Aza‐[4+3] and Aza‐[3+2] Annulations for Synthesis of Dihydroazepines and Dihydropyrroles from Alkynes, Sulfonyl Azides, and 1,3‐Dienes

We report aza‐[4+3] annulation through sequential [3+2]‐[2+1] cycloadditions‐aza‐Cope rearrangement for the synthesis of dihydroazepines. Aza‐[3+2] annulation was achieved through [3+2]‐[2+1]‐aza‐Cope rearrangement‐1,3‐migration or [3+2]‐[2+1]‐Clock rearrangement, leading to the formation of dihydropyrroles. In addition, dihydroazepines thermally 1,3‐migrated to give dihydropyrroles. This method affords a straightforward synthetic pathway from simple triazoles to produce dihydroazepines and dihydropyrroles together with N 2 as the single byproduct. This procedure can be successfully applied to a one‐pot process starting from terminal alkynes, azides, and dienes.