Studies on pyrazines. Part 34.1 Synthetic approach, stability and tautomerism of 2,6-dihydroxypyrazines
作者:Nobuhiro Sato、Kaori Matsumoto、Masayuki Takishima、Katsura Mochizuki
DOI:10.1039/a704415a
日期:——
Demethylation of 2,6-dimethoxy-3,5-diphenylpyrazine with iodotrimethylsilane gives the corresponding 2,6-dihydroxy- and 2-hydroxy-6-methoxy-pyrazines, whilst the 3-methyl-5-phenyl analogue affords only monohydroxy compounds. In contrast, 2,6-dimethoxy-3,5-dimethylpyrazine decomposes completely under the demethylation conditions. Hydrolysis of 2,6-diacetoxypyrazines succeeds only in the formation of 2,6-dihydroxy-3,5-diphenylpyrazine. The stability of 2,6-dihydroxypyrazines is discussed on the basis of observations made in the synthetic approach. In addition, it has been established, on the basis of UV spectral analysis, that the 2-hydroxy-6-methoxypyrazines obtained in our work exist predominantly in the hydroxypyrazine form rather than as 1,2-dihydropyrazin-2-ones.
用碘三甲基硅烷对 2,6-二甲氧基-3,5-二苯基吡嗪进行脱甲基处理,可得到相应的 2,6-二羟基和 2-羟基-6-甲氧基吡嗪,而 3-甲基-5-苯基类似物只能得到单羟基化合物。相反,2,6-二甲氧基-3,5-二甲基吡嗪在去甲基化条件下会完全分解。2,6-二乙酰氧基吡嗪水解后只能生成 2,6-二羟基-3,5-二苯基吡嗪。根据合成方法中的观察结果,讨论了 2,6- 二羟基吡嗪的稳定性。此外,还根据紫外光谱分析确定,我们工作中获得的 2-羟基-6-甲氧基吡嗪主要以羟基吡嗪的形式存在,而不是以 1,2-二氢吡嗪-2-酮的形式存在。