Carbon–Carbon Bond Formation by Reaction of Rhodium Azavinylcarbenes with Secondary Amides: Access to Indigo Analogues from Isatins

A novel protocol for the synthesis of unsymmetrical indigo-like (E)-α-amino enaminones by rhodium-catalyzed transformations of isatins with 1-tosyl-1,2,3-triazoles has been developed. A plausible reaction mechanism is proposed to account for the formation of structurally important unsymmetrical indigo analogues, which represents a new strategy for C–C bond formation based on the transformations of secondary amides and rhodium azavinylcarbenes.