Pyrido 2,3-4/pyrimidine-6-carboxylic acids

A final method for the preparation of pyrido[2,3-carboxylic acid chlorides with enamines in the presence of base to give 6,7,8-trisubstituted 5-ones (253 254)... 

Pyrido[2,3-d]pyrimidine-6-carboxylic acid, 5,6,7,8-tetrahydro-5-0x0-synthesis, 3, 221... 

The A-substituted derivatives of 4-oxo-4//-pyrido[l,2-n]pyrimidine-3-carboxamides and -3-acetamides and l,6-dimethyl-4-oxo-1,6,7,8-tetrahy-dro-4//-pyrido[l,2-n]pyrimidine-3-carboxamide were prepared by treatment of the appropriate 3-carboxylic acids and acetic acid, first with an alkyl chloroformate in the presence ofNEt3 in CHCI3 below — 10°C, then with an amine (98ACH515). A-Phenethyl and A-[2-(3,4-dimethoxyphenyl)ethyl] derivatives of 6-methyl-6,7,8,9-tetrahydro-4//-pyrido[l, 2-n]pyrimidine-3-acetamide were obtained in the reaction of 6-methyl-6,7,8,9-tetrahydro-4//-pyrido[l,2-n]pyrimidine-3-acetic acid and phenethylamines in boiling xylene under a H2O separator. Hydrazides of 4-oxo-4//- and 4-oxo-6,7,8,9-tetrahydro-4//-pyrido[l, 2-n]pyrimidine-3-acetic acid were prepared from the appropriate ester with H2NNH2 H2O in EtOH. Heating 4-oxo-4//- and 6-methyl-4-oxo-6,7,8,9-tetrahydro-4//-pyrido[l, 2-n]pyrimidine-3-acetic hydrazides in EtOH in the presence of excess Raney Ni afforded fhe appropriafe 4-oxo-6,7,8,9-fefrahydro-4//-pyrido[l,2-n]pyrimidine-3-acefa-mide. In the case of the 4-oxo-4// derivative, in addition to N-N bond... 

Methylthio-4//-pyrido[l,2-u]pyrimidin-4-one was prepared by FVT of 2-methylthio-4-oxo-4//-pyrido[l, 2-u]pyrimidine-3-carboxylic acid at 650 °C at 8 X 10 -nbar for 4h (99JCS(P2)1087). 

Fluorophenyl)-3-fluoro-2-hydroxy-6-oxo-6/7-pyrido[],2-n]pyrimidine-7-carboxylic acid (197, R = 4-FPh, R = H) was obtained from the 2-(4-methyl-]-piperazinyl)-7-ester derivative by the treatment with 1 N NaOH in an 1 1 mixture of H2O and THF at room temperature for 6h (95MIP1, 96JMC3070, 96MIP4, 96USP5580872). 

Fischer indolization of 9-arylhydrazono-6,7,8,9-tetrahydro-4//-pyrido-[l,2-u]pyrimidin-4-ones 289 by heating in 85% phosphoric acid, or in PPA yielded 7,12-dihydropyrimido[l, 2 l,2]pyrido[3,4-Z)]indol-4(6//)-ones 290 (96JHC799, 99MI12, 00MI22). From the 3-ester and 3-carboxylic acid derivatives 289 (R = COOEt, COOH) and decarboxylated products 290 (R = H) were obtained. 

Dihydro-2//-pyrido[l,2-n]pyrimidin-2-one was used in the synthesis of antiallergic tricyclic triazolobenzazepine derivatives (99MIP3). 8-[2-(4-f-Propyl-2-thienyl)ethenyl]- and 8-[(4-/-propryl-2-thienyl)methoxy]-4-oxo-4//-pyrido[l,2-n]pyrimidine-3-carboxylic acids were patented for the treatment of preventing and/or treating microbial infectious diseases (OlMIPl). 

Chemical Name 8-ethyl-5,8-dihydro-5-oxo-2-(1-piperazinyl)pyrido[2,3-d] pyrimidine-6-carboxylic acid... 

