Photochemical Deracemization at sp<sup>3</sup>-Hybridized Carbon Centers via a Reversible Hydrogen Atom Transfer
作者:Johannes Großkopf、Manuel Plaza、Antonia Seitz、Stefan Breitenlechner、Golo Storch、Thorsten Bach
DOI:10.1021/jacs.1c11266
日期:2021.12.22
A photochemical deracemization of 5-substituted 3-phenylimidazolidine-2,4-diones (hydantoins) is reported (27 examples, 69%-quant., 80–99% ee). The reaction is catalyzed by a chiral diarylketone which displays a two-point hydrogen bonding site. Mechanistic evidence (DFT calculations, radical clock experiments, H/D labeling) suggests the reaction to occur by selective hydrogen atom transfer (HAT). Upon
报道了 5-取代的 3-苯基咪唑烷-2,4-二酮(乙内酰脲)的光化学去外消旋作用(27 个例子,69%-quant.,80-99% ee)。该反应由具有两点氢键位点的手性二芳基酮催化。机械证据(DFT 计算、自由基时钟实验、H/D 标记)表明反应是通过选择性氢原子转移 (HAT) 发生的。在氢结合后,一种底物对映异构体将立体中心处的氢原子展示给光激发催化剂,从而允许来自底物的 HAT 并最终将其转化为产物对映异构体。产物对映异构体不被催化剂处理,因此在光稳定状态下富集。