Photocatalytic aerobic oxidative carbonylation of methane by iron terpyridine catalysts

Abstract Employing methane as a C1 feedstock for commodity chemicals represents a sustainable and empowering opportunity for chemical catalysis. However, practical demands of industrial development have imposed serve challenges to utilize co-effective catalysts and reagents as well as ecologically benign conditions for highly efficient and selective C(sp3)–H bond functionalizations, constantly driving the development of catalytic strategies. The aerobic oxidative carbonylation of methane represents an ideal approach for sustainable acetic acid synthesis, yet poses a longstanding challenge in selectivity for C2:C1 products. In recent years, metallaphotocatalysis in which photoredox catalysts operate in synergy with transition metal catalysts to facilitate both 1- and 2-electron reaction steps, has provided intriguing opportunities to achieve selective cross-couplings otherwise unattainable. Here, we demonstrate the utilization of an iron terpyridine catalyst to facilitate multiple 1- and 2-electron processes, including photoexcitation, radical generation, oxidative radical capture and carbonylation, in the form of methane aerobic carbonylation to acetic acid. High levels of catalytic efficiency (turnover numbers up to 31480) and selectivity (C2/C1 ratio up to 142:1) have been achieved with a robust iron terpyridine photocatalyst at ambient temperature under LED irradiation. Importantly, this practical catalytic manifold has been adapted to the selective oxidative carbonylation of various feedstock alkanes.