Iodine-Catalyzed Aerobic Diazenylation–Amination of Indole Derivatives

Abstract

A mild strategy for consecutive diazenylation and amination of indole moieties has been demonstrated. The functionalization occurs at C3 and C2 carbon atoms, respectively, at the indole scaffold in the presence of catalytic iodine and air at 40 °C in the 1,1,1,3,3,3-hexafluoroisopropanol (HFIP) solvent. It is noteworthy that the aromatic amines are generated in situ by the reaction of aryl hydrazine with iodine. In general, bright red products are obtained in moderate to good yield. Control reactions are conducted to establish the reaction mechanism.

HFIP in Organic Synthesis

“…A mild diazenylation–amination of indoles at C2 and C3 is effected by treatment with aryl hydrazines and catalytic I 2 in HFIP under aerobic conditions (Scheme ). HFIP provided the best yields of the diazenylated product when compared to MeCN, THF, DCM, DCE, EtOH, and TFE. Added oxidants other than air provided more complex reaction mixtures.…”

Iodine-Catalyzed Cascade Annulation of 4-Hydroxycoumarins with Aurones: Access to Spirocyclic Benzofuran–Furocoumarins

“…Molecular iodine, as a very simple and efficient reagent, has drawn considerable attention from synthetic chemists, and has been widely used in various organic transformations [30,31]. It is widely available, inexpensive, nontoxic, eco-friendly, and moisture resistant, and employed as a catalyst, resulting in the formation of new C-C [32,33], C-N [34,35], C-O [36], and C-S [37,38] bonds. In addition, molecular iodine has been recognized as a powerful tool for constructing the pharmacologically important heterocyclic rings [39][40][41].…”

Oxidative C–H Acyloxylation of Acetone with Carboxylic Acids under Iodine Catalysis

“…Iodine has been applied widely as an effective catalyst for the functionalization of cyclic compounds. It shows good catalytic activity in the sulfenylation of indoles 21 and pyrazolones, 22 selenylation of 2H-indazole, 23 C-3 benzylation 24 and consecutive diazenylation/amination 25 of indoles, diazenylation of N-heterocyclic compounds, 26 C-N bond-forming of heterocyclic thiols and thiones, 27 arylation of substituted 1,4-naphthoquinones, 28 and rearrangement of 3-aminoindazoles. 29 Iodine-catalyzed systems have also been a good choice for oxidative transformations.…”