Enantioselective α-Benzoyloxylation of β-Keto Esters by N-Oxide Phase-Transfer Catalysts.

An efficient and enantioselective α-benzoyloxylation of β-keto esters has been achieved by phase-transfer catalysis. This simple catalytic procedure is applicable to a range of β-keto esters with cinchona-derived N-oxide asymmetric phase-transfer catalysts and gives the corresponding products in good enantiopurity (up to 95% ee) and yield (up to 99%). This simple and effective oxyfunctionalization is a useful synthetic strategy for introducing an oxygen-containing functional group at the α position of β-dicarbonyl compounds.