes, which can be further adapted to continuous reaction processes (such as flow chemistry).56-58 All of these advantages make PPF an appealing novel candidate as support for immobilization of catalytically active species.59,

60

Based on this, a series of polypropylene fiber-supported organic acid-base

bifunctional catalysts were prepared by successive radical grafting and the cooperative effect was rationally evaluated by nitro-aldol and Knoevenagel reactions. In addition, their wide applications in organic synthesis in water were also explored.

RESULTS AND DISSCUSSION Preparation and characterization of the catalysts Since PPF is composed of saturated hydrocarbon chains, most of the modifications focused on grafting methods through free radical polymerization techniques.61-63 Grafting acrylic acid onto PPF has been widely investigated in the modification of PPF,

64-66

based on this, we improved

the grafting method to afford an acrylic acid (AA) modified fiber catalyst A and a 4-


3


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 33

vinylpyridine (4-VP) modified catalyst B (Scheme 1). The details are described in the supporting information. The results show that it is easy to afford the catalyst A with a high grafting degree of 63% (the functionality of acid group carboxyl COOH is 5.37 mmol/g) by grafting acrylic acid onto PPF. Such degree can be controlled by tuning the amount of acrylic acid and the grafting time (see SI). However, the grafting of 4-vinylpyridine to afford catalyst B is much harder and the highest grafting degree of 5% (the functionality of base group of pyridinyl C5H4N is 0.45 mmol/g) is achieved by the first grafting operation. Furthermore, moderate grafting degree (up to 25%) is obtained by repeating the grafting operation for the second run. These results demonstrate that the PPF macroradical (formed by hydrogen abstraction of the PPF) reacts with 4-vinylpyridine more difficult than with acrylic acid and the second run of 4-vinylpyridine are probably attached onto the poly(4-vinylpyridine) chains which were produced in the first grafting step (as the red line of catalyst B in Scheme 1), but not on the PPF backbone. Thus, the grafting density of catalyst A is higher than that of B. For catalyst A, the surface of the fiber is planted with many poly(acrylic acid) chains, however, the amount of poly(4-vinylpyridine) chains that attached onto the fiber surface in catalyst B was much less. A series of FABCs with different acid-base ratios were prepared by grafting 4-vinylpyridine (base group) on catalyst A (Scheme 1). For example, C1/2 means the mole ratio of the acid and base groups is 1:2, and so for C1/1, C2/1 and C3/1. These ratios can be controlled by tuning the amount of 4-vinylpyridine and the grafting time (See SI).


4

Page 5 of 33

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


Scheme 1. Schematic diagram of catalysts A, B, and FABCs. The mechanism of preparation of catalyst FABCs are described in Scheme 2. The free radical R2 is more stable than R1, therefore, R2 was generated more easily when catalyst A was initiated by BPO. As a result, the 4-vinylpyridines were primarily grafted on the poly(acrylic acid) chains of catalyst A.

Scheme 2. Proposed mechanism in the preparation of catalyst FABCs. Based on these analyses, the fiber catalysts have fabricated structures (scheme 1) which are similar to bottlebrush copolymers.67 The shape-persistent nature, remarkable spatial dimensions, and tunable acid-base ratios may provide remarkable advantages for catalysis. For example, the shape-persistent nature of acid and base groups may increase the versatility of FABCs by


5


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 33

providing various optimal distances for cooperative catalysis. The remarkable spatial dimensions with plenty of linear chains make the active sites access to the reactants more easily. Thus, the fabricated structures may effectively enhance the activity of catalysts. The grafting degree of acrylic acid was also determined by acid-base exchange capacity64 (Table 3 in SI). Herein, grafting degree = [(Wg -Wo)/Wo]×100%, where Wo and Wg are the weights of PPF and the grafted fiber, respectively. For instance, catalyst A has a grafting degree of 27%, its acid exchange capacity by titration is 2.49 mmol/g which is lower than 2.95 mmol/g that calculated from the grafting degree of 27%. This implies that during the grafting polymerization, some initiator fragments are attached on the PPF. After catalyst A is further grafted with 4-vinylpyridine to afford catalyst C2/1 (the weight gain of C2/1 based on catalyst A is 13.6%), its acid exchange capacity, i.e. the functionality of COOH, is 2.19 mmol/g (now, 1 g A has been changed to 1.136 g C2/1 due to the subsequent grafting of 4-vinylpyridine, i. e. 2.49/1.136=2.19) which contains the same amount of COOH group as that in fiber catalyst A. This indicates that COOH group isn’t affected after the subsequent grafting of 4-vinylpyridine.


6

Page 7 of 33

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


Figure 1. FTIR spectra of PPF, catalyst A, B, C2/1, and protonated B. The fiber catalysts were ground into powders and prepared as KBr pellets and characterized by FTIR. The IR spectra of PPF, catalysts A, B, C2/1, and protonated B (catalyst B was treated by free propionic acid) are shown in Figure 1. Compared with the spectrum of PPF, the obvious absorption peak at 1730 cm-1 of catalyst A is associated with the stretching vibration of the C=O group from the acrylic acid units. Further, the skeleton vibration of the pyridine unit emerges at 1600 cm-1 in catalyst B. As expected, both the C=O stretching vibration of acrylic acid and skeleton vibrations of pyridine appear in the FTIR spectrum of catalyst C2/1. This strongly illustrates that the acid-base bifunctional catalysts are successfully prepared. Obviously, the wavenumber of skeleton vibration of the pyridine shift from 1600 cm-1 to 1643 cm-1 in propionic acid treated catalyst B, which conversely proved that the pyridine groups are not neutralized by the carboxylic ones even they coexist in the same polymer chains.


7


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 33

The elemental analysis data for PPF, catalyst A, B, and C2/1 are listed in Table 1. Since polypropylene fiber is a kind of commercial synthetic fiber, small amount of nitrogen conaining surfactant and flame retardant may be added in the manufacture process of the fiber. Therefore, 0.54% of nitrogen was detected in PPF. The carbon, hydrogen, and nitrogen contents of catalyst A decrease noticeably compared with that of the original PPF, which is attributed to 44.5% of oxygen content in acrylic acid. The catalyst B has higher nitrogen content and lower carbon and hydrogen contents than PPF, which is attributed to the lower carbon (80%) and hydrogen (6.7%) contents, and higher nitrogen (13.3%) content of the grafting monomer 4-vinylpyridine. Due to the higher carbon, nitrogen contents and lower hydrogen content of 4-vinylpyridine compared with catalyst A, the catalyst C2/1 has higher carbon and nitrogen contents and lower hydrogen content than catalyst A.

