Cuprous salt

An interesting coupling reaction with the diazonium salt derived from anthranilic acid leads to an excellent method for the preparation of dlphenic acid. The reaction occurs with cuprous salts in ammoniacal solution ... 

Vinylacetylene and Ghloroprene. In the presence of cuprous salt solutions, acetylene dimerizes to vinylacetylene [689-97-4], C H. Yields of 87% monovinylacetylene, together with 10% of divinylacetylene, have been described (6). 

With two equivalents of an organomagnesium hahde, a Gtignard reagent is formed, capable of use in further syntheses (35,36). Cuprous salts cataly2e oxidative dimerization of propargyl alcohol to 2,4-hexadiyne-l,6-diol [3031-68-3] (37). 

Cuprous salts catalyze the oligomerization of acetylene to vinylacetylene and divinylacetylene (38). The former compound is the raw material for the production of chloroprene monomer and polymers derived from it. Nickel catalysts with the appropriate ligands smoothly convert acetylene to benzene (39) or 1,3,5,7-cyclooctatetraene (40—42). Polymer formation accompanies these transition-metal catalyzed syntheses. 

General Methods. Traces of acetylene can be detected by passing the gas through Ilosvay s solution which contains a cuprous salt in ammoniacal solution. The presence of acetylene is indicated by a pink or red coloration caused by the formation of cuprous acetyHde, CU2C2. The same method can be used for the quantitative deterrnination of acetylene in parts per biUion concentrations the copper acetyHde is measured colorimetricaHy (87). 

Silver iodomercurate [36011-71-9] Ag2HgI, is a bright yellow compound and is prepared similarly to the cuprous salt where silver nitrate is the precipitant. The silver salt, which darkens reversibly at 50°C, is used for the same appHcation as cuprous iodomercurate. 

SANDMEYER GATTERMANN AramaUcsubstitution Substitution of an annine group via the diazonkim sait by nudeophiies such as Ci, Br, i, CN R-S, HO, soma via cuprous salt catalysis. 

The amine (Imol) is added to a solution of anhydrous zinc chloride (Imol) in concentrated hydrochloric acid (42mL) in ethanol (200mL, or less depending on the solubility of the double salt). The solution is stirred for Ih and the precipitated salt is filtered off and recrystallised from ethanol. The free base is recovered by adding excess of 5-ION NaOH (to dissolve the zinc hydroxide that separates) and is steam distilled. Mercuric chloride in hot water can be used instead of zinc chloride and the salt is crystallised from 1% hydrochloric acid. Other double salts have been used, e.g. cuprous salts, but are not as convenient as the above salts. 

Some of the cuprous chloride compounds of the diazonium salts have been isolated and analysed, and coirespond to the formula CoH.-.NjCl.CuoCIo (Hantzsch). The formation of a crystalline copper compound is rendeied very evident in the present preparation.. A modification of Sandmeyer s reaction IS the introduction of precipitated metallic copper in place of the cuprous salt (Gattermann). 

The addition of Grignard reagents to unsaturated ketones gives mixtures resulting from 1,2-addition and 1,4-addition. In the presence of cuprous salts, however, the conjugate (1,4) addition is enhanced to the extent that the reaction becomes synthetically useful (11). Two examples of this procedure are given. 

Cupro-. cuprous, copper(I), cupro-. -chlorid, n. cuprous chloride, copper(I) chloride, -cy-aniir, n. cuprous cyanide, copper(I) cyanide cuprocyanide, cyanocuprate(I). -jodid, n. cuprous iodide, copper(I) iodide, -mangan, n. cupromanganese. -oxyd, n. cuprous oxide, copper(I) oxide, -salz, n. cuprous salt, cop-per(I) salt, -suifocyantir, n. cuprous thiocyanate, copper (I) thiocyanate, -verbin-dUDg, /. cuprous compound, copper(I) compound. 

Kupferozydul, n. cuprous oxide, copper(I) oxide, -hydrat, n. cuprous hydroxide, cop-per(I) hydroxide, -salz, n. cuprous salt, copper (I) salt, -verblndung,/. cuprous compound, copper(I) compound. 

K has the value of about 1 x 10 at 298 K, and in solutions of copper ions in equilibrium with metallic copper, cupric ions therefore greatly predominate (except in very dilute solutions) over cuprous ions. Cupric ions are therefore normally stable and become unstable only when the cuprous ion concentration is very low. A very low concentration of cuprous ions may be produced, in the presence of a suitable anion, by the formation of either an insoluble cuprous salt or a very stable complex cuprous ion. Cuprous salts can therefore exist in contact with water only if they are very sparingly soluble (e.g. cuprous chloride) or are combined in a complex, e.g. [Cu(CN)2) , Cu(NH3)2l. Cuprous sulphate can be prepared in non-aqueous conditions, but because it is not sparingly soluble in water it is immediately decomposed by water to copper and cupric sulphate. 

