Optimizing Mn/SiO2 catalyst for additive - free epoxidation of long - chain α -olefins in air

Abstract

The epoxidation of long-chain α-olefins presents a significant challenge in synthetic chemistry, particularly when employing molecular oxygen from air as the sole oxidant under additive-free conditions. In this study, we demonstrate that manganese supported on mesoporous silica (Mn/MSN) effectively catalyzes the aerobic epoxidation of long-chain α-olefins without requiring initiators or sacrificial agents. Mechanistic investigations reveal a synergistic interplay between Mn(II) and Mn(III) species, which facilitates the selective cleavage the peroxo bonds (O–O) in alkyl hydroperoxide intermediates. Strategic incorporation of iron and zirconium into the Mn/MSN framework modulates the manganese oxidation states, enriching the Mn(II)/Mn(III) ratio and achieving a remarkable space-time yield of up to 200 mol _epoxide mol⁻¹_Mn h⁻¹ . Radical trapping experiments combined with high-resolution mass spectrometry corroborate the formation of allyl carbon-centered and alkoxy radical intermediates during the reaction. This work provides a feasible strategy for long-chain α-olefin aerobic epoxidation without any additives.