Silver Sonogashira reaction

Van der Eycken s group developed a silver(I)-mediated synthesis of substituted furo[2,3-6]pyrazines.53 Starting from -methoxybenzyl-protected 3,5-dichloropyr-azine-2(l//)-ones 26 (Scheme 5.13), after a regioselective microwave-assisted Sonogashira reaction with various terminal alkynes, the cycloisomerization reaction could occur using AgOTf (2 mol%) with trifluoroacetic acid (TFA, 5 equiv) to yield... 

The convenience of this methodology promoted it as being the most popular protocol for the synthesis of internal alkynes, which is itself (as well as in different variations) closely associated with Sonogashira s name. For instance, couplings involving silver instead of copper salts as additives, as well as copper-free protocols, are also considered Sonogashira reactions. Further, the formation of C(sp )—C(sp)... 

Regardless of the solvent used, various additives have been explored in the Sonogashira reaction to increase yield, and reaction rates. Ammonium and silver salts have shown the most promise in this respect. Mori et al. [123] found that by using 2 equiv. of either tetrabutylammonium fluoride (TBAF) or tetrabutylammonium hydroxide (TBAOH), activation of the cross-coupling with... 

A silver(i) complex having the heterosubstituted 3-methyl-l-(2-pyridylmethyl)imidazol-2-ylidene ligand, [Ag(carbene)2] [I/Agl2] 37, was reported, which was further reacted to give a series of palladium(n) carbene complexes that were demonstrated to be active catalysts toward Heck, Suzuki, and Sonogashira coupling reactions.87... 

In 2006, Li and Wang reported the palladium-free, silver-catalyzed Sonogashira-type coupling of aryl halides and terminal alkynes. The reaction proceeds in high yield in the presence of catalytic silver iodide, triphenylphosphine, and potassium carbonate. Although the mechanism remains unclear, it is evident that the silver acetylide has a role, as the acetylide is formed on mixing of the reagents (Scheme 1.54).122... 

The versatility of silver-catalyzed desilylation has been further extended by its use in a one-pot catalytic desilylation/Sonogashira-type coupling reaction. In the total... 

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