Diastereoselectivity in the synthesis of bicyclic titanacyclopentenes from chiral 6-hepten-1-ynes

A variety of chiral 6-hepten-1-ynes have been found to undergo cyclization to titanabicyclopentenes by (η2-propene)Ti(Oi-Pr)2 with excellent yields and degrees of exo-stereoselectivity depending on the substrate steric requirements. In the framework of a plausible cyclization mechanism several conformational features which can regulate the stereoinduction have been suggested.