Modular Synthesis of Highly Substituted 3-Azapyrroles by Rh(II)-Catalyzed N–H Bond Insertion and Cyclodehydration

[Image: see text] A modular synthesis of highly substituted 3-azapyrroles has been developed using a three-step sequence comprising copper-catalyzed alkyne–azide cycloaddition (CuAAC), N–H bond insertion, and cyclodehydration. 1-Sulfonyl-1,2,3-triazoles (1-STs) can be accessed from common alkyne and sulfonyl azide building blocks by CuAAC using CuTC. Rhodium(II)-acetate-promoted 1-ST denitrogenation results in highly electrophilic rhodium azavinyl carbenes that, here, underwent insertion into the N–H bond of secondary α-aminoketones to form 1,2-aminoalkenes. These products were cyclized and dehydrated using BF(3)·OEt(2) into highly substituted 3-azapyrroles. The three steps (CuAAC, N–H bond insertion, and cyclodehydration) could be telescoped into a one-pot process. The method proved to be highly efficient and tolerated a wide range of substituents.