Solvent strategy for unleashing the Lewis acidity of titanocene dichloride for rapid Mannich reactions

The remarkable activation effect of alcohol solvent on kinetically inert titanocene dichloride was found to promote rapid three-component Mannich reactions. NMR and ESI-MS analyses as well as a control experiment of catalytic active species elucidated that the coordination of MeOH to the titanocene moiety unleashed the Lewis acid [Cp-2-Ti(OMe)(2)] and Bronsted acid HCl, which led to the enhanced catalytic activity of [Cp2TiCl2].