SYNTHESIS with copper bronze

Interestingly, the Fischer indole synthesis does not easily proceed from acetaldehyde to afford indole. Usually, indole-2-carboxylic acid is prepared from phenylhydrazine with a pyruvate ester followed by hydrolysis. Traditional methods for decarboxylation of indole-2-carboxylic acid to form indole are not environmentally benign. They include pyrolysis or heating with copper-bronze powder, copper(I) chloride, copper chromite, copper acetate or copper(II) oxide, in for example, heat-transfer oils, glycerol, quinoline or 2-benzylpyridine. Decomposition of the product during lengthy thermolysis or purification affects the yields. 

Baker and co-workers observed during the synthesis of the biphenyl 74 (Scheme 19) from the iodo compound 73 by the Ullmann reaction at 230°C with copper bronze in nitrobenzene that the dibenzofuran 75 (1%)... 

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... 

The synthesis of arsonium ylides 384 from diazocyclopentadienes 383 and tri-phenylarsine has been reexamined with respect to the efficiency of various copper-containing catalysts Whereas copper bronze gave only ca. 55 % of ylide, yields over 80% were provided by the use of Ou(II) complexes of p-diketonates derived from acetylacetone, 3-methylacetylacetone, benzoylacetone or dibenzoylmethane, as well as by bis[4-(phenylimino)-2-pentanonato-N,0-]copper(II) and Cu(II) acetate, all used in boiling benzene. The sterically more demanding complex bis(dipivaloyl-methanato)copper(II) as well as dichlorodipyridinecopper(II) proved less efficient. CopperfTI) tartrate, the dibenzo-14-crown 6/copper complex and furthermore the acetylacetonate complexes of Co, Ni, Pt and Zn were totally ineffective. When 383a was decomposed by Cu(acac)2 in the presence of pyridine or thioanisole. 

Decarbonylation of cyclopropene acids. In a study of the synthesis of methyl sterculate (6) from methyl stearolate (1), Gensler et al.1 were unable to repeat the apparently straightforward synthesis based on addition of the Simmons-Smith reagent described in 1, 1021-1022. They were also unable to eifect addition of methylene generated by cuprous bromide decomposition of diazomethane. However, the reaction of (1) with diazoacetic ester in the presence of copper bronze, followed by hydrolysis, gives the cyclopropene diacid (2) in 70-90% yield. 

The synthesis of allenes of the type RpCH C CHa is an easier task, now made even easier by a new method based on the reaction of perfluoroalkyl coppers with propargyl halides or alcohols. The alkyl copper is generated in situ from copper bronze and a perfluoroalkyl iodide in DMSO reaction with propargyl bromide is extremely rapid and a minor explosion occurred during work-up. 

The synthesis of SFs-substituted phenothiazine was disclosed in a patent from Smith, Kline French Laboratories (63USP3107242). 3-SFs-Acetanilide (120), prepared by acetylation of d-SFs-aniline (39) with acetic anhydride, was first condensed with bromobenzene under basic conditions, in the presence of Cul and copper-bronze powder, and after add hydrolysis provided 3-SFs-diphenylamine (121). This product was then fused with sulfur in the presence of a catalytic amount of iodine to give 2-SFs-phenothiazine (122) in unreported yield (Scheme 34). 

The formation of a biaryl by the condensation of two molecules of an aryl halide in the presence of finely divided copper is known as the Ullmaim reaction [1-4]. Although several newer methods for synthesis of biaryls were developed, the Ullmann reaction still remained its importance in some specific cases. Due to its efficiency and simplicity, the reaction is very useful in the synthesis of simple symmetrical and some classes of unsymmetrical biaryls. More than a century old, the classical Ullmaim reaction involves heating the mixture of the aryl halide(s) (I) with the copper powder or bronze at 100-360 °C in or without any solvent. Products of this reaction are the biaryl(s) (II) and the corresponding copper(I) halide. Scheme 1. 

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