How Lewis Acids Catalyze Ene Reactions

The catalytic effect of various Lewis acids (LAs) on the ene reaction between propene (ene) and but‐3‐en‐2‐one (enophile) was studied quantum chemically using density functional theory and with coupled‐cluster theory. The studied LAs efficiently accelerate the ene reaction by lowering the reaction barrier up to 12 kcal mol −1 compared to the uncatalyzed reaction. Our detailed activation strain and Kohn‐Sham molecular orbital analyses reveal that...