Catalyst carbonyl reactions

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. 

Acetylene is condensed with carbonyl compounds to give a wide variety of products, some of which are the substrates for the preparation of families of derivatives. The most commercially significant reaction is the condensation of acetylene with formaldehyde. The reaction does not proceed well with base catalysis which works well with other carbonyl compounds and it was discovered by Reppe (33) that acetylene under pressure (304 kPa (3 atm), or above) reacts smoothly with formaldehyde at 100°C in the presence of a copper acetyUde complex catalyst. The reaction can be controlled to give either propargyl alcohol or butynediol (see Acetylene-DERIVED chemicals). 2-Butyne-l,4-diol, its hydroxyethyl ethers, and propargyl alcohol are used as corrosion inhibitors. 2,3-Dibromo-2-butene-l,4-diol is used as a flame retardant in polyurethane and other polymer systems (see Bromine compounds Elame retardants). 

Acetates. Anhydrous iron(II) acetate [3094-87-9J, Ee(C2H202)2, can be prepared by dissolving iron scraps or turnings in anhydrous acetic acid ( 2% acetic anhydride) under an inert atmosphere. It is a colorless compound that can be recrystaUized from water to afford hydrated species. Iron(II) acetate is used in the preparation of dark shades of inks (qv) and dyes and is used as a mordant in dyeing (see Dyes and dye intermediates). An iron acetate salt [2140-52-5] that is a mixture of indefinite proportions of iron(II) and iron(III) can be obtained by concentration of the black Hquors obtained by dissolution of scrap iron in acetic acid. It is used as a catalyst of acetylation and carbonylation reactions. 

Certain molecules that can permit concerted proton transfers are efficient catalysts for reactions at carbonyl centers. An example is the catalytic effect that 2-pyridone has on the aminolysis of esters. Although neither a strong base (pA aH+ = 0.75) nor a strong acid (pJsfa = 11.6), 2-pyridone is an effective catalyst of the reaction of -butylamine with 4-nitrophenyl acetate. The overall rate is more than 500 times greater when 2-pyridone acts... 

The interest in chiral titanium(IV) complexes as catalysts for reactions of carbonyl compounds has, e.g., been the application of BINOL-titanium(IV) complexes for ene reactions [8, 19]. In the field of catalytic enantioselective cycloaddition reactions, methyl glyoxylate 4b reacts with isoprene 5b catalyzed by BINOL-TiX2 20 to give the cycloaddition product 6c and the ene product 7b in 1 4 ratio enantio-selectivity is excellent - 97% ee for the cycloaddition product (Scheme 4.19) [28]. 

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... 

Rhodium Catalysts for Reactions of Carbonyl Ylides 242 Conclusion 244 Acknowledgment 245 References 245... 

The carbonyl complex [Ru(EDTAH)(CO)] has been reported to be a very good catalyst for reactions like hydroformylation of alkenes, carbonylation of ammonia and ammines as well as a very active catalyst for the water gas shift reaction. The nitrosyl [Ru(EDTA)(NO)] is an oxygen-transfer agent for the oxidation of hex-l-ene to hexan-2-one, and cyclohexane to the corresponding epoxide. 

Nickel catalysts were used in most of the methanation catalytic studies they have a rather wide range of operating temperatures, approximately 260°-538°C. Operation of the catalytic reactors at 482°-538°C will ultimately result in carbon deposition and rapid deactivation of the catalysts (10). Reactions below 260°C will usually result in formation of nickel carbonyl and also in rapid deactivation of the catalysts. The best operating range for most fixed-bed nickel catalysts is 288°-482 °C. Several schemes have been proposed to limit the maximum temperature in adiabatic catalytic reactors to 482°C, and IGT has developed a cold-gas recycle process that utilizes a series of fixed-bed adiabatic catalytic reactors to maintain this temperature control. 

According to the above reaction scheme the carbonylation reaction has to be carried out in two steps In the absence of water the olefin is first converted at 20-80°C and 20-100 bar by the aid of mineralic acid and carbon monoxide into an acyliumion. In a second step the acyliumion reacts with water to the carboxylic acid. The mineral acid catalyst is recovered and can be recycled. The formation of tertiary carboxylic acids (carboxylic acids of the pivalic acid type) is enhanced by rising temperature and decreasing CO pressure in the first step of the reaction. Only tertiary carboxylic acids are formed from olefins that have at the same C atom a branching and a double bond (isobutylene-type olefins). 

Carbonylation reactions encompass a diverse set of transformations used to synthesise many important high-value fine chemicals, synthetic intermediates and materials such as polycarbonates [36]. Palladium catalysts modified with PRj ligands facilitate these reactions. However, carbonylation often requires harsh conditions, especially for less reactive C-X bonds, thereby promoting catalyst degradation via P-C bond cleavage. The strength of the NHC bond may demonstrate the utility of... 

The bluish white, hard, yet ductile, metal is inert to all acids and highly non-abrasive. Used for heavy-duty parts in electrical contacts and spinning jets. Reflectors are prepared from the mirror-smooth surfaces (e.g. head mirrors in medicine). Thin coatings provide a corrosion-resistant protective layer, for example, for jewelry, watches, and spectacle frames. The metal is a constituent of three-way catalysts. Rhodium complexes are used with great success in carbonylations (reactions with CO) and oxidations (nitric acid) in industry. Platinum-rhodium alloys are suitable thermocouples. 

The reductive carbonylation has an advantage of low feedstock cost. A wide range of homogenous metal complexes have been tested for both reactions (1-16). The major drawback of the use of metal complex catalysts is the difficulty of catalyst recovery and purification of the reaction products (12). In addition, the gaseous reactants have to be dissolved in the alcohol/amine mixture in order to have an access to the catalyst. The reaction is limited by the solubility of the gaseous CO and 02 reactants in the liquid alcohol reactant (17). 

