Triphenylphosphine as the ligand

Complexes 6 undergo the second migratory insertion in this scheme to form the acyl complexes 7. Complexes 7 can react either with CO to give the saturated acyl intermediates 8, which have been observed spectroscopically, or with H2 to give the aldehyde product and the unsaturated intermediates 3. The reaction with H2 involves presumably oxidative addition and reductive elimination, but for rhodium no trivalent intermediates have been observed. For iridium the trivalent intermediate acyl dihydrides have been observed [29], The Rh-acyl intermediates 8 have also been observed [26] and due to the influence of the more bulky acyl group, as compared to the hydride atom in 2e and 2a, isomer 8ae is the most abundant species. 

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Triglycerides and technical-grade fatty acid esters can be used as the starting material in hydroformylation (Scheme 7). Soybean oil and technical-grade methyl oleate were hydroformylated by [RhH(CO)2PPh3)] with triphenylphosphine as the ligand. 

These conditions are greener than those traditionally employed (e.g., triphenylphosphine as the ligand, triethylamine as base, and acetonitrile as solvent). In addition to the introduction of a modem chemical transformation to the lab, the experiment can be extended by conversion of the initial coupling... 

In medicinal chemistry nitriles are very useful because they can be transformed into biologically important structures such as tetrazoles, triazoles, oxazoles, thia-zoles, oxazolidinones. .. A variety of aryl nitriles has been prepared in excellent yields by Pd-catalyzed coupling of aryl halides with Zn(CN)2 using polymer-supported triphenylphosphine as the ligand and DMF as the solvent under micro-wave irradiation conditions (Scheme 10.34) [76], Products were obtained in high yields and excellent purity without the need for purification. 

The other solution is to use tri-o-tolylphosphine in place of triphenylphosphine as the ligand. This variation was used for vinylic substitution reactions with various heterocyclic bromides. An example is the synthesis of nornicotine (1). 

In the interfacial synthesis, toluene and aqueous s ium hydroxide are used as the biphasic reaction medium, palladium-(4-dimethylaminophenyl) diphenylphospine complex as the surface-active catalyst complex, and DSS as die emulsifier. The nature of the phosphine ligand is important. Little or no reaction occurs with triethoxylphenylphosphine and triphenylphosphine as the ligand. Presumably, (4-dimethylaminophenyl)diphenylphosphine is effective in promoting the reaction because it is surface-active. A cationic surfactant, e.g., cetyltrimethylammonium bromide, may be used in place of DSS as the emulsifier. In that event, however, the surfactant also functions as a phase-transfer agent, and the overall reaction has a phase-transfer component in addition to the interfadal component. 

It is noted that using l,2-bis(diphenylphosphino)-ortfto-carborane(12) (1) as the ligand in the reaction of 1-octene with methylchlorosilane led solely to the terminal product in a 3-5% yield. This is a very low catalytic activity in comparison with the use of triphenylphosphine as the ligand. 

Hydrogenation conditions were optimized by addition of triphenylphosphine as promoter ligand, and the hydrogenation degree of SBS was up to 89%. Hy-... 

It was Ayusman Sen [8] who discovered in 1982 that the use of weakly coordinating anions and phosphines as the ligands together with palladium yielded much more stable and active catalysts for the formation of polyketone from CO and ethene in alcoholic solvents. Cationic palladium-(triphenylphosphine)2(BF4)2 gave a mixture of oligomers having methoxy ester... 

To avoid difficulties with the low solubility of Pd/TPPTS the monosul-fonated triphenylphosphine (TPPMS) was used as the ligand, which is less polar than the trisulfonated TPPTS. With the following solvents s3 a homogeneous phase is obtained DMF, DMSO, PEG 400 and isopropyl alcohol. A smaller amount of the mediator is required if TPPMS is used than with TPPTS as the hgand. hi further experiments the use of polyethylene glycol... 

