Degradative ring opening of pyrido and pyrazino 3-benzenesulfonyloxyuracils and their conversion to condensed pyrazolones and triazolones

Ring opening, followed by an immediate Lossen rearrangement, of 3-benzenesulfonyloxypyrido3,2-d, 3,4-d and 4,3-d]pyrimidine-2,4(1H,3H)diones with sodium methoxide in methanol furnished good yields of the methyl esters of 3-2-(methoxycarbonyl)hydrazino]-2-, 3-2-(methoxycarbonylhydrazino]-4- and 4-2-(methoxycarbonyl)hydrazino]-3-pyridinecarboxylic acids, respectively. These hydrazino esters were cyclized to the corresponding pyridopyrazolones. However, the reaction of 3-benzenesulfonyloxypyrido2,3-d]pyrimidine-2,4(1H,3H)dione with sodium methoxide produced 8-methoxycarbonyl-s-triazolo4,5-a]pyridin-3(2H)one. In similar fashion, sodium methoxide converted 3-benzenesulfonyloxylumazine to 8-methoxycarbonyl-s-triazolo4,3-a]pyrazin-3(2H)one.