Experimental and Mechanistic Exploration of Zn-Catalyzed Sonogashira-type Cross-Coupling Reactions

One of the most straightforward methods for the synthesis of disubstituted alkynes is the transition metal catalyzed Sonogashira-type cross-coupling reactions. Herein we report a detailed study of our recent research on the first Zn-catalyzed protocol for C(sp2)–C(sp) cross-coupling reaction of aryl iodides with terminal alkynes. A wide range of functional groups were tolerated in the reaction and both functionally and structurally diverse diaryl acetylenes were prepared efficiently using this protocol. The reaction mechanism for the Zn-catalyzed Sonogashira-type coupling reaction was investigated by means of density functional theory (DFT) methods on a model system. The calculations were performed using hybrid Becke Perdew Functional (BPV86) in conjugation with LANL-2DZ basis set and found that the reaction pathway involves oxidative addition and reductive elimination mechanism.