Of indol-3-ones

Pyrano[3,4-b]indol-3-ones are the most useful equivalents of the indol-2,3-quinodimethane synthon which are currently available for synthetic application. These compounds can be synthesized readily from indole-3-acetic acids and carboxylic anhydrides[5,6]. On heating with electrophilic alkenes or alkynes, adducts are formed which undergo decarboxylation to 1,2-dihydro-carbazoles or carbazoles, respectively. 

A solution of l-methylpyrano[4,3-b]indol-3-one (1 mmol) and methyl vinyl ketone (5 ml) in toluene (5 ml) containing 5% Pd/C (40 mg) was heated for 48 h in a sealed tube at 110°C. The reaction mixture was evaporated in vacuo and the residue purified by silica gel chromatography to give the product in 80% yield. 

Pyrano[3,4-i]indol-3-one (329) enters the Diels-Alder reaetion with methoxy-butenone as an eleetron-rieh olefin [92JCS(P1)415]. After deearboxylation of the primary adduet330,2-aeetyl-3-methoxy-l, 9-dimethyl-2,3-dihydroearbazole (331) eliminates methanol to form 2-aeetyl-l,9-dimethylearbazole (332) [92JCS (Pl)415]. 

The synthesis of 2-aryl-2,3-dihydro[l,2,4]triazino[5,6-6]indol-3-ones 151 has been carried out (80MI2) by the cyclization of arylazoindolyl... 

Fig. 26 Solid-phase synthesis of indol-2-ones by microwave-assisted radical cyclization. Reagents and conditions a NaH, DMF b BusSnH, AIBN, DMF, MW 170 °C, 45 min, sealed vessel c 10% TFA in CH2CI2. R = H, F, Me, OCF3 R = Phe, 3-OMe - Phe, 4-Me - Phe, 3,4-0CH20-Ph, (CH2)4, diMe R" = H, Me R " = H, Me...

As noted previously, a wide variety of aromatic systems serve as nuclei for arylacetic acid antiinflammatory agents. It is thus to be expected that fused heterocycles can also serve the same function. Synthesis of one such agent (64) begins with condensation of indole-3-ethanol (60) with ethyl 3-oxo-caproate (61) in the presence of tosic acid, leading directly to the pyranoindole 63. The reaction may be rationalized by assuming formation of hemiketal 62, as the first step. Cyclization of the carbonium ion... 

Indigo (or 2-( 1,3-dihydro-3-oxo-2H-indol-2-ylidene)-1,2-dihydro-3H-indol-3-one) (Fig. 5.7.1) is an example of a water-insoluble dye, contributing to its resistance... 

Gronowitz adapted this technology to one-pot syntheses of indole-3-acetic acids and indole-3-pyruvic acid oxime ethers from A-BOC protected o-iodoanilines [328, 329]. Rawal employed the Pd-catalyzed cyclization of A-(o-bromoallyl)anilines to afford 4- and 6-hydroxyindoles, and a 4,6-dihydroxyindole [330], and Yang and co-workers have used a similar cyclization to prepare 8-carbolines 287 and 288 as illustrated by the two examples shown [331]. The apparent extraneous methyl group in 288 is derived from triethylamine. 

Moody et al. reported the sjmthesis of the 3-oxygenated carbazoie alkaloids, hyellazole (245) (591,592) and carazostatin (247) (593,594) based on their pyrano[3,4- 7]indol-3-one methodology (Scheme 5.57). This synthetic strategy involves the use of a 1-substituted pyrano[3,4- 7]indol-3-one 542 as a stable... 

Moody and Rahimtoola reported a short synthesis of staurosporinone (293) without the use of protecting groups at the indole or the lactam nitrogen (761,762). This route involves an intramolecular Diels-Alder reaction of the pyrano[4,3- 7]indol-3-one 1325 and a subsequent cyclization by nitrene insertion. The pyrano[4,3-l7]indol-3-one 1325 was obtained in four steps from ethyl indol-2-yl... 

Isatogens (1) and indolones (2) are brightly colored solids that do not occur naturally. Isatogens (I) are more comprehensively named as 3-oxo-3//-indole 1-oxides, or as the 1-oxides of indolones (2), 3-oxo-3H-indoles, or 3//-indol-3-ones. Both series of compounds are numbered in accordance with IUPAC rules. Isatogens were first reported in 18811,2 and the first indolone in 1912.3 Isatogens (1), indolones (2) and indoxyls (3) form an interrelated redox system. Indolones in which there is a methylene or methine substituent in the 2-position tautomerize to the preferred 2-methylene-3//-indol-3-one (indogenide) structures (4).4 Only passing reference will be made to 3 and 4 in this review. 

Oxidation of indoles by hydrogen peroxide under weakly acidic conditions (72HC(25-l)l) yields 2,2-di(3-indolyl)indolin-3-one (160), indigo (161) and, to a lesser extent, indirubin. All of the products are derived from the initial formation of indolin-3-one by a mechanism... 

Alexander"2 has tried to assess the effect of indole-3-acetic acid, (2,4-dichlorophenoxy) acetic acid, and maleic hydrazide on the soluble carbohydrates and enzyme systems in sugarcane leaves. All of the chemical treatments increased sucrose, total reducing value, D-fructose, and D-glucose in leaves (compared with the controls), with a maximum at nine days after applying about two g. per plant. The indole auxin increased sucrose most, followed by the phenoxy compound and the hydrazide D-glucose increased in the reverse order. Poor translocation from the leaves may have caused the temporary increase in leaf photosynthate. Alterations in the enzyme activities as a result of the chemical treatment are difficult to interpret, partly since so little is known about their relative importance, and partly because the activity in the controls varied by as much as 100% from one sampling period to the next. 

Interaction of 1,2-dimethylindole with malonyl chloride or diketene gives 1,2,5-tri-substituted benzo[c /]indole-3-ones 199 (78S685 80LA971). 

Efficient oxidation of 2-arylindoles to 2-aryl-3W-indol-3-ones occurred under photosensitized conditions. The inital oxidation products are trapped by the solvent methanol and the indolones are obtained by vacuum thermolysis. <95SC3831 >... 

The viability of the azacyclopentanadienone ion 73,63 as proposed in our mechanism, fits in with other literature precedents. Recently, based on mechanistic evidence, the oxidative dimerization of indoles to bisin-dol-3-ones has been suggested to proceed via a-ketoiminium ion analogous to 73.64 The neutral relative to such a species, 3//-indol-3-one (75), has been suggested as a possible intermediate in the base-catalyzed... 

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