A copper-free palladium catalyzed cross coupling reaction of vinyl tosylates with terminal acetylenes

A copper-free palladium-catalyzed cross coupling of vinyl tosylate (2) and terminal acetylenes was investigated, affording a convenient and efficient method for construction of an sp-sp(2) carbon-carbon bond. The tosylate (2) derived from 1,3-cyclohexanedione was reacted with terminal acetylene under the copper-free conditions at ambient temperature, in the presence of palladium acetate and triphenylphosphine, to provide the conjugated en-yn-one products in excellent overall yields while leaving other functional groups intact. This reaction protocol was extended to coumarin tosylate (12). (C) 2002 Elsevier Science Ltd. All rights reserved.