A Synthesis of an Isoindole Derivative

Isoindole or 1H-isoindole, where there is the possibility of tautoinerism, is too unstable to be isolated, and its existence is ascertained only by Diels-Alder addition products with maleic anhydride and N-phenylmaleinimide.¹⁾ Moreover, the systematic preparations of isoindole derivatives have not been confirmed.²⁾ However, several successful isoindole syntheses have been realized from ortho-disubstituted benzene derivatives. For instance,³⁾ catalytic reduction over Raney nickel of o-cyanobenzophenone gave 1-phenylisoindole, accompanied by the oxidative coupling product. We wish to report now a synthesis of an isoindole derivative (2) by the dimerization of o-tolunitrile and several reactions of the compound (2), and the physical data were also reported.