Table 1. Elemental analysis data of PPF, catalyst A, B, and C2/1. Catalyst

C (%)

H (%)

N (%)

PPF

84.48

14.90

0.54

A

68.24

7.94

0.50

B

82.86

12.23

1.63

C2/1

78.34

7.23

1.23

Catalytic activity of the fiber catalysts The condensation reaction of nitroalkanes with carbonyl compounds, the so-called nitro-aldol (or Henry) reaction, is a well-established and thoroughly verified chemical procedure to generate nitroalkenes which are important building blocks in the synthesis of pharmaceutical products.68-71


8

Page 9 of 33

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


The catalytic performances of all the PPF supported catalysts in the following nitro-aldol reaction were investigated (Table 2). First of all, the catalytic activities of the PPF supported catalysts were performed upon one nitro-aldol reaction. Since the apolar surface of PPF is modified by polar functionalities, these fiber catalysts may perform well in polar solvents. Therefore, DMSO was used as solvent. The results show that when the PPF is functionalized by single acid or base, they provide very low yields (entries 1 and 2, Table 2). Furthermore, moderate to excellent yields were obtained by using catalysts FABCs (entries 4-7). Among them, C2/1 which has an acid-base mole ratio of 2:1 exhibits the highest activity. It is essential that the acid and base species must locate on one main polymer chain as shown in Scheme 1, which allows the acid and base units to interact mutually with each other in a beneficial manner for catalysis. To our surprise, a mixture of catalysts A and B exhibits a low yield of 24% (entry 3) which is even lower than that catalyzed by catalysts A only. This may be due to that the distance between acidic group in catalyst A and basic group in catalyst B is too far to form the cooperative catalysis. A yield of 85% was obtained by C2/1’ with a lower loading of 1.83 mmol/g (1.20+0.63mmol/g, entry 8), which was lower than the high density modified catalyst C2/1 (loading: 2.19+1.14 mmol/g, entry 6). Such result demonstrates that higher catalyst loading, i.e. higher functional density, can effectively enhance the mutual interaction between catalyst active sites and reactants, and thus increases the activity of the bifunctional fiber catalyst. In addition, water is observed as a high efficient solvent with yields of 35-87%, which provides a green solvent for this reaction (entries 13-19, Table 2).


9


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 33

Table 2. Catalytic performances of different catalysts on a nitro-aldol reaction.a,b

Entry

Cat.

solvent

Yield/%

Entry

Cat.

solvent

Yield/%

1

A

DMSO

54

13

A

Water

5

2

B

DMSO

20

14

B

Water

3

3c

A+B

DMSO

24

15

A+B

water

3

4

C1/2

DMSO

72

16

C1/2

Water

35

5

C1/1

DMSO

78

17

C1/1

Water

46

6

C2/1

DMSO

93

18

C2/1

Water

87

7

C3/1

DMSO

62

19

C3/1

Water

45

8d

C2/1’

DMSO

85

20

C2/1

Toluene

2

9

PA

DMSO

28

21

C2/1

EtOAc

3

10

Py

DMSO

18

22

C2/1

EtOH

5

11e

Py+PA

DMSO

25

23

C2/1

MeOH

4

12f

B+PA

DMSO

38

24

C2/1

DMF

44

a

All the reactions were performed with 20 mol % (sum of both acid and base groups) of

catalysts at 60 oC for 1 h. standard.

c

b

Yields determined by HPLC using nitrobenzene as an internal

Physical mixture of 10 mol% catalyst A and 10 mol% catalyst B.

loading of C2/1’ is 1.83 mmol/g (acid: 1.20 mmol/g, base: 0.63 mmol/g)

e

d

The catalyst

The mole ratio of

propionic acid (PA) to pyridine (Py) is 2:1. f The mole ratio of propionic acid(PA) to catalyst B is 1:1. In principle, homogeneous catalysts should exhibit better catalytic performances than heterogeneous ones.72-73 But, the use 20 mol% of propionic acid or 20 mol% of pyridine as the catalyst under homogeneous conditions show much lower activities compared with their


10

Page 11 of 33

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


heterogeneous ones under the same condition (entries 1, 2, 9 and 10). Such results demonstrate that the PPF is an ideal support for immobilization of acid-base groups for this reaction. A physical mixture of propionic acid and pyridine with a low yield of 25% (entry 11) demonstrates that free acid and free base are not cooperative catalysis under homogeneous condition. Another question is whether or not the acidic and basic groups in catalysts C forms ionic pair. To verify this, catalyst B was treated by the same amount of free propionic acid and then was used as catalysts (of course, an ionic pair, i.e the supported pyridinium moiety and propionate anion, was formed in this case) for this system, and a yield of 38% was obtained (entry 12), which was much lower than that of catalyst C1/1. Such result inderectly demonstrates that the acid and base groups in catalysts FABCs may not exist in an ionic pair form. Solvents can alter considerably the outcome of heterogeneous reactions, so varied solvents were tested to study the solvent effect. Catalyzed by C2/1, common solvents, such as toluene, EtOAc, EtOH, and MeOH provide low yields of 2-5% (entries 20-23, Table 2). High polar aprotic solvents DMF affords a moderate yield of 44% (entries 24). These results may be attributed to the different swelling abilities of this fiber catalyst in various solvents. Originally, PPF has a good swelling ability in nonpolar aprotic solvent, like toluene and cyclohexane. After the PPF is modified by polar groups, such as carboxylic acid or pyridine, it has good compatibility with polar solvents. Therefore, it is reasonable to see the excellent performance of catalyst C2/1 in water and DMSO. In addition, Knoevenagel condensation of carbonyl functionality with activated methylene compound, catalyzed by base74-77 or acid,78 is a classical reaction for producing important intermediates in the organic synthesis.79-82 The catalytic performances of all the fiber catalysts on the Knoevenagel condensation are listed in Table 3.


11


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 33

Table 3. Catalytic performances of different catalysts on one Knoevenagel reaction.a

Entry

Cat.

Solvent

Yield/%

Entry

Cat.

solvent

Yield/%

1

A

DMSO

46

11

B+PA

DMSO

42

2

B

DMSO

16

12

C2/1

Toluene

1

3b

A+B

DMSO

24

13

C2/1

EtOAc

2

4

C1/2

DMSO

64

14

C2/1

EtOH

5

5

C1/1

DMSO

72

15

C2/1

MeOH

5

6

C2/1

DMSO

95

16

C2/1

DMF

24

7

C3/1

DMSO

89

17e

A

water

53

8

PA

DMSO

46

18e

B

water

46

9

Py

DMSO

49

19e

C2/1

water

84

10c

Py+PA

DMSO

45

a

All the reactions were performed with 20 mol% (sum of both acid and base groups) of

catalysts at 60 oC for 2 h, Yields determined by HPLC using naphthalene as an internal standard. b

Physical mixture of 10 mol% catalyst A and 10 mol% catalyst B. c The mole ratio of propionic

acid(PA) to pyridine(Py) is 2:1. d The mole ratio of propionic acid(PA) to catalyst B is 1:1. e The reaction was performed in water at 60 oC for 5 h. All of the FABCs in DMSO exhibit moderate to excellent yields of 64-95% upon this Knoevenagel condensation (entries 4-7, Table 3), among them, catalyst C2/1 affords the best yield (entry 6). The other mono-functionalized catalysts A and B are much less active (entries 1 and 2). Even under the condition of physical mixture of catalyst A and B, the yield is only 24% (entry 3). All these results confirm again that the cooperative effect may closely connected to the acid-base ratios.


