Sonogashira palladacycle catalysts

Polystyrene-supported soluble palladacycle catalyst as recyclable catalyst for Heck, Suzuki and Sonogashira reactions... 

A new type of soluble polystyrene-supported palladium complex was synthesised (Figure 6.1) as an excellent and recyclable palladacycle catalyst for carbon-carbon bond formation in Heck, Suzuki and Sonogashira reactions to give high yields of the desired products. 

SYNTHESIS OF 1 - [4-(2-PHEN YLETHYNYL)PHEN YL] ETHAN -1-ONE VIA SONOGASHIRA REACTION BY THE USE OF POLYMER-SUPPORTED PALLADACYCLE CATALYST... 

The newly invented polystyrene-supported palladacycle catalyst was prepared in six steps with high yields. The simple precipitation and filtration process to recycle the catalyst after model reactions for Heck, Suzuki, and Sonogashira reactions is noteworthy.[1]... 

Figure 1.31 The palladacycle catalysts used by Dupont s group [109] for copper-free Sonogashira-Hagihara reaction arylations.

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. 

Corma and coworkers attached Najera s palladacycle to polyethylene glycol and used this catalyst in the Suzuki and Sonogashira couplings [130]. They observed the formation of nanoparticles. In this case the virgin catalyst had a higher activity than the nanoparticles obtained from an earUer reaction. 

There is no doubt that palladacycles have great potential as robust catalysts in the cross-coupling between alkynes and aryl halides, and their activities (as reflected by TONS or TOFs) may be far from the impressive results observed for Heck couplings. However, the peculiarities of the Sonogashira reaction, in terms of electronic and coordination properties of the substrates, may be an inherent problem for long-lived catalysts in this chemical transformation. 

Ndjera C, Alonso DA (2008) Appheation of cyclopalladated compounds As catalysts for Heck and Sonogashira reactions. In Dupont J, Pfeffer M (eds) Palladacycles. Synthesis, characterization and appheations. Wiley-VCH, Weinheim, p 155... 

In 2008, Application of CyclopaUadated Compounds as Catalysts for Heck and Sonogashira Reactions, by Najera and Alonso [110], Palladacyclic Precatalysts for Suzuki Coupling, Buchwald-Hartwig Amination and Related Reactions Bedford [111]... 

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