Isoselective Hydroformylation of Propylene by Iodide-Assisted Palladium Catalysis.

Isobutanal is a high value bulk material that, in principle, could be produced with 100 % atom-economy by isoselective hydroformylation of propylene with syngas. However, leading industrial Rh- and Co-catalyzed hydroformylation methods preferentially form n-butanal over the iso-product, and methods offering isoselectivity remain underdeveloped. Here we report an iodide-assisted Pd-catalyzed hydroformylation of propylene that produces isobutanal with unprecedented levels of selectivity. The method involves PdI , simple alkyl monophosphines, such as tricyclohexylphosphine, and common green solvents, enabling the title reaction to occur with isoselectivity in up to 50 : 1 iso/n product ratios under industrially relevant conditions (80-120 °C). The catalytic and preliminary mechanistic experiments indicate a key role of the iodide anions in both the catalytic activity and the isoselectivity.