New Catalytic Reactions using Sulfur Dioxide

ended

Sulfur dioxide is produced in millions of tonnes per annum, and represents an abundant and low-cost feedstock for chemistry. Despite a varied and useful range of reactivity as a reagent for organic synthesis, the use of sulfur dioxide as a feedstock for catalytic processes was extremely limited with only a handful of reactions reported before 2010. This is particularly striking when the wide occurrence of the sulfonyl motif is considered, as it features in a variety of useful organic functional groups such as sulfones and sulfonamides. Together these functional groups appear in an enormous range of intermediates and final compounds used in the pharmaceutical, agrochemical and fine chemical industries. In earlier work we have show that use of an SO2 surrogate, such as DABSO, allows a variety of catalytic reactions to be developed. The take-up of these reactions, particularly the catalytic methods for sulfinate synthesis from aryl halides or aryl boronic acids, has been significant, and these reactions are being used in industrial laboratories. This is a great start, but there are a number of limitations to the chemistry, as well as opportunities to develop exciting related chemistry that we believe will have significant impact. The vast majority of catalytic reactions developed employ Pd catalysts and pre-functionalised “activated” substrates, such as aryl halides, boronic acids, or diazonium salts. These are useful reactions, but the reliance on precious metal catalysts and activated substrates is limiting, both from a sustainability perspective, but also in terms of reactivity, as the majority of these reactions all proceed by 2-electron processes. Accordingly, the main objective of this Fellowship is to develop catalytic reactions for SO2 incorporation that employ more sustainable catalysts, and also to show that readily available feedstocks, such as carboxylic acids and alcohols can be used as substrates.