Chemoselective phosphine-catalyzed cascade annulations between two different activated alkenes: highly diastereoselective syntheses of polysubstituted cyclohexanes and cyclopentenes.

Chemoselective phosphine-catalyzed cascade [2 + 2 + 2] and [2 + 2 + 1] annulations between two molecules of 2-arylmethylidene cyanoacetates or malononitriles and one molecule of α,β-unsaturated ketones have been developed. Under the nucleophilic catalysis of PPh(3) or PBu(3) (10 mol%), a highly diastereoselective synthesis of polysubstituted cyclohexanes or cyclopentenes has been successfully achieved, respectively.