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Nickel-catalyzed carbonylations promoters

Since organoaluminum compounds have been known to add to a,) -unsaturated ketones, it is feasible that cyclopropyl ketones can react in a similar fashion. The nickel-catalyzed addition of trimethylaluminum to aryl cyclopropyl ketones 1 yielded the corresponding 1-arylpentanones 2 in moderate yields. It has been postulated that the first step of this reaction involves the nickel(0)-promoted electrophilic attack of alumimun at the carbonyl oxygen. [Pg.2077]

Several other examples of stereoselective synthesis of polycyclic ketones, via carbonylative [2 + 2 + 1] cycloaddition of organopalladium compounds derived from norbornene and norbor-nadiene, have been reported53,54,121. These reactions are useful in the synthesis of cyclopen-tanoid compounds, such as dihydrojasmone54 The nickel-catalyzed version of this method was used in a total synthesis of methylenomycin B55 and in the stereoselective synthesis of bicy-clo[3.3.0]oct-l-en-3-one derivatives56. Thus, (E)- or (Z)-9-bromo-l-methoxy-7-nonen-2-yne (5), upon intramolecular carbonylative cyclization promoted by tetracarbonyl nickel, afford the same stereoisomer of methyl 1,2,4,5.6,6a-hexahydro-3-methoxymethyl-2-oxo-l-pentaleneac-etate (6) in 43-50% yield with a relative trans configuration of the H-l and H-6a protons. [Pg.491]

Nickel carbonyl charged, or formed in the carbonylation reaction mixture, can catalyze the carbonylation of methanol (11). To maintain the activity of the nickel carbonyl catalyst high temperature and pressure are required (12-14). However, certain promoters can maintain an active, soluble, nickel carbonyl species under much milder conditions. The most reactive promoters are phosphines, alkali metal salts, tin compounds, and 2-hydroxypyridine. Reaction rates of 2 to 7 X 10-3(mol/1.sec) can be achieved without the use of high concentration of iodine (Table II). in addition, high reaction rates... [Pg.63]

It was found that a nickel-activated carbon catalyst was effective for vapor phase carbonylation of dimethyl ether and methyl acetate under pressurized conditions in the presence of an iodide promoter. Methyl acetate was formed from dimethyl ether with a yield of 34% and a selectivity of 80% at 250 C and 40 atm, while acetic anhydride was synthesized from methyl acetate with a yield of 12% and a selectivity of 64% at 250 C and 51 atm. In both reactions, high pressure and high CO partial pressure favored the formation of the desired product. In spite of the reaction occurring under water-free conditions, a fairly large amount of acetic acid was formed in the carbonylation of methyl acetate. The route of acetic acid formation is discussed. A molybdenum-activated carbon catalyst was found to catalyze the carbonylation of dimethyl ether and methyl acetate. [Pg.176]

Neither the palladium nor nickel catalyst described will promote the carbonylation of saturated aliphatic halides as noted above. However, this reaction can be catalyzed with cobalt (17) or iron (77) and probably with manganese (18) carbonyl anion salts. These carbonyl anions are strongly nucleophilic species and readily displace halide or other good leaving groups from primary or secondary positions giving alkyl metal carbonyl complexes. [Pg.330]

The copper(II)-promoted hydrolysis of glycylglycine has been studied in some detail.120 Copper(II) ions catalyze the hydrolysis of glycylglycine in the pH range 3.5 to 6 at 85 °C.120 The pH rate profile has a maximum at pH 4.2, consistent with the view that the catalytically active species in the reaction is the carbonyl-bonded complex. The decrease in rate at higher pH is associated with the formation of a catalytically inactive complex produced by ionization of the peptide hydrogen atom. This view has subsequently been confirmed by other workers,121 in conjunction with an IR investigation of the structures of the copper(II) and zinc(II) complexes in D20 solution.122 Catalysis by cobalt(II),123 and zinc(II), nickel(II) and manganese(II) has also been studied.124-126... [Pg.425]

