Reactivity and Diastereoselectivity in the Diels-Alder Reaction of o-Quinodimethanes. An Experimental and DFT Computational Study

Endo–exo Selectivity in Diels–Alder cycloadditions of several o-quinodimethanes (1–4) with acrylonitrile, 2-(5H)-furanone and N-methylmaleimide has been investigated in acetonitrile solution. Theoretical data reproduce fairly well both experimental absolute reaction rates and diastereoisomer ratios. The high endo selectivity has been rationalized mainly as a result of solvation effects (acetonitrile, PCM model) and reactant deformations. The latter is due to steric interactions.