The mechanism of stereoselectivity in the cycloaddition reactions of α-hydroxy-ortho-quinodimethanes with the fumarate of methyl lactate and mandelate

Abstract

The Diels-Alder cycloaddition reaction of the fumarate of methyl lactate or methyl mandelate with a-hydroxy-orthoquinodimethane produces an unexpected exo product with very high asymmetric induction. Experiments and calculations have been carried out that show that the origin of the stereoselectivity in these reactions is related to hydrogen bonding between the a-hydroxy-o-quinodimethane and the lactate or mandelate group in the dienophile. La reaction de cycloaddition de Diels-Alder du fumarate du lactate de mCthyle ou du mandelate de methyle avec l'ahydroxy-ol-tho-quinodimethane conduit a un produit exo inattendu, avec une induction asymCtrique trks ClevCe. On a effectuC des experiences et des calculs qui montrent que l'origine de la stCrCosClectivitC de ces rkactions est relike a la liaison hydrogkne entre 1'a-hydroxy-ortho-quinodimethane et le groupe lactate ou mandClate du dienophile.[Traduit par la redaction]