Competitive intramolecular Diels-Alder reactions of bis-α,β-unsaturated ester derivatives of enzymatically derived and enantiopure cis-1,2-dihydrocatechols.: Enantiodivergent synthesis of monochiral bicyclo[2.2.2]oct-2-enes

bis-Crotonate and related alpha,beta-unsaturated ester derivatives of readily available and enantiomerically pure cis-1,2- dihydrocatechols engage, upon heating in refluxing toluene, in two competitive intramolecular Diels - Alder reactions to give varying mixtures of chromatographically separable and pseudo-enantiomeric bicyclo[2.2.2] oct-2-enes. Such adducts, many of which have been characterized by single-crystal X-ray analysis, are likely to serve as useful building blocks in natural products synthesis.