Synthesis of Metal Xanthene‐Bridged Bis‐corroles and their Catalytic Activity in Aerobic Baeyer‐Villiger Oxidation Reaction

The metal (M=Co, Cu, Mn, Sn, Fe) xanthene‐bridged bis‐corroles (M2XBC) were synthesized and used for catalyzing aerobic Baeyer‐Villiger (B‐V) oxidation of cyclic ketones to corresponding lactones. It turns out iron (IV) bis‐corrole complex (Fe2XBC) exhibited excellent activity and selectivity towards the B‐V oxidation of various cyclic ketones at very low catalyst loading. The yield of ϵ‐caprolactone could reach 98% with only 0.005 mol% catalyst. The turnover number (TON) of the Fe2XBC catalyst could even be up to 17400 in a gram‐scale oxidation of cyclohexanone, showing the promising for industrial usage. Moreover, the existences of benzoyl radical and benzoylperoxy radical in the reaction were proved by ESI‐HRMS spectra and electron paramagnetic resonance (EPR) spectra. A plausible radical mechanism for the metal bis‐corrole catalyzed aerobic B‐V oxidation of cyclohexanone in the presence benzaldehyde additive was proposed. The cofacial metal xanthene‐bridged bis‐corroles are applied to catalytic aerobic Baeyer‐Villiger oxidation reaction. It turns out iron (IV) bis‐corrole complex (Fe2XBC) exhibited excellent activity and selectivity towards the B‐V oxidation of various cyclic ketones. The yield of ϵ‐caprolactone could reach 98% with only 0.005 mol% catalyst. The turnover number (TON) of the Fe2XBC catalyst could even be up to 17400 in a gram‐scale test of B‐V oxidation of cyclohexanone.