4//-Pyrido pyrimidin -4-ones reduction

The 3-amino group of 3,4-diamino-2//-pyrido[l,2-u]pyrimidin-2-ones 216, obtained from 3-nitroso derivatives by reduction with Na2S204 in 30% NH4OH at 70-80 °C, was acylated with acyl chlorides, and the acylated products 217 were cyclized to pyrido[2,l-Z)]purin-10-ones 218 by treatment with NaOMe (95JHC1725). 

Catalytic hydrogenation of the pyridine ring of 4-hydroxy-2-pyrrolidinopyrido[2,3- pyrimidine in the presence of H2/Pt02 in HCl gave 71. 2-(Pivaloylamino)-6-substituted pyrido[2,3-,7 pyrimidin-4(3//)-one gave the 5,6,7,8-tetra-hydro derivative 72 via similar catalytic reduction conditions in the presence of trifluoroacetic acid (TFA) at 800 psi hydrogen pressure for 40 h <1996WO9603406>. 

Catalytic reduction of 2//-pyrido[l,2-a]pyrimidin-2-one 78 (R = Et, R1 = Ph) with hydrogen over Raney nickel in ethanol at ambient tempera-... 

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. 

Reduction of 3-nitroso derivative 329 by treatment with activated zinc dust in boiling acetic acid for 6 hours gave 3-amino derivative 330 [91IJC(B)839]. 2,3-Diamino-4//-pyrido[ 1,2-a]pyrimidin-4-one was pre-... 

Reduction of 6,7,8,9-tetrahydro-4//-pyrido[l,2-a]pyrimidin-4-ones 341 and their quaternary salts 343 with sodium borohydride in water and methanol yielded the thermodynamically stable epimer 342 of 1,6,7,8,9,9a-hexahydro-4//-pyrido[l, 2-n]pyrimidin-4-ones (83SZP635100 85JOC2918),... 

Catalytic reduction of 3-phenyl-6,7,8,9-tetrahydro-4//-pyrido[ 1,2-a] pyrimidin-4-ones 350 over platinum oxide at 30°C under pressure of... 

The reaction of a molten mixture of 3,4-dihydro-2//-pyrido[ 1,2-a] pyrimidin-2-one 675 and phosphorous acid with phosphorus trichloride, followed by treatment of the reaction mixture with 2 N aqueous hydrochloric acid, afforded 3,4-dihydropyridopyrimidine-2,2-diphosphoric acid 676 in 38% yield (91GEP3930130). Catalytic reduction of diphosphonic acid 676 in water over platinum dioxide gave hexahydropyrido[l,2-a]pyrimi-dine-2,2-diphosphonic acid 677. 

In investigations by the author (1), Chen (2), and Cochran (3), imidazo-, (I), pyrido[2,3-d]pyrimidin-7-ones, (II), and isoquinoline derivatives, (HI), respectively, were prepared, which were effective in treating p38 kinase-mediated disorders by modulating IL-1, IL-6, and IL-8 and TNF-a. These agents were used in treating pathophysiological disorders such as rheumatoid arthritis, fever, and reduction of bone resorption. 

The expected product of reduction of the pyrido[3,4-fi(]pyrimid-4(3//)-one 445 with LAH is the l,2,3,4-tetrahydropyrido[3,4-fi(]pyrimidine 446. However, the product obtained (447) resulted from cleavage at the 2,3 posi-tion. High yields of the pyridine 447 were obtained after 1-h at room temperature with excess LAH. Reductive ring closures of fused pyrimidines and pyrimidin-4(3//)-ones has been reported previously to occur at the 1,2... 

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