We present here a reassessment of our transition-metal free Suzuki-type coupling protocol. We believe that, although the reaction can be run without
the need for addition of a metal catalyst, palladium contaminants down to a level of 50 ppb found in commercially available sodium
carbonate are responsible for the generation of the biaryl rather than, as previously suggested, an alternative non-palladium-mediated
pathway. We present a revised methodology for Suzuki couplings using ultralow palladium concentrations for use with aryl and vinyl boronic acids and
discuss the effects of the purity of the boronic acid on the reaction. |