Reactions of indoles with nitrogen dioxide and nitrous acid in an aprotic solvent.
The reaction of 2-phenyl- and 1-methyl-2-phenylindole with nitrogen dioxide or with nitrous acid (NaNO2-CH3COOH) in benzene leads mainly to the formation of the isonitroso and 3-nitroso indole derivatives, respectively. When reacted with nitrous acid, 1-methyl-2-phenylindole gives also the corresponding azo-bis-indole in good yields. The reaction of indole with nitrogen dioxide leads to 2-(indol-3-yl)-3H-indol-3-one as the main product together with small amounts of 2-(indol-3-yl)-3H-indol-3-oxime; whereas the major product obtained when the same indole is reacted with nitrous acid is represented by 2-(indol-3-yl)-3H-indol-3-oxime. The reaction of 3-alkyl substituted indoles with nitrogen dioxide is rather complex and results in the formation of different nitro indoles, whereas nitrosation is observed when nitrous acid is used. Crystal structures of 2-(indol-3-yl)-3H-indol-3-one and of 4-nitro-N-acetyltryptamine have been determined by X-ray analysis.
Astolfi
Paola
P
Dipartimento di Scienze dei Materiali e della Terra, Università Politecnica delle Marche, via Brecce Bianche, I-60131, Ancona, Italy.
Panagiotaki
Maria
M
Rizzoli
Corrado
C
Greci
Lucedio
L
D009682:Magnetic Resonance Spectroscopy; D008958:Models, Molecular; D008968:Molecular Conformation; D009585:Nitrogen Dioxide; D009603:Nitroso Compounds / Q000138:chemical synthesis* / Q000737:chemistry*; D009608:Nitrous Acid; D011336:Probability; D012997:Solvents; D013053:Spectrophotometry
D009603:Nitroso Compounds; D012997:Solvents; D009585:Nitrogen Dioxide; D009608:Nitrous Acid