Construction of 2,3-Dihydropyrrolo[3,4- b ]Indol-1(4H)-Ones by Formal [3+2] Annulation of 2-Vinylindoles with Isocyanates

An efficient synthesis of the 2,3-dihydropyrrolo[3,4-b]indol-1(4H)-ones has been developed via BF3OEt2-promoted formal [3 + 2] annulation of 2-vinylindoles with isocyanates. The reaction features mild conditions and a broad substrate scope, showing excellent functional group tolerance toward various substituents on both the 2-vinylindole and the isocyanate partners. This protocol provides a facile and practical approach, holding significant potential for the synthesis of bioactive heterocyclic compounds and related pharmaceutical intermediates.