Carbon dioxide catalyzed reactions

A potential green route to dimethyltin carbonate can be based on the reaction of methanol and carbon dioxide, catalyzed by dimethyltin dimethoxide. In supercritical CO2 as solvent, the dimethoxide reacts to give the monocarbonate, which at 180 °C and 300 atm pressure gives dimethyl carbonate, probably by an intramolecular rearrangement, with regeneration of the dimethoxide (Equation (139)).385,386... 

The reaction network for isobutane selective oxidation catalyzed by POMs consists of parallel reactions for the formation of methacrolein, methacrylic acid, carbon monoxide, and carbon dioxide. Consecutive reactions occur on methacrolein, which is transformed to acetic acid, methacrylic acid, and carbon oxides. ° Methacrylic acid undergoes consecutive reactions of combustion to carbon oxides and acetic acid, but only under conditions of high isobutane conversion. Isobutene is believed to be an intermediate of isobutane transformation to methacrylic acid, but it can be isolated as a reaction product only for very low alkane conversion. ... 

This enzyme [EC 1.14.11.7], also known as procolla-gen proline, 2-oxoglutarate 3-dioxygenase, catalyzes the reaction of a prolyl residue in procoUagen with dioxygen and a-ketoglutarate (or, 2-oxoglutarate) to produce a irans-3-hydroxyprolyl residue in procollagen, succinate, and carbon dioxide. This reaction also requires iron ions and ascorbate. 

Recently, the use of carbon dioxide as a carbon building block [152] has attracted increasing attention. The hydrosilylation of carbon dioxide catalyzed preferably by ruthenium complexes leads to the synthesis of silyl formate esters (Eq. 98) [153]. Results of the reaction of hydrosilylation in supercritical carbon dioxide as a solvent and substrate have recently been reported [154]. 

Isocyanates also can react with each other to produce carbodiimides with the loss of carbon dioxide. This reaction requires high temperatures unless catalyzed by specific phosphorus compounds. Formation of carbodiimides normally is not an important cross-linking mechanism in polyurethane adhesives. However, carbodiimides are sold by Dow Chemicals (Ucarlnk ), Nisshinbo Industries (Carbodilite ), and Stahl USA (XR-2569). They have been recommended as water scavengers, crosslinkers, and stabilizers for carboxyl functional polyurethanes. The carbodiimide can react with water to give a urea, which still can react with additional isocyanate to produce a biuret. 

In a few cases, theoretical calculations of transition state and intermediate energies and geometries provide confirmation of experimental studies of the mechanism of enzyme reactions and suggest directions for further study. One of these is the hydration of carbon dioxide catalyzed by carbonic anhydrase, a zinc enzyme. Below pH 7, the uncatalyzed reaction HC03 + H2O + CO2 is favored. Above pH 7, the reaction is... 

S. Fukuzawa, K. Metoki, S. Esumi, Asymmetric Diels-Alder reactions in supercritical carbon dioxide catalyzed by rare earth complexes. Tetrahedron 59, 10445-10452(2003). 

Biotin is a coenzyme for the carbon dioxide fixation reactions catalyzed by acetyl-CoA carboxylase (Chapter 19), propionyl-CoA carboxylase, pyruvate carboxylase, and S-methylcrotonyl-CoA carboxylase. Car-boxylation reactions that do not require biotin are the addition of Ce to the purine ring (Chapter 27), the formation of carbamoyl phosphate (Chapter 17), and the y-carboxylation of glutamyl residues of several of the clotting factors, which requires vitamin K (Chapter 36). 

The first committed step in the biosynthetic pathway of the branched chain amino acids is catalyzed by the enzyme acetohydroxyacid synthase (AHAS, EC 2.2.1.6), which is also referred to as acetolactate synthase (ALS). As depicted in Fig. 2.1.1, the pathway leading to valine and leucine begins with the condensation of two molecules of pyruvate accompanied by loss of carbon dioxide to give (S)-2-acetolactate. A parallel reaction leading to isoleucine involves the condensation of pyruvate with 2-ketobutyrate to afford (S)-2-aceto-2-hydroxybutyrate after loss of carbon dioxide. Both reactions are catalyzed by AHAS, which requires the cofactors thiamin diphosphate (ThDP) and flavin adenine dinudeotide (FAD). A divalent metal ion, most commonly is also required. Several excellent reviews... 

Table 21.1.10. Homogenous reactions in supercritical carbon dioxide catalyzed by organametaliic compounds...

Already in 1977 Inoue discovered the reaction of hexynes with carbon dioxide catalyzed by nickel complexes [86]. 1-Hexyne reacted with CO2 in the presence of a nickel/dppe-catalyst to give the butyl-substituted pyrone in 50 % yield (Figure 31). As by-products the oligomers of 1-hexyne were formed. Similar reactions proved to be possible with alkynes containing internal double bonds, such as 3-hexyne and 4-octyne [87,88], giving tetrasubstituted pyrones. Yields up to 60 % could be obtained. 

In papers [7] and [8] it was proved that an underground storage of hydrogen can function as a natural chemical reactor producing methane from hydrogen and carbon dioxide. The reaction between H2 and CO2 (1) is catalyzed by... 

Inoue Y, Itoh Y, Kazama H, Hashimoto H (1980) Reaction of dialkyl-substituted alkynes with carbon dioxide catalyzed by nickel(O) complexes. Incorporation of carbon dioxide in alkyne dimers and novel cyclotrimerization of the alkynes. Bull Chem Soc Jpn 53 3329-3333... 

