Isatin-3-hydrazones

Cyclocondensation of isatin hydrazones 620 with 621 in strong acid gave thiazolo[3, 4 2,3][l,2,4]triazino[5,6-6]indoles 622, which underwent conventional reaction with 2-methyl-3-ethylbenzothiazolium perchlorate 623 to form unsymmetrical cyanines 624 (83URP1054350 85KGS211). The spectral properties of a series of polymethine dyes were examined (88KGS1547). 

Isatin hydrazones and thiosemicarbazones can also be used as substrates for the Mannich reaction, leading to functionalization at N- . Isatin-3-hydrazone reacts with 1,1-... 

Siddiqui et al. have synthesized an efficient three-component synthesis of highly functionalized 4-methyl-l/7-quinohn-2-ones in one-pot reaction from readily available coumarin, hydrazine and isatin catalysed by a recyclable and moisture-compatible InClj under MWI. The synthesis involves a InClj catalysed dehydrative nucleophilic substitution on the lactone moiety of coumarin by the isatin hydrazone resulting in the formation of iV-substituted lactams, 6-substituted-4-methyl-l-(2-0X0-1,2-dihydroindol-3-ylidenamino)-l/f-qninolin-2-ones (45). The conmarin-based transformation into substituted l/f-quinolin-2-ones proceeded smoothly with quantitative yields at ambient temperature (Scheme 6.18) [57]. 

Hydroxy-2-quinolinecarboxaldehyde 8-quinolylhydrazone, H-00526 Isatin hydrazone, in 1-00056 Isatin 3-(4-Nitrophenylhydrazone), in 1-00056... 

Monosubstituted hydrazones of isatin can exist in at least three tautomeric forms 124-126. According to spectroscopic data, only hydrazone 124 is present in solution (81JOC2764). 

Preliminary studies with a thio derivative of isatin (indole-2-thione-3-phenylhydrazone) also showed the hydrazone structure to be the favored tautomeric form (81JOC2764). 

Aus Isatin-3-hydrazon (bzw. 3-Diazo-2-oxo-2,3-dihydro-indol) entsteht in waBriger Pufferlosung 3-Amino-2-oxo-2,3-dihydro-indol4. 

H(53)323> and 1,2,4-triazinoquinolines have been reported. The preparation of a novel heterocyclic ring system, the indazolotriazinopurine 107, by the condensation of 8-hydrazinotheophylline (103) with 5-substituted isatins 104, via the hemiaminal 105 and hydrazone 106 intermediates, has been described <00JHC373>. 

Z = 0, NH), then the carbonyl group not adjacent to the heteroatom is preferentially attacked. Thus, isatin and indoxyl and their O- and 5-analogues (279, 282) react with hydroxylamine, hydrazine, phenylhydrazine, semicarbazide, etc., to give oximes, hydrazones, phenylhydrazones, semicarbazones, etc. (282 — 283 279 — 284). 

A variety of arylhydrazines have been reacted with isatins to give isatin-3-arylhydrazones (83).15,21,22,24,78,80,107,156,181,216,300-306 Similar reactions have also been carried out with isatins and alkylhydrazines,307 hydrazides,155 188,304 305,308-312 and hydrazine21,156,157,216,313-315 to give 84, 85, and 86, respectively. Aldehyde hydrazones also react with... 

Isatin-3-hydrazones react with aldehydes to give 91.157,314 Compound 91 (R = H, Ar = 2-(5-nitrofuryl)) has also been prepared by reaction of isatin with 5-nitrofurfuraldehyde hydrazone.314 Ammonium isothiocyanate, and 86 gave isatin-3-thiosemicarbazones.318... 

Heating of hydrazones 86 with sodium hydroxide gave oxindole and isatin azine,319 and heating with sodium ethoxide gave oxindole,... 

Isatin-3-hydrazones (86) react with nitrosylsulfuric acid in glacial acetic acid to give, after dilution with water, the diazonium salt 97 as indicated by the formation of an azo dye with A,A-dimethylaniline.325-... 

The first microwave-assisted Wolff-Kishner reduction was described by Parquet and Lin in 199763. The transformation of isatin to oxindole was performed on a small scale in a domestic microwave oven in two steps with a total reaction time of 40 s, as compared to 3—4 h if classical heating was utilised (Scheme 4.36). The first step involved the transformation of the carbonyl group into the hydrazone with 55% hydrazine in ethylene glycol and medium power microwave irradiation for 30 s. In the subsequent reduction step, KOH in ethylene glycol was used to substitute the more hazardous sodium ethoxide. The reaction mixture was irradiated for 10 s and the product was obtained in a yield of 32%. 

The introduction of a phosphorus-containing group into the side chain of the hydrazone fragment of isatin was reported in [97]. The results of a study of the kinetic relationships and mechanism of the addition of dialkyl phosphites to substituted benzylideneamines, which were related to the basicity of the initial amines, were published as abstracts in [98]. 

In a related reaction, isatin-3-phenylhydrazone yields l,3-benzazoxane-2-one-4-hydrazone upon treatment, under reflux, with an ethanolic solution of cupric chloride194 (Scheme 43). 

Isatin, due to its cis a-dicarbonyl moiety, is a potentially good substrate for the synthesis of metal complexes, either alone or with other ligands. Their derivatives, mostly those substituted at C-3, such as isatin-3-hydrazones and isatin-3-imines bearing an extra heteroaromatic ring are also generally employed as ligands. In this manner, Schiff bases... 

In a similar manner, isatin-3-hydrazone has been studied for the colourimetric... 

Indoloquinoxaline 693 was obtained in 83-90% yield by irradiating a mixture of isatin with o-phenylenediamine in acetic acid in an MW oven in either an open flask or closed Teflon vessel for 1-2 min. Carbethoxymethylation of isatin with ethyl chloroacetate in the presence of K2CO3 and Nal was carried out under MWI to give compound 694 in 70% yield within 4min. It could be converted into 695 by reaction with o-phenylenediamine in acetic acid in either an open flask (2 min) or closed Teflon vessel (Imin) (Scheme 134). Alternatively, carbethoxymethylation of 693 under MWI for 6 min afforded a 53% yield of 695. Reaction of 695 with hydrazine hydrate in ethanol under MWI gave the hydrazide 696 in 84% yield. MWI has been also used to condense 696 with aromatic aldehydes and monosaccharides to yield the hydrazone derivatives 697 in 58-99% yields (Scheme 134) (05JCR(S)299). 

The preparation of azido diazo substrates 17a and 17b proved to be feasible (Scheme 3). A three-step, one-pot procedure modified from the literamre converted isatin to azido acid 14 in 84% yield. Treating 14 with p-toluenesulfonyl hydrazine in hot acetic acid afforded hydrazone 15 in 81 % yield. The latter was reacted with thionyl chloride at 80 °C for 1 h in benzene. Removal of excess thionyl chloride and finally recrystallization yielded the stable acyl chloride 16 in 71% yield. Condensations of 16 with 10a or 10b... 

In a later synthesis of the regioisomers of ropinirole, the isatin was formed from cyclization of a hydrazone under strong acidic conditions. After removal of the ketone functionality via hydrogenolysis and removal of the protective group, reductive amination afforded the regioisomer of ropinirole. 

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