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

Graphical The cofacial metal xanthene-bridged bis-corroles are applied to catalytic aerobic Baeyer-Villiger oxidation reaction. It turns out iron (IV) bis-corrole complex (Fe 2 XBC) 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 Fe 2 XBC catalyst could even be up to 17400 in a gram-scale test of B-V oxidation of cyclohexanone. The metal (M=Co, Cu, Mn, Sn, Fe) xanthene-bridged bis-corroles (M 2 XBC) 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 (Fe 2 XBC) 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 Fe 2 XBC 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.