Direct organocatalytic asymmetric α-oxidation of ketones with iodosobenzene and N-sulfonyloxaziridines

The novel, direct amino acid-catalyzed α-oxidation of ketones with iodosobenzene and N-sulfonyloxaziridines is presented. A screen of several synthetically common oxidants revealed that iodosobenzene and N-sulfonyloxaziridines act as electrophiles in the direct organocatalytic asymmetric α-hydroxylation of ketones. The direct proline-catalyzed asymmetric α-oxidation of ketones with iodosobenzene yielded the corresponding α-hydroxylated ketones with up to 77% ee. Furthermore, several amino acid derivatives catalyze the stereoselective α-oxidation of ketones with N-sulfonyloxaziridines. For example, the direct diamine-catalyzed enantioselective α-hydroxylation of ketones with N-sulfonyloxaziridines furnished the corresponding α-hydroxylated products in moderate yield with up to 63% ee.