Controlled Ru (II) & Rh (III) Catalyzed [4+2] & [4+1] Carbo‐Annulations via C−H Activation Using Sulfoxonium Ylide and Maleimide: Facile Access to Fused Benzoisoindole & Spiroindanone

A well‐ordered strategy of sulfoxonium ylides as a directing group as well as carbene source for the Ru‐catalysed [4+2] and Rh‐catalysed [4+1] carbo‐annulations with maleimides has been described. These novel methodologies have been successfully established for the synthesis of complex spiroindanones and benzoisoindoles containing compounds by the transition metal‐mediated C−H activation/functionalization reactions. Further, Rh‐catalysed [4+1] annulated compounds were obtained in the absence of any oxidant. A possible rationale for the remarkable divergent selectivity between the two catalysts has been proposed.