Manganese Catalyzed Reformation of Ethylene Glycol to Glycolic acid and Lactic Acid

Conversion of readily available feedstocks to valuable platform chemicals via a sustainable catalytic pathway has always been one of the key focuses of synthetic chemists. Cheaper, less toxic, and more abundant base metals as a catalyst for performing such transformations provide an additional boost. In this context, herein, we report a reformation of readily available feedstock, ethylene glycol, to value-added platform molecules, glycolic acid, and lactic acid. A bench stable base metal complex {[HN(C2H4PPh2)2]Mn(CO)2Br}, Mn-I, known as Mn-PhMACHO, catalyzed the reformation of ethylene glycol to glycolic acid at 140 oC in high selectivity with a turnover number TON = 2400, surpassing previously used homogeneous catalysts for such a reaction. Pure hydrogen gas is evolved without the need for an acceptor. On the other hand, a bench stable Mn(I)-complex, {(iPrPN5P)Mn(CO)2Br}, Mn-III, with a triazine backbone, efficiently catalyzed the acceptorless dehydrogenative coupling of ethylene glycol and methanol for the synthesis of lactic acid, even at a ppm level of catalyst loading, reaching the TON of 11,500. Detailed mechanistic studies were performed to elucidate the involvements of different manganese(I)-species during the catalysis.