Palladium‐Catalyzed Aerobic α,β‐Dehydrogenation of Carboxylic Acids

Abstract The aerobic dehydrogenation of saturated carboxylic acids to α,β‐unsaturated carboxylic acids proceeded by a simple Pd(OAc) 2 /pyridine catalyst system under 1 atm of O 2 . β‐Acyloxylated carboxylic acids were also produced from propionic acid and butyric acid by the conjugate addition of the substrates to the formed α,β‐unsaturated carboxylic acids. When propionic acid was used as a substrate, trans ‐Pd(OCOEt) 2 (pyridine) 2 was formed in situ as a precatalyst. The kinetic experiments indicated that Pd(OCOR) 2 (pyridine) is a catalytically active species and that β‐C(sp 3 )−H bond activation in the carboxylate ligand is the turnover‐limiting step. The DFT calculations agreed with the mechanism.