One of the first mechanistic proposals for the hydrocarboxylation of alkenes catalyzed by nickel-carbonyl complexes came from Heck in 1963 and is shown in Scheme 24. An alternate possibility suggested by Heck was that HX could add to the alkene, producing an alkyl halide that would then undergo an oxidative addition to the metal center, analogous to the acetic acid mechanism (Scheme 19). Studies of Rh- and Ir-catalyzed hydrocarboxylation reactions have demonstrated that for these metals, the HX addition mechanism, shown in Scheme 24, dominates with ethylene or other short-chain alkene substrates. Once again, HI is the best promoter for this catalytic reaction as long as there are not any other ligands present that are susceptible to acid attack (e g. phosphines). [Pg.680]

Annulation to carbonyl functions has also been achieved with Trost s bifunctional reagents. Whereas the parent silyl acetate (97) yields only simple alkylation products with aldehydes under normal conditions, addition of only a few mole % of trimethyltin acetate to the reaction mixture results in facile formation of methylenetetrahydrofurans Furthermore, excellent diastereoselectivity is observed in the cycloaddition to a galactose-derived aldehyde (125) (equation 136). The tin acetate co-catalyst also promotes addition to relatively unreactive ketone carbonyls, such as in the case of benzofuran (126) and the acetylenic ketone (127) (equations 137, 138). It is remarkable that even the sterically hindered enone (128) reacts preferentially at the ketone function (equation 139). A tributyltin analog (129) of (97) has been used in the stepwise formation of a methylenetetrahydrofuran from aldehydes. Similarly, pyrrolidines can be prepared from the corresponding imines in two steps via a Lewis acid-catalyzed 1,2-addition of the tin reagent, which is then followed by a Pd-catalyzed cyclization (equation 140). Direct formation of pyrrolidine from the imine is possible if one uses a mesylate analog of (97) and a nickel(O) catalyst (equation 141). ... [Pg.307]

The applied nickel catalyst, promoted by copper halides, required rather severe reaction conditions T = 220 °C, F = 10 MPa), but gave good AA yields up to 90% based on acetylene. This so-called catalytic Reppe process was commercially operated in Germany, the USA, and Japan. Due to the limited availability of cheap acetylene as feedstock and the severe reaction conditions involved in the carbonylation process, this process has lost the competition with (heterogeneously catalyzed) oxidation of readily available propene, even though a perfect selectivity to AA is not achieved in the latter process. [Pg.317]

At present, this process utilizes Co2(CO)s as catalyst with I2 as promoter, or Rhl2(CO) as catalyst with Mel as promoter. Other rhodium carbonyls with the addition of iodine compounds may be utilized. Also, this reaction is catalyzed by nickel and iron carbonyls, although at considerably higher pressures and temperature. The process with the application of the cobalt catalyst is carried out at ca 460 K and 20 MPa, while in the presence of Rhl2(CO)T, at 453 K and 3-4 MPa. [Pg.700]


See other pages where Nickel-catalyzed carbonylations promoters is mentioned: [Pg.156]    [Pg.66]    [Pg.496]    [Pg.25]    [Pg.181]    [Pg.726]    [Pg.80]    [Pg.61]    [Pg.63]    [Pg.886]    [Pg.214]    [Pg.324]    [Pg.220]    [Pg.963]    [Pg.99]    [Pg.181]    [Pg.210]    [Pg.15]    [Pg.173]    [Pg.167]    [Pg.213]    [Pg.18]    [Pg.656]    [Pg.62]    [Pg.178]    [Pg.116]    [Pg.160]    [Pg.236]    [Pg.440]    [Pg.65]    [Pg.763]    [Pg.11]    [Pg.205]    [Pg.103]   
See also in sourсe #XX -- [ Pg.116 ]




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Carbonylation catalyzed

Carbonylation promotions

Catalyzed Carbonylations

Nickel carbonyl

Nickel carbonylation

Nickel-catalyzed

Nickel-catalyzed carbonylation

Nickel-catalyzed carbonylations

Promoters carbonylation

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