An unusual example of stereoelectronic control in the ring opening of 3,3-disubstituted 1,2-dichlorocyclopropenes

Abstract

Quantitative SCF-MO calculations at the PM3 and ab initio level reveal that the origin of the stereoselective ring opening of 1,2-dichloro-3,3-disubstituted cyclopropenes (1, R²= CH₂Cl, CH₂OMe or CH₂Ph) to give vinylcarbenes 2via transition state 5 arises from stereoelectronic control, in contrast to that of cyclopropenes having bulky non-polar substituents such as R²= Prⁱ which favours a less hindered transition state 6.