Heterogeneous copper-free Sonogashira coupling reaction of terminal alkynes with aryl halides over a quinoline-2-carboimine palladium complex immobilized on MCM-41

Abstract: Heterogeneous Sonogashira coupling of terminal alkynes with aryl halides was studied over a quinoline-2-carboimine palladium complex immobilized on MCM-41 (Pd-2QC-MCM) catalyst. The cross-coupling reaction occurred within 3h at 80°C by adding a piperidine in N-methyl-2-pyrolidone (NMP) solvent. By varying the combination of alkynes and aryl halides, Pd-2QC-MCM showed effective catalytic activities to produce corresponding tolane derivatives with moderate to excellent yields. Pd-2QC-MCM can be reused without significant loss of its catalytic activity until the fourth recycle under aerobic conditions because of negligible leaching of palladium metal and a high turnover number (∼2850) in the reaction of phenyl acetylene with iodobenzene. The excellent catalytic performance of Pd-2QC-MCM indicates that the reactions effectively occurred by a palladium complex immobilized on mesoporous silica. [Copyright &y& Elsevier]