Dehydrogenative α‑Oxygenation of Ethers with an Iron Catalyst

Selective
α-oxidation of ethers under aerobic conditions
is a long-pursued transformation; however, a green and efficient catalytic
version of this reaction remains challenging. Herein, we report a
new family of iron catalysts capable of promoting chemoselective α-oxidation
of a range of ethers with excellent mass balance and high turnover
numbers under 1 atm of O2 with no need for any additives.
Unlike metalloenzymes and related biomimetics, the catalyst produces
H2 as the only byproduct. Mechanistic investigations provide
evidence for an unexpected two-step reaction pathway, which involves
dehydrogenative incorporation of O2 into the ether to give
a peroxobisether intermediate followed by cleavage of the peroxy bond
to form two ester molecules, releasing stoichiometric H2 gas in each step. The operational simplicity and environmental friendliness
of this methodology affords a useful alternative for performing oxidation,
while the unique ability of the catalyst in oxygenating a substrate
via dehydrogenation points to a new direction for understanding metalloenzymes
and designing new biomimetic catalysts.