Trans- cycloalkenes. Part 8. Bicyclic trans-cyclo-octenes constrained in chair and twist conformations

Abstract

Bicyctic trans-cyclo-octenes locked in twist (1) and chair (2) forms and their unsaturated analogues (18) and (19) have been synthesised. Key steps are: the Diels–Alder addition of the epoxide (7) to butadiene to generate (6) directly, ring-opening of the bicyclic epoxides (6) and (12) to give diastereoisomeric pairs of β-hydroxyphosphine oxides, and stereospecific fragmentation of the latter to the bicyclic trans-cyclo-octenes.