Copper nitrile hydrolysis

Still another powerful method for the regeneration of carbonyl compounds from dialkylhydrazones is copper-catalyzed hydrolysis. The reagents that have been tested for this purpose are 2% aqueous cop-per(II) acetate solution at pH 4, copper(II) chloride in 0.05M phosphate buffer and 75% tetrahydrofu-ran/water, and copper(II) sulfate pentahydrate . Under the conditions of the hydrolysis, no reaction is observed in the absence of the copper(II) ion. Typical yields are 85-100%. Other functional groups like a-dicarbonyl, a-tricarbonyl, acetal and aldehydic formyl groups were not affected by this hydrolysis procedure. Nitrile formation in the case of aldehyde dimethylhydrazones was not a significant side reaction. However, reaction times ranged from 1 to 15 h. The reaction is believed to be nonoxidative in nature rather, the copper is believed to activate the C=N bond and catalyze hydrolysis. The dimethylhydrazine produced during hydrolysis also complexes irreversibly with the copper(II) ion to drive the reaction to completion. 

Adiponitrile undergoes the typical nitrile reactions, eg, hydrolysis to adipamide and adipic acid and alcoholysis to substituted amides and esters. The most important industrial reaction is the catalytic hydrogenation to hexamethylenediarnine. A variety of catalysts are used for this reduction including cobalt—nickel (46), cobalt manganese (47), cobalt boride (48), copper cobalt (49), and iron oxide (50), and Raney nickel (51). An extensive review on the hydrogenation of nitriles has been recendy pubUshed (10). 

Even ia 1960 a catalytic route was considered the answer to the pollution problem and the by-product sulfate, but nearly ten years elapsed before a process was developed that could be used commercially. Some of the eadier attempts iacluded hydrolysis of acrylonitrile on a sulfonic acid ion-exchange resia (69). Manganese dioxide showed some catalytic activity (70), and copper ions present ia two different valence states were described as catalyticaHy active (71), but copper metal by itself was not active. A variety of catalysts, such as Umshibara or I Jllmann copper and nickel, were used for the hydrolysis of aromatic nitriles, but aUphatic nitriles did not react usiag these catalysts (72). Beginning ia 1971 a series of patents were issued to The Dow Chemical Company (73) describiag the use of copper metal catalysis. Full-scale production was achieved the same year. A solution of acrylonitrile ia water was passed over a fixed bed of copper catalyst at 85°C, which produced a solution of acrylamide ia water with very high conversions and selectivities to acrylamide. 

Hydrolysis of primary amides cataly2ed by acids or bases is very slow. Even more difficult is the hydrolysis of substituted amides. The dehydration of amides which produces nitriles is of great commercial value (8). Amides can also be reduced to primary and secondary amines using copper chromite catalyst (9) or metallic hydrides (10). The generally unreactive nature of amides makes them attractive for many appHcations where harsh conditions exist, such as high temperature, pressure, and physical shear. 

Addition of RMgBr to nitriles. Grignard reagents react with nitriles slowly if at all, but even r-butylmagnesium chloride will add to nitriles in refluxing THF when catalyzed by a copper(I) salt. The adduct can be converted to a ketimine by anhydrous protonation, to a primary amine by reduction (Li/NH,), or to a ketone by hydrolysis. The actual reagent may be a cuprate such as R3Cu(MgX)2. 

Hydroxyethyl)carbazole can be oxidized with copper(II) oxide-potassium hydroxide at 240°C to the carbazol-9-ylacetic acid the benzoate ester of the alcohol was cleaved to regenerate alcohol using phenyl Grignard reagent. The 9-acetic acid is also produced by alkaline hydrolysis of the corresponding nitrile. ... 

