CP2TiCl2-catalyzed hydroalumination of internal alkynes: an access to (Z)-olefins

The reduction of alkynols with LiAlH4 in diglyme is a long known process leading to the formation of (E)-alkenols. We have, by serendipity, found that, in the presence of a catalytic amount (10%) of Cp2TiCl2, the stereoselectivity of the reaction is reversed, leading to the selective formation of the (Z)-alkenols. The scope and limitations of this methodology and a postulated catalytic cycle are also discussed.