Diels–Alder addition of the fumarate and acrylate of S-methyl lactate to α-hydroxy orthoquinodimethanes

Abstract

The cycloaddition of α-hydroxy orthoquinodimethane, generated photochemically from 2-methylbenzaldehyde, to the fumarate and acrylate of S-methyl lactate has been found to give a single diastereomer with high asymmetric induction (>95% de). This reaction provides a new and versatile synthetic route to substituted tetralins of high optical purity. A trans stereochemistry between the vicinal hydroxyl and carboxylactyl groups has been established for these cycloadducts. This is in contrast to previous work where cis stereochemistry has always been found for major cycloadducts of α-hydroxy o-QDMs. The high asymmetric induction, unusual diastereoselectivity, and the potential use of these reactions in asymmetric synthesis are discussed. Keywords: o-quinodimethanes, Diels–Alder, asymmetric, cycloaddition, induction, diastereoselective.