Herein we report the studies of Heck alkynylation (copper‐free Sonogashira) with aryl halides (I, Br, Cl) employing various metallic precursors, tertiary phosphanes and bases in [BMIM][BF4] as the solvent. As a result, we provide the first method that allows the coupling of a large array of substrates, either activated or deactivated bromides in an ionic liquid. Furthermore, the system of highest efficiency is unexpectedly the simplest and cheaper combination that employs [Pd(η3‐C3H5)Cl]2/PPh3 at only a 1 mol‐% loading with pyrrolidine as the base and in the absence of a copper salt. The coupling of sterically and electronically deactivated bromides bearing different functional groups to aryl‐ and alkyl acetylenes, as well as the possibility of recycling, make these results of high interest to the future development of Heck‐ and Sonogashira‐type reactions in ionic liquids.(© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2007)
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Hierso et al. (2006) studied this question.
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