2-Hydroxy-3-methyl-477-pyrido

Treatment of alkyl 9-benzyloxycarbonyl-3-methyl-6-oxo-2/7,6//-pyr-ido[2,l-f ][l,3]thiazine-4-carboxylates with BBr3 in CH2CI2 at -70 °C for 0.5-1 h and at room temperature for 3h yielded 9-carboxyl derivatives. The decarboxylation of these acids was unsuccessful. Hydrolysis of diethyl cA-3,4-H-3,4-dihydro-3-methyl-6-oxo-2//,6//-pyrido[2,l-f ][l,3]thiazine-4,9-dicarboxylate in aqueous EtOH with KOH at room temperature for 3 days yielded 4-ethoxycarbonyl-3,4-dihydro-3-methyl-6-oxo-2//,6//-pyrido-[2,l-f ] [1,3]thiazine-9-carboxylic acid (00JCS(P1)4373). Alkyl 9-hydroxy-methyl-3-methyl-6-oxo-3,4-dihydro-2//,6//-pyrido[2,l-f ][l,3]thiazine-4-car-boxylates were O-acylated with AC2O and (PhC0)20 in pyridine at room temperature for 12-48h. 

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. 

Piperazinomethyl)-9-hydroxy-4//-pyrido[l,2-u]pyrimidin-4-one was obtained by hydrolysis of the 2-(4-formylpiperazino)methyl derivative in boiling 10% HCl. The hydrolysis of the 2-(4-ethoxycarbonylpiperazino) derivative in NaOH solution was unsuccessful (95EJM27). 

The 3-formyl group of 8-substituted 3-formyl-2-hydroxy-4//-pyrido[l,2-n]pyrimidin-4-one was reacted with (cyanomethyl)- and (terr-butoxycarbo-nylmethylene)triphenylphosphorane in THF, and with 5-aminotetrazole in boiling MeOH for 9h to yield ( )-3-propenenitrile, terr-butyl ( )-3-propenoate and 3-[(2//-tetrazol-5-yl)imino]methyl derivatives, respectively (OlMIPl). 

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). 

Butyl- and 3-(3-methyl-2-buteny l)-2-hydroxy-4//-pyrido[ 1,2-a]py-rimidin-4-ones were prepared in the reaction of 2-aminopyridine and diethyl 2-butyl- and 2-(3-methyl-2-butenyl)malonates, respectively (84MI-14 89MI16). 

Cyclocondensation of pipecolinic acid and malic acid anhydride in pyridine afforded 3-hydroxy-2,3-dimethylperhydropyrido[l,2-a]pyrazine-l, 4-dione (74CB2804). Cyclocondensation of bis(2,4,6-trichlorophenyl) mal-onates with 2-methyl-, 2-benzyl- and 2-ethoxycarbonylmethylquinoxalines and -3-ones at 250°C afforded 8-hydroxy-10//-pyrido[l,2-a]quinoxalin-10-ones and their 5,6-dihydro-6,10-dione derivatives (77M103). Under Horner-Wittig reaction conditions, the reactions of 2-formylquinoxaline and dialkyl phosphonosuccinates (314) also involved cyclization to give alkyl 10-oxo-10//-pyrido[l,2-a]quinoxahne-8-carboxylate (80LA542). 

Amino-6-hydroxy-4-hydroxy-methyl-3-phenyl- E9a, 589 (7-OH — 4-Ar — < 1,2-oxazolo-[3,4-d]pyridazine)/Red.) Pyrido[l,2-a]benzimidazol 7-Nitro-... 

The reaction of 1,3-disubstituted perhydropyrido[l,2-c][l,3]oxazines (69) and 7-(benzothiazol-l-yl)-6,7-dihydro-17/,3//,5//-pyrido[3,2,l-iy][3,l]benz-oxazine with Grignard reagents led to 2-(/V-substituted 2-piperidyl)ethanols (70) (50JA358 58CLY2081) and l-benzyl-4-(benzotriazol-l-yl)-8-hydroxy-methyl-l,2,3,4-tetrahydroquinoline (95JOC3993), respectively. 

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