Scope and limitations of the combination of cobalt catalyst and choline hydroxide as green media for Sonogashira coupling and hydration of nitriles

The Sonogashira coupling reaction and hydration of nitriles were demonstrated using a facile catalytic system comprising a readily available cobalt salt and an environmentally friendly room-temperature ionic liquid, choline hydroxide (ChOH). The present system offers an alternative pathway for constructing C_sp–C_sp2 bonds through the alkynylation of aryl iodides in an aqueous environment, without the need for palladium- or copper-metal catalysts, phosphine ligands, or any external bases, albeit with some limited scope. Building upon the advantages and drawbacks of the present system employed in the Sonogashira coupling, we further extend its application to showcase the conversion of nitriles into amides, revealing the respective roles of ChOH and cobalt salt in the hydration of nitriles.

Graphic Abstract

The Sonogashira coupling and nitrile hydration were accomplished with cobalt salt and choline hydroxide (ChOH). Aryl iodides underwent alkynylation without external additives, albeit with limitations. Roles of ChOH and cobalt salt in nitrile hydration were also demonstrated.