Under (low) pressure: Glycerol carbonate can be produced from glycidol and CO2 using cheap and abundant biobased catalysts that can be operated under mild pressure conditions, comparatively low temperatures, and no halide additives. The biocatalysts are investigated by kinetics and various controls, showing the importance of a multi-interaction-type substrate activation. The process is extended to a heterogeneous protocol demonstrating high stability and reuse of the biobased catalyst.
Glycerol carbonate (GC) has emerged as an attractive synthetic target due to various promising technological applications. Among several viable strategies to produce GC from CO2 and glycerol and its derivatives, the cycloaddition of CO2 to glycidol represents an atom-economic an efficient strategy that can proceed via a halide-free manifold through a proton-shuttling mechanism. Here, it was shown that the synthesis of GC can be promoted by bio-based and readily available organic salts leading to quantitative GC formation under atmospheric CO2 pressure and moderate temperatures. Comparative and mechanistic experiments using sodium citrate as the most efficient catalyst highlighted the role of both hydrogen bond donor and weakly basic sites in the organic salt towards GC formation. The citrate salt was also used as a catalyst for the conversion of other epoxy alcohols. Importantly, the discovery that homogeneous organic salts catalyze the target reaction inspired us to use metal alginates as heterogeneous and recoverable bio-based catalysts for the same process.Zum Volltext