Synthesis of 3-benzylidene-1-methylpyrrolidin-2-one through 3-chloromethylene-1-methylpyrrolidin-2-one.

Introduction of a carbon chain in the -position of amides is a common step to many organic synthesis. Here we describe an improvement in a simple way to achieve 3-chloromethylene-1-methylpyrrolidin-2-one 2, and its reaction with phenyllithium/CuCN to afford 3-arylidene-1-methylpirrolidin-2-one (3), this would represent an approach to a kind of carbon skeleton present in a wide variety of pharmacologically active compounds1. The preparation of 2 was previously reported2 by addition of dichlorocarbene to N-methyl-2-pyrrolidone (1) under phase transfer catalysis (PTC), but the yield reported , using Bu4NCl, was too low (30%) to make it a practical way to achieve 2 in a preparative scale.