Palladium precatalysts containing meta-terarylphosphine ligands for expedient copper-free Sonogashira cross-coupling reactions

Abstract

Three novel palladium complexes utilizing different variations of the evolutionary meta-terarylphosphine ligand, Cy*Phine, were developed. These air- and moisture-stable complexes, PdCl₂L₂ (L = Cy*Phine, Cy*Phine-CF₃ and Cy*Phine-nBu), demonstrated exceptional broad-based performance and operational simplicity in the copper-free Sonogashira cross-coupling of challenging (hetero-)aryl chlorides and terminal alkynes. Modifications to the periphery of the ligand scaffold showed modest improvements in the reaction rate when more electron-donating substituents were incorporated, which hints at potential design upgrades in the future.