Chiral polymers P-1 and P-2 were synthesized by the polymerization of （R）-3,3＇-diiodo-2,2＇-bisbutoxy-1,1＇- binaphthyl （M- 1 ） with 2,5-di（4-ethynylphenyl）- 1,3,4-oxadiazole （M-3） and （R）-3,3＇-diethylnyl-...Chiral polymers P-1 and P-2 were synthesized by the polymerization of （R）-3,3＇-diiodo-2,2＇-bisbutoxy-1,1＇- binaphthyl （M- 1 ） with 2,5-di（4-ethynylphenyl）- 1,3,4-oxadiazole （M-3） and （R）-3,3＇-diethylnyl-2,2＇-bisbutoxy- 1,1 ＇-binaphthyl （M-2） with 1,2-di（4-bromophenyl）acetylene （M-4） under Sonogashira reaction, respectively. Both monomers and polymers were analyzed by NMR, MS, FT-IR, UV-Vis spectroscopy, DSC-TGA, fluorescence spectroscopy, GPC and CD spectroscopy. CD spectra of P-1 and P-2 are similar due to the same chiral center units and main chain structure. The long wavelengths CD effect of P-1 and P-2 can be regarded as the more extended conjugated structure and a highly rigid backbone in the polymer chain. Polymers have strong blue fluorescence due to the efficient energy migration from the extended n-electronic structure of the polymers to the chiral binaphthyl core and are expected to provide understanding of the relationship between molecular structure and fluorescent property of the chiral polymers.展开更多
Based on DFT calculations, the catalytic mechanism of palladium（0） atom, commonly considered as the catalytic center for Sonogashira cross-coupling reactions, has been analyzed in this study. In the cross-coupling r...Based on DFT calculations, the catalytic mechanism of palladium（0） atom, commonly considered as the catalytic center for Sonogashira cross-coupling reactions, has been analyzed in this study. In the cross-coupling reaction of iodobenzene with phenylacetylene without co-catalysts and bases involved, mechanistically plausible catalytic cycles have been computationally identified. These catalytic cycles typically occur in three stages： 1） oxidative addition of an iodobenzene to the Pd（0） atom, 2） reaction of the product of oxidative addition with phenylacetylene to generate an intermediate with the Csp bound to palladium, and 3） reductive elimination to couple the phenyl group with the phenylethynyl group and to regenerate the Pd（0） atom. The calculations show that the first stage gives rise to a two-coordinate palladium （Ⅱ） intermediate （ArPdI）. Starting from this intermediate, the second oxidative stage, in which the C–H bond of acetylene adds to Pd（Ⅱ） without co-catalyst involved, is called alkynylation instead of transmetalation and proceeds in two steps. Stage 3 of reductive elimination of diphenylacetylene is energetically favorable. The results demonstrate that stage 2 requires the highest activation energy in the whole catalysis cycle and is the most difficult to happen, where co-catalysts help to carry out Sonogashira coupling reaction smoothly.展开更多
An efficient palladium-catalyzed copper- and amine-free Sonogashira coupling reaction of aryl bromides and chlorides was studied using a sterically hindered monooxychlorophosphine as new ligand.The use of 2 mol%Pd（OA...An efficient palladium-catalyzed copper- and amine-free Sonogashira coupling reaction of aryl bromides and chlorides was studied using a sterically hindered monooxychlorophosphine as new ligand.The use of 2 mol%Pd（OAc）_2 in the presence of K_2CO_3 allows the coupling reaction to proceed at mild condition with good to excellent yields.展开更多
A simple Cu（OAc）2 catalyzed Sonogashira coupling protocol is presented. It was found that the couplings of a variety of aryl halides with terminal alkynes were conducted smoothly to afford the corresponding desired ...A simple Cu（OAc）2 catalyzed Sonogashira coupling protocol is presented. It was found that the couplings of a variety of aryl halides with terminal alkynes were conducted smoothly to afford the corresponding desired products in moderate to excellent yields, using Cu（OAc）2 as the catalyst and Et3N as the solvent.展开更多
The mechanism of palladium-catalyzed Sonogashira cross-coupling reaction has been studied theoretically by DFT （density functional theory） calculations. The model system studied consists of Pd（PH3）2 as the startin...The mechanism of palladium-catalyzed Sonogashira cross-coupling reaction has been studied theoretically by DFT （density functional theory） calculations. The model system studied consists of Pd（PH3）2 as the starting catalyst complex, phenyl bromide as the substrate and acetylene as the terminal alkyne, without regarding to the co-catalyst and base. Mechanistically and energetically plausible catalytic cycles for the cross-coupling have been identified. The DFT analysis shows that the catalytic cycle occurs in three stages： oxidative addition of phenyl bromide to the palladium center, alkynylation of palladium（Ⅱ） intermediate, and reductive elimination to phenylacetylene. In the oxidative addition, the neutral and anionic pathways have been investigated, which could both give rise to cis-configured palladium（Ⅱ） diphosphine intermediate. Starting from the palladium（Ⅱ） diphosphine intermediate, the only identifiable pathway in alkynylation involves the dissociation of Br group and the formation of square-planar palladium（Ⅱ） intermediate, in which the phenyl and alkynyl groups are oriented cis to each other. Due to the close proximity of phenyl and alkynyl groups, the reductive elimination of phenylacetylene proceeds smoothly.展开更多
