4,9-Dioxo-6,7,8,9-tetrahydro-47/-pyrido

Aus 2,2, 4,4 -Tetranitro-biphenyl-6,6 -dicarbonsaure labt sich bei —1,8 V (in 20% igem Athanol mit Phosphat-Alkali-Puffer) 2,7-Bis-[hydroxyamino -4,9-dihydroxy-5,10-dioxo-4,5,9,10-tetrahydro-(pyrido-[2,3,4,5-1, m,n]-phenanthridin) (F >400°) ge-winnen ... 

Oxo-2,3,6,7-tetrahydro-5//-pyrido[l,2,3- /e]-l,4-benzoxazine-2-carbox-ylates (291, X = H2) were obtained by hydrogenation of 4-substituted 3, 4-dihydro-2//-1,4-benzoxazine-2-carboxylates (290, X = H2) over 10% Pd/C catalyst, then by the treatment of free acids with (CF3C0)20 (99EUP894796). 5,7-Dioxo-2,3,6,7-tetrahydro derivatives 291 (X = 0) were prepared similarly from 290 (X = O). The products 291 (X = O) exist in 7-hydroxy-5-oxo-2,3-dihydro-5// tautomeric form. 

Thermolysis of 3-alkyloxy- and 3-aroyloxy-5-phenyl-l,2,4-pyrrolo[l,2- ]quinoxaline-l,2,4-triones afforded 5-phenyl-9-(4-phenyl-3-oxo-3,4-dihydro-2-quinoxalinyl)-6,8,10-trioxo-5,6,9,10-tetrahydro-87/-pyrido[l,2-tf ]quinoxaline-7,9-dicarboxylates <2000CHE615, 2004CHE1295> and 7-aroyl-8-aroyloxy-5-phenyl-9-(4-phenyl-3-oxo-3,4-dihydro-2-quinoxalinyl)-5,6-dihydro-1077-pyrido[l,2- ]quinoxaline-6,10-diones <2002CHE498>, respectively. Thermolysis of 3-aryl-2-(5-aryl-2,3-dioxo-2,3-dioxo-4-furanyl)quinoxalines gave 7-aroyl-8-aroyloxy-6-aryl-9-(3-aryl-2-quinoxalyl)-10/7-pyrido[l,2- ]quinoxalin-10-ones <2001CHE1314, 2002RCB850>. 

In other somewhat related work, the synthesis of pyrano[2,3-c]azepines (and pyrido[2,3-c]azepines has been described. Reaction of hydrazoic with iV-(5,6,7.8-tetrahydro-2,5-dioxo-2W-l-benzopyran-3-yl)benzamide (or 8-hydrazono) derivatives afforded pyrano[2,3-c]azepines, which in turn can be transformed to pyrido[2,3-c]azepines <00H(53)1111>. 

Ring transformation of ethyl 2,4-dioxo-l,2,3,4-tetrahydropyrido[2,3- pyrimidine-5-carboxylates 317 with 80% hydrazine hydrate in boiling ethanol gave a mixture of 5-methyl/allyl/benzylamino-l,2,3,4-tetrahydro-l,4-dioxopyr-ido[3,4-i/ pyridazines 318, pyrido[2,3,4-< <7]pyridazino[3,4-/ [l,2,4]triazepines 319, and a low yield of 2,3,4,6,7-penta-azaphenalene 320. The reaction of 317 with hydrazine hydrate was also performed without a solvent in an oil bath at 125 °C for 1 h to give the same products, but higher yields of 318 and lower yield of 319 as well as traces of 320 were obtained (Equation 25) <1997FA657>. 

Dioxo-6,7,8,9-tetrahydro-4//-pyrido[l, 2-a]pyrimidines 35 exhibit an oxo-enol tautomerism, which was studied by UV, IR, and NMR methods (85JHC1253). In the solid phase enol tautomers are present, while in a polar solvent an electron withdrawing substituent at position 3 shifts the equilibrium toward the enol form. The analogous 9-amino derivatives exist exclusively as 9-amino-6,7-dihydropyrido[l,2-a]pyrimidin-4-ones. 

Reaction of (R)-phenylglycinol with dimethyl acetylenedicarboxylate in boiling MeOH 12 h, followed by the treatment of the reaction mixture with acryloyl chloride yielded l,6-dioxo-3,4,7,8-tetrahydro-lH,6H-pyrido [2,l-c][l,4]oxazine-carboxylate 470 (07LOC4). 

Reaction of 9-fluoro-8-isothiocyanato- and 8-iso(thio)cyanato-3,5, 6,7-tetrahydro-2//-pyrido[l,2,3-de]-l,4-benzoxazines with 2-amino-4,4-dimethylpyrroline, then with Br2, and with ethyl pipecolinate yielded 8-(6, 6-dimethyl-3,5,7,7-tetrahydropyrrolo[2,l-c][l,2,4]thiadiazol-3-ylidenamino)-9-fluoro and 8-(l,3-dioxo and l-oxo-3-thioxoperhydroimidazo[l,5-a]-pyridin-2-yl) derivatives, respectively (89EUP406993). Treatment of 9-fluoro-8-(2-hydroxymethylpiperidinothiocarbonylamino)-3,5,6,7-tetrahydro-2//-pyrido[l,2,3-de]-l,4-benzoxazine with HC1 gas in EtOH gave the 8-(perhy-dropyrrolo[l,2-c]thiazol-3-ylidenamino) derivative. 

Pyrido[4,3-d pyrimidin 4-Amino-5,7-dioxo-2-hydroxy-8-phenylhydra-zono-5,6,7,8-tetrahydro- E9c, 210 (H/H - = N-NH-Ar)... 

IH-[Pg.1154]

Ethyl 2-(Methylsulfanyl)-4,5-dioxo-3,4,5,8-tetrahydro-8-(2,3,5-tri-0-acetyl-/J-D-ribofuranosyl)pyrido 2,3-4]-pyrimidine-6-carboxylate 198... 

Cinereain (50), a metabolite with plant growth-regulating activity from Botrytis cinerea, is 1-isopropyl - 4 - isobutylidene - 2,11 - dioxo -1,2,3,4 - tetrahydro - H- oxepino[3,2 - ]pyrido[3,2 - a -pyrazine <88ABC1725>. 

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