Methanol oxidative carbonylation

EniChem set up a project aimed at the development of a nonphosgene synthesis of DMC for large volume usage as a result, a new industrial process was established, based on a liquid-phase methanol oxidative carbonylation in the presence of copper chlorides as catalysts. This catalytic system was highly effective in DMC production the reaction was carried out by feeding at the same time methanol, carbon monoxide, and oxygen to the suspension of the catalyst in a mixture of water, methanol, and DMC and recovering DMC by distillation after the catalyst separation. Besides, the process... 

On the basis of the technical and economical considerations, the methanol oxidative carbonylation process (eq. 2) was selected. 

The addition of a carbonylation step extended a pyrrole synthesis to pyrrole-2-acetic acid derivatives <06ASC2212>. Treatment of enyne amine 1 with palladium diiodide in the presence of CO and methanol produced pyrrole-2-acetic ester 2 via a 5-exo-dig cyclization, oxidative carbonylation, and isomerization. 

The oxidative carbonylation of alcohols and phenols to carbonates can be catalyzed by palladium or copper species [154-213]. This reaction is of particular practical importance, since it can be developed into an industrial process for the phosgene-free synthesis of dimethyl carbonate (DMC) and diphenyl carbonate (DPC), which are important industrial intermediates for the production of polycarbonates. Moreover, DMC can be used as an eco-friendly methylation and carbonylation agent [214,215]. The industrial production of DMC by oxidative carbonylation of methanol has been achieved by Enichem [216] and Ube [217]. 

First of all, DMC is a nontoxic compound since the middle 1980s, in fact, it has not been produced from phosgene, but by catalytic oxidative carbonylation of methanol with oxygen through a process developed by Enichem (Italy) and UBE Industries (Japan) (Scheme 4.3) ... 

Methyl methacrylate may be prepared by the catalytic oxidative carbonylation of propylene in the presence of methanol. 

For the synthesis of fine chemicals, carbonylation, reductive carbonylation, and oxidative carbonylation of methanol can be applied as outlined in Table II. 

The oxidative carbonylation of methanol to dimethyl carbonate has found small industrial application (26-27). The reaction can be carried out in two steps following Equation 10 and 11 or also in one step. 

The adipic acid process we have developed involves butadiene oxidative carbonylation in the presence of methanol, a l, l-dimethoxycyclohexane dehydration agent, and a palladium(ll)/ copper(ll) redox catalyst system (Equation 1.). The reaction sequence includes an oxycarbonylation, hydrogenation and hydrolysis step(17-19). The net result is utilization of butadiene, the elements of synthesis gas, l, -dimethoxycyclohexane and air to give adipic acid, cyclohexanone and methanol. 

Dimethyl Carbonate. An industrial process to manufacture dimethyl carbonate through the oxidative carbonylation of methanol catalyzed by cuprous chloride has been developed and commercialized by EniChem.197,198 The reaction occurs in two steps. Cupric methoxy chloride is formed in the first oxidation step [Eq. (7.21)], which is then reduced to yield dimethyl carbonate and regenerate cuprous chloride [Eq. (7.22)] ... 

In the presence of trace amounts of water, the tetrameric p,2-oxo complex (182) in 1,2-dimethoxyethane is transformed into a p, -oxo tetrameric complex (183 equation 254), characterized by an X-ray structure.574 In contrast, (182) 572,575 is inactive towards the oxidation of phenols. The reaction of N,N,N, AT -tetramethyl-l,3-propanediamine (TMP) with CuCl, C02 and dioxygen results in the quantitative formation of the /z-carbonato complex (184 equation 255).s76 This compound acts as an initiator for the oxidative coupling of phenols by 02. 6 Such jz-carbonato complexes, also prepared from the reaction of Cu(BPI)CO with 02 [BPI = 1,3 bis(2-(4-methyl-pyridyl)imino)isoindoline],577 are presumably involved as reactive intermediates in the oxidative carbonylation of methanol to dimethyl carbonate (see below).578 Upon reaction with methanol, the tetrameric complex (182 L = Py X = Cl) produces the bis(/z-methoxo) complex (185 equation 256), which has been characterized by an X-ray structure,579 and is reactive for the oxidatiye cleavage of pyrocatechol to muconic acid derivatives.580,581... 

The oxidative carbonylation of amines to formamides was also reported in 2001 in up to 94% yield using Ph3PAuTCl as catalyst and oxygen as oxidant in methanol 7... 

Oxidative Carbonylation of Methanol to Dimethyl Carbonate and Dimethyl Oxalate... 

Two oxidative carbonylation processes to DMC have been commercialized, one by EniChem uses a copper chloride catalyst the other, developed by Ube and Bayer uses methyl nitrite (from methanol, NO and oxygen). 

Tundo, 2001). The traditional synthesis of DMC is based on the reaction of phosgene with methanol (see Figure 12.5a). Fortunately, green alternatives such as the catalyzed oxidative carbonylation and carbonyl trans-esterification have been proposed (see Figures 12.5b and c). 

Several further experimental and theoretical studies of the oxidative addition of methyl iodide to Rh(I) complexes have been reported, in part because of its importance in the rhodium-catalyzed carbonylation of methanol (see Carbonylation Processes by Homogeneous Catalysis) to... 

As in the case of catalysts for oxygen reduction, the surface properties of Pt catalysts for methanol oxidation are governed by both the preparation method and the nature of carbon support. As discussed above, the presence of surface groups such as carboxylic, carbonyl, phenolic, lactone, and pyrone functionalities determine... 

The oxidative carbonylation of cw-2-butene in the presence of methanol, catalytic amounts of PdCl2, and stoichiometric quantities of CUCI2 under a reaction pressure of about 3 bar yields a racemic mixture of threo- and erythro- methyl 3-methoxy-2-methylbutyrate (ratio of the isomers, 87 13). Under comparable conditions, but in the presence of sodium acetate, twofold carbonylation is observed, giving m 50-dimethyl 2,3-dimethylsuccinate as the only reaction product. Starting from rra 5-2-butene, in an analogous manner threo- and erythro-met y 3-methoxy-2-methylbutyrates are again obtained, but in a different ratio of the isomers (40 60). If sodium acetate is added, racemic dimethyl R,S)-2,3-dimethylsuccinate is the sole product [7-9]. 

Extensive efforts to achieve the oxidative carbonylation of methanol in the gas phase using CuCl or Cu(OCH3)Cl complexes supported on active carbon have been undertaken to Dow Chemicals [49, 50], Because of the rapid catalyst deactivation this method has not become an alternative to the Enichem process. 

Palladium salts can bring about oxidative carbonylation of alkenes in the presence of copper(II) salts which can reoxidize Pd° to Pd . Oxidative carbonylation is favored over simple hydroesterification by the presence of bases and by low temperatures (25 C) and low pressures (3-15 bar). The products can be a, -unsaturated esters, dicarboxylic acid esters or -alkoxy esters. By careful optimization of the conditions (25 °C, 4 bar CO, methanol solvent, CuCh reoxidant and sodium butyrate buffer) high yields of diesters can be obtained (equation 35). ... 

Photolysis of ring-substituted phenacyl bromides gives ketyl radicals which in the presence of alcohols leads to the corresponding carbonyl compounds.Two different chain mechanisms seem to operate and in the presence of methanol, oxidation predominantly occurs by hydrogen transfer whereas in the presence of isopropanol, acetone is formed mainly by an electron transfer process. 

---