A novel series of calix[4]arene derivatives were synthesized via a Pd-catalyzed Sonogashira coupling reaction from para-substituted iodobenzene and 25,27-dipropargyl-calix[4]arene. Fluorescence studies found that nitr...A novel series of calix[4]arene derivatives were synthesized via a Pd-catalyzed Sonogashira coupling reaction from para-substituted iodobenzene and 25,27-dipropargyl-calix[4]arene. Fluorescence studies found that nitro-phenols clearly exhibited quenching effects on 2c. Moreover, we minimized the free energy of the complexes by theoretical calculations. As the result, the πr-π stacking interactions take place between the 4-nitrophenol and calix[4]arene, which may lead to the significant fluorescence quench.展开更多
Palladium-catalyzed the Sonogashira coupling reaction of 3-halogen-2-aminopyridines 1 with terminal alkynes 2 afforded the corresponding 21 target products 3a-3u in the presence of palladium catalyst. The structure of...Palladium-catalyzed the Sonogashira coupling reaction of 3-halogen-2-aminopyridines 1 with terminal alkynes 2 afforded the corresponding 21 target products 3a-3u in the presence of palladium catalyst. The structure of target products 3a-3u was confirmed and characterized by 1H NMR, 13C NMR, and HRMS. The influences of different kinds of catalyst loading, bases, substrates and temperature were also investigated. Under the optimized conditions, including 2.5 mol% Pd?(CF3COO)2, 5 mol% PPh3 and 5 mol% CuI as additive, 1 mL Et3N, substrate 1 with terminal alkynes 2 for the cross-coupling reactions at 100°C for 3 h in DMF afforded the corresponding products of 2-amino-3-alkynylpyridines 3 in moderate to excellent yields (72%?-?96%). The present methodology has provided an effective synthetic method including operational convenience, high efficiency and wide-application.展开更多
基金This work was supported by the National Natural Science Foundation of China (No. 20474028)Jiangsu Provincial Natural Science Foundation (No. BK2004086)
文摘Chiral polymers P-1 and P-2 were synthesized by the polymerization of （R）-3,3＇-diiodo-2,2＇-bisbutoxy-1,1＇- binaphthyl （M- 1 ） with 2,5-di（4-ethynylphenyl）- 1,3,4-oxadiazole （M-3） and （R）-3,3＇-diethylnyl-2,2＇-bisbutoxy- 1,1 ＇-binaphthyl （M-2） with 1,2-di（4-bromophenyl）acetylene （M-4） under Sonogashira reaction, respectively. Both monomers and polymers were analyzed by NMR, MS, FT-IR, UV-Vis spectroscopy, DSC-TGA, fluorescence spectroscopy, GPC and CD spectroscopy. CD spectra of P-1 and P-2 are similar due to the same chiral center units and main chain structure. The long wavelengths CD effect of P-1 and P-2 can be regarded as the more extended conjugated structure and a highly rigid backbone in the polymer chain. Polymers have strong blue fluorescence due to the efficient energy migration from the extended n-electronic structure of the polymers to the chiral binaphthyl core and are expected to provide understanding of the relationship between molecular structure and fluorescent property of the chiral polymers.
基金Supported by the NNSFC (20674034)Natural Science Youth Foundation of Jiangxi Province (No. 2010GQH0028)
文摘Based on DFT calculations, the catalytic mechanism of palladium（0） atom, commonly considered as the catalytic center for Sonogashira cross-coupling reactions, has been analyzed in this study. In the cross-coupling reaction of iodobenzene with phenylacetylene without co-catalysts and bases involved, mechanistically plausible catalytic cycles have been computationally identified. These catalytic cycles typically occur in three stages： 1） oxidative addition of an iodobenzene to the Pd（0） atom, 2） reaction of the product of oxidative addition with phenylacetylene to generate an intermediate with the Csp bound to palladium, and 3） reductive elimination to couple the phenyl group with the phenylethynyl group and to regenerate the Pd（0） atom. The calculations show that the first stage gives rise to a two-coordinate palladium （Ⅱ） intermediate （ArPdI）. Starting from this intermediate, the second oxidative stage, in which the C–H bond of acetylene adds to Pd（Ⅱ） without co-catalyst involved, is called alkynylation instead of transmetalation and proceeds in two steps. Stage 3 of reductive elimination of diphenylacetylene is energetically favorable. The results demonstrate that stage 2 requires the highest activation energy in the whole catalysis cycle and is the most difficult to happen, where co-catalysts help to carry out Sonogashira coupling reaction smoothly.
