Olefin Cis-Dihydroxylation versus Epoxidation by Non-Heme Iron Catalysts: Two Faces of an Fe<sup>III</sup>−OOH Coin
作者:Kui Chen、Miquel Costas、Jinheung Kim、Adrianne K. Tipton、Lawrence Que
DOI:10.1021/ja0120025
日期:2002.3.1
5-methyl-substituted derivatives. We demonstrate that olefin epoxidation and cis-dihydroxylation are different facets of the reactivity of a common Fe(III)-OOH intermediate, whose spin state can be modulated by the electronic and steric properties of the ligand environment. Highly stereoselective epoxidation is favored by catalysts with no more than one 6-methyl substituent, which give rise to low-spin Fe(III)-OOH species
铁酶对碳-碳双键的氧化通常会导致环氧化物的形成,但在 Rieske 双加氧酶的情况下,会产生顺式二醇。在此,我们报告了由一组非血红素铁配合物催化的 H(2)O(2) 烯烃氧化的系统研究,即 [Fe(II)(BPMEN)(CH(3)CN)(2)] (2+) (1, BPMEN = N,N'-二甲基-N,N'-双(2-吡啶基甲基)-1,2-二氨基乙烷)和[Fe(II)(TPA)(CH(3)CN) (2)](2+) (4, TPA = 三(2-吡啶基甲基)胺)及其6-和5-甲基取代的衍生物。我们证明烯烃环氧化和顺式二羟基化是常见 Fe(III)-OOH 中间体反应性的不同方面,其自旋状态可以通过配体环境的电子和空间特性进行调节。具有不超过一个 6-甲基取代基的催化剂有利于高度立体选择性环氧化,这会产生低自旋 Fe(III)-OOH 物质(A 类)。另一方面,具有多于一个 6-甲基取代基的催化剂有利于顺式二羟基化,提供高自旋