Ethyl 9-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,... 

The structures of ethyl 2-hydroxy-4-oxo-4//-pyrimido[2,l-a]isoquinoline-3-carboxylate (20) (89AJC2161), 6-[2-(4-methyl-l-piperazinyl)acetamido]-ll//-pyrido[2,l-b]quinazolin-ll-one (89JHC1229), and 6,7,8,9-tetrahydro-ll//-pyrido[2,l-b]quinazolin-ll-one (95KPS410) were determined by X-ray crystallography. 

Reaction of 9-bromomethyl-4-oxo-4//-pyrido[ 1,2-a]pyrimidine-3-carboxylates 505 and their homologs with 2,4-dihydroxy-3-propyl-and -3-allyl-acetophenone 506 in boiling methyl ethyl ketone in the presence of potassium carbonate afforded 9-(4-acetyl-3-hydroxy-2-substituted phenoxymethyl) derivatives (507) [87EUP242230 88JAP(K)88/246375]. 

H-Pyrido[1,2-a]pyrimidine-3-acetic acid, 9-hydroxy-4-oxo-, ethyl ester 2601a ... 

Cyclopropyl-3-fluoro-2-hydroxy-6-oxo-6//-pyrido[l,2-n]pyrimidine-7-carboxylates 340 were obtained in the reaction of 2-cyclopropyl-2-(5-fluoro-4-hydroxy-2-pyrimidinyl)acetaldehyde (339) and ethyl, rerr-butyl and dibenzyl malonates in the presence of piperidine and AcOH (95MIP1, 96JMC3070, 96MIP4, 96USP5580872). 

Vilsmeier-Haack formylation of 2-(4-methyl-l-piperazinyl)-4//-pyrido-[l,2-n]pyrimidin-4-one with a mixture of POCI3 and DMF at 95°C gave a 3-formyl derivative (93FES1225) while ethyl 4-oxo-6,7,8, 9-tetrahydro-4//-pyrido[l,2-n]pyrimidine-2-acetate at 50 °C yielded a 9-dimethylaminomethylene-3-formyl derivative (01MI4). 3-Formyl-2-hydroxy-8-[2-(4-isopropyl-l,3-thiazol-2-yl)-l-ethenyl]-4//-pyrido[l,2-n]pyri-midin-4-one was obtained from the 3-unsubstituted derivative with oxalyl chloride-DMF reagent in CH2CI2 at room temperature for 3h (OlMIPl). 

Ring cleavage occurred during the saponification of ethyl 9-benzyloxy-and 9-hydroxy-4-oxo-4//-pyrido[ 1,2-a]pyrimidine-3-carboxylates (89TL1529). 

Heating 10-(4-methyl-l-piperazinyl) and 10-fluoro-substituted derivatives of ethyl 9-fluoro-3-methylene-7-oxo-2,3-dihydro-7//-pyrido[l,2,3-de]-l,4-benzoxazine-6-carboxylate in a 1 1 mixture of cone. HC1 and AcOH afforded 3-hydroxy-3-methyl-6-carboxylic acid derivatives (92CCC216). 

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