Copper-catalyzed dimethyl carbonate

Intramolecular oxonium ylide formation is assumed to initialize the copper-catalyzed transformation of a, (3-epoxy diazomethyl ketones 341 to olefins 342 in the presence of an alcohol 333 . The reaction may be described as an intramolecular oxygen transfer from the epoxide ring to the carbenoid carbon atom, yielding a p,y-unsaturated a-ketoaldehyde which is then acetalized. A detailed reaction mechanism has been proposed. In some cases, the oxonium-ylide pathway gives rise to additional products when the reaction is catalyzed by copper powder. If, on the other hand, diazoketones of type 341 are heated in the presence of olefins (e.g. styrene, cyclohexene, cyclopen-tene, but not isopropenyl acetate or 2,3-dimethyl-2-butene) and palladium(II) acetate, intermolecular cyclopropanation rather than oxonium ylide derived chemistry takes place 334 ). 

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]. 

Examples of the heterocyclic ring acting as 27r-components include the Diels-Alder reaction of 2,3-dimethylbutadiene with the 3,4 N=S bond in the 1,3,2,4-benzodithiadiazine (112) to give (113) (7lLA(749)l7l). The carbon-carbon double bond iri the 2,6-dimethyl derivative of the 1,2,6-thiadiazine (76) is sufficiently nucleophilic to react with carbenes. Thus copper catalyzed decomposition of ethyl diazoacetate in the presence of the thiadiazine gave the exo adduct (114) <82H(l7)40l). 

Several copper-catalyzed 7 -arylation reactions of imidazole have been published. The coupling of arylboronic acids with imidazole in the presence of binuclear bis-p,-hydroxy copper (11) complexes in air has been carried out at ambient temperature without the need for base <04TL7659>. A variety of A -arylimidazoles were prepared in excellent yields through the cross-coupling of arylboronic acids with imidazole in methanol or water with copper(I) chloride <04CC188>. Copper(II) oxide-coated nanoparticles were used catalytically in the Ullmann coupling of imidazole with various aryl chlorides with cesium carbonate in dimethyl sulfoxide <04CC778>. 

U. Romano, R. Tesel, M. M. Mruri, and P. Rebora, Synthesis of Dimethyl Carbonate from Methanol, Carbon Monoxide, and Oxygen Catalyzed by Copper Compounds, Ind. Eng. Chem. Prod. Dev. (1980). 

Ugo R, Tessel R, Mauri MM, Rebaro P. (1980). Synthesis of dimethyl carbonate from methanol, carbon monoxide, and oxygen catalyzed by copper compounds. Ind. Eng. Chem. Prod. Res. Dev., 19(3) 396 03. 

Modhephene, 34, was the first isolated propellane natural product. As such, the Weiss-Cook reaction was the perfect method for its construction. The process began with the condensation of 2 with diketone 27. Standard conditions for decarboxylation produced the core scaffold 28. Hydrogenation of the mono-enol phosphate afforded the monoketone 29. The cyclopropyl derivative 30 was prepared by copper-catalyzed decomposition of a diazoketone. gem-Dimethylation to generate 31 preceded carboxylation and esterification to afford the advanced intermediate 32. Cuprate-induced cyclopropane ring opening and methylation of the 3-ketoester introduced the final carbon atoms giving rise to 33. Lithium iodide induced decarboxylation preceded reduction of the ketone followed by dehydration with Martin s sulfurane, thus producing 34. 

The copper catalyzed oxidative carbonylation of methanol yields dimethyl carbonate instead of the oxalate [78] ... 

Tab. 10.8 summarizes the application of rhodium-catalyzed allylic etherification to a variety of racemic secondary allylic carbonates, using the copper(I) alkoxide derived from 2,4-dimethyl-3-pentanol vide intro). Although the allyhc etherification is tolerant of linear alkyl substituents (entries 1-4), branched derivatives proved more challenging in terms of selectivity and turnover, the y-position being the first point at which branching does not appear to interfere with the substitution (entry 5). The allylic etherification also proved feasible for hydroxymethyl, alkene, and aryl substituents, albeit with lower selectivity (entries 6-9). This transformation is remarkably tolerant, given that the classical alkylation of a hindered metal alkoxide with a secondary alkyl halide would undoubtedly lead to elimination. Hence, regioselective rhodium-catalyzed allylic etherification with a secondary copper(l) alkoxide provides an important method for the synthesis of allylic ethers. 

Reaction of l-chloro-4,4-bis(chloromethyl)pentane with magnesium in diethyl ether, followed by quenching with carbon dioxide, gave 4-(l-methylcyclopropyl)butanoic acid in 68% yield. Cyclopropane derivatives with electron-withdrawing substituents 5 were prepared by elec-troreductive dechlorination of 2,4-dichlorobutanoic acid derivatives in dimethyl sulfoxide solution in the presence of tetraethylammonium 4-toluenesulfonate at ambient temperature (yields 51 -90%).The starting materials for compounds 5 can easily be obtained by copper (I)-catalyzed photochemical addition of dichloromethane to electron-deficient alkenes. Electrochemical reductive 1,3-debromination has also been achieved however, it is of little synthetic value (experimental details are described in ref 16, with yields ranging from 39 to 94%). meso- and dimethyl sulfoxide gave equal amounts of cis- and transA, 2-dimethylpropane. ... 

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