Enan tioselective resoluti on copolymerization of racemic internal epoxides with carb on dioxide(CO_(2))is a challe nging issue because of their poor reactivity and complicated regio/stereoselectivity.Herein,we descri...Enan tioselective resoluti on copolymerization of racemic internal epoxides with carb on dioxide(CO_(2))is a challe nging issue because of their poor reactivity and complicated regio/stereoselectivity.Herein,we describe the first enantioselective resolution copolymeriza-tion of racemic aromatic 2,3-disubstituted c/s-epoxides and CO_(2) using enantiopure dinuclear cobalt(lll)complexes as catalyst under mild conditions,affordi ng the corresp on ding polycarbonates with completely alter nating structure and good enantioselectivity in the range of 70% to 97%ee.The isotactic polycarb on ate from/3-methylstyre ne oxide is a typical semicrystalli ne material,possessi ng a melting point of 241℃;while other isotactic-enriched copolymers from 2,3-disubstituted c/s-epoxides bearing a substitute group on the aromatic ring are amorphous,having glass transition temperatures between 86℃ and 124℃.Interestingly,the copolymer selectivity is correlated well with the Hammett substituent constant,and the highest polymer selectivity of 98%was found in the system using the epoxides bearing an electron-donating group on the benzene ring.展开更多
文摘Enan tioselective resoluti on copolymerization of racemic internal epoxides with carb on dioxide(CO_(2))is a challe nging issue because of their poor reactivity and complicated regio/stereoselectivity.Herein,we describe the first enantioselective resolution copolymeriza-tion of racemic aromatic 2,3-disubstituted c/s-epoxides and CO_(2) using enantiopure dinuclear cobalt(lll)complexes as catalyst under mild conditions,affordi ng the corresp on ding polycarbonates with completely alter nating structure and good enantioselectivity in the range of 70% to 97%ee.The isotactic polycarb on ate from/3-methylstyre ne oxide is a typical semicrystalli ne material,possessi ng a melting point of 241℃;while other isotactic-enriched copolymers from 2,3-disubstituted c/s-epoxides bearing a substitute group on the aromatic ring are amorphous,having glass transition temperatures between 86℃ and 124℃.Interestingly,the copolymer selectivity is correlated well with the Hammett substituent constant,and the highest polymer selectivity of 98%was found in the system using the epoxides bearing an electron-donating group on the benzene ring.
