Reaction of 1-Chlorovinyl p-Tolyl Sulfoxides with Carbanion of Acetonitrile: A Novel Synthesis of Cyclopentanone Derivatives with Three Consecutive Carbon–Carbon Bond-Formations via the Enaminonitriles

Treatment of 1-chlorovinyl p-tolyl sulfoxides derived from ketones with cyanomethyllithium gave cyclopentadienyl enaminonitriles in high yields with three consecutive carbon–carbon bond-formations. However, the 1-chlorovinyl p-tolyl sulfoxides derived from aldehydes did not give good results. The mechanism of this reaction and the reaction of the enaminonitriles to convert cyclopentanone derivatives were investigated. Several α-carbanion of nitriles other than acetonitrile added to the 1-chlorovinyl p-tolyl sulfoxides at low temperature in good yield; however, they did not cyclize upon warming to room temperature.