基金Henan University of Technology for financial support(The Introduction of Talent Fund)
文摘An efficient palladium-catalyzed copper- and amine-free Sonogashira coupling reaction of aryl bromides and chlorides was studied using a sterically hindered monooxychlorophosphine as new ligand.The use of 2 mol%Pd（OAc）_2 in the presence of K_2CO_3 allows the coupling reaction to proceed at mild condition with good to excellent yields.
文摘A simple Cu（OAc）2 catalyzed Sonogashira coupling protocol is presented. It was found that the couplings of a variety of aryl halides with terminal alkynes were conducted smoothly to afford the corresponding desired products in moderate to excellent yields, using Cu（OAc）2 as the catalyst and Et3N as the solvent.
基金Supported by the NNSFC (No. 20464001 and 20674034)
文摘The mechanism of palladium-catalyzed Sonogashira cross-coupling reaction has been studied theoretically by DFT （density functional theory） calculations. The model system studied consists of Pd（PH3）2 as the starting catalyst complex, phenyl bromide as the substrate and acetylene as the terminal alkyne, without regarding to the co-catalyst and base. Mechanistically and energetically plausible catalytic cycles for the cross-coupling have been identified. The DFT analysis shows that the catalytic cycle occurs in three stages： oxidative addition of phenyl bromide to the palladium center, alkynylation of palladium（Ⅱ） intermediate, and reductive elimination to phenylacetylene. In the oxidative addition, the neutral and anionic pathways have been investigated, which could both give rise to cis-configured palladium（Ⅱ） diphosphine intermediate. Starting from the palladium（Ⅱ） diphosphine intermediate, the only identifiable pathway in alkynylation involves the dissociation of Br group and the formation of square-planar palladium（Ⅱ） intermediate, in which the phenyl and alkynyl groups are oriented cis to each other. Due to the close proximity of phenyl and alkynyl groups, the reductive elimination of phenylacetylene proceeds smoothly.
基金financially supported by the National Natural Science Foundation of China(Nos.21372092,21072072, 21102051)PCSIRT(No.IRT0953)+2 种基金Program for New Century Excellent Talent in University(No.NCET-10-0428)self-determined research funds of CCNU from the colleges,basic research and operation of MOE(Nos.CCNU11C01002,CCNU13F005)State Key Laboratory of Chemo/Biosensing and Chemometrics (201003)
文摘A novel series of calix[4]arene derivatives were synthesized via a Pd-catalyzed Sonogashira coupling reaction from para-substituted iodobenzene and 25,27-dipropargyl-calix[4]arene. Fluorescence studies found that nitro-phenols clearly exhibited quenching effects on 2c. Moreover, we minimized the free energy of the complexes by theoretical calculations. As the result, the πr-π stacking interactions take place between the 4-nitrophenol and calix[4]arene, which may lead to the significant fluorescence quench.
文摘Palladium-catalyzed the Sonogashira coupling reaction of 3-halogen-2-aminopyridines 1 with terminal alkynes 2 afforded the corresponding 21 target products 3a-3u in the presence of palladium catalyst. The structure of target products 3a-3u was confirmed and characterized by 1H NMR, 13C NMR, and HRMS. The influences of different kinds of catalyst loading, bases, substrates and temperature were also investigated. Under the optimized conditions, including 2.5 mol% Pd?(CF3COO)2, 5 mol% PPh3 and 5 mol% CuI as additive, 1 mL Et3N, substrate 1 with terminal alkynes 2 for the cross-coupling reactions at 100°C for 3 h in DMF afforded the corresponding products of 2-amino-3-alkynylpyridines 3 in moderate to excellent yields (72%?-?96%). The present methodology has provided an effective synthetic method including operational convenience, high efficiency and wide-application.
基金supported by the National Natural Science Foundation of China (20925310)the National High Technology Research and Development Program of China (863 Program, 2009AA064201)+1 种基金the Science and Technology Commission of Shanghai Municipality (09XD1401500)the Shanghai Leading Academic Discipline Project (B409)~~
