FACILE CATALYTIC COUPLING OF ARYL BROMIDES WITH TERMINAL ALKYNES BY PHOSPHA-PALLADACYCLES

An efficient synthesis of tolane derivatives from substituted aryl bro mides and phenylacetylene catalyzed by air- and moisture-stable phosph a-palladacycles is described. This procedure works without addition of cupric salts. Reaction rates and yields are sensitive to the nature o f solvent and base, Mechanistic features are discussed for a catalytic cycle with Pd(II) and Pd(IV) intermediates, Constitutional stability of the palladacyclic catalyst under reaction conditions is likely; pre cipitation of palladium black is not observed.