作者:S.M.S. Chauhan、H. Junjappa
DOI:10.1016/0040-4020(76)85196-4
日期:1976.1
The α-ketoketene-S,S,-acetals 2a–h have been synthesized from the appropriate ketones 1a–f in good yields by extending the established method. The acetals 2a–d react with guanidine in the presence of sodium ethoxide to give pyrimidines 4a–d in 35–59% overall yields (Scheme 1). Treatment of 2e with guanidine similarly gave 5a in 23% yield. However, the reaction of 2e with guanidine in the presence of
通过扩展既定方法,由适当的酮1a-f以高收率合成了α-酮基-S,S,-缩醛2a-h。乙缩醛2a–d在乙醇钠存在下与胍反应,以总产率35–59%生成嘧啶4a–d(方案1)。类似地,用胍处理2e得到5a,产率为23%。但是,在正丙醇钠存在下2e与胍的反应产生了三种产物的混合物,从中分离出5a作为主要产物(20%)与6a(7%)和7a(5%)。在相似的反应条件下,2f以相同的产率得到5b,6b和7b。在正丙醇钠存在下用胍处理2g–h分别只能得到8a(28%)和8b(23%)。这些嘧啶的形成涉及碱诱导的1,3-质子在2a–h中的迁移,从而生成中间烯烃10a–h。