Models for cytochrome P450 prosthetic heme alkylation. Reaction of diazoacetophenone with (tetraphenylporphyrinato)iron(II) chloride

The reaction of diazoacetophenone with (tetraphenylporphyrinato)iron(II) yields (N-(2-phenyl-2-oxoethyl)tetraphenylporphyrinato)iron(II) chloride. The structure of this product has been established by spectroscopic methods and by x-ray crystallography. The crystal structure shows that the first carbon of the N-alkyl group is 2.94 /angstrom/ from the iron atom and that the oxygen of the N-alkyl group points away from the iron. No evidence is seen for the Fe-C-N product expected from insertion of the diazo carbon into the metalloporphyrin iron-nitrogen bond or for intermediates in which the oxygen of the N-(2-phenyl-2-oxoethyl) group is coordinated to the iron. These results suggest it is unlikely that carbene-insertion or oxygen-coordinated intermediates will be detected during the N-alkylation of cytochrome P450 by diazo ketones. The results also rationalize the failure to detect iron-chelated enol species during N-alkylation of the prosthetic group of cytochrome P450 by catalytically activated phenylacetylene. 43 references, 5 figures, 4 tables.