Electrochemically Driven Deoxydehydration Reactions

Context of the research
In contrast to fossil-fuel resources, renewable feedstocks from biomass are polyoxygenated. The development of
efficient processes that reduce oxygen-rich materials into more tractable substrates is an essential component of
achieving more sustainable chemical synthesis. The catalytic deoxydehydration of vicinal diols into alkenes is an
attractive strategy that removes two oxygen atoms in one-step. To date, scarce and expensive rhenium-based
catalysts have been the most widely explored for deoxydehydration in combination with a stoichiometric reductant
such as triphenylphosphine. More readily available vanadium catalysts are also viable for deoxydehydration
processes using stoichiometric reductants under harsh reaction conditions.
Aims and objectives
The 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 tricoordinate
ligands, starting from cheap vanadium precursors using established synthetic procedures. As only limited studies on
the electrochemistry of V(V) catalysts have been reported, the electrochemical behaviour of these complexes will be
investigated using cyclic voltammetry to correlate structural changes in the ligand with the reduction potential. These
studies 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 knowledge
gained from cyclic voltammetry to aid optimisation of the proton-coupled reduction. The deoxydehydration process
will be optimised in a simple undivided cell through variation of the electrode material, electrolyte, buffer, solvent, and
temperature using ElectraSyn equipment. Once a suitable procedure has bee n developed, the scope of the
methodology will be assessed through variation of the diol structure, including the use of different substitution
patterns and incorporation of various functional groups to test the reaction selectivity. The deoxydehydration protocol
can then be applied to polyoxygenated substrates derived from biomass to generate value-added alkenes that may
act as more suitable feed stocks for the chemical industry.
Potential applications and benefits
The developed deoxydehydration methodology will allow for the reduction of vicinal diols derived from biomass to
give 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 a
more sustainable process. The methodology should also allow for milder reaction conditions.
Relevance to the research council
The 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 and
Physical Science, with particular relevance to the research areas of catalysis, synthetic organic chemistry, and
electrochemical sciences.
Role of the second supervisor
The secondary supervisor of this project is Professor Frank Marken who is an expert in electrochemistry and will be
able to provide expertise on the electrochemistry involved in the project form a more fundamental perspective.