Dimethyl oxalate, production

Dimethyl carbonate [616-38-6] and dimethyl oxalate [553-90-2] are both obtained from carbon monoxide, oxygen, and methanol at 363 K and 10 MPa (100 atm) or less. The choice of catalyst is critical cuprous chloride (66) gives the carbonate (eq. 20) a palladium chloride—copper chloride mixture (67,68) gives the oxalate, (eq. 21). Anhydrous conditions should be maintained by removing product water to minimize the formation of by-product carbon dioxide. 

Reactions of perfluorophenyllithium with dimethyl oxalate give a mixture of products whose composition depends upon experimental conditions [55] (equation 11)... 

Table 1. Effect of Temperature of Decomposition of the Product of Reaction of Pentafluorophenyllithium with Dimethyl Oxalate on Product Distribution [JJ]...

Adipic Acid Precursor Other Carbonylation Products Carbon Dioxide Dimethyl Oxalate... 

The bistetrazine (13) is produced when the bishydrazide (12), formed from benzoyl-hydrazine and dimethyl oxalate is heated with phosphorus pentachloride, the product then being refluxed with hydrazine in ethanol. Aromatisation is completed by treatment with nitrous acid. The bistetrazine acts as a reactive diazadiene in [4+2] cycloaddition reactions [94TL7935J. 

It is postulated that the ionic magnesium complex (4) holds the open-chain progenitor (3) in the proper conformation for intramolecular Michael condensation. Trials with other basic catalysts were unsuccessful. The product of condensation of the ketal (2) with dimethyl oxalate similarly could be cyclized to give 2,5-dihydroxy-l,4-benzoquinone (7). 

An jV-amtdino-aniinopyrazole may be cyclized by reaction with an orthoester, acetic formic anhydride, formic acid, phenyl isocyanate dichloride or dimethyl oxalate according to the substituent that is required at position 2 of the product. 

Japanese workers76 claim the superiority of a phosgene-triethylamine mixture (ratio 1 2) over other conventional dehydrating agents. Thus, they devised a novel synthesis of 4-methyl-5-alkoxyoxazole-2-carboxylic acid esters (17) by condensation of alkyl alaninate hydrochloride with diethyl or dimethyl oxalate followed by cyclization of the product (16). 

The condensation of 3,4-diaminopyridine with glyoxal hydrate in alcohol gives a 50% yield of the parent heterocycle m.p. 97°. This method is more convenient than the use of the bisulfite compound in aqueous acetic acid, which provides only a low yield of the required compound. Benzil and diacetyl and l,4-dibromobutane-2,3-dione provide the expected 2,3-disubstituted products 4 in good yields. Dimethyl oxalate reacts with 3,4-diaminopyridine in refluxing M hydrochloric acid to give the open-chain compound 5." This may be cyclized to the dioxo compound 6 by heating at 230°. 

Hassinen et al. (1985) examined the flash photolysis of dimethyl oxalate in the gas phase to produce CH3, CH3O, and CCX)CH3. They determined rate coefficients bom product analysis for the reactions... 

Ube has also developed Pd/MeONO-based gas-phase processes for the production of dimethyl oxalate and dimethyl carbonate (Eqs. (8.9) and (8.10)) using... 

Other PFHS methods that have been used for the production of crystalline precipitates by the controlled generation of the required anions in an appropriate aqueous solution include the hydrolysis of allyl chloride (Cl ), dimethyl oxalate ( 204 ), triethylphosphate (PO4 ), dimethylsulphate (SO4 ) and thioacetamide (S ). 

After addition of monomethyd methylphosphonite to methyl acrylate, the product is converted in a Claisen reaction with dimethyl oxalate into the corresponding a-keto-acid, which is then subjected to a reductive amination. [14]... 

More recently, Bouwman carried out a detailed study on the carbonylation of nitrobenzene in methanol with palladium bidentate phosphane complexes as catalysts [29-31]. After a careful analysis of the reaction, mixtures revealed that besides the frequently reported reduction products of nitrobenzene [methyl phenyl carbamate (MFC), A, 7/-diphenylurea (DPU), aniline, azobenzene (Azo) and azoxyben-zene (Azoxy)], large quantities of oxidation products of methanol were co-produced (dimethyl carbonate (DMC), dimethyl oxalate (DMO), methyl formate (MF), H2O, and CO). They proposed the Pd-imido species P2Pd = NPh, which is the central key intermediate that can link together all the reduction products of nitrobenzene and all the oxidation products of methanol into one unified mechanistic scheme. 

If palladium/copper halide catalysts are used, C—C coupling occurs and dimethyl oxalate is formed. The by product water can be trapped by addition of orthoformates and, instead of oxygen, quinones can also be used as the oxidizing agent. Typical conditions are 70 bar of CO and temperatures of 125 C. Based on results of Rivetti et aL, product formation can be envisioned via alkoxycarbonyl species [73] ... 

Dimethyl oxalate is of interest as a solvent, in agriculture (oxalamide), the pharmaceutical industry, and food production. It can also serve as a precursor of ethylene glycol, and the catalytic hydrogenation of dimethyl oxalate has been investigated by Union Carbide/Ube Industries [11]. 

Oxalic ester synthesis—Enolesters from ketones. 6 g. dl-zl5,14-3.Ethylenedioxy-lly ,18-oxido-16-oxo-18-tetrahydropyranyloxyandrostadiene and dimethyl oxalate in benzene added dropwise to NaH in oil (Metal Hydrides, Inc., Beverly, Mass., USA) and benzene, stirred 48 hrs. at 30° in a slow Ng-stream, the crude product dissolved in benzene, and allowed to stand at room temp, overnight with acetic anhydride and pyridine 6.61 g. methyl dl-J5,14,17(20)-3-ethylene-dioxy-1 ly, 18- oxid o-16- oxo-18- tetrahydropyranyloxy - 20 - acetoxypregnatrien-21-ate, 6 g. suspended in an ice-cold 10 1 mixture of morpholine and water, stirred 3-4 hrs. until a clear soln. results, allowed to stand 24 hrs. at ca. 10°, evaporated almost to dryness at 35-40°/0.05 mm., a mixture of benzene and ether then pyridine added, ice-cooled, acetic anhydride added, and allowed to stand 24 hrs. at room temp. 5.55 g. dl-j5,14,17(20)-3-ethylenedioxy-ll, 18-oxido-16-oxo-18-tetrahydropyranyloxy-20-acetoxypregnatrien-21-ic acid morpholide.—Morpholine is preferred to other sec. amines because of its good solvent properties (cf. Synth. Meth. lA, 87). Use of anhydrous amines caused decomposition. K. Heus-ler, P. Wieland, and A. Wettstein, Helv. A2, 1586 (1959). 

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