Diphenyl quinoxaline

B. Reaction of 2-Phenyl- and 2,3-Diphenyl-quinoxaline with Dimethyl Acetylenedicarboxylate.221... 

Phenyl- and 2,3-diphenyl-quinoxalines in methanol with DMAD give 1 1 1 adducts (453),410 whereas 2-methyl- and 2,3-dimethyl-quinoxalines in acetonitrile form as major products cyclobutapyrroles (454),337 earlier described432 as azepines. By-products in the last two cases are, respectively, the r-7a,(-9,e-9a-isomer of 454 and a compound analogous to that formed from 2,3,5,6-tetramethylpyrazine. 

Cognate preparations. 2,3-Diphenylquinoxaline. To a warm solution of 2.1 g (0.01 mol) of benzil in 8 ml of rectified spirit add a solution of 1.1 g (0.01 mol) of o-phenylenediamine in 8 ml of rectified spirit. Warm in a water bath for 30 minutes, add water until a slight cloudiness persists and allow to cool. Filter and recrystallise from aqueous ethanol to give 1.43 g (51%) of 2,3-diphenyl-quinoxaline, m.p. 125-126 °C. 

A study of the H chemical shifts of 2,3,6-trimethylquinoxaIine in carbon tetrachloride, trifluoroacetic acid, and fluorosulfonic acid indicated that the carbocyclic ring participates in the positive charge distribution to the extent of about 25-30% in the mono-protonated species and 15-20% in the d/-protonated quinoxaline. 2,3-Diphenyl-quinoxaline forms a stable monocation in trifluoroacetic acid, as indicated by the downfield hydrogen signals in this solvent, compared to those in CH Clj. The NMR spectra of quinoxaline i-oxide, 1,4-dioxide and the A-oxides of 2- and 3-substituted quinoxalines have been reported. Analysis of the chemical shift values of quinoxaline-... 

Aniline, p-Chloraniline, Benzidene Diphenylamine Dialkyl-, Dimethy l-Diethy l-aniline 1,4-Dihydropyridines 2-Pyridone Pyridine, Lutidine, Collidine, 2,2 -Di-pyridyl. Quinoline, 2,3-Diphenyl-quinoxaline... 

Furazano[3,4-/]quinoxaline, 7,8-diphenyl-synthesis, 6, 412 Furazanothiophene synthesis, 6, 417 Furazans, 6, 393-426 biological activity, 6, 425 bond angles, 6, 396 bond lengths, 6, 396 coordination compounds, 6, 403 diamagnetic susceptibilities, 6, 395 dipole moments, 6, 395, 400 heats of combustion, 6, 400 heterocyclic ring reactions, 6, 400-403 IR spectra, 6, 398 isoxazoles from, 6, 81 mass spectra, 6, 399 microwave spectroscopy, 6, 395, 396 MO calculations, 6, 395 monosubstituted... 

Thieno[3,4-h]quinoline, 1,3-diphenyl-synthesis, 4, 1026 Thienoquinolines, 4, 1025 Thieno[2,3-h]quinolines, 4, 1025 Thieno[3,2-c]quinolines synthesis, 4, 785, 788 Thieno[3,4-h]quinolines, 4, 1026 Thieno[3,4-h]quinoxaline, 1,3-diphenyl-synthesis, 4, 1027 Thienoquinoxalines, 4, 1026 Thieno[2,3-h]quinoxalines synthesis, 4, 1026... 

Treatment of bis-lactim ether 420 with BuLi, then with cw-l,4-dichloro-2-butene in the presence of Nal afforded 3,4,9,9n-tetrahydro-6//-pyrido[l,2-fl]pyrazin-4-one (421) with 96% diastereomeric excess (97TA1855). Reaction of l,2-diphenyl-6-methyl-quinoxaline with 1,4-dichlorobutane in THF in the presence of Na at —78°C afforded a 3 1 mixture of 4a,5-diphenyl-9-methyl-l,2,3,4-tetrahydro-4a//-pyrido[l,2-n]quinoxaline and 4-(4-chlorobutyl)-2,3-diphenyl-6-methyl-1,4-dihydroquinoxaline (98JHC1349). 

In contrast, l,2-diphenyl-l,la-dihydroazirino[l,2-fl]quinoxaline-5-carbonitrile (521) gave 2-benzyl-3-phenyl-6-quinoxalinecarbonitrile (522) by rearrangement (HCl-H20-AcMe, reflux, h 86%) also analogs likewise. ... 

Reduction of 7,8-diphenyl[l,2,5]oxadiazolo[3,4-/ quinoxaline (574) with sodium bis(2-methoxyethoxy) aluminum hydride in refluxing toluene for 1 h gave 2,3-diphenyl-5,6-quinoxalinediamine (575) in 64% yield. ... 

