Lewis Acid-Catalyzed Selective Reductive Decarboxylative Pyridylation of <i>N</i>-Hydroxyphthalimide Esters: Synthesis of Congested Pyridine-Substituted Quaternary Carbons
作者:Liuzhou Gao、Guoqiang Wang、Jia Cao、Hui Chen、Yuming Gu、Xueting Liu、Xu Cheng、Jing Ma、Shuhua Li
DOI:10.1021/acscatal.9b03798
日期:2019.11.1
practical and efficient Lewis acid-catalyzed radical–radical coupling reaction of N-hydroxyphthalimide esters and 4-cyanopyridines with inexpensive bis(pinacolato)diboron as reductant has been developed. With ZnCl2 as the catalyst, a wide range of quaternary 4-substituted pyridines, including highly congested diarylmethyl and triarylmethyl substituents, could be selectively obtained in moderate to good
开发了一种实用而有效的路易斯酸催化N-羟基邻苯二甲酰亚胺酯和4-氰基吡啶与廉价的双(频哪醇)二硼烷作为还原剂的自由基-自由基偶联反应。用ZnCl 2作为催化剂,可以选择性地以中等到良好的收率和宽泛的官能团耐受性,选择性地获得包括高度拥挤的二芳基甲基和三芳基甲基取代基在内的各种季4-取代的吡啶。结合理论计算和实验研究表明,路易斯酸可以与吡啶-硼基自由基的氰基配位,从而降低C-C偶联途径的活化势垒,从而导致4取代的吡啶的形成。此外,它还可以促进自由基-自由基偶联中间体的脱氰/芳构化。