Selective Oxyfunctionalisation Reactions Driven by Sulfite Oxidase‐Catalysed In Situ Generation of H2O2

H2O2 can be accepted by several peroxygenases as a clean oxidant, able to supply both the necessary electrons and oxygen atom at the same time. The biocatalysts, in turn, are able to catalyse an array of interesting oxygen insertion reactions at enantio‐ and regio‐selectivities hard to attain with classical chemical methods. The sensitivity of most peroxygenases towards H2O2, however, requires this oxidant to be generated in situ. Here, we suggest the application of (modified) sulfite oxidases to couple the oxidation of sulfites to the reduction of oxygen. This enables us to use calcium sulfite, an industrial waste product from scrubbing flue gases, as an electron donor to reduce oxygen. This will supply the required peroxide in a controlled manner and enables us to perform these challenging reactions at the expense of simple salts. Oxyfunctionalisation: Sulfite oxidases are able to oxidize CaSO3, an industrial waste product, into CaSO4 using a molybdenum cofactor. The redox balance can subsequently be closed by reducing oxygen to H2O2, which is required by peroxygenases for their selective oxyfunctionalisation reactions. We show this biocatalytic cascade can be applied up to semi‐preparative scale.