9-Chloro-6,7,8,9-tetrahydro-4//-pyrido

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). 

In attempts to formylate the bicyclic compound 5-methyl-9-phenylhy-drazono-6,7,8,9-tetrahydro-4-oxo-4//-pyrido[l,2- z]pyrimidine 3-carboxy-late (129) with dimethylformamide-phosphoroxychloride at 90-100°C, a degenerate ring rearrangement took place, resulting in the formation of 7-(o -chloroethyl)-8-chloro-9-(A,A-dimethylaminomethylene)amino-6,7,8,9-tetrahydro-4-oxo-4H-pyrido[l,2-a]pyrimidine-3-carboxylate (131)... 

N-(3-chloro-5-methoxycarbonylphenyl)-5-bromo-l,2,3,4-tetrahydro-quinoline-8-carboxamide was obtained from 8-bromo-6,7-dihydro-lH,3H,5H-pyrido[3,2,l-z/][3,l]benzoxazine-l,3-dione with methyl 3-amino-5-chlorobenzoate in NMP at 170 °C for 16 h (07WOP2007/028789). 

Heating 6-(4-chloro-3-hydroxybutyl)-2,4-dimethoxy-5-methylpyrimidine in MeOH saturated with gaseous NH3 at 60 °C overnight gave 7-hydroxy-3-methoxy-4-methyl-5,6,7,8-tetrahydro-lH-pyrido[l,2-c]pyrimi-din-l-one in 72% yield (05MI3). 

Tetrahydro-4-oxo-4H-pyrido[l,2-a]pyrimidines contain an active methylene group in position 9, which permits versatile transformations. " Depending on the molar ratio, halogenation of 4-oxo-6,7,8,9-tetra-hydro-4//-pyrido[l,2-fl]pyrimidines gave 9-halo or 9,9-dihalo com-pounds. " 9-Bromo- or 9-chloro-6-methyl-4-oxo-6,7,8,9-tetra-hydro-4H-pyrido[l,2-a]pyrimidine-3-carboxylic acids were obtained as 4 1 mixtures of the thermodynamically more stable 6,9-diaxial and the 6-axial, 9-equatorial-substituted diastereoisomers. ... 

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