Department of Pure and Applied Chemistry, University of Strathclyde, 295 Cathedral Street, Glasgow G1 1XL, UK.
Molecules. 2021 Nov 15;26(22):6879. doi: 10.3390/molecules26226879.
Rearrangements of tolyl aryl ethers, amines, and sulfides with the Grubbs-Stoltz reagent (EtSiH + KOBu) were recently announced, in which the ethers were converted to -hydroxydiarylmethanes, while the (tol)(Ar)NH amines were transformed into dihydroacridines. Radical mechanisms were proposed, based on prior evidence for triethylsilyl radicals in this reagent system. A detailed computational investigation of the rearrangements of the aryl tolyl ethers now instead supports an anionic Truce-Smiles rearrangement, where the initial benzyl anion can be formed by either of two pathways: (i) direct deprotonation of the tolyl methyl group under basic conditions or (ii) electron transfer to an initially formed benzyl radical. By contrast, the rearrangements of tolyl aryl amines depend on the nature of the amine. Secondary amines undergo deprotonation of the N-H followed by a radical rearrangement, to form dihydroacridines, while tertiary amines form both dihydroacridines and diarylmethanes through radical and/or anionic pathways. Overall, this study highlights the competition between the reactive intermediates formed by the EtSiH/KOBu system.
最近报道了 Grubbs-Stoltz 试剂（EtSiH + KOBu）与甲苯基芳基醚、胺和硫化物的重排反应，其中醚转化为 - 羟基二芳基甲烷，而（甲苯）（Ar）NH 胺转化为二氢吖啶。根据该试剂体系中三乙基硅自由基的先前证据，提出了自由基机理。现在，对芳基甲苯基醚的重排进行了详细的计算研究，反而支持阴离子 Truce-Smiles 重排，其中初始苄基阴离子可以通过两种途径之一形成：（i）在碱性条件下直接脱质子化甲苯甲基，或（ii）电子转移到最初形成的苄基自由基。相比之下，甲苯基芳基胺的重排取决于胺的性质。仲胺经历 N-H 的去质子化，然后发生自由基重排，形成二氢吖啶，而叔胺通过自由基和/或阴离子途径形成二氢吖啶和二芳基甲烷。总的来说，这项研究强调了 EtSiH/KOBu 体系形成的反应中间体之间的竞争。
