Pyrazolo triazine-2,4 diones

In Scheme 7, ring-opening reactions of some fused pyrazoles are shown. Thus, Baraldi et al. <1999S453> described that the pyrazolo[l,5-<7][l,2,4]triazine-dione derivative 72 is sensitive toward nucleophiles its reaction with benzylamine at room temperature gives rise to the acyl semicarbazide 73 in high yield (78%). 

Chemical Name 5-(dimethylamino)-9-methyl-2-propyl-1 H-pyrazolo [ 1,2-a] [ 1,2,4] benzo-triazine-1,3(2H)-dione... 

Pyrimido[5, 4 4,5]pyrazolo[3,2-c][l,2,4]triazine derivatives 1049and 1050 were prepared by treatment of diazo compound 1048, prepared from 1047, with pentane-2,4-dione and ethyl acetoacetate, respectively [92JCS(Pl)239]. 

Several routes to pyrazolo[4,3-e]-l,2,4-triazines have been reported. Thus, treatment ofpyrazolidine-4,5-dione (141) with semicarbazide hydrochloride or with thiosemicarbazide in cold ethanolic sodium carbonate afforded the corresponding carbazones (142a) or thiosemicarbazones (142b), which cyclized into pyrazolo[4,3-e]-l,2,4-triazines (143), upon treatment with potassium carbonate (Scheme 21) (84JHC923, 84JPR994). 

The coupling of the 4,4,4-trifluoro-l-(thien-2-yl) butane-1,3-dione with azole diazonium salts gives the pyrazolo [5,1-c] triazine (xi), benzimidazo [5-1-c] 1,2,4-triazine (xii) and triazolo [3,3-c] 1,2,4-triazine (xiii) derivatives incorporating trifluoromethyl group [25]. 

Prepared by similar reactions was the 8-()3-D-ribofuranosyl)pyrazolo[l,5-a]l,3 5-triazin-4-one (840) related to inosine and formycin. In one route 832 reacted with iV-ethoxycarbonylformimidate (76JHC1305), and in the other the 3-amino-2-carbamoylpyrazol-4-yl C-nucleoside 839 reacted with triethyl orthoformate (80JHC1435) or l,3-dimethyl-l,3,5-triazine-2,6-dione in the presence of sodium ethoxide (86JHC349) (Scheme 219). 

A mixture of ethyl 4-amino-6-methylpyrazolo[5,l-c][l,2,4]triazine-3-carbonyl-carbamate, Na-carbonate, and water heated 15 min. on a steam bath 8-methyl-pyrazolo[5,l-c]pyrimido[4,5-e][l,2,4]triazine-2,4(lH,3H)-dione. Y 96.3%. J. Slouka, V. Bekarek, and J. Kubata, M. 105, 535 (1974). 

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