Olefin–olefin reactions mediated by Lewis acids may afford cyclopropanes rather than cyclobutanes: a mechanistic study of cyclopropane formation using a 1-seleno-2-silylethene

Abstract

The mechanism of the novel [2 + 1] cycloaddition reaction of 1-seleno-2-silylethenes has been investigated using DFT (density functional theory) calculations. This study revealed a remarkable reaction path; the silicon migration and cyclopropane ring closure occur concertedly with the aid of eight-membered cyclic Se–metal (in the Lewis acid) coordination. The transition state for the crucial silicon-shift and ring-closure steps was obtained. The structures show that a through-space Se–metal (Sn or Zn) interaction causes three-membered ring closure. Cyclopropane vs. cyclobutane product selectivity was elucidated by these calculations.