Electrochemically Driven Deoxydehydration Reactions

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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.