Regioselective Direct C–H Arylations of Protected Uracils. Synthesis of 5- and 6-Aryluracil Bases
作者:Miroslava Čerňová、Igor Čerňa、Radek Pohl、Michal Hocek
DOI:10.1021/jo2006494
日期:2011.7.1
A new regioselective synthesis of 5- and 6-aryluracil bases based on direct C–H arylations of diverse 1,3-protected uracils has been developed. Benzyl-protected uracils were selected as the most practical in terms of stability during the arylation and facile cleavage of the benzyl groups. Pd-catalyzed C–H arylations in the absence of CuI gave preferentially 5-aryl-, whereas the reactions in the presence
基于多种1,3保护的尿嘧啶的直接C–H芳基化反应,已开发了一种5和6芳基尿嘧啶碱基的区域选择性合成新方法。就苄基的芳基化和容易裂解过程中的稳定性而言,选择苄基保护的尿嘧啶是最实用的。在没有CuI的情况下,Pd催化的CH芳基化反应优先生成5-芳基-,而在存在CuI的情况下,反应则生成6-芳基-1,3-二苄基尿嘧啶。通过在Pd / C上转移氢解或通过用BBr 3处理而进行的最终脱保护,以良好的收率得到了所需的游离芳基化的尿嘧啶碱。