Carbonyl Catalysts

The unit has virtually the same flow sheet (see Fig. 2) as that of methanol carbonylation to acetic acid (qv). Any water present in the methyl acetate feed is destroyed by recycle anhydride. Water impairs the catalyst. Carbonylation occurs in a sparged reactor, fitted with baffles to diminish entrainment of the catalyst-rich Hquid. Carbon monoxide is introduced at about 15—18 MPa from centrifugal, multistage compressors. Gaseous dimethyl ether from the reactor is recycled with the CO and occasional injections of methyl iodide and methyl acetate may be introduced. Near the end of the life of a catalyst charge, additional rhodium chloride, with or without a ligand, can be put into the system to increase anhydride production based on net noble metal introduced. The reaction is exothermic, thus no heat need be added and surplus heat can be recovered as low pressure steam. 

The intermolecular version of the above described reaction has also been reported [92]. In the first example the reaction of a rhodium catalyst carbonyl ylide with maleimide was studied. However, only low enantioselectivities of up to 20% ee were obtained [92]. In a more recent report Hashimoto et al. were able to induce high enantioselectivities in the intermolecular carbonyl ylide reaction of the... 

In order to accelerate the reaction, acid catalyst is employed. In the presence of acid catalyst, carbonyl compounds preassociate with the acid followed by proton... 

The concept that acetic acid can be prepared by carbonylation originated in use of routine acids. Carbonylation of methanol was first practiced in a high temperature and pressure process using boron trifluoride or phosphoric acid. A carbon monoxide pressure of 10,000 psi at 300 C was needed for the reaction (10). Metal salts came to replace acids as carbonylation catalysts. Carbonylation of methanol using a metal carbonyl catalyst was first discovered by Reppe and practised later by BASF. However, the process again required high pressure, 7500-10,000 psi, and the selectivity was low (11-14). 

Starting from C-enriched methanol, the Co2(C0)8 l2/ Bu4PBr "melt" catalyst carbonylates to acetic acid in accord with eq. 2, enrichment being detected only on the methyl carbon. 

Suga et al. (197) reported the first stereocontrolled 1,3-dipolar cycloaddition reactions of carbonyl ylides with electron-deficient alkenes using a Lewis acid catalyst. Carbonyl ylides are highly reactive 1,3-dipoles and cannot be isolated. They are mainly generated through transition metal carbenoid intermediates derived in situ from diazo precursors by treatment with a transition metal catalyst. When methyl o-(diazoacetyl)benzoate is treated with A-methylmaleimide at reflux... 

Keywords. Aryl halides, Arylation, Palladium catalysts. Carbonyl compounds. Aromatic compounds... 

The stereoselective total synthesis of ( )-isocycloseychellene was achieved by S.C. Welch and co-workers. One of the key ring forming reactions was an oxidative Prins reaction that took place without the need of a catalyst (carbonyl ene reaction) to afford the desired tricyclic ketone. 

Fe . With CH3I and various inorganic and organic promoters, a Ni based catalyst carbonylates CH3OH at 150-170°C and 2-7 MPa. ... 

Metal ion cofactors have varied roles to enhance the catalytic efficiency of enzymes in hydrolytic reactions, including facilitate substrate binding (water and organic substrate), gathering/template effects, function as an electrostatic catalyst (carbonyl polarization and transition state stabilization), function as a Lewis acid to lower the pA a of metal-water and stabilize the formation of the leaving group. Although their properties make several... 

FTIR spectra of chemisorbed CO on SA-AuJMgO catalyst, carbonyl region. A - catalyst pretreated in air followed by reduction in hydrogen B - catalyst pretreated in hydrogen (Reproduced from ref. 174 with permission)... 

Carbonylation of reactive iodides proceeds using PdCl2(PPh3)2 as a standard catalyst under mild conditions in the presence of a base. Several modified catalyst systems have been reported. For example, ligandless Pd charcoal is an active catalyst at 140 °C [1]. Uozumi reported that the amphiphilic phosphine-Pd complex (Pd-PEP) bound to PEG-PS resin is a very active and useful catalyst. Carbonylation... 

Carbonylation of methanol to methyl formate using sodium methoxide as homogeneous catalyst Carbonylation of dimethyl amine using sodium methoxide as homogeneous catalyst Ethoxylations and propoxylations... 

An early stimulus to cluster chemistry was the cluster-surface analogy, wMch proposed that cluster chemistry would resemble the surface chemistry of metals because both surfaces and clusters consist of arrays of metal atoms. Si ported metals such as Pd/C are very active catalysts. Carbonyl clusters have so far not shown the high catalytic activity of either metal surfaces or mononuclear homogeneous catalysts, probably because clusters are poisoned by the presence... 

Palladiumdiacetate in trifluoroacetic acid (Pd(02CCF3)2) gives a mixture of o- and p-trifluoroacetoxylated products. The reagent is also capable of oxidizing saturated hydrocarbons such as adamantane and methane. In the presence of carbon monoxide and with sodium acetate as co-catalyst, carbonylation of aromatic C-H bonds occurs, eventually yielding acid anhydrides. ... 

Aromatic aldehydes and ketones are reduced to the corresponding hydrocarbons in good yield by catalytic transfer reduction using cyclohexene or limonene as a donor, palladium-carbon as catalyst and a Lewis-acid promotor such as ferric chloride. The major competing reaction is decarbonylation, otherwise the reaction is straightforward and simply involves heating the catalyst, carbonyl compound, and donor under reflux for 3—5 h, furthermore the method is convenient and dispenses with elaborate equipment or potentially explosive hydro n. ... 

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