Analytical Research and Development (Rahway) , Merck & Co., Inc. , Kenilworth , New Jersey 07033 , United States.
Analytical Research and Development (Kenilworth) , Merck & Co., Inc. , Kenilworth , New Jersey 07033 , United States.
J Org Chem. 2019 Aug 16;84(16):10024-10031. doi: 10.1021/acs.joc.9b01190. Epub 2019 Jul 22.
Retro-Brook rearrangements refer to the intramolecular migration of a silyl group from oxygen to carbon. In this study, we report a novel propargylic retro-Brook rearrangement observed in terminal alkynes bearing a silyl ether moiety. Retro-Brook rearrangements involving [1,2]-, [1,4]-, and [1,5]-migrations are described, affording propargylsilanes in reasonable yield. The reaction mechanism was investigated experimentally by deuterium quenching and rationalized by density functional theory calculations. The terminal alkyne and the subsequent propargyl/allenyl dianion were shown to be crucial for the reaction favoring the retro-Brook rearrangement product over the Brook rearrangement. The second deprotonation at the propargylic position was determined to be the rate-limiting step. In addition, a gas-phase Brook-type rearrangement of the propargylsilanes was observed under GC-MS conditions. This observation was also further confirmed by DFT calculations.
反- Brook 重排是指硅基从氧到碳的分子内迁移。在这项研究中，我们报告了一种新型的末端炔烃中含有硅醚部分的丙炔基反- Brook 重排。描述了涉及 [1,2]-、[1,4]-和[1,5]-迁移的反- Brook 重排，以合理的产率得到丙炔基硅烷。通过氘代实验和密度泛函理论计算对反应机理进行了实验和理论研究。末端炔烃和随后的丙炔基/烯丙基二负离子对于有利于反- Brook 重排产物而不是 Brook 重排产物的反应至关重要。在丙炔基位置的第二次去质子化被确定为速率限制步骤。此外，在 GC-MS 条件下观察到丙炔基硅烷的气相 Brook 型重排。这一观察结果也通过 DFT 计算得到了进一步证实。
