Additive‐Free Isomerization of Allylic Alcohols to Ketones with a Cobalt PNP Pincer Catalyst
作者:Brian Spiegelberg、Andrea Dell'Acqua、Tian Xia、Anke Spannenberg、Sergey Tin、Sandra Hinze、Johannes G. de Vries
DOI:10.1002/chem.201901148
日期:2019.6.12
Catalytic isomerization of allylic alcohols in ethanol as a green solvent was achieved by using air and moisture stable cobalt (II) complexes in the absence of any additives. Under mild conditions, the cobalt PNP pincer complex substituted with phenyl groups on the phosphorus atoms appeared to be the most active. High rates were obtained at 120 °C, even though the addition of one equivalent of base
通过在不存在任何添加剂的情况下使用空气和湿气稳定的钴(II)配合物,可以实现烯丙醇在乙醇中的催化异构化(绿色溶剂)。在温和的条件下,被磷原子上的苯基取代的钴PNP钳形络合物似乎是活性最高的。即使加入一当量的碱可大大提高反应速度,但在120°C时仍可获得较高的反应速率。尽管获得了支持脱氢-加氢机理的一些证据,但已证明这不是主要机理。取而代之的是,乙醇脱氢形成的氢化钴配合物能够通过烯烃插入-消除反应实现双键异构化。