Asymmetric Hydroformylation of Aryl Vinyl Ethers to Chiral 2-Aryloxypropanals: Access to Aryloxypropionic Acid Herbicide Precursors.

Enantiopure aryloxypropionic acid herbicides are of considerable importance in modern crop protection, creating a strong demand for efficient catalytic approaches to their synthesis. Herein, we report a Rh/(S,R)-DTB-YanPhos-catalyzed asymmetric hydroformylation of readily available aryl vinyl ethers, affording chiral 2-aryloxypropanals in up to 99% yield and 98% ee with excellent chemo-, regio-, and enantioselectivity. The protocol features broad substrate scope, high catalytic efficiency (TON up to 6300), and excellent catalyst robustness. Gram-scale synthesis and efficient conversion of the aldehydes into optically enriched aryloxypropionic acid herbicides demonstrate the practical utility of this method, providing a straightforward catalytic route to valuable chiral herbicide intermediates and related building blocks.