12

Page 13 of 33

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


Furthermore, the catalytic performances of homogeneous catalysts, such as propionic acid and pyridine, were also investigated (entries 8 and 9). The results show that the activity of propionic acid is similar to its heterogeneous analogue, i.e. the catalyst A, while the activity of pyridine is higher than the catalyst B. For a physical mixture of propionic acid and pyridine (entry 10), the catalytic performance is not improved compared with propionic acid or pyridine only. Such a phenomenon, which is similar to the case of nitro-aldol reaction, demonstrates that the acid and base groups were not performed in cooperative form in homogeneous condition. Catalyzed by free propionic acid protonated catalyst B, a yield of 42% that was much lower than each case of FABCs was obtained (entry 11), which also proves that the acid and base groups in FABCs are not performed in an ionic pair form. Similar with the nitro-aldol reaction, the Knoevenagel condensation catalyzed by these fiber catalysts are also related to the solvents. In the common solvents, such as toluene, EtOAc, EtOH, MeOH, and DMF, the catalyst C2/1 show low yields from 1% to 24% (entries 12-16). Besides, the activities of all the catalysts in water are slightly lower than that in DMSO even if the reaction time is prolonged to 5 h (entries 17-19). The activition of nitro-aldol and Knoevenagel reactions are mainly dominated by two aspects, i.e. mass transfer process and intrinsic reaction rate at active site. Mass transfer process, which includes reactant transfer from bulk liquid to catalyst surface and diffusion of reactant through polymer matrix to active site, can be effectively promoted by the remarkable spatial dimensions of the fabricated structures and well swelling ability of the fibers in polar solvents. Meanwhile, the shape-persistent nature and appropriate acid-base ratio of the fiber catalysts can effectively increase the intrinsic reaction rate at active site by cooperative catalysis. Therefore, the characters of the fiber catalysts can effectively satisfy these reactions.


13


H Nu Nu -

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 33

Scheme 3. The cooperative mechanism of nucleophilic addition. The FTIR spectra of the fiber catalysts showed that the pyridine and COOH groups were not neutralized with each other. The low catalytic performance of B+PA for nitro-aldol reaction (entry 11, Table 2) also demonstrated that the acid and base groups in catalysts FABCs are not existed in an ionic pair form. Therefore, we presume a cooperative mechanism that the pyridine and COOH can activate both of the nucleophile and carbonyl group of aldehyde, respectively. As shown in Scheme 3, the basic pyridine group was responsible for the deprotonation of the active methylene compounds (nitromethane and ethyl cyanoacetate) to form related nucleophiles, meanwhile, an acid group (COOH) could activate the carbonyl group of aldehydes (benzaldehyde and 4-nitrobenzaldehyde) via hydrogen bond, which faciliated the nucleophilic reaction. Therefore, the presence of both pyridine and COOH groups in close proximity could activate cooperatively the electrophile and nucleophile to enhance the reaction rates of the desired catalytic reactions. Taken together, it is obvious that the cooperative effect, which closely relates to the acid-base ratio, takes place on the surface of the functionalized fibers. However, the cooperative effect does not exist under homogeneous conditions. The solvents have significant influence on the


14

Page 15 of 33

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


catalytic performance, of which, water is proved to be a safe, green, and effective solvent. Therefore, the application of catalyst C2/1 for organic synthesis in water was further investigated.

Catalysts performance in three aqueous reactions Three aqueous nucleophilic addition reactions including the Gewald reaction, synthesis of tetrahydrothiophenes, and one three-component reaction catalyzed by C2/1 are listed in Table 4. Table 4. Three reactions catalyzed by C2/1 in water.

Entry

R

Time (h)

Temp. (oC)

Product

Isolated yield of 1 (%)

1

COOEt

5

30

1a

93

2

CN

5

30

1b

97

3

C6H5CO

0.5

60

1c

96

4

2-C10H7CO

1

80

1d

91

5

Ts

1

80

1e

95

Entry

Ar1

Time (min)

Ratio(2/3)

Product

Isolated yield of 2+3 (%)

6

C6H5

10

0.5

2a/3a

95

7

m-MeOC6H4

20

0.6

2b/3b

98

8

p-ClC6H4

60

0.5

2c/3c

99

9

m-CF3C6H4

20

0.4

2d/3d

87

10

p-O2NC6H4

60

0.3

2e/3e

95


15


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

20

0.8

Page 16 of 33

11

2-Thienyl

Entry

Ar2

Time (min)

Temp. (oC)

Product

Isolated yield of 4(%)

12

C6H5

15

80

4a

97

13

p-ClC6H4

15

80

4b

91

14

o-MeOC6H4

40

80

4c

93

15

o-CF3C6H4

15

80

4d

93

16

p-O2NC6H4

40

80

4e

91

17

2-Thienyl

15

80

4f

95

2f/3f

97

Gewald reaction between 2,5-dihydroxy-1,4-dithiane and activated nitriles to afford 3substituted 2-aminothiophenes which are widely applied in biologically active products,83,

84

dyes,85, 86 and conducting polymers,87 is of vital importance in organic synthesis.88-91 To examine the scope of catalyst C2/1, we tested a series of activated nitriles with 2,5-dihydroxy-1,4-dithiane in water and the results are listed in Table 4(entries 1-5). It is worth noting that all the substrates give their corresponding products with excellent yields of 91-97%. In the case of ethyl cyanoacetate, the Gewald reaction proceeded under 30 oC to afford a high yield of 93% (entry 1, Table 4). This result is much better than our previously reported Nmethylpiperazine-functionalized polyacrylonitrile fiber which afforded a yield of 89% under reflux in EtOH for 4 h.92 Besides, a lower yield of 79% was obtained for the same reaction catalyzed by triethylamine in trifluoroethanol at 60 oC for 6.5 h.93


