Breaking conjugation: unusual regioselectivity with 2-substituted allylic substrates in the Tsuji–Trost reaction
作者:Byeong-Seon Kim、Mahmud M. Hussain、Per-Ola Norrby、Patrick J. Walsh
DOI:10.1039/c3sc53035c
日期:——
Tsuji–Trost allylic substitution reactions. It is well known that (η3-1-aryl-3-alkyl substituted allyl)Pd intermediates result in nucleophilic attack at the alkyl substituted terminus. In contrast, the chemistry of (η3-1,2,3-trisubstituted allyl)Pd intermediates is relatively unexplored. Herein we probe the regioselectivity with 1,2,3-trisubstituted allylic substrates in Tsuji–Trost allylic substitution
η 3 -烯丙基钯配合物是Tsuji-Trost烯丙基取代反应的关键中间体。众所周知,(η 3 -1-芳基-3-烷基取代的烯丙基)Pd中间体在烷基取代的末端导致亲核攻击。相比之下,(η 3 -1,2,3-三取代烯丙基)Pd 中间体的化学性质相对未开发。在此,我们探讨了在 Tsuji-Trost 烯丙基取代反应中 1,2,3-三取代的烯丙基底物的区域选择性。阳离子 (η 3 -1-Ph-2-B(pin)-3-烷基-烯丙基)Pd(PPh 3 ) 2中间体的DFT 研究预测亲核攻击应优先发生在反烯丙基上而不是顺式异构体在 Curtin-Hammett 条件下产生苄基取代产物。实验上,对 1,2,3-三取代的烯丙基底物的系统研究表明,当 C-2 取代基的 Charton 空间参数与区域异构体比率的对数作图时,观察到线性自由能关系 (LFER)。1,2,3-三取代的η 3 -烯丙基钯中间体中体积更大