Ring transformation of 5-acylpyrimidines into 4-acylpyrazoles with hydrazine and phenylhydrazine in acidic medium
作者:Kaname Takagi、Abdelilah Bajnati、Michel Hubert-Habart、Hiroshi Terada
DOI:10.1002/jhet.5570270701
日期:1990.11
yrimidine (5a) led to 4-benzoyl-3-methyl-1-phenylpyrazole (11) via the initial formation of phenylhydrazones of pyrimidines 4a and 5a. However, 5-benzoyl-4-methyl-2-phenylpyrimidine (4b) and 5-acetyl-2,4-diphenylpyrimidine (5b) reacted with phenylhydrazine to afford, each of them, a mixture of two isomeric pyrazoles. The mechanism of these ring contraction reactions is discussed.
5-苯甲酰基-4-甲基嘧啶4a,b和5-乙酰基-4-苯基嘧啶5a,b与肼在酒精酸性介质中反应,分别得到4-乙酰基-3-苯基吡唑7、9和10以及4-苯甲酰基-3-甲基吡唑6、8和11。在与苯肼的反应中,5-苯甲酰基-4-甲基-2-甲基硫代嘧啶(4a)仅导致4-乙酰基-1,3-二苯基吡唑(10),而5-乙酰基4-苯基-2-甲基硫代嘧啶(5a)导致4-苯甲酰基-3-甲基-1-苯基吡唑(11)通过嘧啶4a和3d的苯hydr的初始形成5a。然而,5-苯甲酰基-4-甲基-2-苯基嘧啶(4b)和5-乙酰基-2,4-二苯基嘧啶(5b)与苯肼反应,以各自提供两种异构的吡唑的混合物。讨论了这些环收缩反应的机理。