Mechanistic investigations in diastereoselective Diels–Alder additions of chiral 9-anthrylethanol derivatives

Abstract

The preparation and subsequent Diels–Alder addition reactions of chiral 9-functionalised anthracene derivatives have been investigated. 9-(1-Methoxyethyl)anthracene undergoes highly diastereoselective (>95 ∶ 5) thermal and photoinduced Diels–Alder additions with maleic anhydride and N-methylmaleimide. The corresponding reactions of 1-anthracen-9-ylethanol occur with the reverse sense of selectivity for additions with maleic anhydride with a corresponding increase in the reaction rate. The origins of this selectivity have been proposed to lie in hydrogen-bonding effects. The stereochemical outcome of the Diels–Alder additions has been determined from single X-ray crystallography of adducts 5 and 7. Solvent effects on the diastereoselectivity of these reactions have also been observed.