Enantioselective α-Benzoyloxylation of Malonic Diesters by Phase Transfer Catalysis

A highly enantioselective alpha-benzoyloxylation of malonic diester has been achieved by phase-transfer catalysis. The reaction of alpha-monosubstituted tent-butyl methyl malonate with benzoyl peroxide in the presence of aqueous KOH and N-(9-anthracenylmethyl)cinchoninium chloride afforded the corresponding alpha,alpha-disubstituted products in generally excellent chemical yields (up to 99% yield) with high enantioselectivities (up to 96% ee). In addition, the utility of this methodology was exhibited by the synthesis of a mineralocorticoid receptor antagonist.