The Diels-Alder Reaction of 3-Acetoxy-1-vinylcyclohexene with Methyl Vinyl Ketone

Abstract

The Diels-Alder reaction of 3-acetoxy-1-vinylcyclohexene (1c) with methyl vinyl ketone (MVK) at 110 and 150°C gave predominantly the adducts 1-acetoxy-8-acetyl-8aβH-4a(5)-octalin, 3b (8βH) and 3a (8αH), respectively, along with other minor adducts. The stereochemistry of 3a was independently confirmed by X-ray crystallographic analysis of the p-bromobenzoate (3e) derived from 1-desacetyl-3a(3d). The predominant approach of the dienophile (MVK) to 1c was found to have occurred anti to the allylic acetate group, contrary to the empirical rule proposed recently.