Metalated Mesoporous Poly(triphenylphosphine) with Azo

Jan 7, 2016 - Carbon dioxide chemistry (e.g., capture and conversion) has attracted much attention from the scientific community due to global warming...
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Metalated mesoporous poly(triphenylphosphine) with azo-functionality: Efficient catalysts for CO2 conversion Zhen-zhen Yang, Bo Yu, Hong-ye Zhang, Yan-fei Zhao, Yu Chen, Zhishuang Ma, Guipeng Ji, Xiang Gao, Buxing Han, and Zhi-min Liu ACS Catal., Just Accepted Manuscript • DOI: 10.1021/acscatal.5b02583 • Publication Date (Web): 07 Jan 2016 Downloaded from http://pubs.acs.org on January 10, 2016

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Metalated mesoporous poly( (triphenylphosphine) functionality: Efficient catalysts for CO2 conversion

with

azo-

Zhenzhen Yang, Bo Yu, Hongye Zhang, Yanfei Zhao, Yu Chen, Zhishuang Ma, Guipeng Ji, Xiang Gao, Buxing Han and Zhimin Liu* Beijing National Laboratory for Molecular Sciences, Key Laboratory of Colloid, Interface and Thermodynamics, Institute of Chemistry, Chinese Academy of Sciences, Beijing 100190, China ABSTRACT: Mesoporous poly(triphenylphosphine) with azo functionality (poly(PPh3)-azo) was reported, which was synthesized via oxidative polymerization of P(m-NH2Ph)3 at ambient conditions. This kind of polymer could strongly coordinate with metal ions (e.g., Ru3+), and could in-situ reduce Ag+ to metallic form. The resultant metalated poly(PPh3)azo (e.g., poly(PPh3)-azo-Ag or -Ru) were discovered to be highly efficient catalysts for CO2 transformation. Poly(PPh3)-azo-Ag showed more than 400 times higher site-time-yield (STY) for the carboxylative cyclization of propargylic alcohols with CO2 at room temperature compared with the best heterogeneous catalyst reported. Poly(PPh3)-azoRu also exhibited good activity for the methylation of amines with CO2. It was demonstrated that the high performances of the catalysts were originated from the cooperative effects between the polymer and the metal species. In addition, both catalysts showed good stability and easy recyclability, thus demonstrating promising potential for practical utilization of the cost-effective process for the conversion of CO2 into value-added chemicals. KEYWORDS: Porous organic polymer • CO2 conversion • α-alkylidene cyclic carbonate • methylation of amine • heterogeneous catalysis

INTRODUCTION Carbon dioxide chemistry (e.g. capture and conversion) has attracted much attention from the scientific community due to global warming associated with positive carbon accumulation.1 In comparison with toxic phosgene and CO, CO2 is a cheap, green and renewable C1 building block due to its abundance, availability and nontoxicity, thus the CO2-involved synthesis of chemicals has been regarded as green approaches.2 The major challenge in CO2 transformation originates from the inherent thermodynamic stability and kinetic inertness of CO2, which calls for a remarkable driving force to ensure efficient transformation.3 In this respect, the key issue to convert CO2 into useful chemicals inevitably relies on its activation.4 With the rapid development of organometallic chemistry and catalysis, various types of homogeneous and heterogeneous catalysts for CO2 transformation have been reported in the past decades.4 In general, phosphine or nitrogen-containing ligands are involved in most of the homogeneous organometallic catalysts, in order to promote the reactivity and also control the selectivity of CO2 chemical fixation.4 Nevertheless, the heterogeneous catalysts are more desirable for industrial applications owing to the convenience of recovering and recycling of the catalysts. However, low catalytic activity and poor selectivity together with leaching of active species were generally observed in the case of heterogeneous catalysts. Therefore, design of highly efficient heterogeneous catalysts for CO2 conversion is still a great challenge.

