Enantioselective Synthesis of Spirooxindoles: Asymmetric [3+2] Cycloaddition of (3-Isothiocyanato)oxindoles with Azodicarboxylates

The catalytic asymmetric [3+2] cycloaddition of (3-isothiocyanato)oxindoles with azodicarboxylates has been explored in the presence of (DHQD)(2)PHAL. It affords spirooxindoles having two heterocycles at their C3-position in excellent yields, with high enantioselectivities, and under mild conditions within 5 min. Moreover, another spirooxindole derived from the reaction of (3-isothiocyanato)oxindole with two molecules of azodicarboxylate could also be formed in excellent yields with the same high enantioselectivities under the standard conditions.