Enantioconvergent photoredox radical-radical coupling catalyzed by a chiral-at-rhodium complex  

作　　者：Zijun Zhou Xin Nie Klaus Harms Radostan Riedel Lilu Zhang Eric Meggers 

机构地区：[1]Fachbereich Chemie, Philipps-Universit?t Marburg

出　　处：《Science China Chemistry》2019年第11期1512-1518,共7页中国科学（化学英文版）

基　　金：supported by the Deutsche Forschungsgemeinschaft(ME 1805/17-1)

摘　　要：Racemicα-chloro imidazol-2-yl-ketones undergo an enantioconvergent photoactivated C–C bond formation with N-aryl glycines catalyzed by a single bis-cyclometalated chiral-at-rhodium catalyst in yields of up to 80%and up to 98%enantiomeric excess(ee).Control experiments support a mechanism which is initiated by a single electron transfer from N-aryl glycinate to the photochemically excited rhodium-boundα-chloro imidazol-2-yl-ketone,followed by chloride fragmentation of theα-chloroketone,decarboxylation of the glycinate,and a subsequent highly stereocontrolled radical-radical coupling.This work showcases the ability of the chiral rhodium catalyst to serve a dual function as chiral Lewis acid and at the same time as the photoredox active species upon substrate binding.Racemic α-chloro imidazol-2-yl-ketones undergo an enantioconvergent photoactivated C–C bond formation with N-aryl glycines catalyzed by a single bis-cyclometalated chiral-at-rhodium catalyst in yields of up to 80% and up to 98% enantiomeric excess(ee). Control experiments support a mechanism which is initiated by a single electron transfer from N-aryl glycinate to the photochemically excited rhodium-bound α-chloro imidazol-2-yl-ketone, followed by chloride fragmentation of the α-chloroketone, decarboxylation of the glycinate, and a subsequent highly stereocontrolled radical-radical coupling. This work showcases the ability of the chiral rhodium catalyst to serve a dual function as chiral Lewis acid and at the same time as the photoredox active species upon substrate binding.

关 键 词：PHOTOREDOX CATALYSIS asymmetric CATALYSIS VISIBLE light enantioconvergent RADICAL recombination chiral-at-metal RHODIUM 

分 类 号：O62[理学—有机化学]