Efficient Synthesis of 3<i>H</i>-Imidazo[4,5-<i>b</i>]pyridines from Malononitrile and 5-Amino-4-(cyanoformimidoyl)imidazoles
作者:Magdi E. A. Zaki、M. Fernanda Proença、Brian L. Booth
DOI:10.1021/jo020347f
日期:2003.1.1
[4,5-b]pyridines 5, when the reaction was carried out in the presence of DBU, or to 3-aryl-5-amino-6,7-dicyano-3H-imidazo[4,5-b]pyridines 3, in its absence. Both reactions evolved from the adduct formed by nucleophilic attack of the malononitrile anion to the carbon of the cyanoformimidoyl substituent. A 5-amino-1-aryl-4-(1-amino-2,2-dicyanovinyl)imidazole 4 was isolated when this reaction was carried
1-Aryl-5-amino-4-(cyanoformimidoyl)imidazoles 2与丙二腈在温和的实验条件下反应,生成3-aryl-5,7-diamino-6-cyano-3H-咪唑[4,5-b]当在DBU存在下进行反应时,吡啶5或在不存在下与3-芳基-5-氨基-6,7-二氰基-3H-咪唑并[4,5-b]吡啶3进行反应。这两个反应都从丙二腈阴离子的亲核进攻形成的加合物演变为氰基甲亚氨基取代基的碳。当该反应在DBU存在下进行时,分离出5-氨基-1-芳基-4-(1-氨基-2,2-二氰基乙烯基)咪唑4。通过光谱方法以及与原甲酸三乙酯和乙酸酐反应来确认化合物4的结构,分别导致9-芳基-6-(氰基亚甲基)嘌呤11和12。咪唑2b也与乙酰乙酸乙酯反应,pK(a)与丙二腈相当的碳酸。使用了相似的反应条件,分离出的产物是6-氨基甲酰基-1,2-二氢嘌呤10,表明在这种情况下正在发挥不同的作用机理。