The Wacker oxidation of alkenes to carbonyl compounds is a textbook organic transformation and an industrial process for the synthesis of acetaldehyde from ethylene has been commercialized on a large scale. The traditional aerobic Wacker process uses palladium chloride in conjunction with copper chloride and whilst this is a very efficient process for ethylene oxidation, it can become more problematic with longer chain olefins and/or alkenes with additional functionality due to the non-innocent nature of the copper co-catalyst. It is therefore pertinent that new oxidation systems are developed that move away from the use of copper co-catalysts. We have recently developed systems for Wacker-type oxidation of both aliphatic terminal olefins and styrenes using cationic Pd(II) complexes with hydrogen peroxide as the terminal oxidant. These systems show a wider substrate tolerance than many other aerobic Pd(II) systems and allow for the production of methyl ketones at low catalyst loadings (1 mol%) and ambient temperatures. The mechanism of aerobic Wacker oxidation has been well-explored in the literature but little is known about the mechanism of oxidation using hydrogen peroxide as the oxidant. Herein, we describe investigations into the mechanism of oxidation of both aliphatic terminal olefins and styrenes with cationic Pd(II) complexes and hydrogen peroxide using a combination of ligand studies, solvent effects, kinetic studies and isotopic labelling.

Mechanism of Wacker-type oxidation of terminal olefins with cationic Pd(II) complexes using hydrogen peroxide

253rd National Meeting (2017)

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