AbstractRecent years have witnessed marked progress in the efficient synthesis of various enantioenriched 1,2,3,4‐tetrahydroquinoxalines. However, enantio‐ and diastereoselective access to trans‐2,3‐disubstituted 1,2,3,4‐tetrahydroquinoxalines remains much less explored. Herein we report that a frustrated Lewis pair‐based catalyst generated via in situ hydroboration of 2‐vinylnaphthalene with HB(C6F5)2 allows for the one‐pot tandem cyclization/hydrosilylation of 1,2‐diaminobenzenes and 1,2‐diketones with commercially available PhSiH3 to exclusively afford trans‐2,3‐disubstituted 1,2,3,4‐tetrahydroquinoxalines in high yields with excellent diastereoselectivities (>20 : 1 dr). Furthermore, this reaction can be rendered asymmetric by using an enantioenriched borane‐based catalyst derived from HB(C6F5)2 and a binaphthyl‐based chiral diene to give rise to enantioenriched trans‐2,3‐disubstituted 1,2,3,4‐tetrahydroquinoxalines in high yields with almost complete diastereo‐ and enantiocontrol (>20 : 1 dr, up to >99 % ee). A wide substrate scope, good tolerance of diverse functionality and up to 20‐gram scale production are demonstrated. The enantio‐ and diastereocontrol are achieved by the judicious choice of borane catalyst and hydrosilane. The catalytic pathway and the origin of the excellent stereoselectivity are elucidated by mechanistic experiments and DFT calculations.
摘要近年来,在高效合成各种对映体 1,2,3,4-四氢喹喔啉方面取得了显著进展。然而,反式-2,3-二取代的 1,2,3,4-四氢喹喔啉的对映体和非对映体选择性合成方法的探索仍然较少。在此,我们报告了通过 2-乙烯基萘与 HB(C6F5)2原位氢硼化合生成的一种基于挫折路易斯对的催化剂,该催化剂可与市售 PhSiH3 一锅串联环化/氢硅化 1,2- 二氨基苯和 1,2- 二酮,以高产率和优异的非对映选择性(20:1 dr)独家获得反式-2,3-二取代 1,2,3,4-四氢喹喔啉。此外,该反应还可以通过使用源自 HB(C6F5)2 的对映体硼烷基催化剂和二萘基手性二烯而变得不对称,从而产生对映体丰富的反式-2,3-二取代 1,2,3,4-四氢喹喔啉,产量高,对映和对映体控制几乎完全(>20 : 1 dr,高达 99 % ee)。该化合物的底物范围广,对多种官能团具有良好的耐受性,生产规模可达 20 克。通过合理选择硼烷催化剂和氢硅烷,实现了对映体和非对映体控制。机理实验和 DFT 计算阐明了催化途径和优异立体选择性的来源。