Raney cobalt nitriles

Isophorone diamine is synthesized traditionally by aminoreduction of iso-phoronenitrile. Raney cobalt was used for this process. More recently, a new two-step process was patented. The first step consists of synthesizing the imine and the second one of hydrogenating the latter. Ra-Ni was used as catalyst at 150°C and 60 bar hydrogen pressure. Under these conditions, the catalyst reduces the nitrile groups and is able to cleave the N-N bonds, too. Ammonia is required to promote primary amine formation during nitrile hydrogenation (Scheme 4.151).554... 

Various other reducing methods are employed for the conversion of (3-nitro alcohols to amino alcohols, namely, electrochemical reduction.107 The selective electrohydrogenation of ni-troaliphatic and nitroaromatic groups in molecules containing other groups that are easy to hydrogenate (triple bond, nitrile, C-I) are carried out in methanol-water solutions at Devarda copper and Raney cobalt electrodes (Eq. 6.55).107... 

Other Raney catalysts have been prepared. Raney cobalt has been described by several authors (28,29). The active cobalt has been claimed to be especially suitable for the reduction of nitriles. The preparation of an active copper has been described by Faucounau (30). Paul and Hilly (31) have described the preparation of Raney iron. It is claimed that Raney iron reduces acetylenic bonds to ethylenic bonds with no further hydrogenation occurring. 

Nitriles have been hydrogenated at low temperatures and pressures over heterogeneou.s and homogeneous catalysts to produce amines, aldehydes, primary alcohols or alkanes. The reduction to produce amines is by far the most widely used transformation. The most commonly used catalysts are Raney nickel, Raney cobalt, nickel boride, cobalt boride, rhodium, palladium or platinum on various supports. Products formed in the hydrogenation of a nitrile (RCN) are determined by the fate of the intermediate... 

Cobalt catalysts are reasonably active for hydrogenation reactions but they are particularly useful for the hydrogenation of nitriles and aldoximes to primary amines.2. 22 Other than for these reactions cobalt has not been generally used as a hydrogenation catalyst even though there is a similarity between the catalytic activity of cobalt and nickel. Raney cobalt, which is prepared from a commercially available aluminum-cobalt alloy,2 -23 was found to be somewhat less active than Raney nickel and more sensitive to variations in the reaction procedure and catalyst age than the nickel catalyst.22,23... 

Raney cobalt is useful for the hydrogenation of oximes and nitriles to primary amines. 

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... 

A synthesis of the alkaloid narseronine 53 that highlights yet another novel mode of cyclisation of arylated cyclohexenes derived from compound 67 is shown Scheme 9 (White et al., unpublished work [45]). Thus, nitrile 73 (generated from precursor 67 during the course of our synthesis of the lycorine degradation product 79 as shown in Scheme 6) was reduced with dihydrogen in the presence of Raney-cobalt and the resulting primary amine was then protected as the corresponding... 

Poly(propylenimine) (PPI) dendrimers are another series of dendrimers that are commercially available. They are synthesized by the Michael addition of acrylonitrile followed by catalytic hydrogenation of the nitriles with Raney cobalt and hydrogen gas to primary amines [91]. They show a structural similarity to PAMAM dendrimers, with primary amines on the surface and tertiary amines in the interior, resulting in a similar DNA compaction activity and delivery efficiency into cells [92]. However, because of the relatively difficult synthetic procedure and lower delivery efficiency compared with PAMAM dendrimers, only a few reports regarding PPI-based delivery of nucleic acid dmgs have been published. Surface modification of the PPI dendrimer with arginine showed a significant enhancement of delivery efficiency [93]. 

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). 

Nickel in the presence of ammonia is often used for reduction of nitriles to primary amines. The reaction is done at elevated temperatures and pressures ( 100 C, 1000 psig) unless massive amounts of nickel are used. Cobalt is used similarly but mainly under even more vigorous conditions. Nitriles containing a benzylamine can be reduced over Raney nickel to an amine without hydrogenolysis of the benzyl group (7). A solution of butoxycarbonyl)-3-aminopropyl]-N-<3-cyanopropyl)benzylamine (13.6 g) in 100 ml of ethanol containing 4 g. NaOH was reduced over 3.0 g Raney nickel at 40 psig for 28 h. The yield of A/ -benzyl-Air -(f-butoxycarbonyl)s >ermidine was 95% (7). 

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. 

Cobalt boride catalysts have been shown to be highly active and selective in the hydrogenation of nitriles to primary amines.103,104 Barnett used Co boride (5%) supported on carbon for the hydrogenation of aliphatic nitriles and obtained highest yields of primary amines among the transition metals and metal borides investigated including Raney Co.104 An example with propionitrile, where a 99% yield of propylamine was obtained in the presence of ammonia, is seen in eq. 7.29. 

Urushibara Co catalysts can be prepared exactly in the same way as the corresponding Ni catalysts, using cobalt chloride hexahydrate instead of nickel chloride hexahydrate as starting material. Similarly as with Raney catalysts, Urushibara Co has been found to be more effective and selective than Urushibara Ni in the hydrogenation of nitriles, affording high yields of primary amines.105,106... 

The reduction can be carried out in batches or continuously at about 9,000 psig and 125 C in an ammonia atmosphere, over a cobalt-copper catalyst, in yields of over 90 per cent of theory. A number of other catalysts have been described for this reaction, including Raney nickel, cobalt on silica, and cobalt-silver-magnesium. The starting nitrile must be quite pure to avoid poisoning the catalyst. It is claimed that the presence of carbon monoxide, in addition to hydrogen and ammonia, extends the life of the cobalt catalysts normally used. ... 

---