As an emerging material platform, porous organic polymers (POPs) have attracted considerable scientific interest due to their distinctive properties such as large surface areas, low skeleton density, good physicochemical and thermal stability. Most importantly, POPs could be designed with various functional components, showing wide applications in many areas.5-8 For example, the POPs with nitrogen-rich functionalities, such as azo,9-11 triazine,12 tetrazole,13 imidazole14 and amine15 species showed "CO2philic" properties and superior capacity to CO2 uptake, which is generally believed to arise from enhanced CO2framework interactions. Recently, the POPs that can coordinate with metal species have been reported, which widen the applications of POPs in catalysis.16-25 For instance, Tröger's base-derived POPs could coordinate with Ru species, showing high efficiency for the hydrogenation of CO2 to produce HCOOH;17 Ru coordinated azofunctionalized POPs displayed high performances for catalyzing the methylation of amines using CO2.18 However, in these systems, additional high amount of organic ligands (e.g., PPh3) were still required to achieve a high efficiency of the catalysts. Hence, if POPs are designed to possess both CO2-philic moieties and organic ligands, the resultant metalated POPs may have very high ligand concentration as well as the ability for CO2 activation, and thus may exhibit high performance as heterogeneous catalysts for CO2 transformation. Herein, we designed porous poly(triphenylphosphine) with azo functionality (poly(PPh3)-azo), which was synthesized through oxidative polymerization of phosphine-

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containing aromatic amines, P(m-NH2Ph)3, in the presence of t-BuOCl/NaI at 25 oC (Scheme 1). Notably, the reaction proceeded rapidly and afforded almost quantitative product yield. The resultant poly(PPh3)-azo could coordinate with transition metal ions (e.g., Ru3+), and interestingly, it could in-situ reduce Ag+ to metallic form. The resultant metalated poly(PPh3)-azo catalysts displayed high efficiency for catalysing CO2 transformation, originated from the cooperative effects between the polymer and the metal species. The Ag immobilized poly(PPh3)-azo (poly(PPh3)-azo-Ag) could catalyse the carboxylative cyclization of propargyl alcohols with CO2 at room temperature, affording more than 400 times higher site-time-yield (STY) compared with the best heterogeneous catalytic system reported. The Ru coordinated poly(PPh3)-azo (poly(PPh3)-azo-Ru) also exhibited extraordinary activity for the methylation of amines with CO2 under low pressure. Moreover, both poly(PPh3)-azoAg and poly(PPh3)-azo-Ru showed good stability and easy recyclability, thus demonstrating great potential for practical utilization in catalysis.

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polarization magic-angle spinning (CP/MAS) 13C NMR spectra (Figure S3, SI) of poly(PPh3)-azo located in the range of 119.7-151.4 ppm belonged to the aromatic carbons in the backbone. The thermogravimetric analysis (TGA) results (Figure S4, SI) indicated that poly(PPh3)-azo was stable in air up to 400 oC, which met the demands for potential applications in heterogeneous catalysis. The N2 sorption measurements at 77 K of poly(PPh3)-azo showed a Brunauer-Emmett-Teller (BET) surface area and the total pore volume of 118 m2 g-1 and 0.62 cm3 g-1, respectively (Figure 1A and Figure S5A, SI). The pore size distribution suggested that the porosity was dominated by mesopores (Figure 1B). Both the structure of the monomer and the formed azo functionality are not sufficiently rigid to prevent intermolecular packing, which resulted in a relatively low BET surface area. Scanning electron microscopy (SEM, Figure S6, SI) and transmission electron microscopy (TEM, Figure 1C and S7) images of poly(PPh3)-azo further confirmed the existence of mesopores in the polymer particles and very small amount of macropores due to the aggregation of the particles.

NH 2

H 2N

P

P(m-NH2 Ph) 3

NH 2 o

t-BuOCl/NaI 25 C, 1 h N N

N

N

N

N

P

N

N

P

N N

N

poyl(PPh3 )-azo

N

P

N N

Scheme 1 Synthetic process of poly(PPh3)-azo through oxidative polymerization of the monomer P(m-NH2Ph)3.

RESULTS AND DISCUSSION The formation of poly(PPh3)-azo was revealed by Fourier transform infrared (FTIR) spectroscopy (Figure S1, SI). Compared with the monomer P(m-NH2Ph)3, the presence of -N=N- functionality was confirmed by the characteristic bands at 1175 and 1410 cm-1 due to the symmetric and asymmetric vibrations of the azo group. The broad bands located at 3395 cm-1 corresponded to the N-H stretching mode, suggesting the presence of unreacted terminal amino groups.9-11,18 The solid-state ultraviolet-visible analysis for poly(PPh3)-azo showed an intense new absorption band at 440 nm, which revealed that cis configuration of azo functionality predominantly existed (Figure S2, SI).11 The chemical shifts in the solid-state cross-

Figure 1. For poly(PPh3)-Azo: A) Adsorption (filled) and desorption (empty) isotherms of N2 at 77 k; B) Pore size distribution curve obtained from the adsorption branches using non-local density functional theory (NLDFT) method; C) TEM image. D) TEM image for poly(PPh3)-azo-Ag.

