Chiral non-racemic sulfoxides by asymmetric alkylation of alkanesulfenates in the presence of a chiral ammonium phase-transfer catalyst derived fromCinchonaalkaloid

Based on a previous study involving arenesulfenates, the enantioselective S-alkylation of benzyl and alkyl sulfenates R1SO− with alkyl halides, mediated by a cinchonidinium phase-transfer catalyst, was evaluated as a conceptually different synthetic approach to chiral sulfoxides. Direct application of our standard organocatalytic protocol, with methyl iodide as the electrophile, was rather disappointing mainly as a result of a sluggish release of the sulfur nucleophiles. However, slight modifications of the reaction conditions allowed the isolation of (R)-benzyl methyl sulfoxide in a 60% yield and a 38% ee, whereas (R)-cyclohexyl methyl sulfoxide was produced in a 34% yield and a 47% ee.