16

Page 17 of 33

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


In the case of malononitrile, a reported silica-supported piperazine catalyst only afforded a yield of 41% under reflux in EtOH at 80 oC for 4 h.94 In the presence of ZnO, a yield of 50% was obtained under solvent-free conditions at 100 °C.95 Using our catalyst C2/1, a yield of 97% was obtained at 30 oC in water for 5 h. All these results demonstrate that the fiber catalyst is an excellent catalyst for this Gewald reaction. Besides, the arylcarbonyl or arylsufonyl substituted acetonitriles need higher temperatures to obtain similar yields (entries 3-5, Table 4). Tetrahydrothiophenes, which are synthesized by tandem Michael-Henry reactions between 1,4-dithiane-2,5-diol and trans-β-nitrostyrenes, are important intermediates that straightly form thiophene derivatives through dehydration and aromatization.96 A series of trans-β-nitrostyrenes were used to examine the scope of the catalyst C2/1 for this reaction and the results are listed in Table 4 (entries 6-11). Notably, both electron-rich and electron-deficient trans-β-nitrostyrenes as feasible substrates generate the corresponding tetrahydrothiophenes in excellent yields with only 2.5 mol% of catalyst dosage at room temperature within one hour. Such excellent activity of catalyst C2/1 is much higher than our previously reported tertiary amine functionalized polyacrylonitrile fiber catalyst, which required refluxing in EtOH for 5-8 h.97 Furthermore, this fiber catalyst is even more active than the homogeneous catalyst of 20 mol% triethylamine.96 These results suggest that the acid-base bifunctional catalyst C2/1 is an outstanding catalyst for aqueous synthesis of tetrahydrothiophenes. Owing to the trans structure of the β-nitroalkene, the products contain two main diastereomers with ratios arranging from 0.3:1 to 0.8:1(the configuration were determined by 1H NMR96) and the details are described in the supporting information. The three-component condensation among aldehydes, malononitrile and α-naphthols to afford the corresponding 2-amino-2-chromenes represents a kind of important reaction in organic


17


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 33

synthesis. It is usually catalyzed by alkaline catalysts, such as DBU98 and DMAP.99 Herein, both aromatic and heteroaromatic aldehydes were used to investigate the scope of this threecomponent reaction under the catalysis of C2/1. The results listed in Table 4 show that all of the aldehydes afford excellent yields of 91-97% with 10 mol% catalyst at 80 oC within 40 min (entries 12-17). These high activities are with no relation to the influence of substituent effect. In the case of preparing product 4a, 20 mol% of amino-functionalized MCM-41 catalyst afforded a yield of 80% at 70 oC for 30 min.100 Catalyzed by our previously reported DMAPfunctionalized polyacrylonitrile fiber catalyst, a yield of 93% was obtained at 100 °C for 60 min.101 Using catalyst C2/1 in this work, a yield of 97% was obtained at 80 oC in water for 15 min. Furthermore, this catalyst performs even better than many homogeneous catalysts. Under the same catalyst dosage, the DBU afforded a yield of 87% at 100 oC for 60 min,98 i.e. lower yield, higher temperature and longer reaction time than the case of fiber C2/1. The catalyst of [bmim]OH required 10 min to obtain a yield of 91%,102 however, the temperature is higher than the case of catalyst C2/1. Besides, thiourea dioxide provided a yield of 88% at 50 oC for 8 h,103 which demanded much longer time compared with that catalyzed by fiber C2/1. It is clearly that the fiber C2/1 compare favorably to other heterogeneous and homogeneous catalytic materials. Compared with homogeneous catalysts, the products which were catalyzed by the fiber catalyst may contain much less catalyst residue because of the high stability of the fiber catalyst. Besides, the products may be more pure as some water soluble impurities can be easily removed by water. Taken together, this acid-base bifunctional catalyst performs excellently for these three aqueous organic reactions.

Recyclability of catalyst C2/1


18

Page 19 of 33

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


The recyclability of catalyst C2/1 was investigated in aqueous nitro-aldol reaction and the results are depicted in Figure 2. After each run, the catalyst was simply washed with ethyl acetate to remove the absorbed residues and reused for the next iteration. The catalyst C2/1 show excellent conversions from 87% to 84% for ten runs. In a word, this catalyst has the advantages of simple work-up procedure for recovery and excellent reusability.

Figure 2. Recyclability of catalyst C2/1 in aqueous nitro-aldol reaction.

CONCLUSION A series of acid-base bifunctional catalysts were prepared using a synthetic strategy of successively radical grafting of acrylic acid and 4-vinylpyridine onto the polypropylene fiber. Cooperative effect is elucidated in the nitro-aldol and Knoevenagel reactions catalyzed by these heterogeneous catalysts and the results indicate that the cooperative effect is intimately related to the acid-base ratio. C2/1 with an acid-base mole ratio of 2:1 is optimized as the most active fiber catalyst, it can highly catalyze the nitro-aldol and Knoevenagel reactions in DMSO with yields of 93% and 95%, respectively. In addition, the aqueous Gewald (yields: 91-97%), tandem


19


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 33

Michael-Henry (yields: 87-99%) and one three-component (yields: 91-97%) reactions are also efficiently catalyzed by this bifunctionalized catalyst C2/1. The catalytic activities are much higher than many previously reported heterogeneous and homogeneous catalysts. The recycling experiment shows that the catalyst C2/1 can repeatedly and efficiently catalyze the nitro-aldol reaction in water with high yields for 10 times.

ASSOCIATED CONTENT Supporting Information.

Synthesis of the fiber catalysts, general procedures for catalytic

performance, NMR of materials and products and NMR spectra of materials and products. ACKNOWLEDGMENT This work was supported by the National Natural Science Foundation of China (No. 21572156 and No. 21306133), Tianjin Research Program of Application Foundation and Advanced Technology (No. 14JCYBJC22600). REFERENCES (1)

Yasukawa, T.; Suzuki, A.; Miyamura, H.; Nishino, K.; Kobayashi, S. Chiral metal

nanoparticle systems as heterogeneous catalysts beyond homogeneous metal complex catalysts for asymmetric addition of arylboronic acids to α,β-unsaturated carbonyl compounds. J. Am. Chem. Soc. 2015, 137, 6616-6623. (2)

Matsubu, J. C.; Yang, V. N.; Christopher, P. Isolated metal active site concentration and

stability control catalytic CO2 reduction selectivity. J. Am. Chem. Soc. 2015, 137, 3076-3084. (3)

Li, B.; Leng, K.; Zhang, Y.; Dynes, J. J.; Wang, J.; Hu, Y.; Ma, D.; Shi, Z.; Zhu, L.;

Zhang, D.; Sun, Y.; Chrzanowski, M.; Ma, S. Metal–Organic Framework Based upon the


20

Page 21 of 33

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


synergy of a Brønsted acid framework and Lewis acid centers as a highly efficient heterogeneous catalyst for fixed-bed reactions. J. Am. Chem. Soc. 2015, 137, 4243-4248. (4)

