Infrared Irradiation-Assisted Sonogashira Cross-Coupling Reaction.

A sustainable and energy-efficient protocol for the Pd-catalyzed Sonogashira cross-coupling reaction is reported, which is promoted by infrared (IR) irradiation in aqueous media with a recyclable Pd/C catalyst. The methodology enables C(sp2)─C(sp) bond formation under mild conditions with low catalyst loading (1 mol% Pd), affording the coupling products in good to excellent yields from a broad range of aryl iodides, including substrates bearing electron-donating and electron-withdrawing groups, and various terminal alkynes. The use of water as a benign reaction medium, combined with IR irradiation as an alternative energy input, contributes to improved sustainability and shorter reaction times compared to conventional thermal heating, while minimizing the formation of undesired by-products. Notably, the heterogeneous Pd/C catalyst can be easily recovered and reused over several cycles, showing only a slight loss of activity, thus enhancing the overall process sustainability, after the second cycle.