The oxidation of alkenes to carbonyls is a valuable transformation in synthetic chemistry. Palladium(II) based catalysts are well known for such (Wacker-type) oxidation reactions, however there are still exist many challenges in this area. There is a need to avoid the use of co-catalysts and utilize O2 directly as co-catalysts result in poor selectivity. While there has been some success for aliphatic alkenes, styrenes are often more challenging as they often suffer from poor selectivity. To-date, reported methods involve high catalyst loadings and/or harsh reaction conditions. While ligands have been exploited for other areas of palladium oxidation chemistry (e.g. alcohol oxidation), this has not been exploited for Wacker-type reactions. Indeed, there has only been one report in the literature which uses a ligand to improve catalyst performance for styrene oxidation and this method required high catalyst loadings and very long reaction times. We will discuss our recent work which highlights the importance of ligand development for improving catalyst performance for this important reaction. The reaction is not only sensitive to ligand structure, but is greatly influenced by counterion and solvent. We will discuss how we developed a palladium(II) complex which is active at room temperature and for the Wacker-type oxidation of styrenes to ketones using O2 as the sole terminal oxidant.

Cationic palladium(II) complexes for the catalytic Wacker-typeo oxidation of styrenes to ketones using O2 as the terminal oxidant

253rd National Meeting (2017)

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