Kim, S.-W.; Kim, M.; Lee, W. Y.; Hyeon, T. Fabrication of hollow palladium spheres

and their successful application to the recyclable heterogeneous catalyst for Suzuki coupling reactions. J. Am. Chem. Soc. 2002, 124, 7642-7643. (5)

Chughtai, A. H.; Ahmad, N.; Younus, H. A.; Laypkov, A.; Verpoort, F. Metal-organic

frameworks: versatile heterogeneous catalysts for efficient catalytic organic transformations. Chem. Soc. Rev. 2015, 44, 6804-6849. (6)

Sun, Q.; Dai, Z.; Meng, X.; Xiao, F.-S. Porous polymer catalysts with hierarchical

structures. Chem. Soc. Rev. 2015, 44, 6018-6034. (7)

Glöggler, S.; Grunfeld, A. M.; Ertas, Y. N.; McCormick, J.; Wagner, S.; Schleker, P. P.

M.; Bouchard, L.-S. A nanoparticle catalyst for heterogeneous phase Para-Hydrogen-Induced polarization in water. Angew. Chem. Int. Ed. 2015, 54, 2452-2456. (8)

Xiong, H.; Schwartz, T. J.; Andersen, N. I.; Dumesic, J. A.; Datye, A. K. Graphitic-

Carbon layers on oxides: toward stable heterogeneous catalysts for biomass conversion reactions. Angew. Chem. Int. Ed. 2015, 54, 7939-7943. (9)

Maschmeyer, T.; Rey, F.; Sankar, G.; Thomas, J. M. Heterogeneous catalysts obtained by

grafting metallocene complexes onto mesoporous silica. Nature 1995, 378, 159-162. (10) D’Elia, V.; Dong, H.; Rossini, A. J.; Widdifield, C. M.; Vummaleti, S. V. C.; Minenkov, Y.; Poater, A.; Abou-Hamad, E.; Pelletier, J. D. A.; Cavallo, L.; Emsley, L.; Basset, J.-M. Cooperative effect of monopodal silica-supported niobium complex Pairs enhancing catalytic cyclic carbonate production. J. Am. Chem. Soc. 2015, 137, 7728-7739.


21


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 33

(11) Schrader, I.; Warneke, J.; Backenköhler, J.; Kunz, S. Functionalization of platinum nanoparticles with L-proline: simultaneous enhancements of catalytic activity and selectivity. J. Am. Chem. Soc. 2015, 137, 905-912. (12) Jin, L.; Weinberger, D. S.; Melaimi, M.; Moore, C. E.; Rheingold, A. L.; Bertrand, G. Trinuclear gold clusters supported by cyclic (alkyl)(amino)carbene ligands: mimics for gold heterogeneous catalysts. Angew. Chem. Int. Ed. 2014, 53, 9059-9063. (13) Borah, P.; Zhao, Y. β-Diketimine appended periodic mesoporous organosilica as a scaffold for immobilization of palladium acetate: An efficient green catalyst for Wacker type reaction. J. Catal. 2014, 318, 43-52. (14) Brunelli, N. A.; Jones, C. W. Tuning acid–base cooperativity to create next generation silica-supported organocatalysts. J. Catal. 2013, 308, 60-72. (15) Notestein, J. M.; Katz, A. Enhancing heterogeneous catalysis through cooperative hybrid organic–inorganic interfaces. Chem. Eur. J. 2006, 12, 3954-3965. (16) Tada, M.; Iwasawa, Y. Advanced chemical design with supported metal complexes for selective catalysis. Chem. Commun. 2006, 2833-2844. (17) Corma, A.; Garcia, H. Silica-bound homogenous catalysts as recoverable and reusable catalysts in organic synthesis. Adv. Synth. Catal. 2006, 348, 1391-1412. (18) Kobayashi, S.; Sugiura, M. Immobilization of osmium catalysts for asymmetric dihydroxylation of olefins. Adv. Synth. Catal. 2006, 348, 1496-1504. (19) Dioos, B. M.; Vankelecom, I. F.; Jacobs, P. A. Aspects of immobilisation of catalysts on polymeric supports. Adv. Synth. Catal. 2006, 348, 1413-1446.


22

Page 23 of 33

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


(20) Song, C. E.; Kim, D. H.; Choi, D. S. Chiral organometallic catalysts in confined nanospaces: Significantly enhanced enantioselectivity and stability. Eur. J. Inorg. Chem. 2006, 2006, 2927-2935. (21) Stubbe, J.; van der Donk, W. A. Protein radicals in enzyme catalysis. Chem. Rev. 1998, 98, 705-762. (22) Klibanov, A. M. Improving enzymes by using them in organic solvents. Nature 2001, 409, 241. (23) Notz, W.; Tanaka, F.; Barbas, C. F. Enamine-based organocatalysis with proline and diamines: the development of direct catalytic asymmetric Aldol, Mannich, Michael, and Diels−Alder reactions. Acc. Chem. Res. 2004, 37, 580-591. (24) Gross, R. A.; Kumar, A.; Kalra, B. Polymer synthesis by in vitro enzyme catalysis. Chem. Rev. 2001, 101, 2097-2124. (25) Hanoian, P.; Liu, C. T.; Hammes-Schiffer, S.; Benkovic, S. Perspectives on electrostatics and conformational motions in enzyme catalysis. Acc. Chem. Res. 2015, 48, 482-489. (26) Shylesh, S.; Hanna, D.; Gomes, J.; Krishna, S.; Canlas, C. G.; Head-Gordon, M.; Bell, A. T. Tailoring the cooperative acid-base effects in silica-supported amine catalysts: applications in the continuous Gas-Phase self-condensation of n-butanal. ChemCatChem 2014, 6, 1283-1290. (27) Hamasaki, A.; Yasutake, Y.; Norio, T.; Ishida, T.; Akita, T.; Ohashi, H.; Yokoyama, T.; Honma, T.; Tokunaga, M. Cooperative catalysis of palladium nanoparticles and cobalt oxide support for formylation of aryl iodides under syngas atmosphere. Appl. Catal. A- Gen. 2014, 469, 146-152. (28) Katz, A.; Davis, M. E. Molecular imprinting of bulk, microporous silica. Nature 2000, 403, 286-289.


