Pentadienyltitaniums as versatile intermediates: Regio- and stereoselectivities

The adduct obtained upon consecutive treatment of 1,4-dienes with butyllith ium in the presence of potassium tert-butoxide, chlorotri(isopropyloxy)tita nium and a carbonyl compound contains the alpha -hydroxyalkyl group invaria bly and exclusively linked to the 3-position of the former diene. When chlo rotri(isopropyloxy)titanium is replaced by the Duthaler-Hafner reagent [(4R ,5R)-chloro(cyclopentadienyl)(2,2-dimethyl-alpha,alpha,alpha',alpha'-tetrap henyl-1,3-dioxolane-4,5-dimethanolato-O,O-alpha)titanium] the reaction does not only occur regioselectively but also with appreciably high enantiosele ctivity.