Phosphines Sonogashira reaction

Cationic phosphine ligands containing guanidiniumphenyl moieties were originally developed in order to make use of their pronounced solubility in water [72, 73]. They were shown to form active catalytic systems in Pd-mediated C-C coupling reactions between aryl iodides and alkynes (Castro-Stephens-Sonogashira reaction) [72, 74] and Rh-catalyzed hydroformylation of olefins in aqueous two-phase systems [75]. 

Although the Sonogashira reaction is normally performed with a copper cocatalyst, a copper-free, one-pot procedure for direct coupling with l-aryl-2-trimethylsilylacetylenes has been developed <2005T2697>. The procedure uses a mixture of palladium acetate and tri(o-tolyl)phosphine as catalyst in the presence of tetra- -butylammonium chloride... 

Fluor OUS Sonogashira reactions (a) using a fluorous support and no fluorous solvent, (b) using perfluorodecaline under phosphine- and copper-free conditions. 

Alternative ligands were examined as a way of modulating catalyst efficiency. Sonogashira reactions were investigated using Tedicyp 329, a tetradentate phosphine ligand [116]. A wide variety of substituted alkynes 319 could be cross-coupled to halopyridines 51 to afford 330. 

No additional phosphines or cooper salts were required, and InCfi itself catalyzed this transformation. Additional studies are required in order to carefully evaluate the mechanism of this transformation, which undoubtedly is different from that of the palladium-mediated Sonogashira reactions. Nonetheless, the simplicity and activity of the catalytic system, as well as its generality with respect to the nature of the leaving group, renders this a promising alternative for the synthesis of internal alkynes. 

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