Phenylsulphonyloxiranes as functionalised acyl anion equivalents in organic synthesis

Phenylsulphonyloxiranes can be lithiated with butyllithium α to the phenylsulphonyl group at low temperature. The anions formed are unstable, but sufficiently reactive to allow the isolation of adducts in good yield following treatment with a variety of electrophiles. Reaction of functionalised phenylsulphonyloxiranes with magnesium bromide–diethyl ether at room temperature allows the preparation of synthetically useful α-bromo ketones with complete regiocontrol.