Green Chemistry for Catalytic C-C Coupling of Renewable Feedstocks

大多数化工产品（塑料、泡沫、药品、农用化学品）都是由迅速消耗的石油原料制成的。因此，越来越需要开发催化过程，使从丰富的可再生资源中生产无副产品的化学产品。这一领域的进展将取决于化学反应新模式的发现，以及控制催化剂选择性和活性的新策略。因此，拟议合作研究的主要目标是开发选择性的、无副产物的催化C-C偶联，适用于丰富的、可再生的醇（甲醇、乙醇和甘油）和二氧化碳。拟议的研究将融合Breit集团开创的催化剂选择性-活性控制的新概念，以及Krische集团建立的新型C-C键形成氢化（方案1）。方案1。开发丰富可再生原料C-C耦合催化剂。Breit集团开发了一种新型超分子催化剂，该催化剂具有含有酰基胍亚结构的磷化氢配体。在拟议的资助期内，这些配体将用于激活二氧化碳作为亲电试剂，在由Krische集团开发的无副产物氢介导的C-C键形成中。通过氢键供体-受体相互作用稳定羰基加成的过渡态，我们希望开发第一个使用二氧化碳作为c1构建块的无副产物催化羟基化反应（方案2）。方案2。以二氧化碳为C1基的无副产物催化羟基化的发展。(b)大量可再生醇的无副产物C-C偶联（C.4.2）： Krische小组的研究表明，钌和铱配合物催化醇与各种π-不饱和化合物的直接C-C偶联。在这里，我们的目标是(a)将这些工艺扩展到可再生醇（甲醇，乙醇和甘油）和(b)使α-烯烃作为偶联剂的使用成为可能。在这些过程中，通过氢交换产生的亲核-亲电对仅以催化量存在，这提高了C-C偶联的激活熵（ΔS*）。因此，试图偶联α-烯烃只能得到微量的产物。使用Breit基团中开发的氢键给体配体，可以降低这一过程的激活熵。高效催化剂醇-α-烯烃C-C偶联将利用影响巨大的化学过程，例如直接将甲醇或乙醇转化为含量较少的高级醇（方案3）。方案3。低醇直接无副产物转化为高醇。

The majority of chemical commodities (plastics, foams, pharmaceuticals, agrochemicals) are made from rapidly depleting petroleum feedstocks. Consequently, there is a growing need to develop catalytic processes that enable byproduct-free manufacture of chemical products from abundant, renewable resources. Progress in this area will depend on the discovery of new patterns in chemical reactivity, as well as new strategies for controlling catalyst selectivity and activity. Hence, the primary goal of the proposed collaborative research is to develop selective, byproduct-free catalytic C-C couplings applicable to abundant, renewable alcohols (methanol, ethanol and glycerol) and carbon dioxide. The proposed research will merge new concepts catalyst selectivity-activity control pioneered by the Breit Group together with novel C-C bond forming hydrogenations established by the Krische Group (Scheme 1). Scheme 1. Developing catalysts for C-C coupling of abundant renewable feedstocks. The Breit Group has developed novel supramolecular catalysts that possess phosphine ligands incorporating acylguanidine substructures. In the proposed funding period, these ligands will be used to activate carbon dioxide as an electrophile in byproduct-free hydrogen-mediated C-C bond formations developed by the Krische Group. By stabilizing the transition state for carbonyl addition through hydrogen-bond donor-acceptor interactions, we hope to develop the first byproduct-free catalytic hydrocarboxylations employing carbon dioxide as a C1-building block (Scheme 2). Scheme 2. Development of byproduct-free catalytic hydrocarboxylations employing carbon dioxide as a C1- building block. (b) Byproduct-Free C-C Coupling of Abundant Renewable Alcohols (C.4.2): Research from the Krische Group demonstrates that ruthenium and iridium complexes catalyze the direct C-C coupling of alcohols to various π-unsaturated compounds. Here, it is our objective to (a) extend these processes to renewable alcohols (methanol, ethanol and glycerol) and (b) enable use of α-olefins as coupling partners. In these processes, the nucleophile-electrophile pairs generated via hydrogen exchange are present in only catalytic amounts, which raises the entropy of activation (ΔS*) for C-C coupling. For this reason, attempted couplings of α-olefins provide only trace amounts of products. Using hydrogen-bond donor ligands developed in the Breit Group, the entropy of activation such processes will be lowered. Efficient catalysts alcohol-α-olefin C-C coupling would avail chemical processes of enormous impact, e.g. the direct conversion of methanol or ethanol to less abundant higher alcohols (Scheme 3). Scheme 3. Direct byproduct-free conversion of lower alcohols to higher alcohols.