Enantioselective phase-transfer catalytic α-alkylation of 2-methylbenzyl tert-butyl malonates

Abstract

A new asymmetric synthetic method to prepare alpha,alpha-dialkylmalonates for the construction of a quaternary carbon center via phase-transfer catalytic (PTC) alkylation has been developed. Enantioselective alpha-alkylation of 2-methylbenzyl tert-butyl alpha-methylmalonates under phase-transfer catalytic conditions in the presence of (S,S)-3,4,5-trifluorophenyl-NAS bromide (10) afforded the corresponding alpha,alpha-dialkylmalonates in high chemical (up to 99%) and optical yields (up to 91% ee), which were selectively hydrolyzed to malonic monoacids under alkali basic conditions for conversion to versatile chiral intermediates.