Studies On The Dinnuclear Porphyrin Models To Mimic Cytochrome P-450 Monooxygenation For Hydrocarbons

Recently, Chemists have paid much attention to the studies of the dinuclear metalporphyrins. In this paper, we synthesized a series of dinuclear metalporphyrins and studied their catalytic ability to mimic cytochrome P-450 monooxygenation of cyclohexane.1. 3,4-Dimethylpyrrole-2-carboxylate was prepared by using methyl formate and 2-butone as starting materials, and then condensed with phenyl aldehyde, 1,4-phenylene dialdehyde, 1,2-di(4-formylphenyloxy)methane, 1,2-di(4-formyl-phenyloxy)propane, l,2-di(4-formylphenyloxy)butane, respectively, followed by hydrolysis and decarboxylation, gave dipyrrylmethane derivatives 6, 9, 13a-13c. The reaction of 6 with POCl3 and DMF produced dipyrrylmethane-5,5'-dialdehyde 14. Condensation of dipyrrylmethane derivatives 6, 9, 13a-13c with dialdehyde 14 in the presence of HClO4 and tetrachloroquinone (TCQ), followed by dehydrogenation, yielded mono-porphyrins 15a, 15b and bis-porphyrins 16, 17a-17c, respectively.2. Four metalporphyrins(FeIII and MnIII) and eight dinuclear metalporphyrins(FeIII and MnIII) were prepared. All of the porphyrins and their metal complexes were characterized by EA, UV, and 1 H NMR.3. Twelve metalporphyrins were used as models to mimic cytochrome P-450 monooxygenation of cyclohexane. A conclusion was made as follows:(1) The catalytic activities of dinuclear metalporphyrins increase as the linkages of the two porphyrin units are lengthened.(2) The catalytic activities of dinuclear metalporphyrins are much higher than those of corresponding monometal porphyrins.(3) The catalytic activities of manganese porphyrins are higher than those of corresponding iron porphyrins and the catalytic selectivities of iron porphyrins are more effective than those of corresponding manganese porphyrins.(4) Reaction solvents play an important role in the catalytic reaction in affecting both the catalytic activity and the selectivity. The selectivity in cyclohexane solvent (cyclohexanol:cyclohexanone=3) is higher than that in dichloromethane solvent (cyclohexanol:cyclohexanone=2).