Electrochemical incorporation of sulfur dioxide towards value-added products
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Abstract
As part of the BMBF future cluster ETOS (Electrifying Technical Organic Syntheses), this dissertation explored the development, optimization, and application of novel electrochemical multi-component sulfonylation reactions utilizing abundant and broadly applicable starting materials. Stock solutions of sulfur dioxide were used as an efficient and convenient way to incorporate the toxic pollutant SO₂ into value-added products. The electrophilic nature of SO₂ enables its formal insertion into O–H bonds of alcohols, forming monoalkylsulfites in-situ with the assistance of an organic base. The nucleophilic properties of these intermediates were then harnessed to engage with anodically oxidized substrates, facilitating the formation of new C–S bonds.
The methodology was first applied to styrene derivatives, enabling direct electrosulfonylation to afford β-styrenesulfonates. A similar transformation was achieved using cinnamic acids as a biogenic feedstock through a decarboxylative sulfonylation pathway. Furthermore, the scope of the reaction was extended to non-aromatic substrates by employing readily oxidizable tertiary amines as precursors for enamines, resulting in the formation of enaminylsulfonates.
These advancements significantly expanded the applicability of electrochemical sulfonylation reactions, overcoming previous limitations such as the necessity for prefunctionalization, the use of surrogate reagents, toxic solvents, or complex electrochemical setups, while at the same time broadening the substrate scope of electrochemical sulfonylation reactions