A facile protocol for copper‐free palladium‐catalyzed Sonogashira coupling in aqueous media

Abstract

The combination of a readily available palladium catalyst and an eco‐friendly basic aqueous solution of room‐temperature ionic liquid, choline hydroxide (ChOH), was used in a facile protocol alternative to the Sonogashira coupling reaction, alkynylation of aryl halides in the absence of a copper cocatalyst and an external base. The dual nature of ChOH to act as a base and a green solvent played a crucial role in the catalytic cycle. The coupling reaction progressed efficiently to form a CspCsp2 bond under the identified conditions although the reaction outcome depended significantly on the substrates.