Isoselective Hydroformylation of Propylene by Iodide‐Assisted Palladium Catalysis

• Published in: Angewandte Chemie International Edition Vol. 61; no. 17; pp. e202116406 - n/a
• Main Authors: Sigrist, Michel, Zhang, Yang, Antheaume, Cyril, Dydio, Paweł
• Format: Journal Article
• Language: English
• Published: Germany Wiley Subscription Services, Inc 19.04.2022; Wiley-VCH Verlag
• Edition: International ed. in English
• Subjects: Anions; Atom economy; Catalysis; Catalytic activity; Chemical Sciences; Hydroformylation; Iodide Assistance; Iodides; Isobutanal; Palladium; Pd Catalysis; Propylene; Selectivity; Synthesis gas; Propylene; Iodide Assistance; Hydroformylation; Isobutanal; Pd Catalysis
• ISSN: 1433-7851; 1521-3773
• DOI: 10.1002/anie.202116406

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 PdI2, 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. The commercially important but elusive isoselective hydroformylation of propylene is reported to undergo readily in the presence of a simple catalytic system consisting of palladium(II) iodide and electron‐rich alkyl phosphines in common solvents and at industrially relevant temperatures. The assistance of the iodide ligands is shown to play a key role in the process by increasing both the isoselectivity and the activity of the catalyst.