Preparation of Tetrasubstituted 3‑Phosphonopyrroles through Hydroamination: Scope and Limitations

Phosphonylated pyrroles were obtained by a ZnCl₂-catalyzed 5-exo-dig hydroamination of propargylic enamines. These starting compounds were obtained in two steps from commercially available β-ketophosphonates. The method tolerates a wide variety of substituents at the 1,2- and 5-position of the pyrrole, while further derivatization allows for the introduction of substituents at the 4-position via lithiation or halogenation.