2.3- Dihydro-1 //-indole-2-sulfonic acid

Indigocarmine (2[l,3-dihydro-3-oxo-5-sulfo-2ff-indol-2-ylidene]-2,3-dihydro-3-oxo-lff-indole-5-sulfonic acid di-Na salt) [860-22-0] M 466.4, pK 2.8, pK2 12.3. Its... 

Treatment of l-ethylideneamino-3-methylindole 95 with p-toluene sulfonic acid in boiling benzene gave l,2-dihydro[l,2,4]triazino[l,6-a]indole 96 (75CPB2891). The reaction was said to be due to an initial formation of a Diels-Alder-type adduct followed by the liberation of 3-methylindole. Compound % was oxidized either on exposure to air or by the action of chloranil to give 97 (Scheme 24). 

FD C Blue No. 2 is principally the disodium salt of 2-(l,3-dihydro-3-oxo-5-sulfo-27/-indol-2-ylidene)-2,3-dihydro-3-oxo-17/-indole-5-sulfonic acid, with smaller amounts of the disodium salt of 2-(l,3-dihydro-3-oxo-7-sulfo-27/-indol-2-ylidene)-2,3-dihydro-3-oxo- l//-indole-5-sulfonic acid and the sodium salt of 2-(l,3-dihydro-3-oxo-2//-indol-2-ylidene)-2,3-dihydro-3-oxo- 17/-indole-5-sulfonic acid. 

Disodium Salt of 2-( 1,3-Dihydro-3-oxo-7-sulfo-2H-indol-2-ylidene)-2,3-dihydro-3-oxo-lH-indole-5-sulfonic Acid Not more than 18%. 

Indigocarmine (2[l,3-dihydro-3-oxo-5-sulfo-2ff-indol-2-ylidene]-2,3-dihydro-3-oxo-lff-indole-5-sulfonic acid di-Na salt) [860-22-0] M 466.4, pKj 2.8, p K 12.3. Its solubility in H2O is Ig/lOOmL at 25°. It has been purified by dissolving in H2O, filtering and adding EtOH to cause the salt to separate. Wash the solid with EtOH, Et20 and dry in vocmo. [V6rlander Schubert C/jem Ber 34 1860 1901, UV Smit et al. Anal Chem 27 1159 1955, Preisler et al. J Am Chem Soc 81 1991 1959, Beilstein 25 IV 1975.]... 

Dihydro-2,3-dioxo-1 H-indole-5-sulfonic acid. See Sodium 5-isatinsulfonate... 

Synonyms 2,3-Dihydro-2,3-dioxo-1 H-indole-5-sulfonic acid 2,3-Dioxo-5-indolinesulfonic acid, sodium salt 1H-lndole-5-sulfonic acid, 2,3-dihydro-2,3-dioxo-, sodium salt 5-Indolinesulfonic acid, 2,3-dioxo- 5-Isatinsulfonic acid, sodium salt lsatin-5-sulfonic acid, sodium salt Sodium 2,3-dihydro-2,3-dioxo-1H-indole-5-sulfonate Sodium 2,3-dioxo-5-indolinesulfonate Sodium 5-sulfoisatin 5-Sulfoisatin, sodium salt Empirical CsHsNOsS Na Properties Orange powd. sol. 5-10 mg/ml in water sol. < 1 mg/ml in DMSO, 95% ethanol, acetone m.w. 249.18 m.p. > 300 C Toxicology May be harmful by inh., ing., or skin absorp. irritating to eyes, skin, mucous membranes, upper respiratory tract Precaution Probably combustible incompat. with strong oxidizing agents Hazardous Decomp. Prods. Toxic fumes of CO, CO2, NOx, SOx emits toxic fumes underfire conditions... 

Zohuri et al. (2013) synthesized novel 2,9-dihydro-2-oxo-4-aryl-l//-pyrido[2,3-fc] indole-3-carbonitrile derivatives by condensation of substituted (triethoxymethyl) arene, l-methyl-lH-indol-2-ol, and cyanoacetamide using catalytic amounts of crosslinked poly(2-acrylamido-2-methyl propane sulfonic acid) (AMPS) as an efficient and heterogeneous catalyst (Scheme 2.10). This polymeric solid acid catalyst is stable and can be easily recovered and reused without significant change in its... 

CA Index Name l//-Indole-5-sulfonic acid, 2-(l,3-di-hydro-3-oxo-5-sulfo-2//-indol-2-ylidene)-2,3-dihydro-3-OXO-, sodium salt... 

Bennasar extended his research on 2- and 3-indolylacyl radicals to intramolecular cyclizations to yield 2,3-fused indoles [112], Under nomeductive conditions (n-Bu6Sn2, hv), radical 201 underwent a cascade addition-oxidative cyclization sequence with a number of alkene acceptors including dimethyl fumarate (45%), methyl 1-cyclohexenecarboxylate (53%), methyl crotonate (71%), vinyl sulfone (22%), and the a,p-unsaturated lactam ester, 2-oxo-5,6-dihydro-2H-pyridine-l,3-dicarboxylic acid dibenzyl ester (41%) to form cyclopenta[h]indol-3-ones 202. Reaction of 201 with acrylonitrile and methyl acrylate, however, generated cyclo-hepta[h]indoles, the products of bis-addition-cyclization sequences. 

Two isomers occur within indigo carmine, reflecting different sulfonation points on the molecule disodium 3,3 -dioxo-[d -biindoline]-5,5 -disulfonate and disodium 3,3 -dioxo-[D -biin-doline]-5,7 -disulfonate (also given as 2-(l,3-dihydro-3-oxo-5-sulfo-2H-indol-2-ylidene)-2,3-dihydro-3-oxo-lH-indole-5-sulphonic acid disodium salt Merck Index, 1992). It is prepared by treatment of indigo with sulfuric acid. 

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