Concise synthesis of (+)-allo-kainic acid via MgI2-mediated tandem aziridine ring opening-formal [3 + 2] cycloaddition.

3-Methyl vinyl aziridine undergoes a mild MgI2-promoted S(N)2' ring opening and concomitant cyclization with fumarate Michael acceptors to give trisubstituted pyrrolidines. The process is efficient and highly diastereoselective. This methodology has been applied to a concise asymmetric synthesis of (+)-allo-kainic acid.