School of Natural Sciences, Department Chemie, and Catalysis Research Center (CRC), Technische Universität München, Lichtenbergstrasse 4, 85747 Garching, Germany.
J Am Chem Soc. 2021 Dec 22;143(50):21241-21245. doi: 10.1021/jacs.1c11266. Epub 2021 Dec 13.
A photochemical deracemization of 5-substituted 3-phenylimidazolidine-2,4-diones (hydantoins) is reported (27 examples, 69%-quant., 80-99% ). 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 hydrogen binding, one substrate enantiomer displays the hydrogen atom at the stereogenic center to the photoexcited catalyst allowing for a HAT from the substrate and eventually for its conversion into the product enantiomer. The product enantiomer is not processed by the catalyst and is thus enriched in the photostationary state.
报道了 5-取代 3-苯基咪唑烷-2,4-二酮（海因）的光化学外消旋化（27 个实例，69%-定量，80-99%）。该反应由手性二芳基酮催化，其显示出两点氢键结合位点。机理证据（DFT 计算、自由基钟实验、H/D 标记）表明该反应通过选择性氢原子转移（HAT）发生。在氢键形成时，一个底物对映体将手性中心的氢原子转移到光激发的催化剂上，从而从底物中发生 HAT，并最终转化为产物对映体。产物对映体不受催化剂处理，因此在光稳态中富集。
