Alkynes Sonogashira coupling with

Initially, 31 was obtained as the Sonogashira adduct of 2-chloro-3,6-diisobutylpyrazine and trimethylsilylacetylene. Interestingly, 31 underwent an additional Sonogashira coupling with 2-chloropyrazine (13) to afford unsymmetrical 1,2-bispyrazinylacetylene 32 in excellent yield [26], Here, desilylation occurred in situ, and the resulting terminal alkyne was then coupled with 13. 

Scheme 5.17 Sonogashira coupling with electron-withdrawing halide compounds as a peculiar mode of alkyne activation and entry to coupling-Michael addition sequences.

If 2,3-dibromo propene is used as an allylic substrate the substitution product 71 can be either isolated or, after addition of additives and adjustment of the reaction conditions, 71 can readily react in cross-coupling reactions with alkynes (Sonogashira coupling), stannanes (Stille coupling), or boronic acids and boronates (Suzuki coupling) to provide the sequential allylic substitution-cross-coupling products 72-78 in moderate to good yields (Scheme 23). 

Sonogashira coupling. Stereodefmed enynes including those bearing an alkoxy substituent (i.e., enol and ynol ethers) are readily prepared from alkynes on coupling with alkenyl iodides. Alkynylsilanes can be used instead of 1-alkynes in the coupling with alkenyl and aryl triflates. ... 

Sonogashira coupling with various alkynes 82 (Scheme 23) generated an array of 3-alkynyl-5-bromo-2-pyrones 83 in good yields <02OLl 171>. Under these conditions, no C5-alkynylated 2-pyrone products were observed. 

Acyclic diaminocarbene when complexed to palladium has been shown to preclude the homocoupling of alkynes in the Sonogashira coupling with acyl chloride inducing a complete chemoselectivity for the desired product. ... 

The enaminones 67 are readily prepared via Sonogashira coupling of terminal alkynes with acid chlorides, followed by conjugate addition of propargylamine and further Sonogashira coupling with aryl iodides ... 

It is assumed that cyclization proceeds by Cu-promoted intramolecular nucleophilic addition of the imine moiety to the triple bond (77 —78) with loss of the tBu group by formation of isobutene. The imines 77 are accessible from (2-halogeno)benzaldehydes 80 (X = Br, I) by Sonogashira coupling with terminal alkynes and imine formation with (CH3)3C-NH2 or vice versa. 

Furthermore, the pyrazole formation reaction was also combined with a palladium-catalyzed Sonogashira coupling with a terminal alkyne and subsequent intramolecular 6-endo alkyne hydroamination to provide an alternative approach to the facile synthesis of pyrazolo[5,l-a]isoquinoline 36 (Scheme 7.19) [72]. 

More recently, a study with di- and mono-carbene Pd(II) complexes has demonstrated that the Sonogashira coupling of activated and non-activated aryl iodides can be carried out in an aqueous, aerobic medium and in the absence of amines. These results suggest that the moisture-sensitive copper-acetylide may not be present in this particular transformation, and that a Pd-acetyhde could be formed by deprotonation of the coordinated alkyne instead of transmetallation [130]. 

The coupling of terminal alkynes with organic halides, known as the Castro-Stephens-Sonogashira reaction, has wide applications in synthesis. The most widely used method is the Sonogashira coupling, using a combination of palladium and copper as the catalyst.13 Recently,... 

There are many other transition-metal catalyzed coupling reactions that are based on organic halides in aqueous media. One example is the coupling of terminal alkyne with aryl halides, the Sonogashira coupling, which has been discussed in detail in the chapter on alkynes (Chapter 4). An example is the condensation of 2-propynyl or allyl halides with simple acetylenes in the presence of copper salts. 

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