Imidazo triazines, reaction with

Dioxane solutions of 4(5)-aminoimidazole (64) have been treated with several reagents [92JCS(P1)2789], Imidazo[l,5-a]-l,3,5-triazines (65 R = Ph, Me SMe) were obtained by reaction with methyl N-cyanobenzimidate (57 R = Ph), ethyl N-cyanoacetimidate (58 R = Me), and dimethyl yV-cyanodithioiminocarbonate (59 R = SMe). The uncy-clized product (68 R = H) (73%), obtained by condensation with ethyl N-cyanoformimidate (58 R = H), underwent facile cyclization to give the imidazo[l,5-a]-l,3,5-triazine (65 R = H). Likewise, the condensation adduct (69 R = H) (78%) was obtained using ethoxy methyleneurethane (60 R = H) and this underwent base-catalyzed cyclization to give the imidazo[ 1,5-a]-1,3,5-triazinone (67). Imidazo[l, 5-a]pyrimidines (66 R = H, Me) were obtained from the condensation of 4(5)-aminoimidazole... 

In a study involving 3-methylfervenulin 50 (R = Me) <1996JHC949>, shown in Scheme 4, it was found that reaction with methanolic methylamine or ethylamine at room temperature gave the imidazo[4,5-i ]-l,2,4-triazines 52a and 52b, respectively. This transformation is believed to proceed via the intermediate l,2,4-triazin-6-yl urea derivatives 51. The same investigation showed that the reaction of a range of 3-alkylfervenulins 50 with ethanolic sodium hydroxide gave the 3-alkyl imidazo[4,5-i ]-l,2,4-triazines 53. 

The presence or absence of the dioxolane protecting group in dienes dictates whether they participate in normal or inverse-electron-demand Diels-Alder reactions.257 The intramolecular inverse-electron-demand Diels-Alder cycloaddition of 1,2,4-triazines tethered with imidazoles produce tetrahydro-l,5-naphthyridines following the loss of N2 and CH3CN.258 The inverse-electron-demand Diels-Alder reaction of 4,6-dinitrobenzofuroxan (137) with ethyl vinyl ether yields two diastereoisomeric dihydrooxazine /V-oxide adducts (138) and (139) together with a bis(dihydrooxazine A -oxide) product (140) in die presence of excess ethyl vinyl ether (Scheme 52).259 The inverse-electron-demand Diels-Alder reaction of 2,4,6-tris(ethoxycarbonyl)-l,3,5-triazine with 5-aminopyrazoles provides a one-step synthesis of pyrazolo[3,4-djpyrimidines.260 The intermolecular inverse-electron-demand Diels-Alder reactions of trialkyl l,2,4-triazine-4,5,6-tricarboxylates with protected 2-aminoimidazole produced li/-imidazo[4,5-c]pyridines and die rearranged 3//-pyrido[3,2-[Pg.460]

The reaction of the substituted 4-aminoimidazo[l,2-Z>][l,3,5]triazine (55) with ethoxymethylene malonate afforded ethyl 4-oxo-4/f-imidazo[3,4-c]pyrimido [l,2-a][l,3,5]triazine-3-carboxylate (56) (Equation (4)) <92JCS(P1)2789>. 

Upon reaction with thiosemicarbazide, 4,5-dihydroxyimidazolin-2-ones provide the C-C fragment for the 1,2,4-triazine ring of the imidazo[4,5- ]-l,2,4-triazine ring system (Scheme 134) <2006RGB836, 2006RCB865>. 

Imidazo[l,2-c/][l,2,4]triazines 488 were prepared (78USP4096257) from the reaction of 2-imidazocarboxylic acid hydrazide 487 with orthoesters. They inhibited cyclic-AMP phosphodiesterase in the mouse skin phosphodiesterase test and had antiasthina. 

Hydrolysis of isofervenulins 268 with aqueous base occurred at the C2—N3 bond to give A -carboxy-TV-methylcarbamoyltriazines 301, which were transformed to 268 by acidification of the reaction mixture. On the other hand, base-catalyzed hydrolysis of 268 gave imidazo[4,5-< ][l,2,4]tri-azines 302 (87KGS1555). Hydrolysis of the pyrimidotriazine derivatives with alkali gave the triazines 303 and 304 (77JPR522 87JPR290). 

Cyclocondensation of 754 with phenacyl bromide gave (86JHC721) 3-phenyl-7,7,11 -trimethyl-8//-benzopyrano[4,3-e]imidazo[ 1,2-b] [1,2,4]-triazine 755. Cyclization of the 3-hydrazino derivative 756, with formic acid gave 757. Compounds 754 and 756 were prepared by reaction of the triazinobenzopyrane 753 with phosphorus oxychloride, followed by amination or hydrazinolysis (86JHC721). 

By reactions of different 13,4-triazine derivatives, C-ribosyl imidazo[2,l-/][13,4]triazines <99JCS(P1)2929> and C-ribosyl 13.4-triazolo[3,4-/ [13,4]triazines <99JCS(P1)2937> have been synthesized as inhibitors of adenosine and AMP deaminases. Catalytic asymmetric aminohydroxylation with amino substituted 13,4-triazine and 133-tiiazine derivatives, as nitrogen sources, has been described <99AG(E)1080>. 

Reactions of 3-hydrazino-l,2,4-triazin-5-one derivatives with carbonyl compounds to give triazolotriazine derivatives have been reported <03KGS1376>. Intramolecular inverse electron demand cycloadditions of 2-substituted imidazoles with various 1,2,4-triazines produced both imidazo[4,5-c]pyridines (3-deazapurines) and pyrido[3,2-[Pg.387]

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