Peroxide-Mediated Wacker Oxidations

Written by Dr Trevor Laird on Monday, 23 April 2012. Posted in Process Chemistry News

The Wacker oxidation is a powerful synthetic transformation for converting a terminal olefin into a ketone.

Industrially it is widely used for bulk and fine chemicals, employing molecular oxygen as the oxidant, palladium (II) catalyst and a copper co-catalyst in DMF-water. Thus acetaldehyde is manufactured from ethylene by this process on thousands of tonnes scale in a continuous process.

An alternative approach, which may be more convenient in the laboratory on small scale and in pilot plants where use of oxygen may have safety issues, is to use a peroxide or hydroperoxide to generate a metalloperoxide catalyic species.

A recent review from the group of Matthew Sigman at Utah [Aldrichimica Acta, 2011, 44(3) 55-62] summarises progress in this industrially relevant reaction.  Metals such as iridium, ruthenium, platinum, rhodium and palladium have been used with a variety of peroxides and hydroperoxides and sometimes even oxygen itself.  It should be remembered that, if scaling up any of these transformations,  transition metals do catalyse the decomposition of many peroxo species to oxygen, so there is always an oxygen enriched atmosphere; thus flash points of solvents will be much lower than in air or a nitrogen atmosphere.

Interesting transformations include the conversion of allylic acetates to acetoxyketones and the conversion of a butadiene dimer to acetophenone, shown below.

About the Author

Dr Trevor Laird

Dr Trevor Laird

Dr Trevor Laird, Managing Director and Founder of Scientific Update LLP, is an expert in organic process R&D and scale-up of chemical processes and has been an editor-in-chief of the American Chemical Society journal Organic Process Research and Development since its launch in 1996. With over 4 decades of involvement with the chemical and pharmceutical industry, Trevor has consulted for companies in USA, Canada, Australia, South Africa, Singapore, Israel and India, as well as in Western Europe. He is an expert witness on patent cases, and is visiting professor at the University of Sussex, UK. He has authored numerous articles and book chapters. He was educated at London and Sheffield Universities and worked for Imperial Chemical Industries in, and Smith Kline and French, where he was in charge of the Chemical Development Department and of the Pilot Plant.

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