3- Nitro-4//-pyrido pyrimidin-4-ones

Diorganotin(IV) complexes with 4//-pyrido[l,2-n]pyrimidin-4-ones 109 (96MI4), complexes of 2-methyl- and 2-methyl-8-nitro-9-hydroxy-4//-pyrido[l,2-n]pyrimidin-4-ones with Ag(I), Cu(II), Ni(II), Co(II), and Mn(II) ions (00MI23), 2,4-dimethyl-9-hydroxypyrido[l, 2-n]pyrimidinium perchlorate and its complexes with prasedynium, neodymium, samarium and europium (00MI24) were characterized by UV spectroscopy. 

Diorganotin(IV) complexes (109) were prepared from 4/f-pyrido[l,2-a]pyrimidin-4-ones with Me2SnCl2 and Ph2SnCl2 in dry CHCI3 (96MI4). Different complexes of 2-methyl-9-hydroxy-4//-pyrido[l, 2-n]pyrimidin-4-one and its 8-nitro derivative were prepared with Cu(I)Cl, Cu(II)Cl2, Ni(II)Cl2, Co(II)Cl2, Mn(II)Cl2, and Ag(I)N03 m EtOH (00MI23). Complexes of 2,4-dimethyl-9-hydroxypyrido[l,2-n]pyrimidinium salt were obtained with Pr(III), Nd(III), Sm(III), and Eu(III) ions in acetone (00MI24). 

Nitration of 2-substituted 4/7-pyrido[l,2- ]pyrimidin-4-ones with 99% HN03 in cone. H2S04 gave 3-nitro derivatives <2000BMC751, 2001H(55)535>. Mannich reaction of 2-hydroxy-4//-pyrido[l,2-tf]pyrimidin-4-one afforded... 

The reaction of 3-benzyloxy-, 5-methoxy-, and 5-nitro-2-aminopyridines and 3-acetyl-4,5-dihydro-2(3//)-furanone in warm toluene in the presence of phosphoryl chloride afforded 3-(2-chloroethyl)-2-methyl-4//-pyrido[l, 2-a]pyrimidin-4-ones 102 (84EUP110435 90EUP368388 92USP5158952). 

Nitro-4//-pyrido[l,2-a]pyrimidin-4-ones 176 were prepared by the cy-clization of 6-unsubstituted 3-(2-pyridylamino)-2-nitroacrylates 175 (R1 = H) in polyphosphoric acid at 120°C for 1.5 hours in 50-63% yields [90JCR(S)308]. Instead of cyclizing, the 6-substituted derivatives 175 (R1 H) decomposed under these conditions. 

Heating 9-hydroxy-2-methyl-8-nitro-4//-pyrido[ 1,2-a]pyrimidin-4-one 326 in dimethylformamide in the presence of hydrazine hydrate and Raney nickel at 50°C afforded 8-amino derivative 327 (92KGS1660). 8-Amino derivative 327 was also prepared from 8-phenylazo derivative 328. 

Chemical reduction [with aqueous titanium(III) chloride in dilute acetic acid] or catalytic reduction (in the presence of 10% palladium-on-charcoal by transfer hydrogenation from cyclohexene or with hydrogen) of 3-nitro-4//-pyrido[l,2-a]pyrimidin-4-ones 176 (R = H, 8-Me, 8-OMe, 7-C1) gave 3-amino-4//-pyrido[l,2-a]pyrimidin-4-ones [90JCR(S)308]. Chemical and catalytic reduction of 3,8-dinitro-9-hydroxy-4//-pyrido[l,2-a]pyrimidin-4-one yielded an unstable product. 

Nitro-6-methyl-4//-pyrido[l,2-a]pyrimidin-4-one was prepared from 6-methyl-4//-pyrido[l,2-a]pyrimidin-4-one by nitration with a mixture of concentrated nitric and sulfuric acids at ambient temperature for 2 hours (85JHC481). 

Hydroxy-2-methyl-4//-pyrido[ 1,2-a]pyrimidin-4-one 365 gave 8-sub-stituted derivatives in a reaction with different electrophilic reagents (Scheme 28) (92KGS1660). Nitration gave 8-nitro-9-hydroxy-2-methyl-pyridopyrimidin-4-one 326. Reaction with iodine afforded 8-iodo-... 

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). 

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