The Heck reaction between E- and Z-enoates and iodobenzene was studied in the presence of Pd(OAc)2. The stereochemistry in resulting adducts was dependent on the enoate geometry (stereospecific reaction). Best yields were obtained from Z-isomers in acetone using Ag2CO3 as base. The main cationic palladium intermediates possibly involved in the catalytic cycle could be intercepted and characterized by electrospray ionization mass spectrometry (ESI-MS). The stereoselectivity observed was rationalized through the classic mechanism of the Heck reaction.
Heck reaction; enoates; palladium catalysis; mass spectrometry