The reaction of 2-aminothiazole and isopropylidene bis(methylthio)-methylenemalonate (459, R2 = R3 = SMe) or 1-methylthioalkylidenema-lonates (459, R2 = Me, Et, Ph R3 = SMe) in boiling ethanol for 2.5 hr or in dimethylformamide at 120-130°C for 4-5 hr, gave 2-substituted 5-oxo-5//-thiazolo[3,2-a]pyrimidine-6-carboxylates (462) in good yields (89S-317). Similarly, in boiling ethanol, 2-substituted 4-oxo-4//-pyrido[l,2-a]-pyrimidine-3-carboxylic acids (463) were obtained in 80-85% yields. When anilines were reacted with isopropylidene bis(methylthio)methy-lenemalonate (459, R2 = R3 = MeS), (methylthio)(arylamino)methylene-malonates (464) were obtained 61-88% yields. 

Depending on the work-up, pyrido 2,3-t/]pyrimidine-6-carboxylates (1047, R1 = Et) or 6-carboxylic acids (1047, R1 = H) were prepared in high yields on the heating of /V-ethyl-/V-(4-pyrimidinyl)aminomethylene-malonates (1046) in phosphoryl chloride for 6 hr [73JAP(K)91093]. 

In 1996, Borrell and co-workers published58 a two-step procedure to form pyrido[2,3-d]pyrimidines. Mont and co-workers have recently transformed this reaction to a single-step three-component reaction59. a, 3-Unsaturated carboxylic acid esters were... 

Adams and Pachter found that the reaction of 2-aminopyridine and 2-bromoacrylic acid yields a mixture of 2-oxo-2//-pyrido[ l,2-a]pyrimidine (18) and 3,4-dihydroimidazo[l,2-a]pyridine-2-carboxylic acid (17). The product ratio was dependent upon the reaction conditions.18... 

Mendel44 found that reaction of 2-aminopyridine-3-carboxylic acid with ethyl acetoacetate or ethyl benzoylacetate gave rise to a decarboxylated product (36 R1 = Me, Ph R = R2 = H), whereas with ethyl 4,4,4-tri-fluoroacetoacetate, the product was ethyl 2-aminopyridine-3-carboxylate. Yale51 obtained 3-benzoyl-2-hydroxy-4-oxo-4ff-pyrido[ 1,2-a] pyrimidine in 4- 5%, yield from 2-amino-3-methylpyridine and ethyl benzoylacetate in diethylbenzene. 

Thermal cyclization of the isopropylidene ester of the malonates (70) was accompanied by decarboxylation at position 3, whereby 4-oxo-4H-pyrido-[l,2-fl]pyrimidines (74 R1 = H) were obtained.79,142,143 When the cyclization was performed in phosphoryl chloride-polyphosphoric acid and the reaction mixture was treated with alcohol, 4-oxo-4H-pyrido[l,2-a]pyri-midine-3-carboxylic acid esters were isolated.151 Treatment of the reaction mixture with water gave carboxylic acids. 

Okamoto et a/.156 cyclized the dinitriles (86 R = CN, R2 = H) by heating in 15° hydrochloric acid to obtain pyrido[l,2-a]pyrimidine-3-carboxylic acids (89 R2 = H). 2-Aminopyridinium chloride and ethoxymethylene-malononitrile at 110CC yielded 3-cyano-4-imino-4H-pyrido[l,2-a]pyrimi-dine (87 R1 = R2 = H, X = NH) and compound 91. Under similar conditions, 2-amino-3-methylpyridine gave a noncyclized product of type 91. 

Depending on the reaction conditions, alkaline hydrolysis of the 3-alkoxycarbonylpyrido[l,2-a]pyrimidines (71) afforded the corresponding pyrido [ 1,2- ]pyrimidine-3-carboxylic acids,18148 pyridylaminoacrylates (73 R = H)256 or 2-aminopyridines.126 Acidic hydrolysis produced the half-ester of 70.75 133-148... 

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