Enantioselective Trifluoromethylation of Ketones with (Trifluoromethyl)trimethylsilane Catalyzed by Chiral Quaternary Ammonium Phenoxides
作者:Hitoshi Nagao、Yoshikazu Kawano、Teruaki Mukaiyama
DOI:10.1246/bcsj.80.2406
日期:2007.12.15
Chiral quaternary ammonium phenoxides were prepared readily from commercially available cinchona alkaloids and employed as novel useful asymmetric organocatalysts. Among these chiral quaternary ammonium phenoxides, a cinchonidine-derived phenoxide that possesses a sterically hindered N(1)-3,5-bis[3,5-bis(trifluoromethyl)phenyl]benzyl group was the most effective for asymmetric trifluoromethylation. In the presence of a catalytic amount of Lewis bases, such as cinchonidine-derived quaternary ammonium phenoxides, catalyzed the reaction of various ketones with (trifluoromethyl)trimethylsilane to afford the corresponding trifluoromethylated adducts in high yields and with moderate to high enantioselectivities.
手性四级铵酚氧化物是通过商业可得的金雀花生物碱制备的,并作为新型有用的非对称有机催化剂。在这些手性四级铵酚氧化物中,来源于金雀花碱的酚氧化物,具有空间位阻的N(1)-3,5-双[3,5-双(三氟甲基)苯基]苄基,是用于非对称三氟甲基化的最有效的催化剂。在存在少量路易斯碱(如来源于金雀花碱的四级铵酚氧化物)的条件下,催化了各种酮与(三氟甲基)三甲基硅烷的反应,从而以高产率和中到高的对映选择性获得相应的三氟甲基化加合物。