Scientists in the US report the first synthetic compound to catalyse a key step in the degradation of double bonds in aromatic rings.  

The search for synthetic catalysts which mimic the action of enzymes is something which can enhance areas such as drug discovery, synthetic chemistry and environmental issues. In recent years scientists have explored potential synthetic catalysts which mimic the way in which soil bacteria degrades aromatic compounds.

The natural method for the degradation of aromatic compounds starts with the cis-dihydroxylation of an aromatic double bond by non-heme iron enzymes. The best known of these enzymes is naphthalene 1,2-dioxygenase (NDO), which catalyses the conversion of naphthalene to cis-(1R,2S)-1,2-dihydro-1,2-naphthalenediol. Although synthetic catalysts able to cis-hydroxylate olefin double bonds are known, scientists were yet to discover a synthetic catalyst which could carry out the same reaction on aromatic double bonds. Lawrence Que Jr and colleagues from the University of Minnesota, US have now made a synthetic non-heme iron complex able to catalyse this reaction.

Que used a complex which had previously been successful in the cis-dihydroxylation of olefins, [Fe^II(TPA)(NCMe)₂](OTf)₂ [where TPA = tris(2-pyridylmethylamine)]. Using H₂O₂ as the oxidant, Que identified four products, the major of which was the cis-diol, identical to that produced in the enzyme-catalysed reaction. They also carried out mechanistic studies and found that the process is assisted by water.

Que now aims to further develop the potential for biomimetic catalysis of oxidations that were previously only carried out by enzymes. 'The fact that the catalyst is based on iron, an economical and environmentally friendly metal,' says Que, 'makes it even more relevant for today's societal concerns.'

Richard Kelly

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