23


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 33

(29) Zhao, D.; Feng, J.; Huo, Q.; Melosh, N.; Fredrickson, G. H.; Chmelka, B. F.; Stucky, G. D. Triblock copolymer syntheses of mesoporous silica with periodic 50 to 300 angstrom pores. Science 1998, 279, 548-552. (30) Beck, J. S.; Vartuli, J. C.; Roth, W. J.; Leonowicz, M. E.; Kresge, C. T.; Schmitt, K. D.; Chu, C. T. W.; Olson, D. H.; Sheppard, E. W. A new family of mesoporous molecular sieves prepared with liquid crystal templates. J. Am. Chem. Soc. 1992, 114, 10834-10843. (31) Huh, S.; Chen, H.-T.; Wiench, J. W.; Pruski, M.; Lin, V. S. Y. Cooperative catalysis by general acid and base bifunctionalized Mesoporous silica nanospheres. Angew. Chem. Int. Ed. 2005, 44, 1826-1830. (32) Zeidan, R. K.; Hwang, S.-J.; Davis, M. E. Multifunctional heterogeneous catalysts: SBA15-containing primary amines and sulfonic acids. Angew. Chem. Int. Ed. 2006, 45, 6332-6335. (33) Motokura, K.; Tomita, M.; Tada, M.; Iwasawa, Y. Acid–base bifunctional catalysis of silica–alumina-supported organic amines for carbon–carbon bond-forming reactions. Chem. Eur. J. 2008, 14, 4017-4027. (34) Shylesh, S.; Wagner, A.; Seifert, A.; Ernst, S.; Thiel, W. R. Cooperative acid–base effects with functionalized mesoporous silica nanoparticles: applications in carbon–carbon bondformation reactions. Chem. Eur. J. 2009, 15, 7052-7062. (35) Motokura, K.; Tanaka, S.; Tada, M.; Iwasawa, Y. Bifunctional heterogeneous catalysis of silica–alumina-supported tertiary amines with controlled acid–base interactions for efficient 1,4addition reactions. Chem. Eur. J. 2009, 15, 10871-10879. (36) Zhang, M.; Zhao, P.; Leng, Y.; Chen, G.; Wang, J.; Huang, J. Schiff Base Structured Acid–base cooperative dual sites in an ionic solid catalyst lead to efficient heterogeneous Knoevenagel condensations. Chem. Eur. J. 2012, 18, 12773-12782.


24

Page 25 of 33

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


(37) Motokura, K.; Viswanadham, N.; Dhar, G. M.; Iwasawa, Y. Creation of acid–base bifunctional catalysis for efficient C-C coupling reactions by amines immobilization on SiO2, silica-alumina, and nano-H-ZSM-5. Catal. Today 2009, 141, 19-24. (38) Brunelli, N. A.; Jones, C. W. Tuning acid–base cooperativity to create next generation silica-supported organocatalysts. J. Catal. 2013, 308, 60-72. (39) Lauwaert, J.; Moschetta, E. G.; Van Der Voort, P.; Thybaut, J. W.; Jones, C. W.; Marin, G. B. Spatial arrangement and acid strength effects on acid–base cooperatively catalyzed aldol condensation on aminosilica materials. J. Catal. 2015, 325, 19-25 (40) Shylesh, S.; Thiel, W. R. Bifunctional Acid–Base cooperativity in heterogeneous catalytic reactions: advances in silica supported organic functional groups. ChemCatChem 2011, 3, 278-287. (41) Motokura, K.; Tada, M.; Iwasawa, Y. Heterogeneous organic base-catalyzed reactions enhanced by acid supports. J. Am. Chem. Soc. 2007, 129, 9540-9541. (42) Bass, J. D.; Solovyov, A.; Pascall, A. J.; Katz, A. Acid−base bifunctional and dielectric outer-sphere effects in heterogeneous catalysis: a comparative investigation of model primary amine catalysts. J. Am. Chem. Soc. 2006, 128, 3737-3747. (43) Ma, T. Y.; Qiao, S. Z. Acid–base bifunctional periodic mesoporous metal phosphonates for synergistically and heterogeneously catalyzing CO2 conversion. ACS Catal. 2014, 4, 38473855. (44) Merino, E.; Verde-Sesto, E.; Maya, E. M.; Iglesias, M.; Sánchez, F.; Corma, A. Synthesis of structured porous polymers with acid and basic sites and their catalytic application in cascadetype reactions. Chem. Mater. 2013, 25, 981-988.


25


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 33

(45) Zhang, Y.; Li, B.; Ma, S. Dual functionalization of porous aromatic frameworks as a new platform for heterogeneous cascade catalysis. Chem. Commun. 2014, 50, 8507-8510. (46) Kwong, C. K.-W.; Huang, R.; Zhang, M.; Shi, M.; Toy, P. H. Bifunctional polymeric organocatalysts and their application in the cooperative catalysis of Morita–Baylis–Hillman reactions. Chem. Eur. J. 2007, 13, 2369-2376. (47) Youk, S. H.; Oh, S. H.; Rho, H. S.; Lee, J. E.; Lee, J. W.; Song, C. E. A polymersupported cinchona-based bifunctional sulfonamidecatalyst: a highly enantioselective, recyclable heterogeneous organocatalyst. Chem. Commun. 2009, 2220-2222. (48) Tuchman-Shukron, L.; Miller, S. J.; Portnoy, M. Polymer-supported enantioselective bifunctional catalysts for Nitro-Michael addition of ketones and aldehydes. Chem. Eur. J. 2012, 18, 2290-2296. (49) Karian, H. Handbook of polypropylene and polypropylene composites, revised and expanded. CRC press: 2003. (50) Park, H.-J.; Na, C.-K. Preparation of anion exchanger by amination of acrylic acid grafted polypropylene nonwoven fiber and its ion-exchange property. J. Colloid Interface Sci. 2006, 301, 46-54. (51) Van der Vaart, R.; Lebedeva, V. I.; Petrova, I. V.; Plyasova, L. M.; Rudina, N. A.; Kochubey, D. I.; Tereshchenko, G. F.; Volkov, V. V.; van Erkel, J. Preparation and characterisation of palladium-loaded polypropylene porous hollow fibre membranes for hydrogenation of dissolved oxygen in water. J. Colloid Interface Sci. 2006, 301, 46-54. (52) Chuang, L.-C.; Luo, C.-H. Characterization of supported TiO2-based catalysts greenprepared and employed for photodegradation of malodorous DMDS. Mater. Res. Bull. 2013, 48, 238-244.


