Perkin communications. Stereochemistry of substituted 1-alkoxybicyclo[2.2.2]octenes; Diels–Alder synthesis versus Tandem-Michael strategy

Abstract

Diets–Alder reactions of 1 -methoxy- and 1 -ethoxy-cyclohexa-1,3-dienes with ethyl cinnamate or ethyl 4,4,4-trifluorocrotonate favour the (1RS,2RS,3SR,4RS)(exo-carboxylate) bicyclo[2.2.2]octene stereochemistry, 5,6,9, whereas the bicyclo-octenes derived from 3-alkoxycyclohex-2-enones by Tandem-Michael additions are obtained exclusively as the (1RS,2SR,3RS,4RS)(endo-carboxylate) isomers 16.