Pyridinium ylide-assisted one-pot two-step tandem synthesis of polysubstituted cyclopropanes.

A sequential one-pot two-step tandem reaction for efficient synthesis of polysubstituted cyclopropanes has been developed. The three-component reaction of alpha-halogenated methylene compounds, aromatic aldehydes, and acetonitrile derivatives produced first the intermediates pyridinium salts and electron-deficient olefins, followed by cyclopropanation of pyridinium ylide with electron-deficient olefins in situ to afford polysubstituted cyclopropanes. Target compounds were obtained in high yields and were diastereomerically pure after recrystallization.