26

Page 27 of 33

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


(53) Larrondo, L.; St. John Manley, R. Electrostatic fiber spinning from polymer melts. I. Experimental observations on fiber formation and properties. J. Polym. Sci. B-Polym. Phys. 1981, 19, 909-920. (54) Zhang, S.; Horrocks, A. R. A review of flame retardant polypropylene fibres. Prog. Polym. Sci. 2003, 28, 1517-1538. (55) Kearns, J. C.; Shambaugh, R. L. Polypropylene fibers reinforced with carbon nanotubes. J. Appl. Polym. Sci. 2002, 86, 2079-2084. (56) Mason, B. P.; Price, K. E.; Steinbacher, J. L.; Bogdan, A. R.; McQuade, D. T. Greener approaches to organic synthesis using microreactor technology. Chem. Rev. 2007, 107, 23002318. (57) McQuade, D. T.; Seeberger, P. H. Applying flow chemistry: methods, materials, and multistep synthesis. J. Org. Chem. 2013, 78, 6384-6389. (58) Brzozowski, M.; O’Brien, M.; Ley, S. V.; Polyzos, A. Flow Chemistry: Intelligent processing of gas–liquid transformations using a tube-in-tube reactor. Acc. Chem. Res. 2015, 48, 349-362. (59) Shi, X.-L.; Yang, H.; Tao, M.; Zhang, W. Sulfonic acid-functionalized polypropylene fiber: highly efficient and recyclable heterogeneous Bronsted acid catalyst. RSC Adv. 2013, 3, 3939-3945. (60) Shi, X.-L.; Zhang, M.; Li, Y.; Zhang, W. Polypropylene fiber supported ionic liquids for the conversion of fructose to 5-hydroxymethylfurfural under mild conditions. Green Chem. 2013, 15, 3438-3445.


27


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 33

(61) Miwa, Y.; Yamamoto, K.; Sakaguchi, M.; Shimada, S. Well-defined polystyrene grafted to polypropylene backbone by “living” radical polymerization with TEMPO. Macromolecules 2001, 34, 2089-2094. (62) Carroll, T.; Booker, N.; Meier-Haack, J. Polyelectrolyte-grafted microfiltration membranes to control fouling by natural organic matter in drinking water. J. Membrane Sci. 2002, 203, 3-13. (63) Garg, D.; Lenk, W.; Berwald, S.; Lunkwitz, K.; Simon, F.; Eichhorn, K. J. Hydrophilization of microporous polypropylene Celgard® membranes by the chemical modification technique. J Appl Polym Sci 1996, 60, 2087-2104. (64) Wang, W.; Wang, L.; Chen, X.; Yang, Q.; Sun, T.; Zhou, J. Study on the graft reaction of poly(propylene) fiber with acrylic Acid. Macromol. Mater. Eng. 2006, 291, 173-180. (65) Bhattacharya, S. D.; Inamdar, M. S. Polyacrylic acid grafting onto isotactic polypropylene fiber: Methods, characterization, and properties. J. Appl. Polym. Sci. 2007, 103, 1152-1165. (66) Wang, W.; Wang, L.; Wang, C. L.; Sun, T. X.; Yu, H. J.; Chen, T. Study on the surface grafting of polypropylene fibers. J. Appl. Polym. Sci. 2006, 99, 734-737. (67) Verduzco, R.; Li, X.; Pesek, S. L.; Stein, G. E. Structure, function, self-assembly, and applications of bottlebrush copolymers. Chem. Soc. Rev. 2015, 44, 2405-2420. (68) Clarke, M. L.; Fuentes, J. A. Self-assembly of organocatalysts: Fine-tuning organocatalytic reactions. Angew. Chem. Int. Ed. 2007, 46, 930-933. (69) Enders, D.; Hüttl, M. R.; Runsink, J.; Raabe, G.; Wendt, B. Organocatalytic one-pot asymmetric synthesis of functionalized tricyclic carbon frameworks from a triple-cascade/DielsAlder sequence. Angew. Chem. Int. Ed. 2007, 46, 467-469.


28

Page 29 of 33

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


(70) Muruganantham, R.; Mobin, S. M.; Namboothiri, I. N. Base-mediated reaction of the Bestmann-Ohira

reagent

with

nitroalkenes

for

the

regioselective

synthesis

of

phosphonylpyrazoles. Org. Lett. 2007, 9, 1125-1128. (71) Srivastava, S. K.; Husbands, S. M.; Aceto, M. D.; Miller, C. N.; Traynor, J. R.; Lewis, J. W. 4'-Arylpyrrolomorphinans: Effect of a pyrrolo-N-benzyl substituent in enhancing δ-opioid antagonist activity. J. Med. Chem. 2002, 45, 537-540. (72) Cozzi, F. Immobilization of organic catalysts: when, why, and how. Adv. Synth. Catal. 2006, 348, 1367-1390. (73) Trindade, A. F.; Gois, P. M. P.; Afonso, C. A. M. Recyclable stereoselective catalysts. Chem. Rev. 2009, 109, 418-514. (74) Xing, C.; Zhu, S. Unexpected formation of tetrasubstituted 2,3-dihydrofurans from the reactions of β-keto polyfluoroalkanesulfones with aldehydes. J. Org. Chem. 2004, 69, 6486-6488. (75) Gascon, J.; Aktay, U.; Hernandez-Alonso, M. D.; van Klink, G. P.; Kapteijn, F. Aminobased metal-organic frameworks as stable, highly active basic catalysts. J. Catal. 2009, 261, 7587. (76) Forsyth, S. A.; Fröhlich, U.; Goodrich, P.; Gunaratne, H. N.; Hardacre, C.; McKeown, A.; Seddon, K. R. Functionalised ionic liquids: synthesis of ionic liquids with tethered basic groups and their use in Heck and Knoevenagel reactions. New J. Chem. 2010, 34, 723-731. (77) Zhang, Y.; Xia, C. Magnetic hydroxyapatite-encapsulated γ-Fe2O3 nanoparticles functionalized with basic ionic liquids for aqueous Knoevenagel condensation. Appl. Catal. AGen. 2009, 366, 141-147. (78) Harjani, J. R.; Nara, S. J.; Salunkhe, M. M. Lewis acidic ionic liquids for the synthesis of electrophilic alkenes via the Knoevenagel condensation. Tetrahedron Lett. 2002, 43, 1127-1130.


