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Nature:二氧化碳用作一种化学原料

摘要 : 认为温室气体二氧化碳也许可用作一种化学原料的观点是有吸引力的,但通常也不实际尽管它很容易与以碳为中心的亲核试剂发生反应,

 认为温室气体二氧化碳也许可用作一种化学原料的观点是有吸引力的,但通常也不实际——尽管它很容易与以碳为中心的亲核试剂发生反应,但生成亲核试剂却需要高能量输入。但是现在,受RuBisCO酶(该酶催化植物的固碳反应)的启发,Aanindeeta Banerjee等人显示,在中等温度下含有碱金属的熔融盐,能使非常弱酸性的C-H键在碳酸盐帮助下高效发生羧化作用。这一化学反应的潜力通过将2-糠酸 (很容易从不可食用的生物质制取)转化成有用的生源化学原料 “呋喃-2,5-二羧酸”得到了演示。

原文链接:

Carbon dioxide utilization via carbonate-promoted C–H carboxylation

原文摘要:

Using carbon dioxide (CO2) as a feedstock for commodity synthesis is an attractive means of reducing greenhouse gas emissions and a possible stepping-stone towards renewable synthetic fuels1, 2. A major impediment to synthesizing compounds from CO2 is the difficulty of forming carbon–carbon (C–C) bonds efficiently: although CO2 reacts readily with carbon-centred nucleophiles, generating these intermediates requires high-energy reagents (such as highly reducing metals or strong organic bases), carbon–heteroatom bonds or relatively acidic carbon–hydrogen (C–H) bonds3, 4, 5. These requirements negate the environmental benefit of using CO2as a substrate and limit the chemistry to low-volume targets. Here we show that intermediate-temperature (200 to 350 degrees Celsius) molten salts containing caesium or potassium cations enable carbonate ions (CO32–) to deprotonate very weakly acidic C–H bonds (pKa > 40), generating carbon-centred nucleophiles that react with CO2 to form carboxylates. To illustrate a potential application, we use C–H carboxylation followed by protonation to convert 2-furoic acid into furan-2,5-dicarboxylic acid (FDCA)—a highly desirable bio-based feedstock6 with numerous applications, including the synthesis of polyethylene furandicarboxylate (PEF), which is a potential large-scale substitute for petroleum-derived polyethylene terephthalate (PET)7, 8. Since 2-furoic acid can readily be made from lignocellulose9, CO32–-promoted C–H carboxylation thus reveals a way to transform inedible biomass and CO2 into a valuable feedstock chemical. Our results provide a new strategy for using CO2 in the synthesis of multi-carbon compounds.

来源: Nature 浏览次数:0

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