Copper cyanide purification

In an alternative syntliesis of panaatistaliti (S7) by Trost et al. [52], fSdieme 9.15) addilioti of tlie Grlgtiatd teagetil 63 [53] lo a mixture of tlie azide 62 and copper cyanide reprodudbly gave tlie desired adduct 64. Because of tlie difliciilties associated witli purification of adduct, tlie overall yield of tlie two steps ftlie next being diliydroxylation of tlie olefin) was 6 296. 

In an alternative synthesis of pancratistatin (57) by Trost et al. [52], (Scheme 9.15) addition of the Grignard reagent 63 [53] to a mixture of the azide 62 and copper cyanide reproducibly gave the desired adduct 64. Because of the difficulties associated with purification of adduct, the overall yield of the two steps (the next being dihydroxylation of the olefin) was 62%. 

The excess of copper cyanide and the use of a polar, high-boiling point solvent makes the purification of the products difficult. In addition, elevated temperatures (up to 200°C) lower the functional group tolerance. The use of alkali metal cyanides or cyanation reagents such as cyanohydrins, a catalytic amount of copper(I) iodide and kalium iodide, allows a mild, catalytic cyanation of various aryl bromides. 

Different types of methods for purification have been applied. Brauner in 1889, by means of aqua regia, converted crude tellurium into telluric chloride, the aqueous solution of which on precipitation by sulphur dioxide deposited the element together with selenium and traces of copper and lead as the only impurities. The precipitate was dissolved in fused potassium cyanide in an atmosphere of hydrogen and the tellurium separated from the aqueous extract by treatment with a current of air. The element was then distilled in a current of hydrogen, 1 an alternative is distillation in a vacuum.5 Another method of treatment for the telluric chloride solution is to precipitate in three fractions using sulphur dioxide, when it is found that the middle fraction is of a high degree of purity.6... 

There is another oxidase present in S. acidocaldarius (DSM 639) [120], a cytochrome aa3 oxidase (a peak at 605 nm). The cytochrome oxidizes horse-heart cytochrome c and TMPD-ascorbate. The ability to oxidize cytochrome c is lost during purification, whereas the oxidation of TMPD-ascorbate increases. The purified cytochrome (Mr 120000) is composed of a single subunit (Mr 38000) and contains two heme molecules as well as two copper atoms per subunit. TMPD-ascorbate oxidation is inhibited by cyanide, sulfide (1-3 mM) and azide (20 mM). The purified enzyme also oxidizes reduced cytochromec but at too slow a rate to be physiologically significant. The absence of cytochrome c in S. acidocaldarius and the loss of the ability to oxidize cytochrome c upon purification indicates this cytochrome is not a cytochrome c oxidase. The cytochrome oxidizes the indigenous quinone found in the membranes, caldariella... 

Copper is refined electrolytically, the silver and gold present separating as an anode sludge. The last two metals are also recovered during the purification of both lead (p. 310) and nickel (p. 502). Silver and gold are extracted by aqueous sodium cyanide which reduces the oxidation potential of the metals so that atmospheric oxygen brings them, or their salts, into solution as soluble complexes ... 

Gkrld is also recovered from the anode sludge from electrolytic purification of copper Section 21-7. Gktld is so rare that it is also obtained from very low-grade ores by the cyanide process. Air is bubbled through an agitated slurry of the ore mixed with a solution of NaCN. This causes slow oxidation of the metal and the formation of a soluble complex compound. 

Purification this step features the second innovation of the process which, to eliminate the by-product acrolein, favors the formation of cyanohydrin by means of the hydrogen cyanide which is also present This operation takes place at low temperature (20 Q in agitated reactors, either continuously in the presence of a copper-based catalyst, or semi-continuously with a reaction phase in basic medium (caustic soda addition), followed by a neutralization period (sulfuric acid addition). The cyanohydrin obtained is then removed by vacuum distillation. The withdrawal may be sent to a thin layer evaporator to recover entrained acrylonitrile. These treatments must be conducted in the presence of a polymerization inhibitor and at a temperature below 55 C to prevent the rede-composition of cyanohydrin.... .. ... 

The first successful application of activated carbons was made for the purification of nickel plating baths. But it was then extended to the purification of acid copper plating, acid and alkaline tin plating, and to all cyanide baths. However, activated carbon is not suitable for chromium plating baths because activated carbon reduces hexavalent chromium to trivalent chromium. 

The new Monsanto process makes use of a copper catalyst, which is used to reduce diethanolamine to DSIDA, the intermediate to Roundup (see Fig. 9.27). This process totally eliminates the use of ammonia, hydrogen cyanide, and formaldehyde, is free of contaminants and byproducts, and hence does not require further purification steps. The stream can be recycled after filtration of catalyst. Monsanto s process can also be used in the production of other amino acids such as glycine through reduction and is a general method for conversion of primary alcohols to carboxylic acid salts. The development of this technology for processes pertaining to the agricultural, commodity, specialty, and pharmaceutical sectors would have a pronounced impact on the environment. 

Monsanto has developed and implemented an alternative DSIDA process that relies on the copper-catalyzed dehydrogenation of diethanolamine. The raw materials have low volatility and are less toxic. Process operation is inherently safer, because the dehydrogenation reaction is endothermic and, therefore, does not present the danger of a runaway reaction. Moreover, this zero-waste route to DSIDA produces a product stream that, after filtration of the catalyst, is of such high quality that no purification or waste cut is necessary for subsequent use in the manufacture of Roundup . The new technology represents a major breakthrough in the production of DSIDA, because it avoids the use of cyanide and formaldehyde, is safer to operate, produces higher overall yield, and has fewer process steps. 

A 25-mL flame-dried Schlenk tube flushed with argon is charged with ethyl 4-iodobenzoate (2.9 mmol, 773 mg), 1,2-dimethoxyethane (dme) (5 mL) and cooled to -20 °C. Isopropylmagnesium chloride (2.9 mmol, 1.33 mL of a 2.1-M solution in tetrahydrofuran) is then slowly added and the reaction mixture is stirred at -20 °C until GC analysis of reaction aliquots indicates complete exchange. Subsequently, a solution of copper(I) cyanide di(lithium chloride) (2.8 mmol, 2.8 mL of a 1-M solution in tetrahydrofuran) is added and the reaction mixture is stirred for 20 min. A solution of (2,2-diphenylvinyl)trifluoromethanesulfonate (330 mg, 1 mmol) and tris(acetylacetonato)iron (38 mg, 0.1 mmol) in 1,2-dimethoxyethane (3 mL) is added at once at -20 °C and the reaction mixture is stirred at room temperature for 1 h. The reaction is quenched with sat. aq. ammonium chloride and extracted several times with diethyl ether. The combined organic layers are washed with a 2 1 mixture of aq. ammonia and aq. ammonium chloride, and sat. brine, and are dried over magnesium sulfate and concentrated under reduced pressure. Purification by column chromatography (pentane-diethyl ether, 99 1) affords the product as a yellow oil 254 mg (77%). 

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