Ultrasound-assisted synthesis of unsymmetrical biaryls by Stille cross-coupling reactions

We describe herein an efficient method for the synthesis of unsymmetrically-substituted biphenyls using a sonochemical variation of the Stille coupling, whose results have also been compared with the conventional silent reaction. Ultrasound significantly enhances this useful organometallic transformation affording products in higher yields and in shorter reaction times than non-irradiated reactions. The scope has been explored with a selection of arylstannanes as precursors and, remarkably, no by-products resulting from homo-coupling could be detected.

► This work shows our preliminary results with ultrasonically-induced Stille cross-coupling reactions.
► The products were obtained in moderate to good yield (57–97%) without Wurtz-type dimerization products.
► The conventional method requires 20 h at 80 °C and is always accompanied by homo-coupling products between 10% and 15% yield.
► The reactions were performed at the optimal condition: 90 °C, power/cycle: 70/7, 30 min.