Tetraalkylammonium-Free Heck Olefination of Deactivated Chloroarenes by Using a Macrocyclic Catalyst Precursor



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Palladium reservoir: A macrocyclic dinuclear Pd complex is applied to the Heck coupling of strongly deactivated aryl chlorides. The complex serves as a very stable precatalyst, which releases active Pd under normal reaction conditions (see scheme). The controlled release and recapture of active Pd provides sufficient stabilization to supersede the addition of tetrabutylammonium bromide. Quantitative conversions can be achieved under additive-free conditions.