Regioselective Aldehyde Decarbonylation through Palladium-Catalyzed Nitrile Boronic Acid Cross-Coupling

Aldehyde decarbonylation is a vital chemical transformation in the synthesis of natural products. Nature accomplishes this process through a family of decarbonylase enzymes, while in the laboratory, harsh transition metals and elevated temperatures are required. Herein, we report a mild aldehyde decarbonylation reaction that exhibits exclusive selectivity for ortho-aldehydes during a tandem nitrile boronic acid cross-coupling reaction. A wide substrate scope is displayed that includes regioselective removal of the ortho-aldehyde from phenylboronic acids in the presence of meta- or para-aldehydes. A mechanistic investigation of the observed regioselectivity for ortho-aldehydes by density functional theory (DFT) calculations shows that the CO ligand extrusion is energetically more favorable for the ortho position as compared to the para position.