Copper compounds bromide

Although It IS possible to prepare aryl chlorides and aryl bromides by electrophilic aromatic substitution it is often necessary to prepare these compounds from an aromatic amine The amine is converted to the corresponding diazonmm salt and then treated with copper(I) chloride or copper(I) bromide as appropriate... 

Perfluoroacetylentc copper compounds also can be prepared via metathesis of the corresponding zinc or cadmium reagents with copper(l) bromide. The zinc or cadmium reagents are formed from the corresponding pentachloroperfluo-roalkaneorl lodoperfluoroalkyne [727 747] (equations 168 and 169)... 

Reaction.—a too c.c. flask to a short upright condenser (see Fig. 86) and to the upper end of the condensei attach a vertical delivery tube, dipping into an ammoniacal cuprous chloride solution. Pour 2—3 c.c. of ethylene bromide into the flask with 4 times its volume of strong methyl alcoholic potash, which is prepared by boiling methyl alcohol with excess of caustic potash on the water-bath with upright condenser. On gently heating, a rapid evolution of acetylene occurs and the characteristic brown copper compound (C2H,Cu,HjO) is precipitated from the cuprous chloride solution. 

BROMINATION OF AROMATIC COMPOUNDS WITH ALUMINA-SUPPORTED COPPER(II) BROMIDES... 

For instance, bromination of toluene in carbon tetrachloride did not proceed at reflux, even though pentamethylbenzene was brominated at 30°C to give bromopentamethylbenzene quantitatively. Toluene and copper(II) bromide reacted at reflux for 72 h. to give benzyl bromide as the main product. In a similar reaction with alumina-supported copper(II) bromide, bromotoluene (o/p = l) was obtained in good yield and no side-chain-brominated compounds were detected. 

The reaction of 1-alkoxynaphtalenes with copper (II) bromide in benzene produced a mixture of 4-bromo-1-alkoxynaphtalenes and 4,4 -dialkoxy-l,l -binaphtyls. For instance, the reaction of 1-methoxynaphtalene 4 with copper(II) bromide in refluxing benzene for 2 h. gave a mixture of 4-bromo-1-methoxy-naphtalene 5 (47 %) and 4,4 -dimethoxy-l,l -binaphtyl 6 (45 %). In contrast, in similar reaction using alumina-supported copper(II) bromide at 30°C, only dimerization occurred and no brominated compounds were obtained. 

These reactions are postulated to proceed by electro-transfer to give the radical cation of alkoxynaphtalene, which either undergoes reaction with copper(II) bromide or dimerizes (ref. 15). That is, one-electron transfer from the electron-rich alkoxynaphtalene to Cu(II) results in generation of the corresponding radical cation. The radical cation reacts with bromide anion leading to the brominated compound, whereas the radical cation undergoes reaction with another alkoxynaphtalene leading to the binaphtyl (eqns. 2-4). 

Alkylthionaphtalenes reacted with alumina-supported copper(II) bromide to give monobrominated compounds in high yields and dimerization of alkylthionaphtalenes did not occur. 

The usual aromatic bromination are performed by free bromine in the presence of a catalyst, most often iron. However, liquid bromine is not easy to handle because of its volatile and toxic character. On the other hand, alumina-supported copper(II) bromide can be treated easily and safely as a solid brominating reagent for aromatic compounds. The advantages of this procedure using the solid reagent are simple workups, mild conditions, and higher selectivities. Products can be isolated in good yield by simple filtration and solvent evaporation, and no extraction steps are required. 