Copper-catalysts promoted with i) other group VIA or VIIIA metals and ii) alcaline or alcaline earth elements (IA or IIA) are used for selective hydrogenation of various organic compounds (1). Moreover Cu(Co) Zn-Al catalysts were extensively studied for the synthesis of methanol and of light alcohols (2,3). More recently, due to the development of fine chemical processes, detailed studies of copper catalysts were carried out in order to show, like for noble metals, the effect of supports (SMSI), of promoters and of activation-on metal dispersion or reduction, on alloy formation... For example modified copper catalysts are known for their utilization in the dehydrogenation of esters (4-6), in the hydrolysis of nitriles (7), in the selective hydrogenation of nitriles (8), in the amination of alcohols (9)... 

In recent years there has been considerable interest in the reactions of nitriles in the coordination sphere of metal ions. Breslow et al.312 first reported that the hydrolysis of 2-cyano-l,10-phenanthro-line to the corresponding carboxamide is strongly promoted by metal ions such as copper(II), nickel(II) and zinc(II). Base hydrolysis of the 1 1 nickel complex is 107 times faster than that of the uncomplexed substrate. The entire rate acceleration arises from a more positive value of AS. Somewhat similar effects have been observed for base hydrolysis of 2-cyanopyridine to the corresponding carboxamide. In this case rate accelerations of 109 occurred with the nickel(II) complex.313... 

A special example of the hydrolysis of a nitrile is seen in the copper-promoted addition of water (or an alcohol) to 3-cyano-2-azamaleodinitrile (4.5). It is of interest that the nitrile is specifically attacked in preference to the imine (Fig. 4-12). 

Following the development of sponge-metal nickel catalysts by alkali leaching of Ni-Al alloys by Raney, other alloy systems were considered. These include iron [4], cobalt [5], copper [6], platinum [7], ruthenium [8], and palladium [9]. Small amounts of a third metal such as chromium [10], molybdenum [11], or zinc [12] have been added to the binary alloy to promote catalyst activity. The two most common skeletal metal catalysts currently in use are nickel and copper in unpromoted or promoted forms. Skeletal copper is less active and more selective than skeletal nickel in hydrogenation reactions. It also finds use in the selective hydrolysis of nitriles [13]. This chapter is therefore mainly concerned with the preparation, properties and applications of promoted and unpromoted skeletal nickel and skeletal copper catalysts which are produced by the selective leaching of aluminum from binary or ternary alloys. 

A major industrial process that uses skeletal copper catalysts is the liquid-phase hydrolysis of nitriles to... 

Displacement of the bromide by cyanide ion, using the copper (I) salt as the nucleophile, gives a mixture of nitriles in which the more stable primary nitrile predominates even more. These can be separated by a clever device. Hydrolysis in concentrated HCl is successful with the predominant primary nitrile but the more hindered secondary nitrile does not hydrolyse. Separation of compounds having two different functional groups is easy in this case the acid can be extracted into aqueous base, leaving the neutral nitrile in the organic layer. 

Hydrolysis of acid chlorides, acid anhydrides, esters and carboxamides leads to the carboxylic acid, although these compounds are often derived from a carboxylic acid group in the first place (Scheme 5.5). Nitriles are usually derived from amines via diazotization and reaction with copper(I) cyanide (see Chapter 8) and so the hydrolysis of a nitrile group is of more value. In all cases, alkaline hydrolysis gives the salt of the acid, from which the free acid is obtained by addition of mineral acid. 

Raney copper is prepared from the commercially available copper aluminum alloy. It does not have much to offer the synthetic chemist as only a few reactions are reported to be affected by this catalyst. Raney copper, as well as Raney cobalt, generally produces fewer side reactions than Raney nickel even though they usually require higher reaction temperatures for the same reaction. Raney copper is, however, quite usefiil for the selective hydrogenation of substituted dinitro benzenes (Eqn. 8.6) with its activity apparently increasing with continued reuse. Raney copper can also be used for the catalytic hydrolysis of hindered nitriles to the amides (Eqn. 12.13). "2... 

Previous works have shown that copper catalysts are selective in the dehydrogenation of esters (5-7), in the hydrolysis of nitrile (8), in the selective hydrogenation of nitrile or in alcohol amination (10). The catalyst systems such as copper chromite are often used for the preparation of substituted amines. These solids, however, are very sensitive to the presence of water and ammonia (formation of copper nitrides... 

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