Tandem cyclisation and [2,3]-Stevens rearrangement to 2-substituted pyrrolidines

Reaction of N-methylallylamine with diethyl meso-2,5-dibromoadipate in DMF at ambient temperature in the presence of potassium carbonate led directly to the two diastereomers of diethyl 2-allyl-N-methylpyrrolidine-2,5-dicarboxylate. The reaction proceeds via a [2,3]-sigmatropic Stevens rearrangement, which occurred spontaneously under the reaction conditions. This gave a higher yield under milder conditions than the traditional Stevens reaction of diethyl N-allylpyrrolidine-2,5-dicarboxylate with iodomethane. The sequence was a key step in the synthesis of a series of analogues of the alkaloid stemofoline.