Improved Process for Preparation of tert-Butanesulfinyl Ketimines of Hindered Ketones under Nitrogen Flow

An improved process for tert-butanesulfinyl ketimines formation using titanium(IV) alkoxides is described. This new protocol gives better results especially for sterically hindered ketones compared to classical conditions where titanium(IV) isopropoxide is found to be only moderately effective. We found that removal of isopropanol or ethanol from the reaction mixture either under a nitrogen flow or under vacuum dramatically increased reaction rate, extent of conversion, and yield of the reaction. This methodology has been exemplified on several substrates reported in the literature to be difficult.