Sonogashira cross-coupling copper® iodide

The terminal alkyne can also be generated in situ via copper-free Sonogashira cross-coupling of trimethylsilyl acetylene (5a) and aryl halides 6 and subsequent cleavage with TBAF, caibonylation, and cyclization (Scheme 26) (20090L(11)3210). This microwave-assisted sequence allows the rapid synthesis of the title compounds in moderate to good yields. Each compound can be easily varied with exception to trimethylsilyl acetylene. The application of electron-rich aryl bromides and iodides expectedly decreases the yields. 

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). 

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