Azide-alkyne cycloadditions with an electronically activated alkyne: indole formation via 1-aryl-1,2,3-triazole-derived imino carbenes.

We report that the use of a diaminoalkyne in the azide-alkyne cycloaddition with aryl azides leads to 3 H -indoles under mild, uncatalysed conditions. Computations reveal that N 2 extrusion from, in one case, isolable triazoles is facile, generating imino carbenes, which undergo intramolecular aryl C-H bond activation and give 3 H -indoles as products.