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.

Polyphenyl derivatives Q 0700A Reassessment of the Transition Metal Free Suzuki-Type Coupling Methodology.-It is found that the Suzuki-type coupling can be run successfully without the need for addition of a metal catalyst, but palladium contaminations down to a level of 50 ppb found in commercially available Na2CO3 are responsible for the preparation of biaryls. Thus, the previously reported non-palladium-mediated pathway is not correct. High yields of various biaryls can be achieved at a concentration of 1 ppm Pd. -(ARVELA, R. K.; LEADBEATER*, N. E.; SANGI, M. S.; WILLIAMS, V. A.; GRANADOS, P.; SINGER, R. D.; J. Org. Chem. 70 (2005) 1, 161-168; Dep. Chem., Univ. Conn., Storrs, CT 06269, USA; Eng.) -Jannicke 21-101