Cleavage of sp<sup>3</sup> C−O Bonds via Oxidative Addition of C−H Bonds
作者:Jongwook Choi、Yuriy Choliy、Xiawei Zhang、Thomas J. Emge、Karsten Krogh-Jespersen、Alan S. Goldman
DOI:10.1021/ja906930u
日期:2009.11.4
pathway for this reaction that proceeds through C-H addition of the ethoxy methyl group followed by beta-aryl oxide elimination and loss of ethylene. Thus, both of these distinct C-O cleavage reactions proceed via initial addition of a C(sp(3))-H bond, despite the fact that such bonds are typically considered inert and are much stronger than C-O bonds.
(PCP)Ir (PCP = kappa(3)-C(6)H(3)-2,6-[CH(2)P(t-Bu)(2)](2)) 被发现进行氧化加成缺电子甲基芳基醚(包括甲氧基-3,5-双(三氟甲基)苯和甲氧基五氟苯)的甲基-氧键,得到相应的芳基氧化物配合物(PCP)Ir(CH(3))(OAr)。尽管净反应是将 Ir 中心插入到 CO 键中,但密度泛函理论 (DFT) 计算和显着的动力学同位素效应 [k(CH(3))(OAr)/k(CD(3))(OAr) = 4.3(3)] 强烈反对简单的插入机制,并支持涉及 CH 加成和 OAr 基团的 α 迁移以产生亚甲基复合物,然后氢化物到亚甲基迁移以产生观察到的产物的途径。乙氧基芳基醚,包括乙氧基苯,也会通过 (PCP)Ir 进行 CO 键断裂,但在这种情况下,净反应是 1,2-消除 ArO-H,得到 (PCP)Ir(H)(OAr) 和乙烯。DFT 计算表明该反应的低阻障途径通过乙氧基甲基的