Takimoto M, Nakamura Y, Kimura K, Mori M (2004) Highly enantioselective catalytic carbon dioxide incorporation reaction nickel-catalyzed asymmetric carboxylative cycli-zation of bis-1,3-dienes. J Am Chem Soc 126 5956-5957... 

The ring-opening reaction of aziridines with carbon dioxide, catalyzed by (Salen) Cr(III)/DMPA affords oxazolidinones 84 in high yields . ... 

In reaction (10), carbon dioxide was added to AIR to produce the car-boxylated product of AIR (carboxy-AIR) (Fig. 10). It is not known whether carbon dioxide or bicarbonate was the actual substrate for this condensation. An interesting feature of this reaction was the absence of a requirement for ATP. Other carbon dioxide fixation reactions were found to be coupled with TPNH oxidation 1S7,128), participation of phosphate 129, ISO), or degradation of ATP ISl). The enzyme which catalyzed reaction (10) was called AIR-carboxylase, and has been partially purified 1S2). In the next step [Eq. (11)] succino-AICAR was formed when carboxy-AIR reacted with aspartic acid and ATP other nucleoside triphosphates such as GTP, uridine triphosphate (UTP), CTP were ineffective in replacing ATP. This finding of ATP speiMcity may be contrasted with the specific... 

Oxalic and malonic acids, as well as a-hydroxy acids, easily react with cerium(IV) salts (Sheldon and Kochi, 1968). Simple alkanoic acids are much more resistant to attack by cerium(IV) salts. However, silver(I) salts catalyze the thermal decarboxylation of alkanoic acids by ammonium hexanitratocerate(IV) (Nagori et al., 1981). Cerium(IV) carboxylates can be decomposed by either a thermal or a photochemical reaction (Sheldon and Kochi, 1968). Alkyl radicals are released by the decarboxylation reaction, which yields alkanes, alkenes, esters and carbon dioxide. The oxidation of substituted benzilic acids by cerium(IV) salts affords the corresponding benzilic acids in quantitative yield (scheme 19) (Hanna and Sarac, 1977). Trahanovsky and coworkers reported that phenylacetic acid is decarboxylated by reaction with ammonium hexanitratocerate(IV) in aqueous acetonitrile containing nitric acid (Trahanovsky et al., 1974). The reaction products are benzyl alcohol, benzaldehyde, benzyl nitrate and carbon dioxide. The reaction is also applicable to substituted phenylacetic acids. The decarboxylation is a one-electron process and radicals are formed as intermediates. The rate-determining step is the decomposition of the phenylacetic acid/cerium(IV) complex into a benzyl radical and carbon dioxide. 

Miyano and coworkers reported the carboxylation of fused aromatic compounds with carbon dioxide catalyzed by AlBr3 (Scheme 6.8) [10]. Although yields are moderate, the reaction proceeds regioselectively similar to the Friedel-Crafts acylation reaction. 

E.R. Keene and B.P. Sullivan, Mechanism of the electrochemical reduction of carbon dioxide catalyzed by transition metal complexes. In B.P. Sullivan, K. Krist and H.E. Guard (eds.). Electrochemical and Electrocatalytic Reactions of Carbon Dioxide, Elsevier, New York, Amsterdam, 1993,118-140. 

Oxidative Carbonylation of Ethylene—Elimination of Alcohol from p-Alkoxypropionates. Spectacular progress in the 1970s led to the rapid development of organotransition-metal chemistry, particularly to catalyze olefin reactions (93,94). A number of patents have been issued (28,95—97) for the oxidative carbonylation of ethylene to provide acryUc acid and esters. The procedure is based on the palladium catalyzed carbonylation of ethylene in the Hquid phase at temperatures of 50—200°C. Esters are formed when alcohols are included. Anhydrous conditions are desirable to minimize the formation of by-products including acetaldehyde and carbon dioxide (see Acetaldehyde). 

Formaldehyde is readily reduced to methanol by hydrogen over many metal and metal oxide catalysts. It is oxidized to formic acid or carbon dioxide and water. The Cannizzaro reaction gives formic acid and methanol. Similarly, a vapor-phase Tischenko reaction is catalyzed by copper (34) and boric acid (38) to produce methyl formate ... 

Catalysis. Catalytic properties of the activated carbon surface are useful in both inorganic and organic synthesis. For example, the fumigant sulfuryl fluoride is made by reaction of sulfur dioxide with hydrogen fluoride and fluorine over activated carbon (114). Activated carbon also catalyzes the addition of halogens across a carbon—carbon double bond in the production of a variety of organic haUdes (85) and is used in the production of phosgene... 

Initially, the water slowly reacts with the isocyanate. However, the reaction can be catalyzed with an appropriate catalyst, such as dibutyltin dilaurate or a morpholine tertiary amine catalyst. The isocyanate will react with water to form a carbamic acid, which is unstable and splits off carbon dioxide, to produce a terminal amine end group (see p. 76 in [6]). This amine then reacts with more isocyanate-terminated prepolymer, as shown above, to form a polyurea. This process repeats itself, building up molecular weight and curing to become a polyurea-polyurethane adhesive. 

FIGURE 1.19 Carbonic anhydrase, a representative enzyme, and the reaction that it catalyzes. Dissolved carbon dioxide is slowly hydrated by water to form bicarbonate ion and... 

Terephthalic acid is an important monomer for producing polyesters. The main route for obtaining the acid is the catalyzed oxidation of paraxylene. It can also be produced from benzoic acid by a disproportionation reaction of potassium benzoate in the presence of carbon dioxide. Benzene is the coproduct ... 

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