Alkyl 2-hydroxy-4-oxo-477-pyrido

The hydroxy group of ethyl 9-hydroxy-4-oxo-4//-pyrido[l,2-u]pyrimi-dine-3-carboxylate was O-alkylated with 2-chloromethyl-4-isopropyl-l,... 

Alkylation of mesoionic y ro-(2-hydroxy-4-oxo-47/-pyrido[l,2- ]pyrimidinium)hydroxide with 2-chloromethyl-... 

Hydroxy-4-oxo-4//-pyrido[l,2-a] pyrimidines have been O-alkyl-ated46,54,59,78,88,138,140 and O-acetylated.58,78 O-Acetylation of a 9-hydroxy-6,7-dihydro derivative has also been reported.316... 

Alkylation and Acylation of Anhydro-(2-hydroxy-A-oxo-AH-pyrido [ 1,2-a]pyrintid-1 -inium)hydroxides... 

A suspension of methyl (or ethyl) y-(benzothiazol-2-yl)acetoacetate in xylene refluxed 20 min. 3-hydroxy-l-oxo-lH-pyrido[2,l-b]benzothiazole. Y ca. 90%. Also with 4-alkylation s. N. Hawlitzky and R. Haller, M. 102, 718 (1971). 

Treatment of alkyl 9-benzyloxycarbonyl-3-methyl-6-oxo-2/7,6//-pyr-ido[2,l-f ][l,3]thiazine-4-carboxylates with BBr3 in CH2CI2 at -70 °C for 0.5-1 h and at room temperature for 3h yielded 9-carboxyl derivatives. The decarboxylation of these acids was unsuccessful. Hydrolysis of diethyl cA-3,4-H-3,4-dihydro-3-methyl-6-oxo-2//,6//-pyrido[2,l-f ][l,3]thiazine-4,9-dicarboxylate in aqueous EtOH with KOH at room temperature for 3 days yielded 4-ethoxycarbonyl-3,4-dihydro-3-methyl-6-oxo-2//,6//-pyrido-[2,l-f ] [1,3]thiazine-9-carboxylic acid (00JCS(P1)4373). Alkyl 9-hydroxy-methyl-3-methyl-6-oxo-3,4-dihydro-2//,6//-pyrido[2,l-f ][l,3]thiazine-4-car-boxylates were O-acylated with AC2O and (PhC0)20 in pyridine at room temperature for 12-48h. 

The respective amide was prepared from 7-substituted 5-oxo-2,3-dihydro-5//-pyrido[l,2,3-de]-l,4-benzoxazine-6-carboxylic acids via acid chlorides with different benzylamines (00M1P3). 6-Carboxamides were N-benzylated, and a side-chain phenolic hydroxy group was O-alkylated. 7-Aryl-5-oxo-2,3-dihydro-5//-pyrido[l, 2,3-r/e]-1,4-benzoxazine-6-carboxylic acid was obtained from the ethyl ester by alkalic hydrolysis. 

The 1-hydroxymethyl group of l-hydroxymethyl-7-oxo-l//,7//-pyrido [3,2,l-y]cinnoline-8-carboxylate (81) was O-alkylated by treatment with diethylaminosulfur trichloride and an alcohol in THE. The 4-hydroxy group of 4-hydroxy-7-oxo-l//,7//-pyrido[3,2,l-t7]cinnoline-8-carboxylate... 

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). 

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