Yb(NTf2)3-catalyzed [3 + 3] cycloaddition between isatin ketonitrones and cyclopropanes to construct novel spiro[tetrahydro-1,2-oxazine]oxindoles

Yb(NTf(2))(3)-catalyzed [3 + 3] cycloaddition between isatin ketonitrones and cyclopropanes is described. A variety of spiro[tetrahydro-1,2-oxazine]oxindoles were obtained in moderate to good yields along with good regioselectivities. This is the first example of the intermolecular [3 + 3] cycloaddition between ketone-derived nitrones and cyclopropanes.