Raney nickel catalysts modified

Conversion of the nitrile to the amide has been achieved by both chemical and biological means. Several patents have described the use of modified Raney nickel catalysts ia this appHcation (25,26). Also, alkaH metal perborates have demonstrated their utiHty (27). Typically, the hydrolysis is conducted ia the presence of sodium hydroxide (28—31). Owiag to the fact that the rate of hydrolysis of the nitrile to the amide is fast as compared to the hydrolysis of the amide to the acid, good yields of the amide are obtained. Other catalysts such as magnesium oxide (32), ammonia (28,29,33), and manganese dioxide (34) have also been employed. 

In 1956 it was found that when pyridine is refluxed with a modified Raney-nickel catalyst, 2,2 -bipyridine (1) is formed in satisfactory yield. The isomeric bipyridines could not be detected, and the product was readily purified. Similar heterocyclic biaryls have been formed in the same way from substituted pyridines and from some related compounds, the yield being dependent on the nature of the compound. The reaction has become the method of choice for the preparation of 2,2 -bipyridine, and it is now used on an industrial scale. Bipyridyls are of particular importance as chelating agents. 

UHV surface analysis, apparatus designs, 36 4-14 see also Ultrahigh vacuum surface analysis mechanisms, 32 313, 319-320 Modified Raney nickel catalyst defined, 32 215-217 hydrogenation, 32 224-229 Modifying technique of catalysts, 32 262-264 Modulated-beam mass spectrometry, in detection of surface-generated gas-phase radicals, 35 148-149 MojFe S CpjfCOlj, 38 352 Molar integral entropy of adsorption, 38 158, 160-161... 

The V-modified Raney nickel catalyst showed noticeable stability in time-on-stream experiment for 55 h, and tolerated several heating-cooling cycles. It is... 

Pyridine is converted by a modified Raney nickel catalyst into 2,2 -bipyridyl, and the reaction has been extended to many substituted pyridines and quinolines. 2-Substituted pyridines give the 6,6 -bipyridyls. 3-Methylpyridine gives 5,5 -dimethyl-2,2 -bipyridyl, but none of the other isomers. 

The Ni/tartaric acid/NaBr catalyst system has been extensively studied. A variety of ketone substrates have been reduced with Ni/tartaric acid/NaBr catalysts with variable enantioselectivities, but the highest (>85% ee) are obtained for the reductions of P-keto esters and P-diketones (Schemes 12.60 and 12.61).5 Asymmetric reduction of diketones results in the formation of mesa and chiral diols. The highest meso chiral diol ratio of 2 98 and enantioselectivities of 98% ee are obtained with modified Raney nickel catalysts treated by sonication.5... 

Hoffmann-LaRoche has developed a process that uses R,R-tartaric acid/NaBr modified Raney nickel catalyst in the asymmetric hydrogenation of 160 to give 161 in 100% yield and 90-92% ee (6-100-kg scale) for the synthesis of the intermediate of tetrahydrolipstatin (162), a pancreatic lipase inhibitor (Scheme 12.62).5... 

Conversion and selectivity data obtained in the alkylation of ammonia with n-propanol over different Raney nickel catalysts are listed in Table 1. Data given in Table 1 indicate that n-Pr2NH can be obatined on unmodified and vanadium modified Raney nickel catalyst with 70-72 % selectivities at 92-95 % conversions. Upon modifying the Raney nickel catalyst with Mg the selectivity of the secondary amine increased to 74-75 % at 94-97 % conversions. The increase of the reaction temperature from 225 to 245 resulted in slight increase of the conversion and the selectivity to the primary amine both on unmoified and Mg modified catalysts. The introduction of V or Mg modifiers affected both the selectivity of the secondary amine and the ratio of primary to tertiary amines. 

Effect of NH3/n-PrOH molar ratio on the selectivities in the alkylation of ammonia with n-propanol over vanadium modified Raney nickel catalyst (T= 225 °C, WHSV=1.4 h" H2/NH3=3, conversion of n-PrOH=93-95 %). 

Raney nickel modified with Mg or V can be used for the highly selective preparation of symmetrical amines by the alkylation of ammonia with n-propanol or i-butanol. Upon modifying the Raney nickel catalyst with 0.5 wt % V or Mg, 4-5 % increase in the selectivity to secondary amines was observed and the selectivities reached 70-80 % at 90-95 % conversions. In the alkylation of ammonia with an alcohol symmetrical secondary amines can be obtained with 70 % yield over Mg or V modified Raney nickel catalyst at 220-240 °C and ammonia/alcohol ratio of 1.5. In an industrial application 2-4 % increase of the selectivity results in an important finantial benefit. It was shown that pure (100 %) ethylamine and 70 % EtNH2 in water can be used for the preparation of N-ethyl-N-butylamine over a commercial Cu0-Zn0-Al203 catalyst. 

Fukawa, H., Izumi, Y., Komatsu, S., and Akabori, S. (1962) Studies on modified hydrogenation catalyst. 1. Selective hydrogenation activity of modified Raney nickel catalyst for carbonyl group and C=C double bond. Bull. Chem. Soc. Jpn., 35, 1703-1706. 

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