Selective activation of secondary C–H bonds by an iron catalyst: insights into possibilities created by the use of a carboxyl-containing bipyridine ligand
作者:Shi Cheng、Jing Li、Xiaoxiao Yu、Chuncheng Chen、Hongwei Ji、Wanhong Ma、Jincai Zhao
DOI:10.1039/c3nj00656e
日期:——
4′-dicarboxylic acid), which could activate the C–H bonds of cycloalkanes with high secondary (2°) C–H bond selectivity. A turnover number (TN) of 11.8 and a 30% yield (based on the H2O2 oxidant) were achieved during the catalytic oxidation of cyclohexane by 1 under irradiation with visible light. For the transformation of cycloalkanes and bicyclic decalins with both 2° and tertiary (3°) C–H bonds, 1 always preferred
在这项工作中,我们报告发现了一种含羧基的铁催化剂1(Fe II -DCBPY,DCBPY = 2,2'-联吡啶-4,4'-二羧酸),该催化剂可以活化环烷烃的C–H键具有较高的次级(2°)CH键选择性。在H2O2的催化氧化过程中达到了11.8的周转数(TN)和30%的收率(基于H 2 O 2氧化剂)。环己烷在可见光照射下,按1。对于具有2°和叔(3°)C–H键的环烷烃和双环十氢化萘的转化,1总是优选将2°C–H键氧化为相应的酮和醇产物;在7个示例中,2°/ 3°的比率介于78/22和> 99/1之间。用18 O同位素标记实验,ESR实验,PPh 3方法和过氧化氢酶方法表征了氧化过程中的反应过程。1的成功表明,除了使用体积较大的催化剂外,使用体积较小的分子铁络合物作为催化剂也可以实现较高的2°C–H键选择性。