4-Diazo-3,5-dimethylpyrazoleの反応性(第4報)Gomberg-Bachmann反応におけるHydroquinoneの触媒作用

概要

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Refluxing of 4-diazo-3,5-dimethylpyrazole (1) in benzene for a long time afforded 1H, 4H-3-methylpyrazolo [4,3-c] pyrazole (2), 3,5-dimethylpyrazole (6) and biphenyl in 15,12,and 7% yields, respectively, besides 4-phenyl-3,5-dimethylpyrazole (3) in 36% yield. Replacement of benzene with nitrobenzene in this reaction gave o-, m-, and p- isomers of 4-nitrophenyl-3,5-dimethylpyrazole in a ratio of 10 : 2.8 : 3.0. In these reactions, addition of hydroquinone in catalytic quantity (5% by weight of 1) was found to be very effective in increasing the field of 4-aryl-3,5-dimethylpyramle and reduction of reaction time. It was found that the intermediate in these reactions was a diazonium salt (7) which was formed by the addition of one mole of hydroquinone to two moles of diazo compound (1). From those observations, the reaction mechanism was discussed.
公益社団法人日本薬学会の論文
1974-01-25