Site-Selective and Stereoselective C–H Alkylations of Carbohydrates via Combined Diarylborinic Acid and Photoredox Catalysis
作者:Victoria Dimakos、Hsin Y. Su、Graham E. Garrett、Mark S. Taylor
DOI:10.1021/jacs.9b01531
日期:2019.4.3
Diphenylborinic acid serves as a cocatalyst for site- and stereoselective C-H alkylation reactions of carbohydrates under photoredox conditions using quinuclidine as the hydrogen atom transfer mediator. Products arising from selective abstraction of the equatorial hydrogens of cis-1,2-diol moieties, followed by C-C bond formation with net retention of configuration, are obtained. Computational modeling supports
二苯基硼酸在光氧化还原条件下用作碳水化合物的位点和立体选择性 CH 烷基化反应的助催化剂,使用奎宁环作为氢原子转移介体。获得了选择性提取顺式 1,2-二醇部分的赤道氢,然后形成 CC 键并保留构型的产物。计算模型支持涉及形成四配位硼酸酯的机制,该机制通过极性匹配和/或离子配对效应加速氢原子与奎宁环衍生的自由基阳离子的转移。