ANNULATION VIA SEQUENTIAL MULTIFOLD MICHAEL REACTION - ONE ASPECT OF TERPENOID SYNTHESIS

The kinetic enolates or trimethylsityl enol ethers of 1-acetylcyclohexene undergo successive double Michael reactions with alpha,beta-unsaturated carbonyl compounds to give substituted decalones. The kinetic enolates of cyclohexenone provide bicyclo[2.2.2]octane derivatives via double Michael reaction. These double Michael reactions have been extended Lo bicycloannulation leading to tricyclo [4.4.0.0(1,5)] decane or tricyclo [3.2.1.0(2,7)] octane compounds by employing alpha-bromo-alpha,beta-unsaturated esters with cyclohexenone or 1-acetylcyclohexene, respectively. Divinylketone and the trimethylsilyl enol ethers of cyclohexenone undergo Lewis acid assisted triple Michael reactions yielding tricyclo[5.3.1.0(3,8)] undecane derivatives. These successive multifold Michael reactions have enabled the synthetic studies of epsilon-cadinene, khusitone, khusilal, isoeremolactone, ishwarane, and seychellene.