Electrochemically Driven Deoxydehydration Reactions

研究背景与化石燃料资源不同，来自生物质的可再生原料是多氧的。开发将富氧材料还原为更易处理的底物的高效工艺是实现更可持续的化学合成的重要组成部分。邻位二元醇催化脱氧生成烯烃是一种很有吸引力的策略，可以一步除去两个氧原子。到目前为止，稀有而昂贵的Re基催化剂是与化学计量比的还原剂(如三苯基膦)结合使用的最广泛的脱氧脱水催化剂。更易获得的钒催化剂也适用于在恶劣的反应条件下使用化学计量比还原剂的脱氧过程。目的和目的该项目的目的是开发一种在温和的条件下用于钒催化脱氧的电化学方法，并避免以水为唯一副产物的化学计量比废物。初步研究将包括从廉价的钒前体开始使用现有的合成方法制备一系列含有各种三配位配体的氧钒(V)络合物。由于对V(V)催化剂的电化学研究有限，将用循环伏安法研究这些络合物的电化学行为，以将配体的结构变化与还原电位联系起来。这些研究将提供关于还原过程的性质和电子转移的可逆性的关键信息。然后，催化剂将在1-苯乙烷-1，2-二醇的模型脱氧反应中进行测试，使用从循环伏安获得的知识来辅助质子偶联还原的优化。使用电子同步设备，通过改变电极材料、电解液、缓冲液、溶剂和温度，在一个简单的整体槽中优化脱氧脱水过程。一旦开发出合适的程序，将通过改变二醇结构来评估方法的范围，包括使用不同的取代模式和加入不同的官能团来测试反应选择性。然后，脱氧脱水协议可以应用于生物质衍生的多氧底物，以产生增值的烯烃，这些烯烃可以作为更适合于化工的原料。潜在的应用和好处开发的脱氧方法将允许减少来自生物质的邻二醇类，以得到可用作化工原料的烯烃。与以前开发的方法相比，该过程将不需要使用化学计量比的还原剂，从而使水成为唯一的副产品，使其更可持续。该方法还应考虑到较温和的反应条件。与研究委员会相关的是，该项目由工程和物理科学研究委员会博士培训伙伴关系(EPSRC DTP)资助。该项目的目标与EPSRC的制造未来和物理科学的研究主题一致，特别是与催化、合成有机化学和电化学科学的研究领域相关。第二主管的角色这个项目的二级主管是Frank Marken教授，他是一名电化学专家，将能够从更基本的角度提供项目所涉及的电化学专业知识。

Context of the researchIn contrast to fossil-fuel resources, renewable feedstocks from biomass are polyoxygenated. The development ofefficient processes that reduce oxygen-rich materials into more tractable substrates is an essential component ofachieving more sustainable chemical synthesis. The catalytic deoxydehydration of vicinal diols into alkenes is anattractive strategy that removes two oxygen atoms in one-step. To date, scarce and expensive rhenium-basedcatalysts have been the most widely explored for deoxydehydration in combination with a stoichiometric reductantsuch as triphenylphosphine. More readily available vanadium catalysts are also viable for deoxydehydrationprocesses using stoichiometric reductants under harsh reaction conditions.Aims and objectivesThe aim of the project is to develop an electrochemical methodology for vanadium-catalysed deoxydehydration,under mild conditions and avoiding stoichiometric waste with water as the only by-product.Initial studies will involve the preparation of a range of oxo-vanadium(V) complexes bearing various tricoordinateligands, starting from cheap vanadium precursors using established synthetic procedures. As only limited studies onthe electrochemistry of V(V) catalysts have been reported, the electrochemical behaviour of these complexes will beinvestigated using cyclic voltammetry to correlate structural changes in the ligand with the reduction potential. Thesestudies will provide key information on the nature of the reduction process and the reversibility of electron transfer.The catalysts will then be tested in a model deoxydehydration reaction of 1-phenylethane-1,2-diol, using knowledgegained from cyclic voltammetry to aid optimisation of the proton-coupled reduction. The deoxydehydration processwill be optimised in a simple undivided cell through variation of the electrode material, electrolyte, buffer, solvent, andtemperature using ElectraSyn equipment. Once a suitable procedure has bee n developed, the scope of themethodology will be assessed through variation of the diol structure, including the use of different substitutionpatterns and incorporation of various functional groups to test the reaction selectivity. The deoxydehydration protocolcan then be applied to polyoxygenated substrates derived from biomass to generate value-added alkenes that mayact as more suitable feed stocks for the chemical industry.Potential applications and benefitsThe developed deoxydehydration methodology will allow for the reduction of vicinal diols derived from biomass togive alkenes that may be used as feed stocks for the chemical industry. Compared to previously developed methods,the process will not require the use of a stoichiometric reductant, leading to water as the only by product making it amore sustainable process. The methodology should also allow for milder reaction conditions.Relevance to the research councilThe project is funded by the Engineering and Physical Sciences Research Council Doctoral Training Partnership(EPSRC DTP). The aims of the project align with the EPSRC research themes of Manufacturing the Future andPhysical Science, with particular relevance to the research areas of catalysis, synthetic organic chemistry, andelectrochemical sciences.Role of the second supervisorThe secondary supervisor of this project is Professor Frank Marken who is an expert in electrochemistry and will beable to provide expertise on the electrochemistry involved in the project form a more fundamental perspective.