New application of metathesis catalyst revealed

A new application of Grubbs’ metathesis catalyst has been discovered by UK researchers. David Hodgson and Deepshikha Angrish from the University of Oxford have been investigating the dimerisation of diazoacetates to form unsaturated diesters using Grubbs’ second-generation ruthenium carbene complex as a catalyst.

Acrylates are already known to undergo this reaction to form the trans-diester, but Hodgson’s work has revealed that diazoacetates react to form mainly the cis-diester. 

When they treated a mixture of an acrylate and a diazoacetate with the catalyst, the same two products were formed and no cross-coupling of product or cyclopropane generation was seen. These results indicate that the reactions of acrylates and diazoacetates proceed by different mechanisms, the details of which been proposed.

The ability of Grubbs’ catalyst to separately catalyse diazoacetate dimerisation and alkene metathesis led the researchers to examine unsaturated diazoacetates, which contain both functionalities. They found that head-to-tail dimerisation occurred, providing dilactones, with the stereochemistry varying according to ring size. 

Hodgson says that this work should be of ’significant and immediate interest’ to organic chemists. Reactions of other unsaturated diazo-compounds are currently under investigation. 

David J Barden