Oxindoles nitration

This and other evidence (16) indicated that eseretholemethine (VI R = C2H5) was a pseudo base or carbinol amine. Thus, on oxidation with silver nitrate an oxindole was obtained (dehydroeseretholemethine, VII R = C2H5), which on subsequent Hofmann degradation and reduction of the Hofmann elimination product gave 5-ethoxy-l,3-dimethyl-3-ethyloxindole (13). The methyl homolog (VII R = CHa),... 

Reactions of Indoles. 2-Arylindoles react with tosyl azide under phase-transfer conditions to give 3-diazo-compounds (148). The phenylazoindole (149 R = N2Ph) is converted into the nitroindole (149 R = NO2) by ipso-nitration. Indoles are oxidized by thallium(III) nitrate to mixtures of oxindoles and isatins. Sensitized photo-oxygenation of the indole (150) yields the hydroperoxide (151), which forms compound (152) on treatment with methanolic potassium borohydride. Vilsmeier-Haack formylation of... 

Pummerer-like cyclization reactions were utilized to prepare spirocyclic oxindole derivatives <04OL1869, 04OL2849>. For example, treatment of 2-sulfenylindole 215 with an iodonium reagent in the presence of 2,6-lutidine produced thioimidate 216. Oxidation of the latter with cerium ammonium nitrate (CAN) gave spirooxindole 217. 

Baeyer confirmed his results by the total synthesis of oxindole, isatin and indole. Nitration ofphenylacetic acid, isolation of the o-nitro isomer, and reduction of the latter followed by ring closure gave oxindole. Reaction with nitrous acid ( .e. potassium nitrate and sulfuric acid) gave isatin oxime, from which by reduction, dehydrogenation with iron(lll) chloride and final hydrolysis, isatin itself was obtained. 

Baeyer nitrated phenylacetic acid, and reduced this to o-aminophenylacetic acid, which lost water to form oxindole. By reducing nitroso-oxindole (prepared by Baeyer and Knop) to amino-oxindole, and oxidising this, Baeyer obtained isatin ... 

The AgN03-catalyzed reactions of V-arylacrylamides with Ph2P(0)H or (EtO)2P(0)H afford the phosphorylated oxindoles in high yields (eq 26). Silver nitrate in combination with a chelating ligand efficiently catalyzes the oxidative imination of sulfoxides and sulfides with sulfonylamides and PhI(OAc)2- ... 

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