A simple and efficient copper-free catalytic system based on a palladacycle for the arylation of alkynes

The palladacycle [Pd(k(2)-C,N-C=(C6H5)C(Cl)CH2NMe2)(mu-Cl)](2) (1) derived from the chloropalladation of 3-(dimethylamino)-1-phenyl-1-propyne and its phosphine adduct [Pd(k(2)-C,N-C=(C6H5)C(Cl)CH2NMe2)P(4-CF3C6H4)(3)(Cl)] (3) promote the alkynylation of bromo- and iodoarenes under relatively mild reaction conditions. The coupling of iodoarenes and activated bromoarenes with terminal alkynes can be conducted at room temperature. Turnover numbers have been achieved up to 10(5) with iodoarenes and up to 94 for deactivated bromoarenes but at higher temperatures (120 degrees C). Selective poisoning experiments (Hg, Collman and Crabtree tests) suggest that soluble Pd(0) species are the most probable catalytically active species involved in this Csp(2)-Csp coupling reaction.