Triflates Sonogashira reactions, copper iodide

The original Sonogashira reaction uses copper(l) iodide as a co-catalyst, which converts the alkyne in situ into a copper acetylide. In a subsequent transmeta-lation reaction, the copper is replaced by the palladium complex. The reaction mechanism, with respect to the catalytic cycle, largely corresponds to the Heck reaction.Besides the usual aryl and vinyl halides, i.e. bromides and iodides, trifluoromethanesulfonates (triflates) may be employed. The Sonogashira reaction is well-suited for the synthesis of unsymmetrical bis-2xy ethynes, e.g. 23, which can be prepared as outlined in the following scheme, in a one-pot reaction by applying the so-called sila-Sonogashira reaction ... 

The palladium-catalyzed arylation and alkenylation of terminal alkynes with aryl or alkenyl hahdes in presence of a copper(l) co-catalyst is called Sonogashira reaction. In the same way as in the other cross-coupling reactions described before, it is possible to immobihze the alkyne or the aromatic bromides, iodides or triflates on sohd supports (Scheme 3.15). 

Terminal alkynes can be alkenylated by alkenyl triflates (bromides, iodides) in the presence of catalytic amounts of a palladium(O) complex (or a precursor thereof) and usually an additional substoichiometric amount of copper(I) iodide (Cul), and they can be arylated by aryl triflates (bromides, iodides). These reactions are called Cacchi coupling reactions if triflate reagents are employed, and Sonogashira-Hagihara coupling reactions if halides are used. 

---