In aromatic compds, an amino group may be replaced by the nitro group by diazotization and reaction with nitric acid in the presence of cuprous salts (the Sandmeyer reaction). This method is used for lab work only and is described in standard textbooks on preparative organic chemistry... 

On the basis of these redox potentials it seems likely that direct electron release to the benzenediazonium ion takes place only with iodide. This corresponds well with experience in organic synthesis iodo-de-diazoniations are possible without catalysts, light, or other special procedures (Sec. 10.6). For bromo- and chloro-de-di-azoniations, catalysis by cuprous salts (Sandmeyer reaction, Sec. 10.5) is necessary. For fluorination the Balz-Schiemann reaction of arenediazonium tetrafluoroborates in the solid state (thermolysis) or in special solvents must be chosen (see Sec. 10.4). With astatide (211At-), the heaviest of the halide ions, Meyer et al. (1979) found higher yields for astato-de-diazoniation than for iodo-de-diazoniation, a result consistent with the position of At in the Periodic System. It has to be emphasized, however, that in investigations based on measuring yields of final products (Ar-Hal), the possibility that part of the yield may be due to heterolytic dediazoniation is very difficult to quantify. 

The central C—C bond in bicyclo[ 1.1.0] butane has a high -character and is known to behave as an olefin. Thus, 1-arylsulfonylbicyclobutanes 312 reacted with Grignard reagents in the presence of lithium dialkylcuprates or cuprous salts (Me2S, CuBr or CuCl) giving 3-alkyl-1-arylsulfonylcyclobutanes 313406. 

Despite its synthetic importance, the mechanism of the copper-quinoline method has been studied very little, but it has been shown that the actual catalyst is cuprous ion. In fact, the reaction proceeds much faster if the acid is heated in quinoline with cuprous oxide instead of copper, provided that atmospheric oxygen is rigorously excluded. A mechanism has been suggested in which it is the cuprous salt of the acid that actually undergoes the decarboxylation. It has been shown that cuprous salts of aromatic acids are easily decarboxylated by heating in quinoline and that arylcopper compounds are intermediates that can be isolated in some cases. Metallic silver has been used in place of copper, with higher yields. ... 

On addition to boiling water, black cupric thiocyanate converts to the white cuprous salt with violent gas evolution. It is suggested that the gas is hydrogen cyanide, though carbon dioxide seems probable. 

The benzo[14]annulenedione 181 has been prepared by Castro reaction of the cuprous salt of the o-iodocinnamoylacetylene 18064 ... 

Simple olefins can photodimerize to cyclobutanes in the presence of cuprous salts as sensitizers (4.20) 423>. Copper (I) trifluoromethanesulfonate has been utilized successfully (4.21) 424). 

The coupling process, which has been extended successfully to functionalized cuprates, can also be performed with alkylzinc chlorides in the presence of catalytic amounts of cuprous salts (e.g. CuCN-2LiCl, CuBr-Me2S and LiCuBr2), providing products with excellent alkyne/allene selectivity (143 144= 91 9 to 100 0) (Scheme... 

In 1884, Sandmeyer, however, made the important discovery that in the presence of the corresponding cuprous salt chlorine and bromine are also directed to the nucleus. This catalytic action has not yet been explained. Perhaps a double salt is formed, or else a complex salt in which the halogen is more firmly bound than in the simple halide. According to Gattermann, the cuprous salt may be replaced by copper powder. In general, the decomposition of labile diazo-compounds, by elimination of elementary nitrogen, is accelerated by copper. 

The thienylacetylenes give the usual tests for the free ethynyl group with cuprous salts as well as with ammoniacal silver. The /9-thienyl acetylenes are more stable than the a-thienylacetylenes, as was noticed both in this laboratory and by French investigators (75). They darken on standing and slowly decompose. 

This compound has been prepared by air oxidation of the preformed cuprous salt. Another method uses aqueous cuprous chloride-ammonium chloride and an oxidant (e.g., oxygen). ... 

Meerwein reaction consists of condensation of ethylenic compounds with aryldiazonium salts in the presence of cupric and cuprous salts ... 

Knifton reported that solutions of cuprous salts in amine solvents are excellent catalysts for the selective reduction of nitroalkanes to the corresponding oximes. 

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