Enantioselective Benzylation and Allylation of α-Trifluoromethoxy Indanones under Phase-Transfer Catalysis

Abstract

The organo-catalyzed enantioselective benzylation reaction of α-trifluoromethoxy indanones afforded α-benzyl-α-trifluoromethoxy indanones with a tetrasubstituted stereogenic carbon center in excellent yield with moderate enantioselectivity (up to 57% ee). Cinchona alkaloid-based chiral phase transfer catalysts were found to be effective for this transformation, and both enantiomers of α-benzyl-α-trifluoromethoxy indanones were accessed, depended on the use of cinchonidine and cinchonine-derived catalyst. The method was extended to the enantioselective allylation reaction of α-trifluoromethoxy indanones to give the allylation products in moderate yield with good enantioselectivity (up to 76% ee).

Silver-Catalyzed Trifluoromethoxylation of Alkyl Trifluoroborates

“…The metabolic stability and lipophilicity of organic molecules could be increased by introducing “OCF 3 ” groups, which, in turn, can significantly change their biological properties (Scheme a). − Accordingly, developing new approaches to obtaining trifluoromethoxylated compounds has become a hot topic in synthetic organic chemistry. − Particularly, radical trifluoromethoxylation is becoming a promising tool to synthesize trifluoromethoxy-containing compounds. − For example, with the new N -OCF 3 reagents, the radical trifluoromethoxylation of arenes under photocatalytic conditions was reported by Ngai and Togni, respectively. − Our group has reported the silver-promoted oxidative benzylic C–H trifluoromethoxylation through a radical mechanism . However, site-specific radical trifluoromethoxylation is still challenging.…”