Room-Temperature Copper-Catalyzed Oxidation of Electron-Deficient Arenes and Heteroarenes Using Air

摘要

Although transition-metal-catalyzed direct functionalization of C-H bonds has emerged as a powerful method to construct new C-C and C-heteroatom bonds, oxidative functionalization of C-H bonds under mild conditions (at room temperature and using air as the oxidant) still remains a very challenging field. In particular, the synthesis of phenols by direct oxidation of arenes with O2 as the oxidant is still regarded as one of the main challenges for catalysis, and is rarely reported. A groundbreaking method reported by Fujiwara and co-workers used Pd(OAc)2 as the catalyst to convert benzene into phenol with molecular oxygen; however, this method gave low yields (2-3 % ) and used extremely forcing reaction conditions (15 atm O2,15 atm CO, 180 °C). Recently, Yu and Zhang reported a novel Pd-catalyzed direct ortho hydroxylation of potassium benzoates in the presence of O2 (1 atm) as the oxidant. However, several drawbacks still remain including the high catalyst loading (10 mol % of Pd(OAc)2) and high temperature (115 °C). Thus, it is still necessary to develop a powerful synthetic method for the oxidative hydroxylation of C-H bonds under mild reaction conditions.