Special Collection: Women of Catalysis 2024Combination of Bio‐ and Organometallic Catalysis for the Synthesis of Dioxolane in Organic Solvents

In the catalytic conversion of renewable raw materials, it is essential to adapt the reaction media to match the complexity of the substrates. Recently, integrated bio‐ and organometallic catalysis processes have emerged; however, only a few operate in purely organic solvents, which would be advantageous for energy‐efficient processes. Here, we present a process using one enzymatic step and two chemocatalytic steps to produce the cyclic acetals 4,5‐dipropyl‐1,3‐dioxolane and 4,5‐dibutyl‐1,3‐dioxolane in a single organic solvent. The enzymatic step, using a lyase, starts from an aldehyde, butanal and pentanal, to form the 2‐hydroxy ketones butyroin or valeroin, respectively. Subsequently, two chemocatalytic steps were carried out sequentially in one reaction vessel. In a first step, the 2‐hydroxy ketones are hydrogenated to 4,5‐octanediol and 5,6‐decanediol and in the second step the dioxolanes are formed using hydrogen and carbon dioxide. Either formic acid or polyoxymethylene was used as an alternative carbon source to CO2, which allowed considerable raw material flexibility. Since these dioxolanes are being investigated as additives in biofuel blends, the derived cetane number of the synthesized compounds was measured in addition to the viscosity and density. The cetane numbers determined suggest that the produced dioxolanes could be used as additives in fuel blends.