Pyrido quinoxaline-9-carboxylate

Reaction of ethyl 7-bromo-8-fluoro-l-(2-bromo-l-methylethyl)-4-oxo-l,4-dihydroquinoline-3-carboxylate with MeNH2 yielded 10-bromo-A, 1, 3-trimethyl-7-oxo-2,3-dihydro-7//-pyrido[l,2,3-<7e]quinoxaline-3-carboxamide (OOMIPIO). 

Catalytic hydrogenation of 1-arylpipecolinate 338 over 10% Pd/C catalyst yielded 6-oxo-6,6a,7,8,9,10-hexahydro-5H-pyrido[l,2-a]quinoxaline-3-carboxylate 339 (08USA2008/0161292, 09BML4050). 

The alternative Scheme B is based on A-nucleophilic attack. Thus, bubbling air through a boiling solution of ethyl 3-amino-2-(quinoxaline-2-carbonyl)crotonoate 66 in DMF furnishes pyrido[2,3-Zr]quinoxaline 67 (Scheme 20) (04RCB1267). The latter has a structural similarity to derivatives of 4-quinolone-3-carboxylic acid, well known because of their high antibacterial activity. 

Oxidation of 9-hydroxy-5,6-dihydro-8//-pyrido[l,2-a]quinoxalin-8-one with KMn04 in H20 gave quinoxaline-2-carboxylic acid (75MI1). 

Cyclocondensation of pipecolinic acid and malic acid anhydride in pyridine afforded 3-hydroxy-2,3-dimethylperhydropyrido[l,2-a]pyrazine-l, 4-dione (74CB2804). Cyclocondensation of bis(2,4,6-trichlorophenyl) mal-onates with 2-methyl-, 2-benzyl- and 2-ethoxycarbonylmethylquinoxalines and -3-ones at 250°C afforded 8-hydroxy-10//-pyrido[l,2-a]quinoxalin-10-ones and their 5,6-dihydro-6,10-dione derivatives (77M103). Under Horner-Wittig reaction conditions, the reactions of 2-formylquinoxaline and dialkyl phosphonosuccinates (314) also involved cyclization to give alkyl 10-oxo-10//-pyrido[l,2-a]quinoxahne-8-carboxylate (80LA542). 

Isomerization of benzo[/]-l,5-diazabicyclo[3,2,2]nonene in 8.8 N HBr at 140°C yielded l,2,3,5,6,7-hexahydropyrido[l,2,3-de]quinoxaline (83 KGS677). Photolysis of dimethyl l-(quinolin-8-yl)-l,2,3-triazole-4,5-di-carboxylates in MeCN resulted in stable an/tydro-2,3-dimethoxycarbonyl-3//-pyrido[l,2,3-de]quinoxalin-4-ium hydroxides [87JCS(P1)403]. 6-Hy-droxymethyl-2-methyl-7-methoxy-l,2,3,4-tetrahydro-6//-pyrazino-[1,2-h]isoquinolin-4-one (138) was prepared from 5- [A-methyl-Ar-(ethoxy-... 

Although the side chain reactions in this series are similar to those in quinoxaline chemistry, the cyclization of ureides such as compound 129 to the hydantoin 130 occurs more readily in the pyrido[2,3-i)]pyrazine series. Boiling dilute hydrochloric acid converts 129 into acid-stable 130, whereas it hydrolyzes the quinoxaline analogue of 129 to the corresponding carboxylic acid. Compounds of both series are readily hydrolyzed to the acid by aqueous alkali. ... 

Both D-threo-2,5-hexodiulose (7) and kojic acid (10) afford the pyrido[l,2-a]quinoxaline 11 on treatment with o-phenylenediamine. The pathway via 8 and 9 explains the formation of the tricyclic compound from the hexodiulose. The product 11 forms the N-benzenesulfonate 12 on reaction with benzenesulfonyl chloride. Treatment with acetic anhydride in pyridine gives the diacetyl derivative 13. Quinoxaline-2-carboxylic acid is produced when 11 is oxidized with potassium permanganate. The condensation of o-phenylenediamine with the pyrylium salt 14 affords the pyridoquinoxalinium salt 16 by way of the intermediate N-phenylpyridinium salt 15. ... 

Base-catalyzed cyclization of the quinoxalinylaminopropionic esters 29 has recently been shown to give the pyrido[2,3-6]quinoxalines 30. These may be dehydrogenated by sequential treatment with bromine and triethylamine to give the compounds 30a. The carboxylic acids derived... 

Elchaninov and Elchaninov 2014) reactions. The formation of 2-(lH-imidazo[4,5-Z7]pyridin-2-yl)-3-arylquinoxahnes 96a-d from pyrido[2,3-fe]pyrazin-2(lfl)-ones 95a-d and 1,2-DAB 5a proceeds in AcOH under reflux for 35-47 h. It should be noted, that carrying out the reaction with refluxed AcOH for 3 h leads to the formation of 2-amino-3-azaanylide quinoxaline 3-phenyl-2-carboxylic acids 97. This has been illustrated by the reaction of 2-(lH-imidazo[4,5-fc]pyridin-2-yl)-3-phenylquinoxahne 95a and 1,2-DAB 5a (Table 6.4) (Mamedov et al. 2010a). 

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