Selective Cu-Catalyzed Intramolecular Annulation of 3‑Aryl/Heteryl-2-(diazoacetyl)‑1H‑pyrroles: Synthesis of Benzo/Furo/Thieno[e]‑Fused 1H‑Indol-7-oles and Their Transformations

The Co­(III)-catalyzed reaction of 1,3-dicarbonyl compounds with 2-(diazoacetyl)-2H-azirines, prepared by a simplified procedure from 2H-azirin-2-carbonyl chlorides, led in high yields to the formation of 2-(diazoacetyl)­pyrroles, while leaving the diazoacetyl function intact. The intramolecular aromatic substitution reaction of 2-(diazoacetyl)­pyrroles, catalyzed by Cu­(OTf)2, provided selectively previously unknown benzo­[e]- and hetero­[e]-fused indol-7-oles in good yields. Formylation of benzo­[e]­indol-4-ol led selectively to the 5-formyl derivative, which is a good precursor for an unusual salen ligand and its Ni-complex. Triflates prepared from benzo­[e]­indol-4-oles gave various 4-substituted benzo­[e]­indoles carrying aryl, 2-thienyl, 2-pyridyl, and alkynyl groups, in excellent yields using cross-coupling reactions. 4-(2-Pyridyl)­benzo­[e]­indoles, upon treatment with BF3·Et2O/Et3N, afforded a new type of fluorescent boron complexes with large Stokes shifts.