Suzuki ligand-free catalysts

However, efforts were also directed to the development of phosphine-free catalysts. For example, the ligand-free Pd(OAc)2 promoted Suzuki reaction in water was reported using microwave heating. In this way, a low palladium loading (0.4 mol.%) was required and the cross coupling proceeded quickly (5-10 min reaction time), using boronic acids and aryl iodides, bromides and chlorides. 

A facile surfactant-mediated Heck and Suzuki coupling procedure in water has been developed nsing ligand-free Pd catalysts. The procedure which involves nanometric palladinm colloids is operationally simple, environmentally benign, and synthetically as efficient as conventional procednres using organic solvents [21]. 

Bhattacharya S, Srivastava A, Sengupta S (2005) Remarkably facile Heck and Suzuki reactions in water using a simple cationic surfactant and ligand-free palladium catalysts. Tetrahedron Lett 46(20) 3557-3560... 

Hallberg et al. have shown that microwaves accelerate palladium-catalyzed reactions (e.g. Suzuki, Heck, Tsuji-Trost, Stille) in solution or with supported polymers [127]. Most recently, Villemin and Caillot have reported that, in the Suzuki reaction, the use of a ligand-free palladium catalyst, palladium acetate, without the use of solvent under microwave irradiation produces good yields of biphenyl products, one of which is shown in Equation 89 [128]. 

Palladacycles [17] have been established as important class of catalysts, an unusual phosphine-free sulfur containing catalyst was introduced by Zim [18] et al. A phosphinite based palladacycle [19] proved to be very efficient in Suzuki coupling reactions. An N,P-Ligand type was synthesized by Kocovsky [20] et al. Tridentate pincer ligands [21] have been proved use-fill in the Heck reaction. Recent developments regarding Heck (22] and Suzuki [23] reactions have been reviewed by Fu and Littke. A new catalyst especially suitable for Heck couplings has been introduced by Beller [24] et al. 

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