Pd-catalyzed decarbonylative Heck olefination of aromatic carboxylic acids activated in situ with di-tert-butyl dicarbonate

The first protocol for a direct Heck olefination of aromatic carboxylic acids has been developed. By treatment with commercially available di-tert-butyl dicarbonate, the carboxylic acids are converted in situ into the mixed anhydrides, which in the presence of a palladium catalyst react with olefins to give styrene derivatives. As by-products, only volatile CO and CO2, along with tert-butanol are formed, making the work-up of the reaction products particuarly easy. A mixture of PdCl2, LiCl and gamma-picoline was identified to be the most effective catalyst system.