Selective oxidation of alpha,beta-unsaturated aldehydes to alpha,beta-unsaturated carboxylic acids was performed using O-2 as the oxidant in the presence of a simple iron catalyst. The addition of an alkali metal carboxylate as a cocatalyst enhanced the selectivity for the desired product. Redox tuning of the iron catalyst via association with the alkali metal led to a controlled radical generation during the catalytic O-2 oxidation.