α-Regioselective Asymmetric [3+2] Annulations of Morita-Baylis-Hillman Carbonates with Cyclic 1-Azadienes and Mechanism Elucidation

An alpha-regio-, diastereo-, and,enantioselective [3 + 2] annulation reaction of Morita-Baylis-Hillman carbonates of isatins and activated alkenes with a bulky electron withdrawing 1,2-benzoisothiazole 1,1-dioxide or 1,2,3-benzoxathiazine 2,2-dioxide motif is reported, furnishing an array of spirooxindoles (>19:1 dr, up to, >99% ee) catalyzed by cinchona-derived tertiary amines. Density functional theory calculation studies have been conducted to elucidate the originality, of the alpha-regioselective annulations.