Cobalt (II)-catalyzed oxidation of 2-aryl benzoic acids to access biaryl lactones

Cobalt/peroxymonosulfate (Co/PMS) system is an efficient advanced oxidation process (AOP) for degradation of organic pollutants in wastewater, however, has limitations in organic synthesis. Herein, we employ a Co/PMS system to the preparation of biaryl lactones by the valorization of 2-aryl aromatic acids via intramolecular O-H/C-X oxidative coupling. This system exhibits intriguing advantages, such as non-noble metal catalyst, common oxidant, mild condition, easy workup and product isolation. Mechanism studies, including the radical quenching experiments and multiple probe substrates, suggest that a high-valent cobalt-oxo intermediate should be one major active species. Meanwhile, both persulfate radical anion (SO4 center dot-) and hydroxyl radical (center dot OH) are present in the process and contribute to the organic reaction. This work not only expands the synthetic application of Co/Oxone system beyond environmental fields, but also provides more active intermediates than generally-accepted SO4 center dot- in the known metal-based AOPs.

Automated summary

The Cobalt/peroxymonosulfate (Co/PMS) system is an efficient oxidation process for degrading organic pollutants in wastewater. This study demonstrates the use of this system for the preparation of biaryl lactones, offering several advantages. Mechanism studies indicate the presence of a high-valent cobalt-oxo intermediate and the involvement of persulfate radical anion and hydroxyl radical in the organic reaction.