中国科学技术大学汪义丰团队报道了硼基自由基催化实现不对称自由基环异构化反应。相关研究成果发表在2023年12月1日出版的《科学》。

开发用于对映选择性合成的功能不同的催化剂，是合成化学的一个突出但具有挑战性的目标。

该文中，研究人员报道了一类手性N-杂环卡宾（NHC）连接的硼基自由基作为催化剂，使催化不对称自由基环异构化反应成为可能。自由基催化剂可以由容易制备的NHC硼烷络合物产生，手性NHC组分的广泛可用性为立体化学控制提供了实质性的好处。

机理研究支持一个催化循环，该催化循环包括硼基自由基加成、氢原子转移、环化和消除硼基催化剂的序列，其中手性NHC亚基决定了自由基环化的对映选择性。这种催化作用能够从简单的起始材料不对称构建有价值的手性杂环产物。

附：英文原文

Title: Boryl radical catalysis enables asymmetric radical cycloisomerization reactions

Author: Chang-Ling Wang, Jie Wang, Ji-Kang Jin, Bin Li, Yee Lin Phang, Feng-Lian Zhang, Tian Ye, Hui-Min Xia, Li-Wen Hui, Ji-Hu Su, Yao Fu, Yi-Feng Wang

Issue&Volume: 2023-12-01

Abstract: The development of functionally distinct catalysts for enantioselective synthesis is a prominent yet challenging goal of synthetic chemistry. In this work, we report a family of chiral N-heterocyclic carbene (NHC)–ligated boryl radicals as catalysts that enable catalytic asymmetric radical cycloisomerization reactions. The radical catalysts can be generated from easily prepared NHC-borane complexes, and the broad availability of the chiral NHC component provides substantial benefits for stereochemical control. Mechanistic studies support a catalytic cycle comprising a sequence of boryl radical addition, hydrogen atom transfer, cyclization, and elimination of the boryl radical catalyst, wherein the chiral NHC subunit determines the enantioselectivity of the radical cyclization. This catalysis allows asymmetric construction of valuable chiral heterocyclic products from simple starting materials.

DOI: adg1322

Source: https://www.science.org/doi/10.1126/science.adg1322