Sonogashira palladacycle

Sonogashira reaction. The first system consisted in the use of the oxime palladacycles 7a-f at elevated temperatures, without the aid of Cul or an amine base, for the coupling of aryl iodides and bromides. They also reported on the use of complex 48b in aqueous media for the coupling of aryl iodides and bromides and terminal acetylenes in excellent yields. ... 

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]... 

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. 

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]... 

Catalytic activity in the Sonogashira reaction has also been demonstrated for a variety of palladacycles (Table 9.4). They typically exhibit an interesting combination of characteristics including both high catalytic activity and stability and are usually encountered as precatalyst precursors of active Pd clusters in many C-C coupling reactions [80]. 

I 9 Cross-Coupling Reactions to sp Carbon Atoms Table 9.4 Selected examples of palladacycles in the Sonogashira reaction. 

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

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