Both the azo- and phosphine-type ligands are versatile in coordination chemistry.18,26,27 In this work, the resultant poly(PPh3)-azo was a polymer composed of PPh3 connected with large amount of azo bonds, which may have unique features. Ag or Ru metalated poly(PPh3)-azo were obtained by treating the polymer with AgBF4 or RuCl3·3H2O in tetrahydrofuran (THF) or ethanol (EtOH), respectively, under refluxing conditions (for synthetic process, see SI). The contents of Ag and Ru species immobilized onto poly(PPh3)-azo were 0.17 wt% and 3.72 wt%, respectively, determined by inductively coupled plasma-optical emission spectroscopy (ICP-OES) analysis. The energy dispersive spectrometer (EDS) profile obtained during the TEM observation also indicated the

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presence of metal species (Figure S9, SI). Both of the metallated polymeric materials exhibited good thermal stability confirmed by TGA analysis (Figure S4, SI). Compared with those of poly(PPh3)-azo (118 m2 g-1 and 0.62 cm3 g-1), both the BET surface areas and total pore volumes of the metallated polymers decreased: 80 m2 g-1 and 0.53 cm3 g-1 for poly(PPh3)-azo-Ag, and 78 m2 g-1 and 0.40 cm3 g-1 for poly(PPh3)-azo-Ru (Figures S5 and S8, SI). This was probably due to the weight increase and the slight block of the cavities by metal species. X-ray photoelectron spectroscopy (XPS) measurements were performed to investigate the coordination site and oxidation state of N, P and metal species. Vast majority of the incorporated N could be regarded as stable structural azo nitrogen with N1s binding energy (BE) at 399.97 eV (Figure S10, SI).28 The other two peaks with the BEs of 397.87eV and 403.22 eV for N1s were associated to unreacted aryl amino group and quaternary-type nitrogen formed during the oxidative process as intermediate, respectively.29 The presence of P in the backbone of poly(PPh3)-azo was confirmed by the peaks at 132.32 eV (P2p3/2) and 133.1 eV (P2p1/2). The XPS spectrum of poly(PPh3)-azo-Ag demonstrated two peaks of Ag3d5/2 and Ag3d3/2 with BEs at 368.12 and 374.12 eV, respectively (Figure S11, SI), ascribing to metallic Ag species, which suggested that the polymer could in-situ reduce Ag+ to metallic Ag0, probably by the residual aryl amino groups.30,31 The TEM image also supported the formation of Ag0 nanoparticles, which were evenly distributed throughout the polymer support and the particle sizes were centred around 2.7 nm (Figure 1D). The BE of N1s in poly(PPh3)-azo-Ag exhibited a slightly higher value of 400.07 eV than that in poly(PPh3)-azo (i.e., 399.97 eV), while the BE of P2p showed no difference. This implies that Ag nanoparticles were prone to nucleate and grow at the azo sites in the as-prepared poly(PPh3)-azo-Ag. Due to the uniform presence of azo sites throughout the polymer, the Ag nanoparticles were uniformly distributed. Notably, only 0.17 wt% Ag species were immobilized onto the polymer support in poly(PPh3)-azo-Ag, meaning Ag particles were embedded with PPh3 ligand and azo functionality in high concentration, which was important for catalytic CO2 conversion as shown below. Interestingly, Ru species were coordinated with both azo and phosphine functionalities in poly(PPh3)-azo-Ru, which was confirmed by the higher BEs of N1s (400.02 eV) and P2p3/2 (132.42 eV) compared with those in the support poly(PPh3)-azo (Figure S12, SI). The four peaks with the BEs of 281.57 eV (Ru3d5/2), 285.62 eV (Ru3d3/2, overlapping with the peak for C1s), 463.07 eV (Ru3p3/2) and 485.17 eV (Ru3p1/2) were consistent with those of the Ru species in the +3 state, however, shifting to lower values compared to those of RuCl3, suggesting the coordination of Ru(III) with the polymer.18 In addition, the TEM image supported a very homogeneous ruthenium distribution without detectable ruthenium clusters or nanoparticles in poly(PPh3)-azo-Ru (Figure S13, SI).

