Nickel-catalysed denitrogenative alkyne insertion reactions of N-sulfonyl-1,2,3-triazoles

N-Sulfonyl-1,2,3-triazoles reacted with alkynes in the presence of a nickel(0)/phosphine catalyst to give substituted pyrroles, with the extrusion of molecular nitrogen; the triazole moiety isomerised to an alpha-imino diazo species, and the denitrogenative addition to nickel(0) was followed by the insertion of alkynes and reductive elimination.