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

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 3 h 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.

Graphical abstractHeterogeneous Sonogashira cross-coupling of terminal alkynes with aryl halides was studied over a quinoline-carboimine palladium complex immobilized on MCM-41 (Pd-2QC-MCM) as catalyst. Cross-coupling of phenyl acetylene with iodobenzene proceeded within 3 h at 80 °C by adding two-fold amount of piperidine in NMP solvent to afford tolane in excellent yield. Pd-2QC-MCM can be reused without significant loss of activity until 4th recycles.Figure optionsDownload full-size imageDownload as PowerPoint slide