Palladium acetate detection

The second related ESI-MS mechanistic study [50] examined the substitution of allylic acetate Sib with para-toluenesulfinate 54 using [(7t-allyl)PdCl]2 and the same water-soluble ligand 56 as the catalytic system (Eq. (2) in Scheme 7.27). Entries 6-8 of Table 7.11 give the most significant palladium species detected in these experiments. 

Figure 5 gives the results obtained in the following reaction conditions starch 12g, butadiene ca 40g, catalyst Pd(OAc)2/TPPTS 1/3, aqueous NaOH (O.IM) 50ml/iPrOH 10ml, 3h. At 90°C, with 0.5 wt.% of Pd(OAc)2, the DS reached almost 0.6 while less than 0.3 was achieved with 0.12 wt% catalyst. At 50°C, the DS was lower but much less affected by the catalyst/starch ratio, thus the DS decreased from 0.15 to 0.08 as the amount of catalyst decreased from 0.5% to 0.05%. This is because at 90°C Pd/TPPTS complex is unstable and decomposes progressively into palladium metal whereas at 50°C the catalyst is stable enough. When the reaction was performed in the presence of 0.25% palladium acetate, 0.08 wt% residual palladium was detected by chemical analysis of modified starch after reaction at 50°C. In contrast, no palladium was detected in the modified polymer when the reaction was conducted in the presence of 0.05% palladium. An optimum DS of 0.06 suitable for application in latex preparation for decorative paints was obtained with 0.03% palladium at 50X. 

Ihe resulting polymer prepared using Pd-Gr was less colored than the polymer prepared using die homogeneous palladium catalysts. The amount of residual palladium in the polymer prepared by Pd-Gr was determined to be ca. 50 ppm by the ICP plasma emission spectroscopy. However, the residual palladium of ca, 500 ppm was detected in the polymer prepared by palladium acetate. The fact that the amount of palladium in the polymer prepared by Pd-Gr was 10 times less than that in the polymer prepared by p ladium acetate may affect the color of the polymer. 

Hydrogenation of dibenzofuran over a platinum catalyst in acetic acid at 50°C and moderate pressure affords perhydrodibenzofuran. At higher temperatures and pressures with platinum or palladium catalysts the product is 2-biphenylol. When dibenzofuran is hydrogenated in ethanol over Raney nickel at 190°C and 200 atm for 23 h, the products isolated were perhydrodibenzofuran (36%), trans-2-cyclohexylcyclohexanol (27%), cis-2-cyclohexylcyclohexanol (20%), and dicyclohexyl (3%). When the hydrogenation, under these conditions, was terminated after the absorption of only 3 mol equiv of hydrogen, the only product detected was perhydrodibenzo-furan. ° Hydrogenation of dibenzofuran over a sodium-rubidium catalyst,... 

The selective hydrogenation of the olefinic double bond in the acetylated carbohydrate C-nitroolefins, using palladium black as catalyst, depends to a marked degree on the solvent employed. In absolute ethanol a sharp decrease in the rate of hydrogen absorption usually occurs when the double bond has been saturated. This decrease in rate is not sharply defined in 95 percent ethanol and is not detectable when absolute ethyl acetate is employed as the hydrogenation solvent. 

Metal(0) deposited at the Ti02 surface may enhance yields and selectivity of the reduction products [28-30], In the presence of copper(0)-loaded Ti02 formaldehyde and methanol were detected as main products [31]. Mercury- and platinum-loaded Ti02 favoured formation of carbon and formaldehyde [28,29], Methane was obtained with a high selectivity in the case of palladium-doped Ti02, whereas in the presence of Rh, Au, and Ru metals acetic acid was also produced [30],... 

In the oxidation of 2-octenyl acetate, in addition to the normal oxidation, palladium-catalyzed allylic rearrangement and subsequent oxidation took place to give a small amount of 3-acetoxy-2-octanone as a byproduct. Ethers of secondary allylic alcohols also underwent the regioselective oxidation to give the corresponding 3-alkoxy ketones in 30-40% yields. But in this case too, by-products derived from the allylic reanangement a subsequent oxidation were also detected. Results of the oxidation of some allyl ethers are shown in Table 3. °... 

