Synthesis and intramolecular photocycloadditions of 2-acyloxy-3-hexenoyl cyclohexenones: Diastereoselectivity in the intramolecular [2+2] photocycloadditions of alkenes and cyclohexenones tethered by four atoms

The intramolecular [2+2] photocycloaddition of 2-acyloxy-2-3-hexenoylcyclohexenones has been shown to be highly diastereoselective. The cycloadditions produce exclusively cis fused products and the sense and level of selectivity is consistent with a molecular mechanics model for initial bond formation in the stepwise cycloaddition. (C) 1997 Elsevier Science Ltd.