Ln(OTf)(3)-catalyzed insertion of aryl isocyanides into the cyclopropane ring

The insertion of two molecules of an aryl isocyanide into bisacceptor-activated cyclopropane derivatives has been observed for the first time. The reaction proceeds best under the catalysis of Pr(OTf)(3) and offers a facile access to the synthetically useful and potentially pharmacologically relevant substituted dialkyl 3-(arylamino)-2-(arylimino)cyclopent-3-ene-1,1-dicarboxylates in moderate yields (21-65%).