Stereochemical course of the cyclization of olefinic aldehydes

Abstract

The stereochemistry of the homoallylic alcohols produced in the stannic chloride-catalysed cyclization of aldehydes (Ia), (Ib), and (IX), determined by X-ray crystallography and proton resonance data using lanthanide shift reagents, are consistent with a concerted intramolecular ‘ene reaction’ mechanism for the cyclization and afford the first example of a nearly undistorted twist-chair conformation for a cycloheptane.