Isoindigo

Indigo is considered as one of the most important dyes. Its preparations are usually analysed by HPLC with UV-Vis [46,60] or APCI MS detection. [61,62] Separation of the colouring components of indigo extracted with DMSO is usually performed with the use of a Cl 8 column. Spectrophotometric detection of blue indigotin is performed at 617 nm, red indirubin at 540 nm, and brown isoindigo at 365 and 490 nm. As mobile phases, mixtures of methanol or acetonitrile and water with the addition of TFA or formic acid are used to ensure compatibility with the requirements of the APCI source. 

Indigoid species are also present in another dyestuff, Tyrian Purple, extracted from molluscs from the Muricidae family. It owes its specific red shade to the presence of bromoindigoids. In the extract of the dyestuff, after chromatographic separation of its components,[44] in addition to indigotin, indirubin and isoindigo, 6,6 -dibromoindigotin is... 

Baphicanthus cusia (Nees.) Bremek. Ban Lan or Da Qing Ye (leaf, root) Indirubin, indigo, indo-brown, indo-yellow, isoindigo, lacerol, tryptanthrin.53 Antidotal, febrifugal, treat fever, epidemic mumps, erysipelas, rashes, sore throat. 

The following exemplify reactions of the aldol type. 3-Hydroxythiophene with benzaldehyde forms (269). Anions derived from oxindole (270 Z = NH) and indoxyl (271) react with isatin (272) to give isoindigo (273) and indirubin (274). 

Isoindigo, obtained from isatin and oxindole, is converted diastereoselectively into diazacrisenodiones by reduction with Zn/AcOH, and subsequent acid-catalyzed rearrangement148 (Scheme 37). 

Various complex derivatives of the ring system have been patented as photographic sensitizers. Others are claimed as isoindigo pigments. ... 

Further, disulfur dichloride was used by Chovin545 869 with success in similar syntheses in that way he obtained N,W-diphenylisoindigo in 78% yield from 1-phenyloxindole, and isoindigo itself in 90% yield from oxindole. 

Trimethoxyphosphoranes (6) are among the products reported in new examples of reactions of the carbene intermediates (5). A re-investigation of the reaction of triphenylphosphine with isatin (7) has shown the previous reports to be incorrect and that the products are in fact the new phosphonium ylide (8) and isoindigo (9). ... 

Figure 1.30 Chemical structures of representative CPs based on DPP or isoindigo and synthetic scheme for formation of conjugated random copolymers. Reprinted from [254] with permission from RSC.

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