A novel synthesis of 2-alkyl(aryl)pyrrolidines from proline via 2,3-diphenylhexahydropyrrolo[2,1-b]oxazoles

Diphenyloxapyrrolizidines, products of the reaction between proline and benzaldehyde, are convenient building blocks for synthesizing 2-substituted pyrrolidines. The opening of their oxazolidine ring by treatment with Grignard reagents has been performed and conditions for subsequent removal of the N-hydroxyethyl moiety have been found. Though the yields are moderate (36–42%), the suggested synthesis of 2-alkyl(aryl)pyrrolidines is rather simple since it does not require purification of intermediate products and is easy scalable.