Two diphosphane ligands -2,5-bis(2-(diphenylphosphino)-5-R)phenyl)-1,3,4-oxadiazole (L1, R = H, L2, R = OMe) and their binuclear complexes, L1Cu and L2Cu, were prepared and characterized. The molecular structures of L1Cu and L2Cu, as perchlorate salts, were established by X-ray crystallography, which showed them to be binuclear complexes with each Cu atom tetrahedrally coordinated by two P atoms and two N atoms. The ligands and their Cu(I) complexes catalyzed Sonogashira coupling reactions of iodobenzene with phenylacetylene in the presence of K 2 CO 3 under Pd-free conditions. Coupling reactions catalyzed by L1 or L2 with Cu(MeCN) 4 ClO 4 in situ exhibited better yields than those by the corresponding Cu(I) complexes L1Cu or L2Cu. Detailed studies showed L1 or L2 with Cu(MeCN) 4 ClO 4 to be suitable catalysts for the coupling reaction of terminal alkynes and aryl halides. The coupling reactions of aryl iodides with electron-withdrawing groups showed better results.
2,5-Bis(2-(diphenylphosphino)phenyl)-1,3,4-oxadiazole Ligands and Their Cu(I) Complexes for Sonogashira Coupling Reaction. -Reactions performed in the presence of the ligand MOD succeed with slightly higher yields than the ones performed in the presence of ligand HOD. Whereas aryl iodides are transformed in good to excellent yields, aryl bromides give the corresponding products in moderate yields and aryl chlorides in trace amounts only. The reaction of o-iodophenol with phenylacetylene leads to 2-phenylbenzofuran (VII). -(LIN, C.-X.; ZHU, J.-F.; LI, Q.-S.; AO, L.-H.; JIN, Y.-J.; XU*, F.-B.; HU, F.-Z.; YUAN, Y.-F.; Appl. Organomet. Chem. 28 (2014) 4, 298-303, http://dx.doi.org/10.1002/aoc.3124 ; State Key Lab. Elem.-Org.
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