Investigations into ambient temperature biaryl coupling reactions

An ambient temperature, unsymmetrical, biaryl coupling reaction for hindered systems based on Suzuki methodology has been developed. A description of the optimisation of this process leading to the recommendation of aqueous thallium hydroxide as base, in dimethylacetamide, with hindered boronic acids and aryl halides to achieve good to moderate yields of hindered biaryls is presented, along with an interpretation of the reaction conditons. The yields of hindered Stille biaryl coupling reactions seemed to be little enhanced by the use of less coordinating ligands such as tri-2-furylphosphine and triphenylarsine. (C) 1997 Elsevier Science Ltd.