29


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 30 of 33

(79) Bigi, F.; Chesini, L.; Maggi, R.; Sartori, G. Montmorillonite KSF as an Inorganic, Water Stable, and Reusable Catalyst for the Knoevenagel Synthesis of Coumarin-3-carboxylic Acids. J. Org. Chem. 1999, 64, 1033-1035. (80) Ramachary, D. B.; Kishor, M. Organocatalytic sequential one-pot double cascade asymmetric synthesis of Wieland−Miescher ketone analogues from a Knoevenagel/ Hydrogenation/ Robinson annulation sequence: Scope and applications of organocatalytic biomimetic reductions. J. Org. Chem. 2007, 72, 5056-5068. (81) Nishiyabu, R.; Anzenbacher, P. 1,3-Indane-based chromogenic calixpyrroles with push−pull chromophores: Synthesis and anion sensing. Org. Lett. 2006, 8, 359-362. (82) Hayashi, Y.; Toyoshima, M.; Gotoh, H.; Ishikawa, H. Diphenylprolinol silyl ether catalysis in an asymmetric formal carbo [3 + 3] cycloaddition reaction via a domino Michael/Knoevenagel condensation. Org. Lett. 2009, 11, 45-48. (83) Hesse, S.; Perspicace, E.; Kirsch, G. Microwave-assisted synthesis of 2-aminothiophene3-carboxylic acid derivatives, 3H-thieno [2, 3-d] pyrimidin-4-one and 4-chlorothieno [2, 3-d] pyrimidine. Tetrahedron Lett. 2007, 48, 5261-5264. (84) Wu, H.; Zhou, W.; Pinkerton, F. E.; Meyer, M. S.; Srinivas, G.; Yildirim, T.; Udovic, T. J.; Rush, J. J. A new family of metal borohydride ammonia borane complexes: Synthesis, structures, and hydrogen storage properties. J. Mater. Chem. 2010, 20, 6550-6556. (85) Hallas, G.; Towns, A. D. Dyes derived from aminothiophenes. Part 4: Synthesis of some nitro-substituted thiophene-based azo disperse dyes. Dyes. Pigments 1997, 33, 319-336. (86) Yen, M. S.; Wang, J. Synthesis and solvent characteristics of bishetaryl monoazo dyes derived from polysubstituted-2-aminothiophene derivatives. Dyes. Pigments 2005, 67, 183-188.


30

Page 31 of 33

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


(87) Dufresne, S.; Bourgeaux, M.; Skene, W. G. Tunable spectroscopic and electrochemical properties of conjugated push-push, push-pull and pull-pull thiopheno azomethines. J. Mater. Chem. 2007, 17, 1166-1177. (88) Gewald, K. Methods for the synthesis of 2-aminothiophenes and their reactions (review). Heterocycl. Compds. 1976, 12, 1077-1090. (89) Puterová, Z.; Krutošíková, A.; Végh, D. Gewald reaction: Synthesis, properties and applications of substituted 2-aminothiophenes. Arkivoc 2010, 1, 209-246. (90) Huang, Y.; Dömling, A. The Gewald multicomponent reaction. Mol. Divers. 2011, 15, 333. (91) Sabnis, R.; Rangnekar, D.; Sonawane, N. 2-Aminothiophenes by the Gewald reaction. J. Heterocyclic. Chem. 1999, 36, 333-345. (92) Ma, L.; Yuan, L.; Xu, C.; Li, G.; Tao, M.; Zhang, W. An efficient synthesis of 2aminothiophenes via the Gewald reaction catalyzed by an N-methylpiperazine-functionalized polyacrylonitrile fiber. Synthesis 2013, 45, 45-52. (93) Mallia, C. J.; Englert, L.; Walter, G. C.; Baxendale, I. R. Thiazole formation through a modified Gewald reaction. Beilstein J. Org. Chem. 2015, 11, 875-883. (94) Rezaei-Seresht, E.; Tayebee, R.; Yasemi, M. KG-60-piperazine as a new heterogeneous catalyst for Gewald three-component reaction. Synthetic. Commun. 2013, 43, 1859-1864. (95) Tayebee, R.; Ahmadi, S. J.; Rezaei Seresht, E.; Javadi, F.; Yasemi, M. A.; Hosseinpour, M.; Maleki, B. Commercial zinc oxide: A facile, efficient, and eco-friendly catalyst for the onepot three-component synthesis of multisubstituted 2-aminothiophenes via the Gewald reaction. Ind. Eng. Chem. Res. 2012, 51, 14577-14582.


31


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 33

(96) O’ Connor, C. J.; Roydhouse, M. D.; Przybył, A. M.; Wall, M. D.; Southern, J. M. Facile synthesis of 3-nitro-2-substituted thiophenes. J. Org. Chem. 2010, 75, 2534-2538. (97) Xu, C.; Du, J.; Ma, L.; Li, G.; Tao, M.; Zhang, W. Tertiary amine functionalized polyacrylonitrile fiber catalyst for the synthesis of tetrahydrothiophenes. Tetrahedron 2013, 69, 4749-4757. (98) Khurana, J. M.; Nand, B.; Saluja, P. DBU: a highly efficient catalyst for one-pot synthesis of substituted 3,4-dihydropyrano[3,2-c]chromenes, dihydropyrano[4,3-b]pyranes, 2amino-4H-benzo[h]chromenes and 2-amino-4H benzo[g]chromenes in aqueous medium. Tetrahedron 2010, 66, 5637-5641. (99) Khan, A. T.; Lal, M.; Ali, S.; Khan, M. M. One-pot three-component reaction for the synthesis of pyran annulated heterocyclic compounds using DMAP as a catalyst. Tetrahedron Lett. 2011, 52, 5327-5332. (100) Mirza-Aghayan, M.; Nazmdeh, S.; Boukherroub, R.; Rahimifard, M.; Tarlani, A.; Abolghasemi-Malakshah, M. Convenient and efficient one-pot method for the synthesis of 2amino-tetrahydro-4H-chromenes and 2-amino-4H-benzo [h]-chromenes using catalytic amount of amino-functionalized MCM-41 in aqueous media. Synthetic. Commun. 2013, 43, 1499-1507. (101) Zhen, Y.; Lin, H.; Wang, S.; Tao, M. A water-ethanol on-off fiber catalyst for the synthesis of substituted 2-amino-2-chromenes. RSC Adv. 2014, 4, 26122-26128. (102) Gong, K.; Wang, H.-L.; Fang, D.; Liu, Z.-L. Basic ionic liquid as catalyst for the rapid and green synthesis of substituted 2-amino-2-chromenes in aqueous media. Catal. Commun. 2008, 9, 650-653. (103) Verma, S.; Jain, S. L. Thiourea dioxide catalyzed multi-component coupling reaction for the one step synthesis of naphthopyran derivatives. Tetrahedron Lett. 2012, 53, 6055-6058.


32

Page 33 of 33

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


For Table of Contents Use Only.

Authors: Jianguo Du, Minli Tao,* Wenqin Zhang* Title: Fiber-supported acid-base bifunctional catalysts for efficient nucleophilic addition in water Synopsis: A number of reactions whose key steps involve in nucleophilic addition were catalysed by fiber supported acid-base bifunctional catalysts, efficiently. Sustainability: All the reactions catalysed by fiber supported acid-base bifunctional catalysts are performed in water and the catalyst can be recycled at least for 10 times.


33

Fiber-Supported AcidâBase Bifunctional Catalysts ... - ACS Publications

Recommend Documents

Fiber-Supported AcidâBase Bifunctional Catalysts ... - ACS Publications