Glyoxal-promoted homogeneous catalytic oxygenation of cyclohexane with hydrogen peroxide in the presence of V and Co compounds

Fe(III) Complexes in Cyclohexane Oxidation: Comparison of Catalytic Activities under Different Energy Stimuli

In this study, the mononuclear Fe(III) complex [Fe(HL)(NO3)(H2O)2]NO3 (1) derived from Nʹ-acetylpyrazine-2-carbohydrazide (H2L) was synthesized and characterized by several physicochemical methods, e.g., elemental analysis, infrared (IR) spectroscopy, electrospray ionization mass spectrometry (ESI-MS), and single crystal X-ray diffraction analysis. The catalytic performances of 1 and the previously reported complexes [Fe(HL)Cl2] (2) and [Fe(HL)Cl(μ-OMe)]2 (3) towards the peroxidative oxidation of cyclohexane under three different energy stimuli (microwave irradiation, ultrasound, and conventional heating) were compared. 1-3 displayed homogeneous catalytic activity, leading to the formation of cyclohexanol and cyclohexanone as final products, with a high selectivity for the alcohol (up to 95%). Complex 1 exhibited the highest catalytic activity, with a total product yield of 38% (cyclohexanol + cyclohexanone) under optimized microwave-assisted conditions.

Synthesis and catalytic properties of trans-A2B2-type metalloporphyrins in cyclohexane oxidation

A new efficient and mild protocol for synthesizing a series of trans-A2B2-porphyrins through a TFA-catalyzed condensation reaction between various aldehydes and dipyrromethanes has been developed. Several trans-A2B2-metalloporphyrins (cobalt, nickel) were synthesized and used to catalyze cyclohexane oxidation C–H bonds with dioxygen in the absence of additives and solvents. The results show that the catalytic activities were relative to the nature of the substituted groups and the central metal ions of trans-A2B2-metalloporphyrin. Cobalt metalloporphyrin presents better catalytic performance in the conversion of cyclohexane than the nickel metalloporphyrin under the same reaction conditions.