Thiol ester-boronic acid cross-coupling. Catalysis using alkylative activation of the palladium thiolate intermediate

[GRAPHICS] Thiol esters and boronic acids do not participate in cross-coupling in the presence of palladium catalysts. However, efficient palladium-catalyzed thiol ester-boronic acid cross-coupling is observed when simple alkylating agents are present. Alkylative conversion of the very stable palladium-thiolate bond to a labile palladium-thioether bond is presumed to be crucial to the catalysis. Of the systems studied, 4-halo-nbutyl thiol esters were most effective in this cross-coupling.