Aqueous ethanol: a suitable medium for the diastereoselective Diels–Alder reaction mediated by chiral bases

The effect of aqueous ethanol medium on the outcome of a Diels–Alder (DA) reaction with regard to yields, reaction time, and the stereoselectivity observed has been studied. When the reaction between anthrone and (R)-(+)-N-α-methylbenzylmaleimide was carried out in aqueous ethanol in presence of achiral base no diastereoselectivity could be obtained. Moderate diastereoselectivity could be achieved in presence of chiral bases. Use of biodegradable aqueous ethanol solvent for the reaction and stereoselective nature of the reactions studied provide a greener approach.