Phosphines Castro-Stephens reaction, catalytic

Copper-mediated alkynylations of alkenyl- or aryl-substituted compounds should be considered as variations of the original Castro-Stephens reaction under catalytic reaction conditions. Copper(I) salts stabilized by aryl-substituted phosphines can mediate the coupling of aryl iodides in polar aprotic solvents using either conventional heating [87] or microwave irradiation [88]. More recently, weU-defined 1,10-phenanthroline-derived copper complexes were shown to be effective catalysts for the coupling of activated and deactivated aryl iodides at 10mol% catalyst loading in an apolar solvent (Scheme 6.29) [89]. 

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]. 

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