Synthesizing Lactic Acid by the Manganese-Catalyzed Dehydrogenative Coupling of Ethylene Glycol and Methanol

Herein, an efficient and green procedure for the synthesis of lactic acid via the dehydrogenative coupling of ethylene glycol with methanol is reported. The reaction is carried out under mild conditions in the presence of a catalytic amount of ^CyPNP-Mn as the catalyst and ^tBuOK as the base and is an example of the deoxygenative coupling of a lower alcohol to form lactic acid via elegant metal–ligand cooperation with a homogeneous non-noble-metal catalyst in >99% conversion and selectivity. This transformation proceeds at low catalyst loading (0.00625 mol%) with a high turnover number (TON) of up to 6080 for lactic acid.