aza-Wittig Reaction with Nitriles: How Carbonyl Function Switches from Reacting to Activating

Transformations of α-EWG-substituted (electron-withdrawing group, EWG) γ-azidobutyronitriles proceeding via unusual aza-Wittig reactions between the phosphazene and nitrile functions and affording pyrrole-derived iminophosphazenes were developed. α-EWGs were found to control chemoselectivity and, depending on their nature, act as CN group activators (e.g., ester, amide, or nitrile) or competitors (e.g., ketone) in aza-Wittig reactions. To demonstrate the synthetic utility of the obtained iminophosphazenes as N,N-binucleophiles, their transformations into pyrrole-fused systems, pyrrolo[1,2-a]imidazoles and pyrrolo[1,2-a][1,3]diazepines, were carried out.