Palladium-catalyzed cross-coupling reaction of ethynylstibanes with organic halides

The reaction of ethynylstibanes (1a–g) with vinyl halides or triflate in the presence of a palladium catalyst led to the formation of cross-coupling products (5a–g, 10–12) in good to moderate yield, along with homo-coupling products (6a–g). A similar reaction of ethynyldiphenylstibane (1a) with aryl iodides (13a–i) also gave cross-coupling products (14a–i), although the yields were relatively low. The yields of the cross-coupling products were highly dependent on the nature of the solvent employed, and good results were obtained when the reaction was carried out in HMPA or amines such as diethylamine and morpholine. The results imply that HMPA and amine used as solvents facilitate transmetallation of the ethynyl group on 1 to the palladium by intermolecular coordination between antimony and oxygen (for HMPA) or nitrogen (for amine).