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

A new efficient and mild protocol for synthesizing a series of trans-A(2)B(2)-porphyrins through a TFA-catalyzed condensation reaction between various aldehydes and dipyrromethanes has been developed. Several trans-A(2)B(2)-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-A(2)B(2)-metalloporphyrin. Cobalt metalloporphyrin presents better catalytic performance in the conversion of cyclohexane than the nickel metalloporphyrin under the same reaction conditions.