Synthesis of Chlorinated Biphenyls by Suzuki Cross‐Coupling Using Diamine or Diimine‐Palladium Complexes

Abstract

Abstract Several novel diimines (Salen‐type ligands) 2a – 2i and their reduced diamine counterparts 3b , 3d – 3g and 3i form complexes 4a – 4i , 5b , 5d – 5g , and 5i with PdCl 2 in DMF or methanol. Using 1 mol‐% of the isolated complexes 4e and 5f many polychlorinated biphenyls (PCBs) can be prepared in moderate to excellent yields according to the Suzuki cross‐coupling protocol with contact to air. Several 4‐acetylbiphenyls prepared by this method can be converted in moderate yields into the corresponding biphenylcarboxylic acids (BCAs) by alkaline cleavage. An X‐ray crystal structure determination confirms the structure of complex 5f .(© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2008)