The coupling of aryl or vinyl halide with terminal alkyne catalyzed by palladium and other transition metal, communally termed as Sonogashira cross-coupling reaction, is one of the most important and widely used sp- and sp2-hybridized carbon formation reaction in organic synthesis. A catalytic system composed of well-defined copper complexes supported by N-heterocyclic ligands was developed to perform Sonogashira coupling reaction. We describe the synthesis of three new Cu(I) complexes with pincer N-heterocyclic carbene (NHC) ligands, I(R)C^N^C (R = Me, Et and iPr) bearing methylpyridine as linkers. All of these compounds, namely [Cu(IMeC^N^C)](PF6), 1; [Cu(IEtC^N^C)](PF6), 2; and [Cu(IiPrC^N^C)](PF6), 3 have been characterized by 1H- and 13C NMR spectroscopies, elemental analysis, and single crystal X-ray structures. For comparison, we have also synthesized some cationic and neutral Cu-NHC complexes, [Cu(IiPr)2]PF6 4 and [Cu(SIMes)Cl] 5, respectively, and characterized them by elemental analysis and NMR spectroscopy. We have shown that [Cu(SIMes)Cl] and [Cu(IRC^N^C)](PF6) complexes can provide the cross-coupled product with 60-96% isolated yield with no require of expensive Pd, co-catalyst or amine.

Cu(I) Complexes of pincer pyridine-based N-heterocycliccarbenes with a small wingtips substituents: Synthesis, characterization and application in Sonogashira coupling reactions

254th National Meeting (2017)

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