In the presence of a palladium(O) catalyst, allyl acetates having hydroxy functions afford cyclic ethers. Thus, exposure of (117a)- 117c), 1 1 diastereomeric mixtures, to [(DBA)3Pd2]/CHCb-Ph3P at room temperature gives rise to the same cyclic ether (118) in 92-96% yields as a 9 1 isomeric mixture. No cy-clization products derived from the secondary alcohol serving as the nucleophile are detected (Scheme 49). By this procedure, five- to seven-membered cyclic ethers have been prepared. ... 

Photochemical decomposition of diazo(trimethylsilyl)methane (1) in the presence of alkenes has not been thoroughly investigated (see Houben-Weyl Vol. E19b, p 1415). The available experimental data [trimethylsilylcyclopropane (17% yield) and la,2a,3j8-2,3-dimethyl-l-trimethylsilylcyclopropane (23% yield)] indicate that cyclopropanation occurs only in low yield with ethene and ( )-but-2-ene. In both cases the formal carbene dimer is the main product. In reactions with other alkenes, such as 2,3-dimethylbut-2-ene, tetrafluoroethene or hexafluoro-propene, no cyclopropanes could be detected.The transition-metal-catalyzed decomposition of diazo(trimethylsilyl)methane (1) has been applied to the synthesis of many different silicon-substituted cyclopropanes (see Table 3 and Houben-Weyl Vol.E19b, p 1415) 3.20a,b,2i.25 ( iQp. per(I) chloride has been most commonly used for carbene transfer to ethyl-substituted alkenes, cycloalkenes, styrene, and related arylalkenes. For the cyclopropanation of acyl-substituted alkenes, palladium(II) chloride is the catalyst of choice, while palladium(II) acetate was less efficient, and copper(I) chloride, copper(II) sulfate and rhodium(II) acetate dimer were totally unproductive. The cyclopropanation of ( )-but-2-ene represents a unique... 

Powell et al. (113) have utilized NMR to aid in the detection of a tri-haptoidimexy-pentahaptoijaonovaeT) equilibrium for a series of hepta-2,6-dienylpalladium acetate complexes in chloroform solution. The chemical shifts for C(l) and C(2) in IV (W = H, X = O2CCF3) are compatible with a coordinated olefin, but for IV (W = Cl, X = O2CCF3) these shifts are almost identical to those of III (W = Cl, X = hfacac) in which the olefin C(l) = C(2) is not coordinated to palladium. This evidence together with molecular weight data led the authors to conclude that IV existed in an /t (dimer)-A (monomer) equilibrium the position of equilibrium being dependent on both the olefinic substituent W and the carboxylate substituent R. 

In a first stage, a 1 2 mixture of [(7t-allyl)PdCl]2 and 56 revealed a peak corresponding to the intermediate I79b, which again showed the coordination of the palladium atom with the hydrophilic ligand. This complex had an allyl moiety coordinated to the metal in an or coordination mode (Entry 6). No new peaks were observed when the allylic acetate 51b was added to the above mixture. However, when nucleophile 54 was added, two new peaks were detected after 1 h. at 50 °C (i) a 7t-allyl palladium complex (I81b) and (ii) an intermediate... 

A slight modification of reaction conditions causes a dramatic change in the reaction course. o-Iodoaniline reacts with phenylacetylene in the presence of 4% of Pd(PPh3)4 and 1 equiv of potassium acetate under 1 atm of CO in anisole to provide a mixture of 2-benzylidene derivative of indoxyl and acetylenic ketone in a good combined isolated yield (Scheme 45). " The former may be formed via an exo-mode cyclization of the latter. No endo-mode cyclization product as in Schemes 42 and 43 is detected. A similar type cyclization proceeds with the carbon nucleophile analog (Scheme 45). The cyclization of the isolated alkynyl ketone is promoted by Pd(OAc)2(PPh3)2 at 40 °C, where Pd(II) species may form C-palladium(II) enolate and at the same time coordinate with the triple bond to facilitate the exo-mode cyclization. The first formed 2-(Z)-benzylideneindanone may isomerize to the thermodynamically more stable ( )-isomer under the reaction conditions. 

If a suspension of red nickel dimethylglyoxime is treated with a dilute neutral or acetic acid solution of a palladium salt, there is no visible change, such as conversion into the yellow palladium dimethylglyoxime. Not more than traces of nickel can be detected in the filtrate. When dilute... 

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