3- Chloro-2-hydroxy-4//-pyrido

Chlorination of 2-hydroxy-4//-pyrido[l,2-n]pyrimidin-4-one with NCS in a mixture of AcOH and TFA at room temperature for 72 h yielded a 3-chloro-2-hydroxy derivative (95JMC4687). Bromination of 2-chloro-4//-pyrido[l, 2-n]pyrimidone with Br2 in a mixture of CH2CI2 and pyridine at room temperature for 15 min gave a 3-bromo derivative (00BMC751). 

Methoxy-4//-pyrido[],2-n]pyrimidin-4-one was prepared from 2-chloro-4//-pyrido[],2-n]pyrimidin-4-one with NaOMe in MeOH for 16h, and from n /iyJro-(2-hydroxy-4-oxo-4//-pyrido[l, 2-n]pyridinium)hydroxide with Me2S04 in the presence of NaOMe in MeOH for 3h at room temperature in 93% and 41% yields, respectively (99JCS(P2)1087). 2-(2-Hydroxyethoxy)-4//-pyrido[],2-n]pyrimidin-4-one was prepared from the 2-chloro derivative with HOCH2CH2OH in the presence of K2CO3 at 160 °C for 1 h (00BMC751). 

Heating 2-chloro-4-phenylimino-4//-pyrido[ 1,2-a]pyrimidine 80 in 6N aqueous hydrogen chloride under reflux for 30 minutes afforded a mixture of 2-chloro-4//-pyrido[ 1,2-a]pyrimidin-4-one 312 and 2-hydroxy-4-phenylimino-4//-pyrido[ 1,2-a Jpyrimidine 313 in 10% and 24% yields, respectively (87JHC329). 

Reaction of 2-hydroxy-4//-pyrido[l,2-u]pyrimidin-4-ones 168 and 2-chloromethylsaccharins 169 in the presence of a base gave 2-<9-alkylated products 170 (94EUP626378, 95JMC4687, 95USP5378720). From the reaction mixture of 3-chloro derivative 168 (R = H, R = Cl) and... 

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). 

Chloro-5-oxo-2,3-dihydro-5/7-pyrido[l,2,3-.S( ]-l,4-benzothiazine-6-carboxylate 1,1-dioxide was prepared from the 7-hydroxy derivative by treatment with Ph3P and CC14 <2000WO00/006580>. 

Reduction of 3-benzyl-8-chloro-4-oxo-4//-pyrido[l,2- ]pyrimidine-2-carboxylate <2004W004/064741> and 2-methyl-4-oxo-4//-pyrido[l,2-tf]pyrimidine-3-carboxylate <2003T4123> with DIBAL-H afforded 2- and 3-formyl derivatives, respectively. Reduction of /V-(4-fluorobenzyl)-3-hydroxy-8-[methoxy(methyl)amino]-4-oxo-6,7,8,9-tetra-hydro-4//-pyrido[l,2- ]pyrimidine-2-carboxamide with Zn-dust in aqueous AcOH afforded the 8-methylamino derivative, which was acylated with AcOH in the presence of Hiinig s base, HOBt, and l-(3-dimethylaminopro-pyl)-3-ethylcarbodiimide-HCl <2004W004/058756>. 3-(Perhydropyrido[l,2- ]pyrimidin-2-yl)propylamine was obtained by catalytic hydrogenation of 2-(perhydropyrido[l,2- ]pyrimidin-2-yl)propionitrile over a Pt02 catalyst <2003FRP1275647>. 

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