Palladium, dimethyl

A more successful route to cationic palladium and nickel ether adducts is through protonation of the nickel and palladium dimethyl precursors with H+(OEt2)2BAF in the presence of diethyl ether, illustrated by eq 3. The ether ligand is extremely... 

We were delighted to find that the NHCP ligands with a direct N-P hnkage R-34 form stable chelating complexes with metals of the nickel triade and ruthenium, featuring very small bite angles between 65 and 70 as determined by X-ray crystal structure analysis of all new compounds made (Scheme 10.10) [44]. The NHCP palladium dimethyl complexes 45 show reactivity toward electron-poor... 

Allenes also react with aryl and alkenyl halides, or triflates, and the 7r-allyl-palladium intermediates are trapped with carbon nucleophiles. The formation of 283 with malonate is an example[186]. The steroid skeleton 287 has been constructed by two-step reactions of allene with the enol trillate 284, followed by trapping with 2-methyl-l,3-cyclopentanedione (285) to give 286[187]. The inter- and intramolecular reactions of dimethyl 2,3-butenylmalonate (288) with iodobenzene afford the 3-cyclopentenedicarboxylate 289 as a main product) 188]. 

CO, and methanol react in the first step in the presence of cobalt carbonyl catalyst and pyridine [110-86-1] to produce methyl pentenoates. A similar second step, but at lower pressure and higher temperature with rhodium catalyst, produces dimethyl adipate [627-93-0]. This is then hydrolyzed to give adipic acid and methanol (135), which is recovered for recycle. Many variations to this basic process exist. Examples are ARCO s palladium/copper-catalyzed oxycarbonylation process (136—138), and Monsanto s palladium and quinone [106-51-4] process, which uses oxygen to reoxidize the by-product... 

The first CO route to make adipic acid is a BASF process employing CO and methanol in a two-step process producing dimethyl adipate [627-93-0] which is then hydroly2ed to the acid (43—46). Cobalt carbonyl catalysts such as Co2(CO)g are used. Palladium catalysts can be used to effect the same reactions at lower pressures (47—49). 

Dimethyl carbonate [616-38-6] and dimethyl oxalate [553-90-2] are both obtained from carbon monoxide, oxygen, and methanol at 363 K and 10 MPa (100 atm) or less. The choice of catalyst is critical cuprous chloride (66) gives the carbonate (eq. 20) a palladium chloride—copper chloride mixture (67,68) gives the oxalate, (eq. 21). Anhydrous conditions should be maintained by removing product water to minimize the formation of by-product carbon dioxide. 

With hydrogen sulfide at 500—600°C, monochlorotoluenes form the corresponding thiophenol derivatives (30). In the presence of palladium catalysts and carbon monoxide, monochlorotoluenes undergo carbonylation at 150—300°C and 0.1—20 MPa (1—200 atm) to give carboxyHc acids (31). Oxidative coupling of -chlorotoluene to form 4,4 -dimethylbiphenyl can be achieved in the presence of an organonickel catalyst, generated in situ, and zinc in dipolar aprotic solvents such as dimethyl acetamide (32,33). An example is shown in equation 4. 

Another alternative method to produce sebacic acid iavolves a four-step process. First, butadiene [106-99-0] is oxycarbonylated to methyl pentadienoate which is then dimerized, usiag a palladium catalyst, to give a triply unsaturated dimethyl sebacate iatermediate. This unsaturated iatermediate is hydrogenated to dimethyl sebacate which can be hydrolyzed to sebacic acid. Small amounts of branched chain isomers are removed through solvent crystallizations giving sebacic acid purities of greater than 98% (66). 

A solution of 4,4-dimethyl-5a-androst-l-en-3-one (128, 14 mg) in cyclohexane (3 ml) is stirred in a microhydrogenation apparatus in the presence of 10 % palladium-on-charcoal (15 mg) at atmospheric pressure and room temperature. The uptake of one eq of deuterium (1.15 ml) is complete in about 1 min and no more deuterium is consumed. After 5 min the catalyst is removed by filtration, and the solvent evaporated under reduced pressure. The resulting l<, 2< -d2-4,4-dimethyl-5a-androstan-3-one (129, 13 mg, 93%), mp 120-122°, exhibits 87% isotopic purity and 13% d species. ... 

Indolizine (18) combines with dimethyl acetylenedicarboxylate in the presence of palladium on charcoal yielding two products, (19) and (20), which may be formed as indicated. 

The zwitterion (22) obtained from 1-phenacylpyridinium bromide (21) and dimethyl acetylenedicarboxylate in the presence of palladium on charcoal yields the indolizine (23) possibly through the route shown. 

Phenacylpyridinium bromide (155) with aqueous sodium carbonate yields the chloroform soluble zwitterion (156) which, with dimethyl acetylenedicarboxylate in the presence of palladium on charcoal, cyclized to the indolizine (157) in ca. 20% yield. In a similar way the pyrazine (158) gave a mixture of (159) and (160) through loss of the benzoyl group. The last compound was also ob-... 

