Catalyst‐ and Base‐Free Asymmetric Synthesis of Functionalized Prolines via One‐Pot Cascade Reactions.

A one pot, three‐step cascade reaction to provide functionalized proline derivatives was developed. The Michael addition reaction of N‐allylated proline and activated alkyne forms a zwitterionic intermediate that further undergoes cyclization and [2,3]‐rearrangement to provide Cα‐alkylated proline bicyclic derivatives. This transformation was highly stereoselective and the chirality of the N‐allylated prolines was completely transferred to the product via a C−N−C chirality transfer process. The developed reaction is operationally simple and does not require any reagents other than the substrates. [ABSTRACT FROM AUTHOR]