1- Propene, palladium complex

In line with the above mechanism, catalyst deactivation by formation of palladium black can be retarded by increasing the [P]/[Pd] ratio, however, only on the expense of the reaction rate. Bidentate phosphines form stronger chelate complexes than TPPMS which may allow at working with lower phosphine to palladium ratios. Indeed, the palladium complex of sulfonated XANTPHOS (51) proved to be an effective and selective catalyst for hydroxycarbonylation of propene, although at [51]/[Pd] < 2 formation of palladium black was still observed. The catalyst was selective towards the formation of butyric acid, with 1/b = 65/35 [41]. 

The water-soluble palladium complex prepared from [Pd(MeCN)4](Bp4)2 and tetrasulfonated DPPP (34, n=3, m=0) catalyzed the copolymerization of CO and ethene in neutral aqueous solutions with much lower activity [21 g copolymer (g Pd) h ] [53] than the organosoluble analogue in methanol. Addition of strong Brpnsted acids with weakly coordinating anions substantially accelerated the reaction, and with a catalyst obtained from the same ligand and from [Pd(OTs)2(MeCN)2] but in the presence of p-toluenesulfonic acid (TsOH) 4 kg copolymer was produced per g Pd in one hour [54-56] (Scheme 7.16). Other tetrasulfonated diphosphines (34, n=2, 4 or 5, m=0) were also tried in place of the DPPP derivative, but only the sulfonated DPPB (n=4) gave a catalyst with considerably higher activity [56], Albeit with lower productivity, these Pd-complexes also catalyze the CO/ethene/propene terpolymerization. 

Scheme 3 Asymmetric allylic amination of l,3-diphenyl-l-propene-3-acetate catalyzed by Pyrphos-palladium complexes...

The presence of five-membered rings such as cyclopentanes, cyclopentenes, and dihydrofurans in a wide range of target molecules has led to a variety of methods for their preparation. One of the most successful of these is the use of trimethylenemethane [3 + 2] cycloaddition, catalysed by pal-ladium(O) complexes. The trimethylenemethane unit in these reactions is derived from 2-[ (trimethylsilyl)methyl]-2-propen- 1-yl acetate which is at the same time an allyl silane and an allylic acetate. This makes it a weak nucleophile and an electrophile in the presence of palladium(0). Formation of the palladium 7t-allyl complex is followed by removal of the trimethylsilyl group by nucleophilic attack of the resulting acetate ion, thus producing a zwitterionic palladium complex that can undergo cycloaddition reactions. 

The polymer with low molecular weight, prepared from the reaction at a small [monomer]/[Pd] ratio (20 1), shows the C H NMR signals of the carbons of the initiating polymer end. The polymer from 1-phenyl- -allyl-palladium complex contains the 3-phenyl-1-propen-3-yl end group (Eq. 42) (<5141.7 [CH2=], 114.3 [=CH-], 47.8 [CHPh]), whereas the end group of the polymer from -allylpalladium complex contains the signals due to the allyl group (<5138.4 [CH2=], 114.4 [=CH-], 34.1 [CH2]). 

Acetoxymethyl)-3-(trimethylsilyl)propene (1) is used as a trimethylenemethane precursor in palladium(0)-catalvzed [3 + 2] cycloaddition with electron-deficient alkenes, such as enones, acrylonitriles and a,/ -unsaturaled esters23,26. Mechanistically, this reaction, which gives methylenecyclopentane derivatives 2. is interpreted to proceed via trimethylenemethane-palladium complexes 27,28. 

Bronco, S. Consigho, G Regio- and stereoregular copolymerisation of propene with carbon monoxide catalysed by palladium complexes containing atropisomeric diphosphine ligands. Macromol. Chem. Phys. 1996,197,355-365. 

An interesting regiochemistry has been observed in the palladium-catalyzed allylic alkylation of ( )-3-substituted-2-propene acetate and 1-substituted 2-propenyl acetate. In this allylic substitution catalyzed by a palladium complex prepared from 1 in the presence of (/ )-MeO-MOP catalyst (P/Pd = 2/1), a selective substitution at the position originally substituted with acetate was observed (eq 62). Studies with 3-deuterio-2-cyclohexenyl acetate revealed that neutral phosphane Pd-complex is formed during the process. 

Fuchikami T, Ojima I. New and direct route to 5-trifIuoro-methyl-5,6-dihydrouracils by means of palladium complex catalyzed ureidocarbonylation of 2-bromo-3,3,3-trrfluoro-propene. Tetrahedron Lett. 1982 23 4099-4100. 

Ionic liquids have already been demonstrated to be effective membrane materials for gas separation when supported within a porous polymer support. However, supported ionic liquid membranes offer another versatile approach by which to perform two-phase catalysis. This technology combines some of the advantages of the ionic liquid as a catalyst solvent with the ruggedness of the ionic liquid-polymer gels. Transition metal complexes based on palladium or rhodium have been incorporated into gas-permeable polymer gels composed of [BMIM][PFg] and poly(vinyli-dene fluoride)-hexafluoropropylene copolymer and have been used to investigate the hydrogenation of propene [21]. 

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