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Ligand-enabled site-selectivity in a versatile rhodium( ii )-catalysed aryl C–H carboxylation with CO 2
Nature Catalysis ( IF 42.8 ) Pub Date : 2018-06-04 , DOI: 10.1038/s41929-018-0080-y
Lei Fu , Shangda Li , Zhihua Cai , Yongzheng Ding , Xiao-Qing Guo , Li-Peng Zhou , Daqiang Yuan , Qing-Fu Sun , Gang Li

Although carbon dioxide (CO2) is an attractive renewable carbon source, its utilization to produce fine chemicals through the catalytic carboxylation of unactivated carbon–hydrogen (C–H) bonds is still very limited and remains a challenge, largely because CO2 is thermodynamically and kinetically stable. In particular, the generation of (hetero)aromatic carboxylic acids via a transition-metal-catalysed C–H carboxylation of arenes with CO2 is extremely rare. Here we report a ligand-enabled site-selective carboxylation of 2-arylphenols under atmospheric pressure of CO2 through a Rh2(OAc)4-catalysed and chelation-assisted C–H bond activation. Remarkably, the reaction occurs selectively on the less nucleophilic phenyl group with the promotion of a phosphine ligand, which overrides the site selectivity dictated by the well-known Kolbe–Schmitt type reaction. The non-acidic C–H bonds within several important classes of heterocycles were also efficiently carboxylated with this method. A mechanistic investigation revealed complexes of active catalysts and that this reaction proceeds under redox-neutral reaction conditions.



中文翻译:

多功能铑(ii)催化的CO 2芳基CH羧基的配体活化位点选择性

尽管二氧化碳(CO 2)是一种有吸引力的可再生碳源,但其通过未活化的碳氢键(C–H)的催化羧化来生产精细化学品的应用仍然非常有限,并且仍然是一个挑战,主要是因为CO 2具有热力学性质并且动力学稳定。特别是,通过过渡金属催化的芳烃与CO 2的C–H羧化反应生成(杂)芳族羧酸的情况极为罕见。在这里,我们报告了在大气压下,通过Rh 2(OAc)4在CO 2大气压下2-芳基酚的配位体能位选择性羧化催化和螯合辅助的CH键活化。值得注意的是,该反应选择性地在亲核性较低的苯基上发生,并带有膦配体,这超出了众所周知的Kolbe-Schmitt型反应所决定的位点选择性。该方法还可以有效地将几个重要类别的杂环中的非酸性C–H键羧基化。机理研究揭示了活性催化剂的配合物,并且该反应在氧化还原中性反应条件下进行。

更新日期:2018-06-05
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