Green Chemistry for Catalytic C-C Coupling of Renewable Feedstocks

大多数化学商品（塑料、泡沫、药品、农用化学品）都是由迅速枯竭的石油原料制成的。因此，越来越需要开发能够从丰富的可再生资源无副产物地制造化学产品的催化方法。这一领域的进展将取决于化学反应性新模式的发现，以及控制催化剂选择性和活性的新策略。因此，拟议的合作研究的主要目标是开发适用于丰富的可再生醇（甲醇，乙醇和甘油）和二氧化碳的选择性，无副产物的催化C-C耦合。拟议的研究将合并由Breit Group开创的新概念催化剂选择性-活性控制与由Krische Group建立的新型C-C键形成氢化（方案1）。方案1.开发用于丰富的可再生原料的C-C偶联的催化剂。Breit集团已经开发了具有结合酰基胍亚结构的膦配体的新型超分子催化剂。在拟议的资助期内，这些配体将用于激活二氧化碳作为Krische集团开发的无副产物氢介导的C-C键形成中的亲电体。通过稳定过渡态的羰基加成通过氢键供体-受体相互作用，我们希望开发第一个无副产物的催化加氢羰基化，采用二氧化碳作为C1-积木（方案2）。方案2.采用二氧化碳作为C1-结构单元的无副产物的催化加氢羧化的开发。(b)丰富的可再生醇的无副产物C-C偶联（C.4.2）：Krische Group的研究表明，钌和铱络合物催化醇直接C-C偶联成各种π-不饱和化合物。在这里，我们的目标是（a）将这些方法扩展到可再生醇（甲醇、乙醇和甘油）和（B）使得能够使用α-烯烃作为偶联配体。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偶联的活化熵（ΔS*）。由于这个原因，尝试的α-烯烃偶联仅提供痕量的产物。使用Breit Group开发的氢键供体配体，将降低此类过程的活化熵。有效的催化剂醇-α-烯烃C-C偶联将有助于具有巨大影响的化学过程，例如甲醇或乙醇直接转化为不太丰富的高级醇（方案3）。方案3.将低级醇直接无副产物地转化为高级醇。

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.