Sonogashira and Suzuki couplings

Scheme 24 Sequential allylic substitution-Sonogashira and Suzuki coupling [80]...

Solid-phase synthesized polymer-bound 3-iodoindole 845 subjected to the Sonogashira and Suzuki coupling reactions afforded the corresponding coupling products 846 and 847 in 91% and 80% yields, respectively, as determined by transesterification and isolation of the corresponding methyl esters (Scheme 161) <2005JC0809>. 

Sonogashira and Suzuki couplings that were effected in toluene, though the conversions in these reactions dropped from near quantitative values into the low 80% range after four to six cycles. The Heck reaction required more polar solvents hke DMA. In these solvents the membrane degraded - a problem that could be alleviated only if the reaction mixture was diluted with a large amount of cyclohexane. The conversions in the Heck reaction also notably decreased after only a few cycles. 

A. Datta, K. Ebert, H. Plenio, Nanofiltration for homogeneous catalysis separation Soluble polymer-supported palladium catalysts for Heck, Sonogashira, and Suzuki coupling of aryl halides, OrganometaUics 22 (2003) 4685-4691. 

The coupling of terminal alkynes with aryl or vinyl halides under palladium catalysis is known as the Sonogashira reaction. This catalytic process requires the use of a palladium(0) complex, is performed in the presence of base, and generally uses copper iodide as a co-catalyst. One partner, the aryl or vinyl halide, is the same as in the Stille and Suzuki couplings but the other has hydrogen instead of tin or boron as the metal to be exchanged for palladium. 

Some carbanion equivalents are used to perform transition metal catalyzed reactions. Very common examples, such as the Suzuki, Sonogashira, and Heck couplings, have been mentioned in Section 4.2.1. Some related examples with aliphatic systems are presented below. 

The Sonogashira coupling of 2,4-dichloroquinoline in water with a palladium-carbon catalyst (triphenylphosphine, triethylamine, Cul, 80 °C) shows complete selectivity for the 2-position and Suzuki couplings of 1,3-dichloroisoquinoline are selective for C-1. ... 

Coupling reactions. Various (Heck, Stille, Suzuki, Sonogashira, and Ullmann) coupling reactions are mediated by a stable palladacycle 1. ... 

Palladacycles have also been used extensively as catalysts in other C—C bond forming reactions such as the Suzuki, Sonogashira and Stille couplings. Particularly active in this fleld are the groups of Bedford [107] and Najera (Fig. 10.13) [127, 128]. Usually these catalysts perform better in the presence of Bu4NBr. Surprisingly, much less mechanistic work has been performed in this area. 

Heck, Suzuki, and Sonogashira coupling reactions [19], The same group later described an scC02-soluble nonfluorinated catalyst system formed by the combination of Pd(OAc)2 with PBu 3, which was applied to Heck and Suzuki coupling reactions [20],... 

Suzuki-Miyaura, Ullmann, Sonogashira, and Heck Coupling Reactions... 

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