Quinoxalines synthesis

Pyrazolopyrimidinones C NMR, 5, 308 methylation, 5, 310 synthesis, 5, 329 Pyrazolopyrimidinones, thioxo-synthesis, 5, 324 Pyrazoloquinazolines synthesis, 5, 317, 322 Pyrazolo[ 1,5-n]quinazolines synthesis, 5, 273 Pyrazolo[ 1,5-c]quinazolines synthesis, 5, 324 Pyrazolo[2,3-n]quinazolines synthesis, 3, 378 Pyrazoloquinazolinones synthesis, 5, 342 Pyrazolo[4,3-/]quinazolinones synthesis, 5, 273 Pyrazolo[4,3-g]quinazolinones synthesis, 5, 273 Pyrazolo[3,4-/]quinolines synthesis, 5, 273 Pyrazolo[4,3-/]quinolines synthesis, 5, 273 Pyrazolo[l,5-n]quinoxalines synthesis, 5, 339 Pyrazolo[3,4-6]quinoxalines synthesis, 5, 272... 

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... 

An interesting variation of this quinoxaline synthesis is outlined by the synthesis of sydnoquinoxalines shown in Scheme 103. The starting material is phenylsydnone 288 with an iminophosphorane group in an o-position. With isocyanate or isothiocyanate carbodiimide intermediates 289 are formed by an electrophilic aromatic substitution at the sydnone ring (4 position), the 4-(arylamino)sydno[3,4-a]quinoxalines (290) are obtained (91S745). 

Quinazosin, 382 Quinbolone, 154 Quindonium bromide, 139 Quinolone synthesis, 363 Quinoxaline synthesis, 388 Quinterenol, 366... 

A further extension of the classical reaction sequence for quinoxaline synthesis involves the use of alicyclic or heterocyclic cr-dicarbonyl compounds or their derivatives. The quinoxalinylglyoxal oxime 25 thus yields the 2,2 -bisquinoxaline 26.32... 

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... 

Catalysts and conditions for catalytic reduction were also carefully examined, as reduction of nitrated intermediates also posed dangers and required control strategies. These steps appear late in the quinoxaline synthesis therefore, full purging of anilines (e.g., 15) is essential for quality control. After a thorough analysis of all reaction steps, the team concluded that the direct and efficient discovery approach from benzazepine (8) to varenicline (1) could be safely and efficiently operated in a manufacturing setting with further development.34... 

Quinoxaline synthesis. Condensation of glyoxal bisulfite with o-phenylenediamine in aqueous solution at about 80° affords quinoxaline in high yield, and this base on permanganate oxidation affords 2,3-pyrazinedicarboxylic acid. In the absence of sodium bisulfite, aqueous glyoxal reacts with o-phenylenediamine to give quinoxaline in only about 30% yield along with resinous by-products. 

Quinoxalin-2-ones are readily converted into 2-chloroquinoxalines on treatment with phosphoryl chloride or thionyl chloride containing dimethylformamide, and in view of the highly reactive nature of 2-chloroquinoxalines, quinoxalin-2-ones are much used intermediates in quinoxaline synthesis. 

Quinoxalinyl ketones have been prepared by application of the classical quinoxaline synthesis, an o-phenylenediamine being condensed with an appropriate 1,2,3-tricarbonyl compound. Reactions of this type do not provide an unambiguous synthesis of quinoxalinyl ketones, since an alternative mode of condensation is possible leading to a benzo-1,5-diazepinone. The latter possibility is eliminated in the example cited in Scheme 1 because NMR examination of the condensation product... 

The condensation of 1,2-diaminonaphthalene with an a-dicarbonyl compound to give a benzo[/]quinoxaline represents a simple extension of the classical quinoxaline synthesis. As a result of the unsymmetrical structure of the diamine, isomeric mixtures of benzo[/]quinoxalines can in principle be formed when the dicarbonyl compound is also unsymmetrical (Scheme 1). In practice only one isomer may be formed in appreciable quantities and be thus readily isolated. The orientation of a number of the products obtained from the condensation reactions of 1,2-diaminonaphthalene is uncertain, though, as discussed in the following sections, unambiguous syntheses of benzo[/]quinoxalines may be achieved using o-aminonitroso- and o-aminophenylazonaphthalenes. 

---