were examined in carboxylative cyclization of propargyl alcohols and methylation of amines with CO2, respectively. The carboxylative cyclization of propargyl alcohols with CO2 is a green approach to synthesize α-alkylidene cyclic carbonates that have potential bioactivity with a broad range of applications as intermediates in organic synthesis.32-34 Heterogeneous catalysts including (dimethylamino)-methyl-polystyrene-supported CuI (DMAMPS-CuI),35 polystyrene-supported NHC-Ag complexes (PSNHC-Ag)36 have been reported for this reaction. However, high CO2 pressure (up to 14 MPa), high catalyst loading of transition metals (up to 10 mol%) together with very low STY (< 1 h-1) were generally the cases. Poly(PPh3)-azo-Ag prepared in this work was found to show very high performance for catalysing the cyclization of propargyl alcohols with CO2 at room temperature, as illustrated in Table 1 and Scheme 2. As a model reaction the cyclization of 2-emthylbut-3yn-2-ol (1a) with CO2 was investigated over poly(PPh3)azo-Ag and different catalytic systems. The control experiments indicated that nearly no product was detected without catalyst (Table 1, entry 1), and poly(PPh3)-azo showed no catalytic activity either (entry 2). Excitingly, quantitative yield of α-alkylidene cyclic carbonate (2a) was obtained by employing only 0.064 mol% poly(PPh3)azo-Ag as the catalyst, giving a STY of 87 h-1 for the production of 2a (entry 3). The evolution of the catalytic performance of poly(PPh3)-azo-Ag along with reaction time indicated that the STY values increased with shortening the time, and the highest STY value of 469 h-1 was obtained at the reaction time of 1 h, together with 2a yield of 30%. A comparable STY value of 438 h-1 was observed by further reducing the reaction time to 0.5 h (entries 3-8). It was noteworthy that the STY value of 182 h-1 achieved by poly(PPh3)-azo-Ag was much higher than that obtained over the homogeneous AgBF4 catalyst with 10 mol% loading (1.5 h-1) within the same reaction time of 6 h (entries 5 vs 9). To achieve a comparable yield of 2a (30%) by poly(PPh3)-azo-Ag (0.064 mol%) within 1 h, at least 2 mol% of AgBF4 was required, yet with an inferior STY value (13 h-1) (entries 7 vs. 10). In addition, the advantage of poly(PPh3)-azo-Ag was prominent compared with the reported heterogeneous catalytic systems bearing Ag (1 h-1) or Cu species (0.52 h-1) even under harsh reaction conditions (Table 1, entries 11, 12). To explore the reasons of the high performance of poly(PPh3)-azo-Ag, control experiments were performed using AgBF4 as the catalyst with azobenzene or/and PPh3 as additives. It was demonstrated that azobenzene and PPh3 in the AgBF4- catalyzed reaction process could improve the yields of 2a (entries 10 vs. 13-16). Particularly, the coexistence of azobenzene and PPh3 increased the STY values from 28 to 37 h-1 by increasing the molar ratio of additives to AgBF4 (entry 15 vs. 16). These results suggested that the presence of azobenzene or/and PPh3 Table 1. Carboxylative cyclization of propargyl alcohol (1a) with CO2 a

Ag- and Ru-based catalysts have been applied in the CO2 transformation. In this work, the catalytic performances of poly(PPh3)-azo-Ag and poly(PPh3)-azo-Ru

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Entry 1

STY/

/h

Yield of b 2a /%

No

18

90% yields.

CONCLUSIONS a

Reaction conditions: substrate 0.5 mmol, catalyst loading (poly(PPh3)-azo-Ru) 1 mol% Ru based on the substrate, organosilane PhSiH3 4 mmol, CO2 pressure 0.5 MPa, THF 2 mL, 120 oC, 24 h; b Isolated yield; c Catalyst loading (Azo-MOP-3-Ru) 1 mol% Ru based on the substrate, additive PPh3 0.05 mmol; d RuCl3·3H2O 4 mol%, PPh3 0.1 mmol. also reflected by the high performance of poly(PPh3)azo-Ru for catalyzing the methylation of amines with CO2. The methylation of amines with CO2 in the presence of hydrosilanes is a promising method to produce methylamines that are basic reagents with many usages in nitrogen chemistry.38,39 Homogeneous N-heterocyclic carbenes (NHCs) zinc complex,38 ruthenium complex,39 NHCs40 catalysts have been developed to afford Nmethylated compounds using CO2 as a C1 building block. However, these catalytic systems all needed to be manipulated under inert atmosphere. The heterogeneous catalysts for this kind of reactions under mild conditions are rarely reported.18,41 Although Ru-coordinated Azo-MOPs (e.g., Azo-MOP-3-Ru) reported in our previous work displayed activity for this kind of reactions, tremendous PPh3 was required.18 Excitingly, poly(PPh3)-azo-Ru prepared in this work was found to be very effective for catalysing the methylation of amines with CO2 without any additive at low CO2 pressure, as listed in Table 2. In contrast, 1 mol% of Azo-MOP-3-Ru together with 10 equiv. of PPh3 (that is, the Ru:PPh3 ratio was identical to that in poly(PPh3)-azo-Ru) only afforded a yield of 26% (entry 2, Table 2), meaning that poly(PPh3)-azo-Ru showed near 4 times higher activity than Azo-MOP-3-Ru under the similar conditions. Moreover, poly(PPh3)-azo-Ru showed activity even much better than the homogenous RuCl3·3H2O catalyst (4 mol%) combined with PPh3 (entry 1 vs. 3). From these findings, it can be deduced that the

