Rhodium(III)-Catalyzed Oxidative [3 + 2] Annulation of 2-Acetyl-1-arylhydrazines with Maleimides: Synthesis of Pyrrolo[3,4-b]indole-1,3-diones.

A rhodium-catalyzed oxidative [3 + 2] annulation of 2-acetyl-1-phenylhydrazines with maleimides was accomplished using AgNTf2 and Ag2CO3 as additive and oxidant, respectively. A variety of 2-acetyl-1-phenylhydrazines with maleimides were converted into pyrrolo[3,4-b]indole-1,3-diones in satisfactory to excellent yields. Synthetically useful functional groups, such as halogen atoms (F, Cl, Br, and I), ester, cyano, and nitro, remained intact during tandem C-H activation and annulation reactions.