Origins of Diastereoselectivity in Lewis Acid Promoted Ketene Alkene [2+2] Cycloadditions

A detailed analysis of a Lewis acid promoted ketene-alkene [2 + 2] cycloaddition is reported. The studies have led to a rationalization for an observed inversion of diastereoselectivity between thermally induced and Lewis acid promoted ketene-alkene [2+2] cycloadditions. The model is supported with both experimental and computational results.