Dimethyl-1,2,4-triazolium iodide with palladium acetate yields the carbene adduct 182 (97JOM(530)259). Under water it undergoes cis-trans isomerization to 183. Some other derivatives were reported in 1981 (81BCSJ800). 1,1 -Methylenebis(4-alkyl-l,2,4-triazolium)diiodides (alkyl = /-Pr, n-Bu, octyl) with palladium(II) acetate give the mononuclear complexes [L Pdl ] (99EJIC1965), where L2= l,l -methylenebis(4-R-l,2,4-triazol-2-ylidene) (R = /-Pr, n-Bu, octyl). Thermolysis of the products in THF gives the rran -dinuclear complexes 184... 

Reaction of -picoline with a nickel-alumina catalyst has been reported to give a mixture of four isomeric dimethylbipyridines, one of which has been identified at 6,6 -dimethyl-2,2 -bipyridine. With palladium-on-carbon, 2,4-lutidine was found to be more reactive than pyridine,and the isolated biaryl has been assigned the structure (2). However, some confusion arises from the statement that this... 

Several products other than 2,2 -biaryls have been isolated following reaction of pyridines with metal catalysts. From the reaction of a-picoline with nickel-alumina, Willink and Wibaut isolated three dimethylbipyridines in addition to the 6,6 -dimethyl-2,2 -bipyridine but their structures have not been elucidated. From the reaction of quinaldine with palladium-on-carbon, Rapoport and his co-workers " obtained a by-product which they regarded as l,2-di(2-quinolyl)-ethane. From the reactions of pyridines and quinolines with degassed Raney nickel several different types of by-product have been identified. The structures and modes of formation of these compounds are of interest as they lead to a better insight into the processes occurring when pyridines interact with metal catalysts. 

Reaction of the cyclopropyl-substituted pivalate (25) with dimethyl benzylidenema-lonate in the presence of a palladium catalyst gave a mixture of alkylidenecyclo-propane (26) and vinylcyclopropane (27). The ratio of these two adducts is found to be quite sensitive to the choice of ligand and solvent. While triisopropyl phosphite favors the formation of the methylenecyclopropane (26), this selectivity is completely reversed with the use of the bidentate phosphite ligand dptp (12). Interestingly there was no evidence for any products that would have derived from the ring opening of the cyclopropyl-TMM intermediate (Scheme 2.8) [18]. 

Hydrogenation of 2,5-diacetoxy-2,5-dimethyl-3-hexyne 10 over 0% palladium-on-carbon is exceptionally complex. Seven different products are formed together with acetic acid. All are hydrogenolysis products arising from the initially formed 2,5-diacetoxy-2,5-dimethyl-3-hexene 11. One of these, 2,5-dimethyl-2-acetoxy-4-hexene 12 forms in as much as 4S yield. 

In pyridinium chloride ionic liquids and in l,2-dimethyl-3-hexylimida2olium chloride ([HMMIMjCl), where the C(2) position is protected by a methyl group, only [PdClJ was observed, whereas in [HMIMjCl, the EXAFS showed the formation of a bis-carbene complex. In the presence of triphenylphosphine, Pd-P coordination was observed in all ionic liquids except where the carbene complex was formed. During the Heck reaction, the formation of palladium was found to be quicker than in the absence of reagents. Overall, the EXAFS showed the presence of small palladium clusters of approximately 1 nm diameter formed in solution. 

When dimethyl 3-benzoxepin-2,4-dicarboxylate is reacted under controlled conditions (15 min) with hydrogen it is possible to isolate dimethyl l,2-dihydro-3-benzoxepin-2,4-dicarboxylate.17 Hydrogenation of 2-nitrodibenz[, /]oxepin-10-carboxylic acid in the presence of palladium on potassium carbonate results in the reduction of the nonaromatic C C double bond and the nitro group to give 2-amino-10,l l-dihydrodibenz[i,/]oxepin-10-carboxylic acid.107... 

Catalytic hydrogenation of dimethyl 3-methyl-3//-3-benzazepine-2,4-dicarboxylate (10) to the 1,2,4,5-tetrahydro derivative with hydrogen and a palladium-barium sulfate catalyst, followed by treatment of the reaction mixture with iodomethane in refluxing methanol, yields a mixture of the 2,4-dicarboxylic acid 11 and the methiodide salt 12.24... 

To a mixture of vinyl bromide (40 mmol) and the catalyst dichloro-[(R)-Af,N-dimethyl-l-[(.S)-2-(diphenylphosphino)ferrocenyl]ethylamine]-palladium(n) (0.2 mmol) was added an ethereal solution of [a-(trimethyl-silyl)benzyl]magnesium bromide (0.6-1 m, 80 mmol) at —78 °C. The mixture was stirred at 30 °C for 4 days, and then cooled to 0 °C and hydrolysed with dilute aqueous HC1 (3 m). The organic layer was separated, and the aqueous layer was re-extracted with ether. The combined organic extracts were washed with saturated sodium hydrogen carbonate solution and water, and dried. Concentration and distillation gave the chiral allylsilane (79%, 66% ee), b.p. 55°C/0.4mmHg. 

Trost and coworkers7 have reported the use of palladium(O) as a catalyst for displacement of the phenylsulfonyl group by soft nucleophiles. Thus, treatment of allyl sulfone 12 with the sodium salt of dimethyl malonate in the presence of 5 mol % of... 

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