This study details Ni-catalyzed cross coupling of aryl Grignard reagents with aryl halides in toluene, a nonpolar solvent with a high boiling point. The reaction was applied for the synthesis of various biaryls in goo...This study details Ni-catalyzed cross coupling of aryl Grignard reagents with aryl halides in toluene, a nonpolar solvent with a high boiling point. The reaction was applied for the synthesis of various biaryls in good yields without the introduction of a large steric ligand. The Kumada-Tamao-Corriu（KTC） reaction in toluene was then successfully modified to proceed under neat conditions for the efficient syntheses of symmetrical biaryls, particularly in large-scale preparations. Unactivated aryl chlorides show higher reactivity than aryl bromides, particularly under neat conditions. Mechanistic investigations suggest a radical procedure for the catalytic cycle, and the origin of the radical intermediates being aryl halides.展开更多
Imidazole-containing polyimide/silica（PI/SiO2） hybrid films were prepared from 3,3＇,4,4＇-biphenyltetra- carboxylic dianhydride（BPDA） and 2,2＇-di（p-aminophenyl）-5,5＇-bibenzimidazole in N,N-dimethylacetamide（...Imidazole-containing polyimide/silica（PI/SiO2） hybrid films were prepared from 3,3＇,4,4＇-biphenyltetra- carboxylic dianhydride（BPDA） and 2,2＇-di（p-aminophenyl）-5,5＇-bibenzimidazole in N,N-dimethylacetamide（DMAc） by sol-gel method and thermal imidization. The hybrid film with high silica mass fraction up to 40% was transparent. Scanning electron microscope（SEM） and transmission electron microscope（TEM） results of the film indicate a ho- mogeneous dispersion of silica nanoparticles in the polyimide matrix. One hybrid film PI/SiO2 with 15% SiO2 exhi- bits better mechanical properties with a tensile strength of 222 MPa, an elongation at break of 12%, and a tensile modulus of 5.66 GPa. The reinforced mechanism on mechanical Drooerties was also studied.展开更多
文摘This study details Ni-catalyzed cross coupling of aryl Grignard reagents with aryl halides in toluene, a nonpolar solvent with a high boiling point. The reaction was applied for the synthesis of various biaryls in good yields without the introduction of a large steric ligand. The Kumada-Tamao-Corriu（KTC） reaction in toluene was then successfully modified to proceed under neat conditions for the efficient syntheses of symmetrical biaryls, particularly in large-scale preparations. Unactivated aryl chlorides show higher reactivity than aryl bromides, particularly under neat conditions. Mechanistic investigations suggest a radical procedure for the catalytic cycle, and the origin of the radical intermediates being aryl halides.
基金Supported by the National Natural Science Foundation of China（No.2 1104085）, the National High Technology Research and Development Program of China（No.2012AA03A211） and the Major State Basic Research Development Program of China （No.2014CB643603）.
文摘Imidazole-containing polyimide/silica（PI/SiO2） hybrid films were prepared from 3,3＇,4,4＇-biphenyltetra- carboxylic dianhydride（BPDA） and 2,2＇-di（p-aminophenyl）-5,5＇-bibenzimidazole in N,N-dimethylacetamide（DMAc） by sol-gel method and thermal imidization. The hybrid film with high silica mass fraction up to 40% was transparent. Scanning electron microscope（SEM） and transmission electron microscope（TEM） results of the film indicate a ho- mogeneous dispersion of silica nanoparticles in the polyimide matrix. One hybrid film PI/SiO2 with 15% SiO2 exhi- bits better mechanical properties with a tensile strength of 222 MPa, an elongation at break of 12%, and a tensile modulus of 5.66 GPa. The reinforced mechanism on mechanical Drooerties was also studied.
