Steric and Electronic Control in the Addition of Hydrazine and Phenylhydrazine to α-[(Dimethylamino)methylene]-β-oxoarylpropanenitriles
作者:David E. Tupper、Mark R. Bray
DOI:10.1055/s-1997-1186
日期:1997.3
Reaction of hydrazine with α-[(dimethylamino)methylene]-β-oxoarylpropanenitriles 2 gives a mixture of the 4-aroyl-5-aminopyrazoles 3 and the 5-aryl-4-cyanopyrazoles 4. Similarly reaction of 2 with phenylhydrazine gives rise to the 5-amino-4-aroyl-1-phenylpyrazoles 5 and 5-aryl-4-cyano-1-phenylpyrazoles 6. The regioselectivity of addition has been investigated with respect to the electronic nature and steric requirements of the aromatic substitution. The ratio of products was found to be independent of the electronic nature of the substituent. The outcome of the reaction was however very sensitive to steric factors. Substituents in the para- and meta-positions favoured formation of the pyrazole-nitrile products 4 and 6, whereas sterically demanding ortho-substituents favoured the pyrazole-amino ketones 3 and 5.
肼与α-[(二甲氨基)亚甲基]-β-氧基芳烷腈 2 的反应生成4-酰基-5-氨基吡唑 3和5-芳基-4-氰吡唑 4的混合物。同样,2与苯肼的反应产生5-氨基-4-酰基-1-苯基吡唑 5和5-芳基-4-氰-1-苯基吡唑 6。关于芳香取代的电子性质和立体要求,添加的区域选择性进行了研究。发现产物的比例与取代基的电子性质无关。然而,反应的结果对立体因素非常敏感。对位和间位的取代基有利于形成吡唑腈产物 4 和 6,而立体要求较大的邻位取代基则有利于生成吡唑氨基酮 3 和 5。