ASYMMETRIC INTRAMOLECULAR ENE REACTION CATALYZED BY A CHIRAL TITANIUM REAGENT AND SYNTHESIS OF (-)-EPSILON-CADINENE

A highly diastereo- and enantio-selective intramolecular ene reaction was developed by employing a chiral titanium reagent generated in situ from TiCl2(OPr(i))2 and a tartrate-derived chiral 1,4-diol. This reaction afforded masked cyclohexanone and cyclopentanone derivatives with high optical purities which were synthetically useful chiral building blocks. From the intramolecular ene product (-)-epsilon-cadinene was synthesized by the use of the newly developed intramolecular Michael reaction.