Stereoselective Titanium-Mediated Aldol Reactions of a Chiral Lactate-Derived Ethyl Ketone with Ketones

Aldol reactions of
titanium enolates of lactate-derived ethyl ketone 1 with
other ketones proceed in a very efficient and stereocontrolled
manner provided that a further equivalent of TiCl4 is added
to the reacting mixture. The scope of these reactions encompasses
simple ketones such as acetone or cyclohexanone as well as other ketones
that contain potential chelating groups such as pyruvate esters or
α- and β-hydroxy ketones.