17646-95-6

Upstream product

• 120-72-9 indole 
• 586-96-9 Nitrosobenzene 
• 104-15-4 toluene-4-sulfonic acid 

Relevant academic research and scientific papers

Indigo dye production by enzymatic mimicking based on an iron(III)porphyrin

A novel indigo synthesis is based on a simple and cost-effective model system of the enzymes involved in the natural and biocatalytic productions. The method considers the oxidation of indole by hydrogen peroxide, being catalyzed by an iron(III)porphyrin in ethanol, as solvent, and no other additives. The yields of indigo and of the other oxidized indolinoid derivatives were found to be dependent on the metalloporphyrin system used and on the control of the oxidation conditions. Significant reductions of the environmental impact relatively to the present industrial production and of the costs relatively to the biocatalytic methodologies were obtained. The enhanced indigo production in the presence of the iron(III)porphyrin-ethanol catalytic system relatively to the manganese(III)porphyrin-acetonitrile system can be rationalized by the formation of different active species in the two systems.

Acid-promoted competing pathways in the oxidative polymerization of 5,6- dihydroxyindoles and related compounds: Straightforward cyclotrimerization routes to diindolocarbazole derivatives

Oxidation of 5,6-dihydroxyindole (1a) in acidic aqueous media led to isomeric hexahydroxydiindolocarbazoles, isolated as the acetyl derivatives 5a (29%) and 6a (19%). When the reaction is stopped in the very early stages, small amounts of the indolylindoline 17 and the open trimer 18 can be isolated. Similar oxidation of the N-methyl (1b) and O,O-dimethyl (1c) derivatives of 1a, as well as of 5-methoxyindole (9b), 6-hydroxyindole (14a), and 6-benzyloxyindole (14b), afforded the corresponding diindolocarbazoles 5b and 6b, and 6c, 10, 16, and the related tetramer 15 in up to 70% overall yield, whereas 5,6-diacetoxyindole (1d), 5-hydroxyindole (9a), and indole failed to give cyclotrimerization products. Formation of diindolocarbazoles could be explained by a mechanism in which the electron-donating substituents propitiate an array of acid-induced couplings and subsequent dehydrogenation steps driven by the energetically favorable closure of the fused aromatic framework.

Biomimetic oxidation of indole by Mn(III)porphyrins

The oxidation of indole under biomimetic conditions in the presence of Mn(III)porphyrins and using hydrogen peroxide as a green oxidant is described. The metalloporphyrins act as chemical models of the enzymes involved in the natural and biocatalytic oxidation of indole to afford indigo dye, but leading to simplified systems, with significantly lower cost requirements, as higher indole conversions and easier product isolation are obtained. The distribution of the products that include 2-oxoindole, isatin, 2,2′-bis(3′- indolyl)-3-oxoindole and the indigoid pigments, indigo and indirrubin, was found to be dependent on the reaction time, the amount of oxidant and the electronic characteristics of the metalloporphyrin catalyst. Upon 30 min of reaction time, 85% of indole conversion was achieved. The best conditions for pigment formation and isolation included the separation of the initially formed 3-indoxyl from the oxidizing reaction mixture, followed by heating to obtain the air oxidative dimerization.

Metal-free catalyzed oxidative trimerization of indoles by using TEMPO in air: A biomimetic approach to 2-(1H-indol-3-yl)-2,3′-biindolin-3-ones

A simple, convenient and efficient metal-free catalyzed oxidative trimeric reaction of indoles toward a variety of 2-(1H-indol-3-yl)-2,3′-biindolin- 3-one derivatives in moderate to excellent yields has been developed. This transformation proceeds via a tandem oxidative homocoupling reaction by using TEMPO in air as an environmentally benign oxidant. This methodology provides an alternative approach for the direct generation of all-carbon quaternary centers at the C3 position of indoles. This journal is

Oxidative trimerization of indole: On the formation of dications and radical cations by reaction of indole and nitrosobenzene in the presence of acids

The reactions of indole with nitrosobenzene in the presence of acetic, monochloroacetic, monobromoacetic and trichloroacetic acid afford as the main product a deep-green precipitate, which in a preceding study had been erroneously identified as the aminyl radical of a trimer indole. The identity of the minor products was confirmed. This paper deals with the determination of the correct structure of the compounds contained in the precipitate through a study based on chemical reactions, electrochemical measurements and X-ray analysis.