Iron-Promoted<i>ortho</i>- and/or<i>ipso</i>-Hydroxylation of Benzoic Acids with H<sub>2</sub>O<sub>2</sub>
作者:Olgaâ
V. Makhlynets、Parthapratim Das、Sonia Taktak、Margaret Flook、Rubén Mas-Ballesté、Elenaâ
V. Rybak-Akimova、Lawrence Que
DOI:10.1002/chem.200901296
日期:2009.12.7
peroxide proceeds readily in the presence of iron(II) complexes with tetradentate aminopyridine ligands [FeII(BPMEN)(CH3CN)2](ClO4)2 (1) and [FeII(TPA)(CH3CN)2](OTf)2 (2), where BPMEN=N,N′‐dimethyl‐N,N′‐bis(2‐pyridylmethyl)‐1,2‐ethylenediamine, TPA=tris‐(2‐pyridylmethyl)amine. Two cis‐sites, which are occupied by labile acetonitrile molecules in 1 and 2, are available for coordination of H2O2 and substituted
在具有四齿氨基吡啶配体[Fe II(BPMEN)(CH 3 CN)2 ](ClO 4)2(1)和[Fe II(TPA) )(CH 3 CN)2 ](OTf)2(2),其中BPMEN = N,N'-二甲基-N,N'-双(2-吡啶基甲基)-1,2-乙二胺,TPA = tris-(2 -吡啶基甲基)胺。两个顺式位点被1中不稳定的乙腈分子占据1和2可用于配位H 2 O 2和取代的苯甲酸。芳环的羟基化仅发生在锚固的羧酸酯官能团附近:邻羟基化提供水杨酸酯,而ipso羟基化伴随脱羧生成酚盐。取代基定向的羟基化的结果取决于电子性质和取代基在底物分子中的位置:3-取代的苯甲酸优先被邻羟基化,而2-以及(在较小程度上)4-取代的底物倾向于接受ipso羟化/脱羧。这两个途径不是互斥的,可能通过共同的中间体进行。羧酸芳环上的吸电子取代基不利于羟基化,表明活性氧化剂具有亲电子性质。配合物1和2表现出相似的反应模式,