Catalyst copper bronze

With regard to the use of heterogeneous catalysts, copper bronze is a traditional catalyst in cyclopropanation reactions [7] and the use of zeolite CuNaX in the reactions of ethyl diazoacetate with several olefins has been described [8]. 

Yields are, in general, highest with rhodium catalysts. Copper bronze as a suspension was practically the only catalyst for cyclopropanation before the 1960 s (see Fuson and Cleveland s Organic Syntheses procedure for its preparation, 1955). It is still used, obviously because it is cheap and easily available. The yields with copper bronze, however, are clearly lower than with Cu- or Rh-catalyst in a homogeneous system Doyle (1986, Table I) found four cyclopropanations described in the literature that were conducted under heterogeneous (Cu bronze) and homogeneous... 

Natur Kupfer C is a good catalyst, but ordinary copper bronze may be used. 

The Rh2(OAc)+-catalyzed reaction between crotyl bromide and ethyl diazoacetate at or below room temperature follows the pathway 129 - 131 - 132 exclusively. At higher temperature, when ethyl bromoacetate and increasing amounts of the [1,2] rearrangement product 126 are found additionally, the 129 -> 130 - 132 -f 133 route becomes a competing process. With copper catalysts, this situation may be applicable at all temperatures, but it has been suggested that the route via complex 130 operates solely, when copper bronze is the catalyst154). 

Rh2(OAc)4-catalyzed decomposition of 2-diazocyclohexane-l,3-dione 380a or its 5,5-dimethyl derivate 380b in the presence of an aryl iodide leads to an iodonium ylide 381 355). The mild reaction conditions unique to the rhodium catalyst are essential to the successful isolation of the ylide which rearranges to 382 under the more forcing conditions required upon copper catalysis (copper bronze, Cu(acac)2, CuCl2) 355). 

The use of copper as a catalyst in carbenoid transfer has its roots in the Amdt-Eistert reaction, Eq. 1 (3). Although the original 1935 paper describes the Wolff rearrangement of a-diazo ketones to homologous carboxylic acids using silver, the authors mention that copper may be substituted in this reaction. In 1952, Yates (4) demonstrated that copper bronze induces insertion of diazo compounds into the X-H bond of alcohols, amines, and phenols without rearrangement, Eq. 2. Yates proposal of a distinct metal carbenoid intermediate formed the basis of the currently accepted mechanistic construct for the cyclopropanation reaction using diazo compounds. 

Continuous steam distillation, 147, 148 Cooling baths, 61 Cooling curve method, 26 Copper bronze, activated, 193 Copper - chromium oxide catalyst, for aldehyde synthesis, 318, 321 for hydrogenation, 872, 873 hydrogenolysis with, 872J Copper phthalocyanine, 983 Copper powder, 192 Copper sulphate, as desiccant, 40, 41 Cork stoppers, 55 boring of, 56... 

Golden obtained polymeric materials with molecular weights up to 1800 from potassium />-chlorophenoxide in refluxing nitrobenzene as solvent in the presence of copper bronze as catalyst (28). 

This method was extended to different diazonium salts and several arsonium ylides (14) were prepared (23, 32). The reaction is greatly facilitated by the presence of copper, copper-bronze, or copper salts. For example, attempts to prepare the bis(carbethoxy)methylene ylide by thermolysis of diethyl diazomalonate in the presence of triphenylarsine without the presence of a catalyst proved abortive, whereas this ylide was obtained in 61% yield if the reactants were heated at 150°C with copper-bronze (32). 

Other catalysts which have been used include iodine (reference 28), copper bronze (reference 40), s-butyl alcohol (reference 28), or a small amount of an aluminum alkoxide (reference 13). 

Caro s acid, 22, 44, 74 Carvacrylamine, 22, 9 Catalyst, alumina, 22, 40 boron trifluoride, 20, 6 copper bronze, 20, 45 copper-chromium oxide for decarboxylation, 22, 67... 

Furan carboxylic acids usually decarboxylate readily, and this method is often used in the laboratory for the preparation of furans. Furan itself can be obtained in good yield from 2-furoic acid in quinoline, with a copper catalyst, while industrial methods employ the catalytic decarbonylation of furfural. Copper powder, copper oxide or copper bronze, or heavy metal oxides,22 are the best catalysts, in combination with quinoline as solvent and weak base.23-28 Dann et al,2fl decarboxylated 2,5-dimethyl-3-furoic acid in 50% yield using barium hydroxide. 3-Furoic acid, which is difficult to obtain in large quantities, is best prepared by controlled decarboxylation of the easily prepared furan tetracarboxylic acid. 

C4)4N]Br Copper bronze [(C4)4N][OAc] 130 °C. Coupling of aryliodides and activated bromides activity increases upon recycling due to formation of more active nanoparticles catalysts remains stable for more than 15 runs products extracted with cyclohexane. [84]... 

Arylphenoxazines have been obtained similarly with aryl halides in the presence of sodamide,67 or on heating phenoxazine and an aryl iodide or aryl bromide with anhydrous potassium carbonate and a small amount of copper bronze as catalyst.10... 

A carboxyl group is removed from a heterocyclic nucleus in much the same way as from an aromatic nucleus (method 13), i.e., by thermal decomposition. The pyrolysis is catalyzed by copper or copper salts and is frequently carried out in quinoline solution. The reaction is important in the synthesis of various alkyl and halo furans. Furoic acid loses carbon dioxide at its boiling point (205°) to give furan (85%). A series of halo furans have been made in 20-97% yields by pyrolysis of the corresponding halofuroic acids. The 5-iodo acid decarboxylates at a temperature of 140°, whereas the 3- and 5-chloro acids requite copper-bronze catalyst at 250°. ... 

---