Institute of Chemical Research of Catalonia (ICIQ), The Barcelona Institute of Science and Technology, Avinguda Països Catalans 16, 43007 Tarragona, Spain.
ICREA, Passeig Lluïs Companys 23, 08010 Barcelona, Spain.
Nature. 2017 May 3;545(7652):84-88. doi: 10.1038/nature22316.
Catalytic carbon-carbon bond formation has enabled the streamlining of synthetic routes when assembling complex molecules. It is particularly important when incorporating saturated hydrocarbons, which are common motifs in petrochemicals and biologically relevant molecules. However, cross-coupling methods that involve alkyl electrophiles result in catalytic bond formation only at specific and previously functionalized sites. Here we describe a catalytic method that is capable of promoting carboxylation reactions at remote and unfunctionalized aliphatic sites with carbon dioxide at atmospheric pressure. The reaction occurs via selective migration of the catalyst along the hydrocarbon side-chain with excellent regio- and chemoselectivity, representing a remarkable reactivity relay when compared with classical cross-coupling reactions. Our results demonstrate that site-selectivity can be switched and controlled, enabling the functionalization of less-reactive positions in the presence of a priori more reactive ones. Furthermore, we show that raw materials obtained in bulk from petroleum processing, such as alkanes and unrefined mixtures of olefins, can be used as substrates. This offers an opportunity to integrate a catalytic platform en route to valuable fatty acids by transforming petroleum-derived feedstocks directly.
催化碳-碳键形成在组装复杂分子时实现了合成路线的精简。当引入饱和烃时,这一点尤其重要,因为饱和烃是石化和生物相关分子中的常见结构单元。然而,涉及烷基亲电试剂的交叉偶联方法只能在特定的、之前功能化的位置催化键的形成。在这里,我们描述了一种催化方法,该方法能够在大气压下用二氧化碳在远程和非功能化的脂肪族位点促进羧化反应。该反应通过催化剂沿着烃侧链的选择性迁移发生,具有极好的区域和化学选择性,与经典的交叉偶联反应相比,代表了一种显著的反应中继。我们的结果表明,可以切换和控制位点选择性,从而在存在先前更具反应性的位置的情况下对反应性较低的位置进行功能化。此外,我们表明,可以使用从石油加工中获得的大宗原料,如烷烃和未经精制的烯烃混合物作为底物。这为通过直接转化石油衍生原料在通往有价值的脂肪酸的途径中集成催化平台提供了机会。