Diels–Alder Reactions of d-Glucose-Derived Dienophiles with Cyclopentadiene: A Computational Study

AM1 and B3LYP calculations were performed for the Diels–Alder reactions of a series of d-glucose-derived dienophiles with cyclopentadiene. The preferred β vs. α diastereofacial addition and exo vs. endo selectivities are explained on the basis of products and transition states stabilities. Computed exo/endo ratios change in the correct direction although they do not agree quantitatively with available experimental data. The relative reactivity of the dienophiles bearing a carbonyl group can be interpreted in terms of FMO theory as well as of repulsive interactions in the corresponding transition states. The calculations fail to explain the observed lack of reactivity for the dienophile bearing a cyano group.