Synthesis of geometrically defined exocyclic olefins

Abstract

The treatment of bicyclic and tricyclic ketones with lithium ethynyl acetylide, followed by the addition of a catalytic amount of CSA or p-TSA, affords the corresponding exocyclic olefinic ester in good yields, and geometric ratios up to 13:1 favoring the cis olefin. This procedure represents an addition to the repertoire of olefination methods and can readily be extended to other cyclic and acyclic systems.