The carbonylation of methanol was developed by Monsanto in the late 1960s. It is a large-scale operation employing a rhodium/iodide catalyst converting methanol and carbon monoxide into acetic acid. An older method involves the same carbonylation reaction carried out with a cobalt catalyst (see Section 9.3.2.4). For many years the Monsanto process has been the most attractive route for the preparation of acetic acid, but in recent years the iridium-based CATIVA process, developed by BP, has come on stream (see Section 9.3.2) ... 

Palladium-catalyzed (PdCl2(PPh3)2) decarboxylative carbonylation reactions for the formation of lactams are known to proceed under carbon monoxide at a pressure of 60 atmospheres. The scheme below highlights a new procedure utilizing a different Pd catalyst, where the formation of lactams 171 from oxazolidinones 172 takes place at atmospheric pressure <06S227>. 

A second example of aldolization (Eq. 42) is the dry reaction of ferrocene carbal-dehyde with carbonyl compounds in the presence of potassium hydroxide, and Aliquat as catalyst [63]. Reactions which are too slow at room temperature are efficiently accelerated by use of microwaves, giving good yields within a few minutes. 

MW irradiation conditions [80]. More recently, however, Varma and Kocevar s group have shown that a solvent-free and catalyst-free reaction of hydrazines with carbonyl compounds is possible upon MW irradiation (Scheme 6.24) [81]. Interestingly, the general reaction proceeds smoothly even for solid reactants and is completed below the melting points of the two reactants possibly via the formation of a eutectic. The reactions have been conducted in household MW oven and the control experiments are conducted concurrently in separate open beakers the reactions can be essentially followed by visual observation when a melt is obtained [82],... 

Most hydroformylation investigations reported since 1960 have involved trialkyl or triarylphosphine complexes of cobalt and, more recently, of rhodium. Infrared studies of phosphine complex catalysts under reaction conditions as well as simple metal carbonyl systems have provided substantial information about the postulated mechanisms. Spectra of a cobalt 1-octene system at 250 atm pressure and 150°C (21) contained absorptions characteristic for the acyl intermediate C8H17COCo(CO)4 (2103 and 2002 cm-1) and Co2(CO)8. The amount of acyl species present under these steady-state conditions increased with a change in the CO/ H2 ratio in the order 3/1 > 1/1 > 1/3. This suggests that for this system under these conditions, hydrogenolysis of the acyl cobalt species is a rate-determining step. 

Thus, two quite different forms of rhodium catalyst precursor can give the same rhodium species under the carbonylation reaction conditions. 

The rate of the methanol carbonylation reaction in the presence of iridium catalysts is very similar to that observed in the presence of rhodium catalysts under comparable conditions (29). This is perhaps initially surprising in view of the well-recognized greater nucleophilicity of iridium(I) complexes as compared to their rhodium(I) analogues. It can be seen from the above studies that the difference in the chemistry of the metals at the trivalent stage of the catalytic cycle serves to produce faster rates of alkyl migration with the rhodium system thus, overall the two metal catalysts give comparable rates. 

The carbonylation of imidazole derivatives with several olefins takes place in high yields with the aid of an Ru3(CO)i2 catalyst.112,112a The carbonylation occurs exclusively at the a-position to the sp2 nitrogen (Equation (85)). A wide range of olefins can be utilized in this reaction, and a variety of functional groups are compatible under the reaction conditions. The (/i-H)triruthenium clusters such as 12 are proposed as a key species in this carbonylation reaction. Other five-membered A-heteroaromatic compounds, such as pyrazoles, oxazoles, and thiazoles, can be used for the carbonylation reactions, where the carbonylation takes place at the a-C-H bond to the sp2 nitrogen. 

The carbonylation of the sp3 C-H bond adjacent to a nitrogen atom is also possible by means of chelation-assisted C-H bond activation.121 The carbonylation reaction of A-(2-pyridyl)pyrrolidine occurs at the a-position of the pyrrolidine ring by using [RhCl(cod)]2 as a catalyst and 2-propanol as a solvent. Cyclic amines exhibit a high reactivity (up to 84%) (Equation (93)), while acyclic amines show relatively low reactivity (18%). The use of Ru3(CO)i2 as a catalyst does not result in a carbonylation reaction, but instead the addition of the sp3 C-H bond across the olefin bond to give an alkylation product, as mentioned before (Section 10.05.4). 

The stereoselective hydrogenation of alkynes to alkenes can be effected by a wide variety of homogeneous catalysts. The appropriate choice of catalyst and reaction conditions allows the selective formation of either the (Z)- or the (l )-a1-kene. Most of the catalysts display a very high chemoselectivity, as they are not reactive towards reducible functional groups such as carbonyl, ester, and double bonds. Many of the details related to catalyst behavior and intricate mechanistic details concerning semihydrogenation of alkynes have often not been unraveled, and will remain a topic of research for the coming years. 

Keywords Asymmetric Hydrogenation m Carbon Dioxide m Carbonylation m Dimethylformamide Enantioselectivity m Formic Acid m Homogeneous Hydrogenation n Palladium Catalysts Radical Reactions m Ruthenium Catalysts m Supercritical Fluids m Solvent Replacement... 

Cross double carbonylation of amines and alcohols Oxamates can be prepared by double carbonylation of amines and alcohols in the presence of (CH,CN)2PdCl2 as catalyst with 02 and Cul as oxidant and co-catalyst. This reaction is particularly efficient when applied to (3-amino alcohols. 

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