Water-based reactions Sonogashira reaction

A palladium catalyst with a less electron-rich ligand, 2,2-dipyridyl-methylamine-based palladium complexes (4.2), is effective for coupling of aryl iodides or bromides with terminal alkynes in the presence of pyrrolidine and tetrabutylammonium acetate (TBAB) at 100°C in water.37 However, the reactions were shown to be faster in NMP solvent than in water under the reaction conditions. Palladium-phosphinous acid (POPd) was also reported as an effective catalyst for the Sonogashira cross-coupling reaction of aryl alkynes with aryl iodides, bromides, or chlorides in water (Eq. 4.18).38... 

Fig. 6. Sonogashira reaction in a microflow system. lodobenzene (2a), phenylacetylene (3a) and amine base were mixed in the micromixer. The coupling product (4a) was formed and was easily isolated by extraction with hexane/water. Adapted from Fukuyama et al. (2002). Reproduced by permission of the American Chemical Society.

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