Cuprous salts, derivatives

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 ... 

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. 

Cuprous salts are derived from cuprous oxide, Cu20, and are generally unstable in contact with air and water. No soluble cuprous salts which dissolve in water to give cuprous ions, Cu+, are known. 

Both cupric and cuprous salts act as oxidizers, the cupric derivatives being reduced to the cuprous or metallic condition, and the cuprous compounds to metallic copper. Alkaline solutions of cupric salts are employed in oxidation-processes in organic chemistry.2... 

The eyelization of diacciylene derivatives 152 is earned out in two steps through the synthesis of a methoxymethyl intermediate, whieh then undergoes eyelization in the jxesence of a cuprous salt as catalyst (Fig. 53). In addition to the main product 153, macrocycle 154 is formed in a relative amount of about 1/5. ... 

Derivation Reaction of acetylene with aqueous soluble of cuprous salts. 

The halogen substitution-products of the hydrocarbons of the acetylene series resemble those derived from hydrocarbons which contain a double bond. The derivatives of acetylene are very unstable. Chloroacetylene is a gas which decomposes instantaneously, with explosion. The substitution-products which contain the =CH group form precipitates with ammoni-acal solutions of silver and cuprous salts. 

Treatment of diazonium salts with cuprous, Cu(I), salts generates aryl halides. When 398 reacts with CuCl (cuprous chloride) or CuBr (cuprous bromide), the products are chlorobenzene or bromobenzene via what is probably a radical reaction.29l jhis conversion is known as the Sandmeyer reaction. 2 The use of copper powder rather than cuprous salts for this transformation is often called the Gattermann reaction. 93,292b,c Aryl iodides are also produced from diazonium salts by reaction with potassium iodide (KI) but the actual reactive species may be l3-.294,295 Treatment of aniline derivative 403 with sodium nitrite and HCl followed by treatment with KI, for example, gave a 89% yield of 404.Aryl nitriles are generated under Sandmeyer conditions using cuprous cyanide (CuCN), as in the conversion of 405 to benzonitrile derivative 407 via diazonium chloride, 406. 

Aniline reacts with nitrous acid to give benzenediazonium salts, which react with a variety of reagents via a substitution reaction. These reagents include cuprous salts, aqueous acid, iodide, hypophosphorous acid, and activated benzene derivatives. Nucleophilic substitution at the sp carbon of a halo-benzene derivative does not occur unless high heat and pressure are used. Electron-withdrawing substituents on the benzene ring significantly lower the temperature required for the reaction. Nucleophiles for this nucleophilic aromatic substitution reaction include water, hydroxide, alkoxide, and amines. 

Metallic Derivatives, (a) Cuprous Acetylide. CujCg. Prepare an ammoniacal solution of cuprous chloride by first adding dilute ammonia to 2-3 ml. of dilute copper sulphate solution until the initial precipitate just redissolves and a clear deep-blue solution is obtained now add an aqueous solution of hydroxylamine hydrochloride drop by drop with shaking until the solution becomes first green and then completely colourless, the cupric salt being thus reduced to the cuprous derivative. 

Aniline [62-53-3] M 93.1, f -6.0", b 68.3/lOmm, 184.4"/760mm, d 1.0220, n 1.585, n s 1.5832, pK 4.60. Aniline is hygroscopic. It can be dried with KOH or CaH2, and distd at reduced pressure. Treatment with stannous chloride removes sulfur-containing impurities, reducing the tendency to become coloured by aerial oxidn. Can be crystd from Et20 at low temps. More extensive purifications involve preparation of derivatives, such as the double salt of aniline hydrochloride and cuprous chloride or zinc chloride, or A -acetylaniline (m 114") which can be recrystd from water. 

Copper salts, cupric or cuprous also will catalyze the carbonylation of amines. Piperidine, for example, gives a urea derivative with carbon monoxide, and it, too, is probably a metal amide—carbon monoxide insertion reaction. 

Amino- and 7-aminothiocoumarin have been thoroughly explored as useful precursors to a wide variety of thiocoumarins. Thus, substituents such as Cl, Br, I, SCN, CN, OH, and OMe have been introduced by way of the Sandmeyer reaction. 6-Aminothiocoumarin is brominated in the 5-posi-tion, whereby 5-bromo- or 5,6-dibromothiocoumarin may be made by way of the corresponding diazonium salt, using hypophosphorous acid or cuprous bromide, respectively. Alternatively, 6-acetylaminothiocoumarin may be nitrated in the 5-position and thus 5-nitro-, 5-amino-, 5,6-diamino-, or 6-chloro-5-nitrothiocoumarins can be prepared by classical syntheses. These derivatives are useful intermediates for the synthesis of further fused thiocoumarins (e.g., 23, 24 and 25 ). 

The reactions of thiocyanogen may roughly be divided into two types (1) Reactions in which the radical combines directly with metals to form the corresponding thiocyanates, and with cuprous thiocyanate to form the cupric salt. (2) Reactions in which a substitution is effected for example, with aniline, dimethylaniline and phenol, the corresponding jj-thiocyano-derivatives and thiocyanie acid are formed.1... 

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