Organocatalytic Asymmetric Neber Reaction for the Synthesis of 2H-Azirine Carboxylic Esters

The first enantioselective Neber reaction of beta-ketoxime sulfonates catalyzed by a bifunctional thiourea has been developed. The reaction proceeds stereoselectively with 5 mol % of the catalyst to give the 2H-azirine carboxylic esters in good yields with up to 93% ee. In addition, the resulting azirines can be successfully employed in the stereoselective synthesis of di- and trisubstituted aziridines.