Palladium catalysts containing sulfonated

The problems associated with the in situ approaches can be avoided by using a discrete catalyst. The presumed structure of the monometallic palladium catalyst contains the sulfonated phosphine ligand chelated to the palladium and a palladium-carbon bond (polymer), most probably in cis geometry with respect to the phosphorous (Fig. 8). 

More recently, monometallic palladium catalysts " containing a sulfonated phosphine ligand have been developed that are able to homopolymerize ethylene and copolymerize ethylene with acrylates and other polar monomers in both solution and aqueous phase. In solution, the activity... 

Replacement of tppts by a ligand containing less -S03Na groups such as tppms gave rise to a dramatic drop in the catalytic activity and selectivity to ibuprofen. A palladium catalyst generated from the sulfonated diphosphine 29 (Table 2 x=3 m=n=0 86% and m=0,n=l 14%) exhibited low catalytic activity and the major product was 3-IPPA (78%).451... 

Huser and Perron have extended this work to the isomerization of 2-methyl-3-butenenitrile (2M3 BN) to 3-PN (isomerization step Eq. (6) 92% yield) [17]. This patent mentions the use of iron and palladium catalysts but does not provide examples beyond nickel. In other work these same inventors discuss the use of other water-soluble ligands such as those containing carboxylate, phosphate, and alkyl-sulfonate substituents [18], while also exploring a wide range of Lewis acid co-catalysts for the addition of HCN to 3-pentenenitrile (Eq. 7) [19]. In general, the addi-... 

Similarly, a water-soluble palladium complex of a sulfonated phenanthroline ligand catalyzed the highly selective aerobic oxidation of primary and secondary alcohols in an aqueous biphasic system in the absence of any organic solvent (Figure 1.8) [40]. The liquid product could be recovered by simple phase separation, and the aqueous phase, containing the catalyst, used with a fresh batch of alcohol substrate, affording a truly green method for the oxidation of alcohols. 

Since sulfur is the most effective of all catalyst poisons, the hydrogenation of sulfur containing heterocycles is not easily accomplished unless there are no unshared electron pairs on the sulfur atom or the catalyst used is not affected by the poison. The hydrogenation of the cyelie sulfone, 58, takes palace over an excess of palladium in acetic acid at room temperature and atmospheric pressure (Eqn. 17.57). Thiophene, itself, can be hydrogenated to tetrahydrothiophene over rhenium heptasulfide at 250°C and 300 atmospheres of hydrogen or over a large excess of palladium in methanolic sulfuric acid at room temperature and 3-4 atmospheres. No hydrogenolysis of the carbon-sulfiir bond was observed in these reactions. 

Cyano-4 -methylbiphenyl is produced by coupling of 4-tolylboronic acid and 2-chlorobenzonitrile in the presence of a palladium/snlfonated triphenylphosphine (TPPTS) catalyst in yields higher than 90%. The reaction is conducted at 120 °C in a polyhydric alcohol solvent (e.g., ethyleneglycol), which contains small amounts of sulfoxide or sulfone for catalyst stability reasons. At the end of the reaction two phases form. The catalyst and salts remain in the polar phase, and the product forms the organic phase. This biphasic procedure allows an efficient recycling of the homogeneous catalyst. 

Henbest and Trocha-Grimshaw have shown that sulfoxides may be oxidized to sulfones in the presence of iridium and rhodium complexes [139, 140]. Oxidations were studied by passing air through a solution of the sulfoxide in hot wopropanol containing 10% water in the presence of the catalyst. Sulfones were formed when chlorides of iridium or rhodium were used while chlorides of ruthenium, osmium and palladium were not effective. Under reaction conditions the chlorides should be converted wholly or partly to metal sulfoxide complexes. 

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