Metal-Ligand Cooperative Catalytic Coupling of Terminal Alkynes and Carboxylic Acids for the Stereoselective Synthesis of Dienyl Esters

Catalytic stereoselective synthesis of substituted 1,3-dienes represents an important facet of modern synthetic chemistry. In this study, we introduce novel ruthenium complexes with triazole-based phosphine ligands, demonstrating their high catalytic activity in synthesizing (1E,3E)-1,4-disubstituted-1,3-dienyl esters from aryl acetylenes and carboxylic acids. Our research unveils the cooperative role of the Ru-triazole complexes, elucidating that the internal basicity of the triazole unit likely plays a role in the activation of carboxylic acids. Various alkynes and carboxylic acids featuring diverse stereoelectronic substituents were found to be compatible with our synthetic protocol. Our work offers an alternative mechanistic pathway for stereodefined product formation, avoiding the formation of Ru-biscarbene intermediates observed in related catalytic systems.