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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 N2 as the single byproduct. This procedure can be successfully applied to a one-pot process starting from terminal alkynes, azides, and dienes. |
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