C-H Oxidation
Posted by naturalproductman on June 27, 2009
Miquel Costas and Xavi Ribas et al at the Universitat de Girona in Spain has recently published in ACIEE on a iron-catalyzed (1 mol%) aliphatic C-H oxidation of alkanes using hydrogen peroxide as the oxidant. What’s notable is that these Fe catalyzed oxidations can be found in nature (ie: cytochrome P450’s) and I wouldn’t be surprised if they were originally inspired to use iron because of iron’s occurence in nature.
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Edinburgher said
Just to prepare the catalyst is difficult actually. Fe(II) and Fe(III) are quite tough to work with.
Is the reaction stereoselective BTW, and to what extent?
naturalproductman said
Good point: these reactions are indeed stereoselective and more specifically, they are stereospecific since stereospecific reactions are a subset of stereoselective ones.
Interestingly, they do explain in the paper that because of the stereospecificity of the reactions, long-lived radical type intermediates are not involved. However, the C-H bond strength indicates site selectivity since they only see hydroxylation at tertiary carbon centers in the presence of secondary ones. Steric and electronic factors also seem to play a role in site oxidation.
In the supporting information they show the GC chiral column chromatogram of the product distribution for the cis-1,2-dimethylcyclohexane meso starting material.