Highly Selective Hydrolysis of Chloropyrimidines to Pyrimidones in 12 N Hydrochloric Acid
作者:Amphlett G. Padilla、Bruce A. Pearlman
DOI:10.1021/op060093q
日期:2006.9.1
using methodological tools developed by Bunnett established that the transition state for hydrolysis of the 6-chloro isomer involves two more molecules of water (each acting as a base) than does the transition state for hydrolysis of the 2-chloro isomer. As the concentration of HCl increases from 3 N to 6 N to 12 N, there are fewer unprotonated water molecules. Thus, the transition state that involves
描述了无色谱法合成异构纯形式的6-哌嗪基-2,4-双-吡咯烷基基嘧啶。关键步骤是通过以下方法纯化粗制的6-氯-2,4-双-吡咯烷基基嘧啶/ 2-氯-4,6-双-吡咯烷基基嘧啶异构体混合物(通过2,4,6-三氯嘧啶与吡咯烷的反应生成) 2-氯异构体的高选择性酸催化水解为嘧啶酮。在6 N HCl中,2-氯异构体的水解速度是6-氯异构体的350倍,在12 N HCl中的水解速度是1750倍。为了正确看待这些比率,2-氯异构体与胺和醇盐的反应仅比6-氯异构体快约10-17倍。使用Bunnett开发的方法学工具进行的机械研究确定,6-氯异构体水解的过渡态比2-氯异构体水解的过渡态所涉及的水分子多于两个分子(每个都作为碱)。随着HCl浓度从3 N增加到6 N再增加到12 N,未质子化的水分子就会减少。因此,如所观察到的,涉及较多数量的未质子化的水分子(6-氯-2,4-双-吡咯烷基基嘧啶)的过渡态预计将