9-Hydroxy-2,3-dimethyl-477-pyrido

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). 

Reaction of 2-aminopyridine with dimethyl 2-methylmalonate in the presence of some drops of cone. HCl at 150°C for 1 h (96EUP733633), and with diethyl 2-(l-decyl)malonate at 120°C for 5 min (94JCR(S)206) gave 2-hydroxy-3-methyl- and 2-hydroxy-3-(l-decyl)-4//-pyrido[l, 2-n]pyrimidin-4-ones in 2.2% and 7.5% yields, respectively. Reaction of 3-benzyl-2-aminopyridine and diethylmalonate at 190-200 °C for 4 h yielded 9-benzyl-2-hydroxy-4//-pyrido[l, 2-n]pyrimidin-4-one (01MIP9). Cyclocondensation... 

PPA and AcOH at 100°C for 4 h gave 9-hydroxy-2,3-dimethyl-4/f-pyrido-[1,2-n]pyrimidin-4-one in 24% yield (96EUP733633). Reaetion of 2-aminopyridine and ethyl 2-aeetoxyaeetoaeetate in boiling EtOH gave 2-methyl-3-hydroxy-4//-pyrido[l,2-n]pyrimidin-4-one in 47% yield (94KFZ(10)23). 

The 2-hydroxyl group of 3-[4-(2-cyanophenyl)phenyl]-2-hydroxy-4//-pyrido[l,2-a]pyrimidin-4-ones were alkylated with various alkyl bromides (94MI2). O-Alkylation of 2-hydroxy-4//-pyrido[ 1,2-a]pyrimidin-4-ones 378 with 2-chloromethyl-4-isopropyl-6-methoxysaccharine 379 in dimeth-ylformamide in the presence of potassium tert-butoxide or sodium hydride for 1 hour or for 2.5 days, or in a mixture of methanol and dimethyl-formamide in the presence of cesium carbonate for 2 days at room temperature, gave proteolytic enzyme inhibitor pyridopyrimidinones 380 (93EUP547708). 

The relative stereostructure of 9-acetyl-7-hydroxy-l,2-dimethyl-7-meth-oxycarbonyl-4-phenyl-6-oxo-l, 4,7,8-tetrahydro-6/7-pyrido[l, 2-u]pyri-midine-3-carboxylate 122 was justified by an X-ray diffraction analysis (97JOC3109). The stereochemistry and solid state structure of racemic trans-6,9-//-l, 6-dimethyl-9 z-ethoxy-9-hydroxy-4-oxo-l,6,7,8,9,9 z-hexahydro-4//-pyrido[l,2- z]pyrimidine-3-carboxylate (123), adopting a cw-fused conformation, were determined by X-ray investigations (97H(45)2175). 

Oxidation of 7-hydroxy- and 7-aryl-5-oxo-2,3-dihydro-5//-pyrido[l,2,3- f< ]-l,4-benzothiazine-6-carboxylates and 6-carboxamides with 3-chloroper-oxybenzoic acid in CH2CI2 yielded sulfoxides and sulfones, depending on the molar ratio of the substrate and oxidizing agent (00MIP7). A sulfoxide was prepared by the oxidation of ethyl (3S)-3-methyl-10-(2,6-dimethyl-4-pyridyl)-7-oxo-2,3-dihydro-7//-pyrido[l,2,3-<7c]-l,4-benzothiazine-6-carbox-ylate (OOMIPIO). 

The 5-methyl derivative 43 was obtained from pyrido[l,2-h]cinnolin-6-ium hydroxide inner salt 17 (R = H) with dimethyl sulfate (74JHC125). Protonation of 17 (R = H) occurred on the 5-nitrogen and not the oxygen, but its 1,2,3,4,7,8,9-octahydro derivative 45 was protonated on the oxygen to produce the 11-hydroxy salt. 

The structures of anhydro 9,9-dimethyl-4-hydroxy-2-oxo-6,7,8,9-tetrahy-dro-2H-pyrido[2,l- >] [1,3]thiazinium hydroxide (95JOC3795,95T6651) and llh-isopropyl-2-methoxy-3,4-diphenyl-2,6,7,llh-tetrahydro-[l,3]thiazino-[2,3-a]isoquinoline [79AX(B)1285] were determined by means of X-ray diffraction analysis. 

The cyclocondensation of 2-aminopyridines and dimethyl diacetoxy-fumarate in refluxing methanol in the presence of p-toluenesulfonic acid for 3 hours gave 3-hydroxy-4-oxo-4//-pyrido[l, 2-a]pyrimidine-3-carboxylates 208 (90OPP532). 

When 7-nitro-2-hydroxy-4-oxo-4//-pyrido[ 1,2-a]pyrimidine-3-carboxyl-ate 119 (R = N02, R1 = H) was boiled in an alcohol for 15 minutes, it was partly converted to diesters 315 (R = COOalkyl) (92AJC1825). If the 7-nitro derivative was heated in hexachloroacetone or in dimethyl sufoxide, malonamate 315 (R = H) was formed, presumably due to traces of adventitious water. 

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