Developing Continuous Electroorganic Catalysis - It's Got Potential

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The combination of electricity with chemical reactions has a long history. The ability to use a single electron from an electric current in order to trigger a chemical reaction is an exciting concept, especially from the perspective of sustainability. Electrons are one of the cleanest possible chemical reagents (i.e. there is no waste generated from their use) with photons of light representing a complementary alternative. It is surprising therefore that organic chemistry, the branch of chemistry involved with creating molecules for society, such as pharmaceuticals, crop-protection agents, dyes, pigments, flavours, fragrances and polymers does not often use such electro-chemical methods at both the discovery and manufacture stages. One of the key reasons for this lack of adoption is that often the applied current, or the energy of the electron, is not properly tuned to the reaction system. This can lead to undesired reactions and impure reaction profiles. However, there have been some recent pioneering developments in the field that may permit broadening of the application of this electro-organic chemistry. The developments are two-fold and concern the chemistry and the reactor design.1) With regards to the chemistry, several examples now exist where complex reaction processes can be triggered by appropriate choice of electrolyte and careful planning of the chemical reactants. Furthermore, it has recently been proven that catalytic systems can be sustained by the input of electrons, with such processes giving rise to complex and interesting molecules of the kind that could feature in 'molecules for society'.2) With regards to the reactor design, the development and advancement of continuous flow chemistry (chemistry in pipes and tubing circuits rather than beakers and flasks) has permitted the lowering of the electric current and thus allows more sensitive 'surgical incisions' to be made in the reaction process, thus reducing the undesired reactions and propensity to yield impure reaction profiles. This proposal looks to work in an area of catalysis known as organo-catalysis, where a small amount of an organic molecule is used to accelerate the rate of reactions (this is in contrast to a precious metal-based system). Here the electro-chemistry approach will help to sustain and maintain the catalytic cycle. Notably, in all other organo-catalytic processes of this type an equal amount of an addition chemical is needed to maintain the catalytic activity. This chemical is purely sacrificial in nature and is thus extremely wasteful. A preliminary hit from the UK has already demonstrated that organo-catalytic reactions can be sustained using electro-chemical methods. This proposal aims to greatly diversify the application of this observation. The combination of an organo-catalytic, electro-chemical and continuous flow approach will serve to amplify the sustainability of the processes that we use to deliver these industrially useful reactions.