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 γ-picoline was
identified to be the most effective catalyst system.
carboxylic acids - catalysis - palladium - Heck reaction - di-tert-butyl
dicarbonate