Accessing benzo[f]indole-4,9-diones via a ring expansion strategy: silver-catalyzed tandem reaction of tosylmethyl isocyanide (TosMIC) with 2-methyleneindene-1,3-diones

A silver-catalyzed tandem reaction of TosMIC with 2-methyleneindene-1,3-diones was developed for the direct synthesis of benzo[f]indole-4,9-diones. In this reaction, a domino [3+2]-cycloaddition/imidoyl anion cyclization/ring opening of cyclopropanolate/aromatization is proposed and three CC bonds are formed successively.