Suzuki reactions supercritical carbon dioxide

Gordon and Holmes32 used a supported triphenylphosphine-Pd(II) complex as an effective catalyst for Heck and Suzuki couplings in supercritical carbon dioxide (entry 27). After optimization of the amine base for the reaction, the final products have been isolated in good yields and high purity with no traces of metal. 

Coupling reactions. The Suzuki coupling involving chloroarenes uses (dbajjPdj, /-BujP, and CsjCOj. For other coupling reactions (e.g., Stille coupling) good results are obtained in supercritical carbon dioxide. ... 

Other biphasic C—C bonding reactions were carried out with fluorous solvents, for instance Suzuki- and Sonogashira-couplings [124] or ethene or propene oligomerizations [125, 126], Further new solvent systems use ionic liquids for the linear dimerisation of 1-butene to octenes [127] or the hydrovinylation of styrene with a combination ionic liquid/supercritical carbon dioxide [128] (cf. Section 7.4). 

However, the practical use of supercritical carbon dioxide has been limited by its solvating power. Although SCCO2 dissolves most non-polar compounds of low molecular mass, many catalysts, substrates and reagents are only poorly soluble. Most recently, it was reported that Suzuki reactions proceed in good yield in SCCO2 in the presence of palladium acetate and tri-tert-butylphosphine, with DIPEA (N,N-diiso-propylethylamine) as the base (Equations 94 and 95) [137]. 

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