在该研究中，团队报道了芳基硼酸酯配合物中从硼向碳的自由基1,5-芳基迁移。研究人员发现，预先生成的通过自由基加成到烯基芳基硼酸酯配合物上的碳自由基可以参与1,5-芳基迁移反应，生成4-芳基烷基硼酸酯。由于可以通过烯基硼酸酯与芳基锂试剂的反应原位生成硼酸酯配合物，芳基的部分很容易变化，使得一系列芳基化产物通过差异化反应可以用相同的烯基硼酸酯开始合成。该反应在温和的条件下具有高的非对映选择性，而且类似的1,4-芳基转移也是可行的。密度泛函理论计算支持了研究人员提出的机理。
据了解，自由基芳基迁移反应是一种独特的有机转化类型，涉及芳基通过螺环中间体从碳或杂原子向以碳或杂原子为中心的自由基进行分子内迁移。N、O、Si、P、S、Sn、Ge、Se等不同元素都被报道可参与自由基芳基迁移。然而，从硼中心开始的自由基芳基迁移在此前尚未见报道。
附：英文原文
Title: Radical Aryl Migration from Boron to Carbon
Author: Dinghai Wang, Christian Mück-Lichtenfeld, Constantin G. Daniliuc, Armido Studer
Issue&Volume: June 20, 2021
Abstract: Radical aryl migration reactions represent a unique type of organic transformations that involve the intramolecular migration of an aryl group from a carbon or heteroatom to a C- or heteroatom-centered radical through a spirocyclic intermediate. Various elements, including N, O, Si, P, S, Sn, Ge, and Se, have been reported to participate in radical aryl migrations. However, radical aryl migration from a boron center has not been reported to date. In this communication, radical 1,5-aryl migration from boron to carbon in aryl boronate complexes is presented. C-radicals readily generated through radical addition onto alkenyl aryl boronate complexes are shown to engage in 1,5-aryl migration reactions to provide 4-aryl-alkylboronic esters. As boronate complexes can be generated in situ by the reaction of alkenylboronic acid esters with aryl lithium reagents, the aryl moiety is readily varied, providing access to a series of arylated products starting from the same alkenylboronic acid ester via divergent chemistry. Reactions proceed with high diastereoselectivity under mild conditions, and also the analogous 1,4-aryl shifts are feasible. The suggested mechanism is supported by DFT calculations.
DOI: 10.1021/jacs.1c04217
Source: https://pubs.acs.org/doi/10.1021/jacs.1c04217