CHROMIUM TRIOXIDE-PYRIDINE COMPLEX, preparation in situ, 55, 84 Chrysene, 58,15, 16 fzans-Cinnamaldehyde, 57, 85 Cinnamaldehyde dimethylacetal, 57, 84 Cinnamyl alcohol, 56,105 58, 9 2-Cinnamylthio-2-thiazoline, 56, 82 Citric acid, 58,43 Citronellal, 58, 107, 112 Cleavage of methyl ethers with iodotri-methylsilane, 59, 35 Cobalt(II) acetylacetonate, 57, 13 Conjugate addition of aryl aldehydes, 59, 53 Copper (I) bromide, 58, 52, 54, 56 59,123 COPPER CATALYZED ARYLATION OF /3-DlCARBONYL COMPOUNDS, 58, 52 Copper (I) chloride, 57, 34 Copper (II) chloride, 56, 10 Copper(I) iodide, 55, 105, 123, 124 Copper(I) oxide, 59, 206 Copper(ll) oxide, 56, 10 Copper salts of carboxylic acids, 59, 127 Copper(l) thiophenoxide, 55, 123 59, 210 Copper(l) trifluoromethanesulfonate, 59, 202... 

In order to modulate the reactivity of intermediate 331, it was transformed into its copper derivative by treatment with copper(I) bromide or iodide in THF at —78 °C, and then was allowed to react with a,/3-unsaturated carbonyl compounds (to give compounds 343 resulting from a conjugated addition), acyl chlorides (to give ketones 344) and copper(II) chloride (to dimerize giving compounds 345) (Scheme 100)"° ". ... 

Bromo- and iododibenzofurans have been converted to the amino-compounds by reaction with ammonia, or to phenols by reaction with hydroxide, both in the presence of copper catalysts at high temperatures and pressures. Thus 2-iododibenzofuran is converted to the 2-amino compound (95%) with ammonia in the presence of copper(I) bromide at 200-210°C for 24 h, and 2-bromodibenzofuran affords the corresponding phenol (56-75%) on treatment with aqueous sodium hydroxide in the presence of copper and copper(II) sulfate at 240°C for 12 h. ... 

Nucleophilic substitution of dibenzofurans has been little studied. Bromo and iodo compounds are converted into the amino compounds on autoclaving with aqueous ammonia in the presence of copper(I) bromide (730PP125). Iodo compounds can be converted into phenols with aqueous potassium hydroxide at 250 °C (65MI31100), but dibenzofuran is cleaved to 2,2 -dihydroxybiphenyl on fusion with sodium hydroxide. Animation of halo compounds can be achieved with sodamide but 4-halo compounds undergo cine substitution on treatment with sodamide or lithium dialkylamides and the 2-substituted compounds result (56JOC457). 1,2,3,4-Tetrafluoro- and octafluoro-dibenzofuran react with nucleophiles at the 3-position (Scheme 101) (67T4041,68JCS(C)1560). 

A systematic investigation of the copper-catalyzed reaction between 2-bromobenzoic acid and the anions of 1,3-dicarbonyl compounds has established the optimum conditions for the direct arylation of the /3-dicarbonyl moiety (75T2607). The use of sodium hydride as the base and copper(I) bromide as catalyst is recommended. The absence of a protic solvent ensures that competitive attack on the bromobenzoic acid by a solvent-derived base leading to a salicylic acid is eliminated. For larger scale reactions the addition of toluene offers some practical advantages. 

Copper Compounds Bis(acetonitrile)chloronitropalla-dium(II)-Copper(II) chloride, 33 t-Butyllithium-Copper(I) bromide-Di-methyl sulfide, 58 Copper(II) acetate-Bis(2-amino-phenyl) disulfide, 156 Copper(II) acetate-2,2 -Dipyridyl disulfide, 156... 

The pale yellow solid quickly decomposes when exposed to air however, it may be stored in a closed container or desiccator. An analogous compound with similar stability characteristics may be prepared by the reaction of 1,4-butadiene and copper(I) bromide. 

All of the neutral (organo-)copper compounds just listed can be arylated by aryl iodides and/or -bromides Ar-Cu and R-C=C-Cu can also be alkynylated by alkynyl iodides and/or -bromides. Table 16.2 summarizes the whole spectrum of corresponding products. After having grasped the mechanism of these reactions by way of Figure 16.3, we will discuss their synthetic potential by means of the examples given in Figures 16.4-16.9. 

It has proven possible to add oxidatively highly activated copper metal ( Rieke copper ) to alkynyl bromides in moderate yields, to furnish acetylenic copper compounds (equation 44)10. Bubbling oxygen through the system resulted in the formation of homocoupling products. 

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