Iridium‐Catalyzed Selective Cross‐Coupling of Ethylene Glycol and Methanol to Lactic Acid

• Published in: Angewandte Chemie International Edition Vol. 59; no. 26; pp. 10421 - 10425
• Main Authors: Wu, Jiajie, Shen, Lingyun, Chen, Zhe‐Ning, Zheng, Qingshu, Xu, Xin, Tu, Tao
• Format: Journal Article
• Language: English
• Published: Germany Wiley Subscription Services, Inc 22.06.2020
• Edition: International ed. in English
• Subjects: Atom economy; Carbenes; Catalysts; Cross coupling; Dehydrogenation; Ethylene; Ethylene glycol; Iridium; Lactic acid; Methanol; N-heterocyclic carbenes; Salts; Selectivity; iridium; lactic acid; cross-coupling; ethylene glycol; N-heterocyclic carbenes
• ISSN: 1433-7851; 1521-3773; 1521-3773
• DOI: 10.1002/anie.202002403

An atom‐economic approach that has an unprecedented high selectivity for the synthesis of lactic acid (LA) based on a catalytic dehydrogenative cross‐coupling by using inexpensive bulk ethylene glycol and methanol is described. This method relies on the synthesis and utilization of a novel iridium catalyst bearing three N‐heterocyclic carbenes derived from 1,3‐dimethylbenzimidazolium salts, and exhibits outstanding activity in the production of LA [turnover frequency (TOF) up to 3660 h−1] owing to an elegant metal–ligand cooperation. Good things come in threes: An unprecedented dehydrogenative C−C cross‐coupling with inexpensive bulk ethylene glycol and methanol has been developed by using a novel iridium catalyst bearing three N‐heterocyclic carbenes (NHCs). This procedure represents a highly selective and atom‐economic approach for the synthesis of lactic acid (TOF up to 3660 h−1). TOF=turnover frequency; TON=turnover number.