Attempts to directly iodinate quinoxaline failed, and the synthesis of 2,3-diphenyl-5,8-dibromoquinoxaline is somewhat more involved (Scheme 9) [61]. Starting from ort/zo-phenylenediamine, reaction with SOCI2 gives benzothia-diazole in high yield. Bromination in HBr furnishes 4,7-dibromobenzothiadi-azole, which can be alkynylated or directly reduced [62]. Reduction of the dibromide with sodium borohydride leaves the halide substituents unmolested but opens the ring to furnish l,4-dibromo-2,3-diaminobenzene. Reaction of this intermediate with a 1,2-dione furnishes a 2,3-disubstituted 5,8-dibromo-quinoxaline. Pd-catalyzed alkynylation finishes the sequence off and removal of the TMS groups yields the desired 5,8-diethynylquinoxaline monomers (Table 9, entries 13,14). 

A few extensions of the Conrad-Limpach synthesis have been applied to the synthesis of 4,7-phenanthrolines. Unlike o-phenylenediamine, which gives a quinoxaline derivative, p-phenylenediamine reacts with excess of ethyl ethoxalylpropionate to give an intermediate bisanil, which cyclizes in hot diphenyl ether to afford 3,8-dicarboethoxy-l,10-dihydroxy-2,9-dimethyl-4,7-phenanthroline in high yield.237 With diethyl ethoxymethylenemalonate as condensing agent, 6-amino-8-methoxy-quinoline has been converted into 2-carboethoxy-l-hydroxy-6-methoxy-4,7-phenanthroline.238 A related condensation affording 1-... 

Substituted quinoxalines undergo unusual reactions with nucleophiles. Thus, 2,3-diphenyl-6-nitroquinoxaline (67) with potassium cyanide undergoes substitution in the 5-position, with simultaneous nucleophilic displacement of the 6-nitro group by the methanol solvent to give compound 68 (52%) 5-aminoisoxazolo[4,3-/]quinoxaline (69) is also obtained (35%). The structure of the product 68 was proved by an unambiguous synthesis.85... 

Quinoxaline 1-oxide (209) reacts with phenyl isocyanate to give 2-anilinoquinoxaline (210) together with 1,3-diphenyl-l-(2-quinoxalinyl)-urea (211) and cyclized oxidation product of the urea 212.215 2-Quinoxalinone 4-oxide (205) and its 1-methyl derivative undergo addition reactions, e.g., with phenyl isocyanate and benzyne to give compounds 214 and 216, respectively.216 These reactions are formulated as proceeding via the intermediate cycloadducts 213 and 215. Compound 216 has also been obtained by photolysis of 3-(o-hydroxy-phenyl)quinoxaline 1-oxide.51 1,3-Dipolar cycloaddition of quinoxaline... 

Quinoxaline /V-oxides undergo rearrangements when UV-irradiated. 2,3-Diphenylquinoxaline 1-oxide (224) was originally thought to rearrange to the oxazirino[2,3-a]quinoxaline (225).225 However, subsequently the product was found to be 2,4-diphenyl-3,l,5-benz-oxadiazepine (226).226 This reassignment was supported by NMR spectroscopy, and oxadiazepine formation on irradiation of 2,3-bis(4-bromophenyl)quinoxaline 1-oxide was confirmed by X-ray crystallography.227... 

Vilsmeier reaction, 4, 1051 Furo[3,2-6]pyrroles MO calculations, 6, 979 synthesis, 4, 1069 6, 1009 Furo[3,4-a]pyrrolo[2,1,5-cd]indolizine nomenclature, 1, 22 Furopyrylium salts, 4, 993-995 Furoquinolines biosynthesis, 4, 992 occurrence, 4, 988 pharmacology, 4, 992 reactions, 4, 988 synthesis, 4, 989 Furo[3,2-c]quinolines, 4, 991 Furo[3,4-fe]quinoxaline, 1,3-diphenyl-synthesis, 4, 993 Furoquinoxalines, 4, 992 Furo[2,3-6]quinoxalines synthesis, 4, 992 Furosemide toxicity, 1, 136 Furospinulosin UV spectra, 4, 587 Furospongin-I mass spectrometry, 4, 583 Furo[3,4-d][l,2,3]triazole, 2,6-dihydro-synthesis, 6, 996 Furo[3,4 -d][ 1,2,3]triazoles synthesis, 6, 996 Furoxan, 4-amino-3-aryl-tautomerism, 6, 404 Furoxan, 4-amino-3-methyl-synthesis, 4, 414 Furoxan, 4-aryl-3-methyl-rearrangement, 6, 408 Furoxan, 3-aryl-4-nitro-synthesis, 6, 414 Furoxan, 4-benzoyl-3-methyl-oxime... 

Thermodynamically stable aromatic selenaheterocycles such as selenophene (1), 1,3-selenazole (3), 1,2,5-selenadiazole (5), and 1,2,4-selenadiazole undergo [l,4]cycloaddition followed by spontaneous deselenation, which is a convenient way for construction of nonselenium azaaromatic rings [3, 6, 42], 3,4-Diphenyl-1,2,5-selenadiazole reacted with DMAD to give methyl 2,3-diphenylpyrazine-5,6-dicarboxylate. The similar reaction of 1,2,4-selenadiazoles resulted in pyrimidine -5,6-dicarboxylate, while 2,1,3-benzoselenadiazoles reacted with DMAD to give the quinoxalines [6, 110]. (For deselenation see also Sect. 5.1). 

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