9-Nitro-4-oxo-l,6,7,8-tetrahydro

Nitro-4-oxo-l, 6,7,8-tetrahydro-4/f-pyrido[l, 2-a]pyrimidines 534 (R = 6-, 7-, and 8-Me) or 538 were also obtained from 9-formyl-4-oxo-1,6,7,8-tetrahydro-4i/-pyrido[l,2-a]pyrimidine-3-carboxylates 536 with Clayfen in 24-54% yields (90JOC6198), or from 9-bromo-6-methyl-6,7,8,9-tetrahydro-4//-pyrido[l,2-a]pyrimidin-4-ones 537 with sodium nitrite in 40-62% yields (87H869). From the reaction mixture of 9-formyl-6-methyltetrahydropyridopyrimidine-3-carboxylate 536 (R = 6-Me) both 32% of 9-nitro derivative 534 (R = 6-Me) and 5% of dinitro compound 535 (R = Me) were isolated following column chromatography (90JOC6198). 

Nitro-4-oxo-l,6,7,8-tetrahydro- and 9,9-dinitro-4-oxo-6,7,8,9-tetrahydro-47/- derivatives of (12) and its 2,3-benzologue could be prepared from 9-hydroxyimino-4-oxo-6,7,8,9-tetrahydro- and 9-formyl-4-oxo-l,6,7,8,9-tetrahydro-47/ derivatives of (12) and its 2,3-benzologue using Clayfen <90JOC6198>. 

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