3-Hydroxy-3,4-dihydro-27/-pyrido

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). 

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. 

Reaction of 2-amino-3-hydroxypyridine and cyclohexanone 433 in boiling AcOH yielded N, 1 -diphenyl-6-hydroxy-3-methyl-11 -0x0-1,2-dihydro-11 //-pyrido[2,l-Z)]quinazoline-2-carboxamide (434) (98MI2, 99USP5908840, 99USP5914327). 

Reduction of 2,3,6,7-tetrahydro-177,5i/-pyrido[3,2,l-//]quinazoline-l,3,7-trione and 7-chloro-6-formyl-2,3-dihydro-177,5i/-pyrido[3,2,1 -(/]quinazo-line-l,3-dione with NaBH4 in THF in the presence of 60% aqueous solution of NaOH gave 7-hydroxy and 7-chloro-6-hydroxymethyl derivatives, respectively (01MI28). 

Vilsmeyer-Haack formylation of 7-hydroxy-2,3,6,7-tetrahydro-l//,5//-pyrido[3,2,l-y]quinazoline-l,3-dione with POCI3/DMF gave 7-chloro-6-formyl-2,3-dihydro-l//,5// derivative. Boiling a toluene solution of the aforementioned 7-hydroxy derivative in the presence of pTSA yielded dehydrated 2,3-dihydro derivative (01MI28). 

Hydrazone of 1 -hydrazino-1 -hydroxy-4-phenyl-1,2-dihydro-3//-pyrido [l,2-c]pyrimidin-3-one was patented as cross-linkers for making physiologically compatible and H2O insoluble hydrazine or hydrazono compounds (97JAP(K)97/59303). 

Reaction of 2,3-dihydro-3-hydroxy-3-methyl- 240 (R = Me), or a mixture of 2,3-dihydro-3-hydroxy-3-aryl-57/-pyrido[l,2,3-dfe]-l,4-benzoxazin-5-ones 240 (R = Ar) and (8-aroylmethoxy)quinolin-2(l//)-ones 241 (R = Ar) with ethyl 2-(bromomethyl)acrylate in the presence of activated Zn and hydroquinone gave 8-[(2,3,4,5-tetrahydro-4-methylidene-5-oxo-2-furanyl)-methoxy]quinolin-2(l//)-ones (242) (97HCA1161). 6,7-Dihydro derivatives of 240 reacted similarly (00HCA349). 

Catalytic hydrogenation of 9-(3-hydroxy-l-propynyl)-A-(4-chloroben-zyl)-7-oxo-2,3-dihydro-7//-pyrido[l,2,3- 7e]-l,4-benzoxazine-6-carboxamide over 5%) Pd/C in a 1 1 mixture of THE and MeOH afforded a mixture of... 

Reaction of 9,10-difluoro-3-methyl-2,3-dihydro-7-oxo-7//-pyrido[l,2,3- /e]-l,4-benzoxazine-6-carboxylic acid (252 X = F, R = H, R = Me) with 8 M aquous solution of KOH under reflux for 6 h, and in the presence of an alcohol or phenol afforded 10-hydroxy, 10-alkoxy and 10-aryloxy derivatives, respectively (96JAP(K)96/291144, 99MI5). 

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. 

Methoxy derivative was obtained from 2-(4,5-dihydro-l//-imidazol-2-yl)-7-hydroxy-8-methyl-2,3-dihydro-5//-pyrido[l,2,3- /e]-l,4-benzoxazin-5-one with methyl tosylate in DMF in the presence of K2CO3 at 50 °C for 1 h (99EUP894796). 

Oxo-2,3,6,7-tetrahydro-5//-pyrido[l,2,3- /e]-l,4-benzoxazine-2-carbox-ylates (291, X = H2) were obtained by hydrogenation of 4-substituted 3, 4-dihydro-2//-1,4-benzoxazine-2-carboxylates (290, X = H2) over 10% Pd/C catalyst, then by the treatment of free acids with (CF3C0)20 (99EUP894796). 5,7-Dioxo-2,3,6,7-tetrahydro derivatives 291 (X = 0) were prepared similarly from 290 (X = O). The products 291 (X = O) exist in 7-hydroxy-5-oxo-2,3-dihydro-5// tautomeric form. 

Stmctures of 3-hydroxy-3-phenyl-3,4-dihydro-l/7- <2006JST(792)36>, l-hydroxy-l-methyl-3-phenyl-17/-pyrido[2,l-c]-... 

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