作者:M. Alice Carvalho、Magdi E. A. Zaki、Yolanda Álvares、M. Fernanda Proença、Brian L. Booth
DOI:10.1039/b406806h
日期:——
malononitrile and methylcyanoacetate with a mild acid catalysis (ammonium acetate or piperidinium acetate) to give 6-enaminopurines 6a, 6d, 6f, 6g and 6k in very good yields. Only low yields were obtained for the 6-enaminopurine 6j, as competing nucleophilic attack on C-8 of either 3d or 6jcauses ring opening with formation of pyrimido-pyrimidines 11 and 10a respectively.
从5-氨基-4-氰基甲酰亚胺基咪唑合成6-烯氨基嘌呤6已经使用了两种不同的方法。在第一种方法中,将咪唑1与乙氧基亚甲基丙二腈或乙氧基亚甲基氰乙酸酯在温和的实验条件下反应,生成9-取代的6-(1-氨基-2,2-二氰基乙烯基)嘌呤6a-f或9-取代的6-(1 -氨基-2-氰基-2-甲氧基羰基乙烯基)嘌呤6g-k。假定这些反应是通过咪唑-吡咯烷中间体7发生的,该中间体迅速重排为6-烯氨基嘌呤6。在第二种方法中,由5个氨基步骤从5-氨基-4-氰基甲酰亚胺基咪唑制备的6-甲氧基甲酰亚胺基嘌呤3,1在温和的酸催化下(乙酸铵或乙酸哌啶)与丙二腈和氰基乙酸甲酯反应,生成6-烯氨基嘌呤6a,6d,6f,6g和6k的产量非常高。对于6-烯氨基嘌呤6j仅获得低产率,因为对3d或6j的C-8的竞争性亲核攻击导致开环并分别形成嘧啶基-嘧啶11和10a。