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1.1.4.1.2.2 Hydroformylation in Ionic Liquids Using an Imidazolium-Modified Phosphorus Ligand

DOI: 10.1055/sos-SD-212-00096

Mortreux, A.; Sauthier, M.; Monflier, E.; Tilloy, S.Science of Synthesis: C-1 Building Blocks in Organic Synthesis, (20141171.

Taking into account the results in homogeneous systems where phenoxaphosphino-modified Xantphos-based ligands exhibit both high activities and selectivities (high linear/branched product ratios in hydroformylation), van Leeuwenʼs group designed a modified Xantphos-based ligand 24 on which two pendant imidazolium groups are grafted to ensure ideal solubility in structurally analogous ionic liquids (Scheme 9).[‌24‌] Optimization of the reaction rate using this system was published two years later[‌25‌] and this system represents the best one available to date, combining all the advantages of activity, selectivity for the linear aldehyde, and recyclability. For example, oct-1-ene reacts with 87% selectivity for aldehyde products and the catalyst system shows a turnover frequency (TOF) of 6200 h−1 at 40% conversion. The major drawback for this methodology is that the ligand synthesis requires a five-step procedure from the original phenoxaphosphino-Xantphos ligand, which itself is also not easily accessible.

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