In summary, mesoporous poly(PPh3) with azo functionality was obtained through simple oxidative polymerization of P(m-NH2Ph)3 under ambient conditions, which was a highly efficient supports for transition metal species. The resultant metalated poly(PPh3)-azo demonstrated extraordinary performances for the conversion of CO2 into value-added chemicals (e.g. α-alkylidene cyclic carbonates and methylamines), together with high stability and easy recyclability. The cooperative effects of poly(PPh3)-azo and the metal species were responsible for the high performances of the catalysts for CO2 transformation. This work provides multifunctional catalysts for CO2 conversion, which may have great potential in applications.

ASSOCIATED CONTENT Supporting Information available: general experimental methods, synthetic procedures, Figure S1-S17, Scheme S1, S2 and characterization (NMR) of the αalkylidene cyclic carbonates and methylamine products.

AUTHOR INFORMATION Corresponding Author *E-mail: [email protected]

ACKNOWLEDGMENT This work was financially supported by the National Natural Science Foundation of China (Grants Nos. 21533011, 21125314, 21402208).

REFERENCES (1) He, M.; Sun, Y.; Han, B. Angew. Chem. Int. Ed. 2013, 52, 9620-9633.

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(2) Sakakura, T.; Choi, J.-C.; Yasuda, H. Chem. Rev. 2007, 107, 2365-2387. (3) Liu, Q.; Wu, L.; Jackstell, R.; Beller, M. Nat. Commun. 2015, 6, 1-15. (4) Cokoja, M.; Bruckmeier, C.; Rieger, B.; Herrmann, W. A.; Kühn, F. E. Angew. Chem. Int. Ed. 2011, 50, 8510-8537. (5) Slater, A. G.; Cooper, A. I. Science 2015, 348, no. 6283. (6) Sun, Q.; Dai, Z.; Meng, X.; Xiao, F.-S. Chem. Soc. Rev. 2015, 44, 6018-6034. (7) Xu, Y.; Jin, S.; Xu, H.; Nagai, A.; Jiang, D. Chem. Soc. Rev. 2013, 42, 8012-8031. (8) Wu, D.; Xu, F.; Sun, B.; Fu, R.; He, H.; Matyjaszewski, K. Chem. Rev. 2012, 112, 3959-4015. (9) Lu, J.; Zhang, J. J. Mater. Chem. A 2014, 2, 13831-13834. (10) Arab, P.; Rabbani, M. G.; Sekizkardes, A. K.; Đslamoğlu, T.; El-Kaderi, H. M. Chem. Mater. 2014, 26, 1385-1392. (11) Patel, H. A.; Hyun Je, S.; Park, J.; Chen, D. P.; Jung, Y.; Yavuz, C. T.; Coskun, A. Nat. Commun. 2013, 4, 1357. (12) Thomas, A. Angew. Chem. Int. Ed. 2010, 49, 8328-8344. (13) Du, N.; Park, H. B.; Robertson, G. P.; Dal-Cin, M. M.; Visser, T.; Scoles, L.; Guiver, M. D. Nat Mater 2011, 10, 372375. (14) Rabbani, M. G.; El-Kaderi, H. M. Chem. Mater. 2011, 23, 1650-1653. (15) Dawson, R.; Stockel, E.; Holst, J. R.; Adams, D. J.; Cooper, A. I. Energy Environ. Sci. 2011, 4, 4239-4245. (16) Sun, Q.; Jiang, M.; Shen, Z.; Jin, Y.; Pan, S.; Wang, L.; Meng, X.; Chen, W.; Ding, Y.; Li, J.; Xiao, F.