Asymmetric base-catalyzed cycloaddition between anthrone and some dienophiles

Abstract

Anthrone has been found to react with N-methylmaleimide in the presence of catalytic amounts of various chiral β-aminoalcohols. The cycloadduct 3a has been obtained in excellent yield with enantiomeric excess of up to 61%. Its absolute configuration has been assigned by X-ray crystallography. Several features of the reaction have been studied: variation of dienophile; competition between cycloaddition and formation of the optically active Michael adduct 4; solvent and temperature effects. Mechanistic studies are in agreement with a concerted [4+2] process, providing an unique case of a base-catalyzed asymmetric Diels-Alder reaction.