Polyurea-encapsulated palladium

Leadbeater NE, Pillsbury SJ, Shanahan E, Williams VA (2005) An assessment of the technique of simultaneous cooling in conjunction with microwave heating for organic synthesis. Tetrahedron 61 3565-3585 Lee CKY, Holmes AB, Ley SV, McConvey IF, Al-Duri B, Leeke GA, Santos RCD, Seville JPK (2005) Efficient batch and continuous flow Suzuki crosscoupling reactions under mild conditions, catalysed by polyurea-encapsulated palladium (II) acetate and tetra-n-butylammonium salts. J Chem Soc Chem Commun 2175-2177... 

Yu J-Q, Wu H-C, Ramarao C, Spencer JB, Ley SV 2003) Transfer hydrogenation using recyclable polyurea-encapsulated palladium efficient and chemoselective reduction of aryl ketones. J Chem Soc Chem Commun 678-679... 

Ley SV, Ramarao C, Gordon RS, Holmes AB, Morrison AJ, McConvey IF, Shirley IM, Smith SC, Smith MD. Polyurea-encapsulated palladium(II) acetate a robust and recyclable catalyst for use in conventional and supercritical media. Chem Commun 2002 1134-1135. 

Polyurea-encapsulated palladium catalysts promote the phosphine-free Mizoroki-Heck reaction, which results in a high yield of cinnamates 46 (Scheme 86). The catalyst, which is easily recovered by filtration, is also applicable to the Suzuki-Miyaura and Stifle coupling reactions. 

R. C. D. Santos, J. P. K. Seville, EfEdent batch and continuous flow Suzuki crosscoupling reactions under mild conditions, catalyzed by polyurea-encapsulated palladium(II) acetate and tetra-ti-butylammonium salts, Chem. Commun. 2005, 2175-2177. 

For completeness, it should be noted that other groups have also developed encapsulated palladium materials but starting from palladium salts.Palladium-containing polyurea microcapsules have been synthesized and used in... 

Ramarao C, Ley SV, Smith SC, Shirley IM, DeAlmeida NJ (2002) Encapsulation of palladium in polyurea microcapsules. Chem Soc Chem Commun 1132-1133... 

Palladium(II) acetate micro-encapsulated in polyurea is an economical and versatile heterogeneous catalyst for a range of phosphine-free cross-coupling reactions in both conventional solvents and supercritical carbon dioxide. The catalyst can be recovered by simple filtration and recycled up to four times [93]. The potential of these materials has been demonstrated by their efficacy in Suzuld-type couplings. Investigations have centered upon carbonylation reactions to prepare aryl esters from commercially available aryl iodides. Treatment of iodo-methyl benzene tvith 3 mol% of catalyst in butanol and triethylamine at 90 °C under an atmosphere of carbon monoxide afforded butyl-methyl benzoate in an excellent yield of 89% in 16 h. 

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