Development of a decarboxylative palladation reaction and its use in a Heck-type olefination of arene carboxylates

The development of a palladium-catalyzed decarboxylative coupling reaction of arene carboxylates with olefinic substrates is described. The optimized procedure for decarboxylative palladation employs Pd(O2CCF3)2 as catalyst (0.2 equiv) in the presence of Ag2CO3 (3 equiv) in the solvent 5% DMSO-DMF and proceeds at temperatures of 80-120 degrees C with a wide range of arene carboxylates and alkenes as substrates. The process is proposed to proceed by an initial Ar-SE reaction involving ipso attack of an electrophilic Pd(II) intermediate on an arene carboxylate to form an arylpalladium(II) species with loss of carbon dioxide. This intermediate is then proposed to react with an olefinic substrate by steps common to the Heck coupling process. Reoxidation of the liberated Pd(0) in situ is proposed to establish the catalytic cycle.