5-En-1-yn-3-ol substrates bearing a free hydroxyl group or an acyl group are highly versatile partners for PtCl2-catalyzed cycloisomerizations. Electrophilic activation of the alkyne moiety triggers at wish a hydride or an O-acyl migration yielding at the end to regioisomeric keto derivatives. The efficient preparation of Sabina ketone, an important monoterpene precursor, has been worked out.
1,5-Enynes are highly reactive under PtCl2 catalysis and give a range of [3.1.0] bicyclic skeletons. The scope and limitations of this process are presented. Regioisomeric keto derivatives are obtained depending upon the nature of the oxygenated substituent at the propargylic position of the starting substrate.