-S. Chem. Commun. 2014, 50, 11844-11847. (17) Yang, Z.-Z.; Zhang, H.; Yu, B.; Zhao, Y.; Ji, G.; Liu, Z. Chem. Commun. 2015, 51, 1271-1274. (18) Yang, Z.; Zhang, H.; Yu, B.; Zhao, Y.; Ma, Z.; Ji, G.; Han, B.; Liu, Z. Chem. Commun. 2015, 51, 11576-11579. (19) Sun, Q.; Dai, Z.; Liu, X.; Sheng, N.; Deng, F.; Meng, X.; Xiao, F.-S. J. Am. Chem. Soc. 2015, 137, 5204-5209. (20) Sun, Q.; Dai, Z.; Meng, X.; Xiao, F.-S. Chem. Soc. Rev. 2015, 44, 6018-6034. (21) Zhang, Y.; Riduan, S. N. Chem. Soc. Rev. 2012, 41, 20832094. (22) Zhang, P.; Qiao, Z.-A.; Jiang, X.; Veith, G. M.; Dai, S. Nano Letters 2015, 15, 823-828. (23) Xu, P.; Han, X.; Zhang, B.; Du, Y.; Wang, H.-L. Chem. Soc. Rev. 2014, 43, 1349-1360. (24) Liu, Q.; Tang, Z.; Wu, M.; Zhou, Z. Polym. Int. 2014, 63, 381-392. (25) Perego, C.; Millini, R. Chem. Soc. Rev. 2013, 42, 39563976. (26) Garn, D.; Knoch, F.; Kisch, H. J. Organomet. Chem. 1993, 444, 155-164. (27) Huang, K.; Sun, C.-L.; Shi, Z.-J. Chem. Soc. Rev. 2011, 40, 2435-2452. (28) Moulder, J. F.; Stickle, W. F.; Sobol, P. E.; Bomben, K. D. Handbook of X-ray photoelectron spectroscopy, Chastain, J., King, R. C., Eds.; Physical Electronics, Inc.: Minnesota (USA), 1995, page 213. (29) Takeda, Y.; Okumura, S.; Minakata, S. Angew. Chem. Int. Ed. 2012, 51, 7804-7808. (30) Wang, Y.; Liu, Z.; Han, B.; Sun, Z.; Huang, Y.; Yang, G. Langmuir 2005, 21, 833-836. (31) Liu, J.; Cui, J.; Vilela, F.; He, J.; Zeller, M.; Hunter, A. D.; Xu, Z. Chem. Commun. 2015, 51, 12197-12200. (32) Zhang, H.; Liu, H.-B.; Yue, J.-M. Chem. Rev. 2014, 114, 883-898. (33) Cui, M.; Qian, Q.; He, Z.; Ma, J.; Kang, X.; Hu, J.; Liu, Z.; Han, B. Chem. Eur. J. 2015, 21, 15924-15928. (34) Song, Q.-W.; Yu, B.; Li, X.-D.; Ma, R.; Diao, Z.-F.; Li, R.G.; Li, W.; He, L.-N. Green Chem. 2014, 16, 1633-1638.

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(35) Jiang, H.-F.; Wang, A. Z.; Liu, H.-L.; Qi, C.-R. Eur. J. Org. Chem. 2008, 2008, 2309-2312. (36) Tang, X.; Qi, C.; He, H.; Jiang, H.; Ren, Y.; Yuan, G. Adv. Synth. Catal. 2013, 355, 2019-2028. (37) Luska, K. L.; Migowski, P.; El Sayed, S.; Leitner, W. Angew. Chem. Int. Ed. 2015, 54, 15750-15755. (38) Jacquet, O.; Frogneux, X.; Das Neves Gomes, C.; Cantat, T. Chem. Sci. 2013, 4, 2127-2131. (39) Li, Y.; Fang, X.; Junge, K.; Beller, M. Angew. Chem. Int. Ed. 2013, 52, 9568-9571. (40) Das, S.; Bobbink, F. D.; Laurenczy, G.; Dyson, P. J. Angew. Chem. Int. Ed. 2014, 53, 12876-12879. (41) Cui, X.; Dai, X.; Zhang, Y.; Deng, Y.; Shi, F. Chem. Sci. 2014, 5, 649-655.

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