Efficient Copper-Free Sonogashira Coupling in Water and under Ambient Atmosphere

Sonogashira coupling is one of the cornerstone Palladium mediated cross coupling reactions, giving a direct and high yield access to symmetric and non-symmetric alkynes with high tolerance of substituents. The method generally requires the use of CuI as a cocatalyst, an inert atmosphere to protect palladium catalyst, somewhat harsh conditions like prolonged heating and the use of organic solvents due to the hydrophobicity of reagents and products. Leveraging on the opportunities offered by micellar catalysis, we here present a general methodology to perform Sonogashira coupling in water, with moderate or no heating, under air, without copper co-catalysts and at very low catalyst loading. The method offers the same generality and scope of organic solvents based couplings, but strongly improves sustainability while offering excellent yields. Sonogashira coupling on aryl bromides can be carried out under micellar conditions, in the absence of copper(I) catalyst, and under ambient atmosphere. Key of the success is the use of Kolliphor EL, a surfactant capable to form oxygen-free lipophilic domains in water. The method is applied toward the preparation of both (hetero)arylalkynes and luminescent molecular materials. image