To investigate the use of a non-polar catalyst phase and a polar product phase EC, PC and acetonitrile were chosen as polar solvents and cyclohexane and p-xylene as non-polar solvents. Tricyclohexylphosphine, triphenylphos-phine and bisadamantyl-n-butyl-phosphine were used as the ligand for Pd(acac)2. If cyclohexane is used as the non-polar solvent, the palladium complexes of tricyclohexylphosphine and triphenylphosphine are situated in the polar solvent and with p-xylene the complex of tricyclohexylphosphine is located in the non-polar phase, hi the solvent system EC/cyclohexane the palladium complex of bisadamantyl-n-butyl-phosphine can be found in the cyclohexane phase. 

Larhed and coworkers employed fluorous triphenylphosphine as a ligand and Mo(CO)6 as a CO source for palladium-catalyzed hydrazidocarbonyla-tions of aryl iodides and bromides (Scheme 9) [36]. The fluorous ligand was recovered by extraction with fluorous solvent FC-84. 

Cyclohexadiene afforded allylsulfone 15 in 90% yield in a similar hydrosulfonation reaction [Eq.(12)] [28]. In this case it was necessary to employ triphenylphosphite as the ligand since triphenylphosphine gave a slow reaction and resulted in only a modest yield of... 

A far more elegant solution was the one offered by the Ruhrchemie/Rhone-Poulenc (RCH/RP) process, which was established in 1984 on an industrial scale threefold in mem-sulfonated triphenylphosphine (TPPTS, as sodium salt) as the ligand yields the water-soluble catalyst HRh(CO)(TPPTS)3. Because of the mutual insolubility, the separation of the aqueous catalyst phase and the butanals was extremely simplified, circumventing all the common difficulties and leading to very efficient operation. 

The Tsuji-Trost ally lie substitution catalyzed by Pd complexes using CH-acidic nucleophiles can be performed in an ionic liquid of type 1 alone [30] as well as in a biphasic system [31]. In the latter case the use of trisulfonated triphenylphosphine (TPPTS) prevents the catalyst from leaching into the organic phase. In comparison with water as the catalyst-supporting phase, the ionic liquid system exhibits higher activity and selectivity. The enantio-selective version of the allylic substitution with dimethyl malonate can also be performed in ionic liquids with a homochiral ferrocenylphosphine as the ligand [32]. 

By addition of triphenylphosphine as promoter ligand, hydrogenation degrees of up to 89% could be achieved. Hydrogenation of the benzene ring and gel formation was not observed. The active catalyst vras found to be well immobilized in the ionic liquid and the ionic catalyst phase could be reused three times vyithout significant loss in catalytic activity. 

In contrast to the use of PPhs as the ligand, the reaction takes place solely in the ionic liquid layer when the guanidinium-modified triphenylphosphine is applied. In the first catalytic run the hydroformylation activity was found to be somewhat lower thanwithPPhs (probably due to the ct that some ofthe activity observed with PPhs... 

In conjunction with the aforementioned trapping experiment, several attempts were made to isolate a nickel complex such as 10 analogous to the PT complex 11 [114] or such as 12 similar to the Fe complex 13 [115] by using 1,5-cyclooctadiene, 2,2 -bipyridine, triethylphosphine, or triphenylphosphine as stabilizing ligands see Figure 7.3. 

The hydrogenation of (Z)-a-N-acetamidocinnamic acid to give N-acetylphenylalanine is shown in Scheme 1, top. Rh compounds of the Wilkinson-type catalyze this reaction. With triphenylphosphine as a ligand, the product is formed as a racemic mixture in an achiral catalysis. If triphenylphosphine is replaced by an optically active phosphine, N-acetylphenylalanine is obtained in optically active form in an enantioselective catalysis. In 1968, pioneering studies used optically active phosphines of the Homer-type, such as PMePrPh as ligands [1,2]. Optical inductions, however, remained low with catalysts containing these monodentate phosphines. 

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