Quinoxalone

Although 1- and/or 4-acylated hydroquinoxalines might not be considered as regular quinoxalone ketones, they are included here for pragmatic reasons. Examination of the NMR chemical shifts for H5 and H8 in l,4-diacyl-l,2,3,4-tetrahydroquinoxalines (197, R = Me, Et, Ph, etc.) indicated that the endo-exo conformation (shown) predominated in most such compounds at ambient temperatures. " However, this was disturbed in l,4-dibenzoyl-6,7-dimethyl-l,2,3,4-tetra-hydroquinoxaline (198), which showed a predominance of the exo-exo conformation (shown) below the coalescence temperature. ... 

Kaempferol glucoside la 323 Kedde s reagent lb 236,237 1 -Kestose lb 423,424 6-Kestose lb 423 Ketazon lb 280 Keto acids la 262 a-Keto acids la 249,262,372 -, quinoxalone derivatives lb 343... 

The acylation of 1,4-benzodiazepine 4-oxides, e.g. (230), leads to a Polonovski-type rearrangement giving (231) and provides a useful way of functionalizing the 3-position. Treatment of (230) with p-toluenesulfonyl chloride gives the quinoxalone (233) via a Beckmann type of rearrangement (72JHC747, p. 755) and similar rearrangements have been observed in the reactions of 4-hydroxy derivatives with thionyl chloride or phosphorus oxychloride. 

Subsequently, Brill and Schultz hydrogenated 5,6,7,8-tetrahydro-2-quinoxalone (50), prepared by condensing 1,2-cyclohxanedione with glycinamide, over platinum oxide to give quantitative yield of cA-decahydro-2-quinoxalone (eq. 12.90), which was transformed into ci.v-dccah ydroq u i n ox al inc by reduction with lithium aluminum hydride.170... 

Reduction of 3-alkylated 2-hydroxyquinoxalines produces, besides the 3,4-dihydroquinoxalone, a product dimerized at N-4, whereas 3-aryl quinoxalones form only the 3,4-dihydro derivative on reduction.240... 

The quinoxalone derivatives of pyruvate and 2-ketobutyrate were separated on a /iBondapak Qg reversed-phase column (3.9 mm x 300 mm). The mobile phase was a mixture of acetonitrile, methanol, and 40 mM phosphate buffer (pH 7) (5 8 12, v/v/v) run at a flow rate of 1 mL/min. Detection could be carried out spectrophotometrically at 254 nm, or fluorometrically with excitation and emission wavelengths of 340 and 389 nm, respectively. 

A furanoquinoxaline (21) was unexpectedly obtained on attempted formylation of the quinoxalone (20).25... 

The synthesis of some fluorine-containing polycyclic compounds involves intramolecular cyclization. Thus, heating quinoxalone, obtained by the reaction of the copper chelate of ethyl pentafluorobenzoylpyruvate with ortho-aminophenol in dimethylsulfoxide or DMSO-NEt3 leads to the product of intramolecular... 

Treatment of aryl(aroyl)pyruvic acid ester metal chelates with ortho-phenylene-diamine and ethylenediamine is accompanied by an attack at the a-ketoester fragment, forming quinoxalones and piperazinones, respectively (95ZOR266, 99JFC(96)87) (Scheme 60). 

Other azaquinoxalines are prepared from 2,3-diaminopyridine and a-dicar-bonyl compounds. For example, 2,3-diaminopyridine and IX-205 in hot acetic acid gives 5-aza-2-styiyl-3-quinoxalone (IX-206). ... 

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