Recrossing and Dynamic Matching Effects on Selectivity in a Diels–Alder Reaction

Up and down the hill: The products from the hetero-Diels–Alder reaction of acrolein with methyl vinyl ketone arise from a single transition state (see scheme) and trajectory studies accurately predict the selectivity. In an extension of the dynamic matching idea of Carpenter, the product formed is determined by the direction of motion passing through the transition state. Recrossing occurs extensively and decreases formation of the minor product.