Nitrile reduction

In nitrile reduction a nitrile is reduced to either an amine or an aldehyde with a suitable chemical reagent.[1][2]

Catalytic hydrogenation

The catalytic hydrogenation of nitriles is often the most economical route available for the production of primary amines.[3] Catalysts for the reaction often include group 10 metals such as Raney nickel,[4][5][6] palladium black, or platinum dioxide.[1] However, other catalysts, such as cobalt boride, also can be selective for primary amine production:

R-C≡N + 2 H2 → R-CH2NH2

Depending on reaction conditions, intermediate imines can also undergo attack by amine products to afford secondary and tertiary amines:

2 R-C≡N + 4 H2 → (R-CH2)2NH + NH3
3 R-C≡N + 6 H2 → (R-CH2)3N + 2 NH3

Such reactions proceed via enamine intermediates.[7] The most important reaction condition for selective primary amine production is catalyst choice.[1] Other important factors include solvent choice, solution pH, steric effects, temperature, and the pressure of hydrogen inside the hydrogenation vessel.

Industrial significance

A commercial application of this technology includes the production of hexamethylenediamine from adiponitrile, a precursor to Nylon 66.[8]

Non-catalytic routes to amines

Reducing agents for the non-catalytic conversion to amines include lithium aluminium hydride, lithium borohydride,[9] diborane,[10] or elemental sodium in alcohol solvents.[11]

Non-catalytic routes to aldehydes

Nitriles can also be reduced to aldehydes. For example, one method, called Stephen aldehyde synthesis, uses Tin(II) chloride and hydrochloric acid to yield an aldehyde via the hydrolysis of a resulting iminum salt. Aldehydes can also form using a hydrogen donor followed by in-situ hydrolysis of an imine. Useful reagents for this reaction include formic acid with a hydrogenation catalysis[12] or metal hydrides, such as sodium borohydride.

Electrochemical methods

Nitriles can also be reduced electrochemically.[13][14]

See also

References

  1. 1 2 3 Nishimura, Shigeo (2001). Handbook of Heterogeneous Catalytic Hydrogenation for Organic Synthesis (1st ed.). Newyork: Wiley-Interscience. pp. 254–277. ISBN 9780471396987.
  2. ↑ March, Jerry (1985), Advanced Organic Chemistry: Reactions, Mechanisms, and Structure (3rd ed.), New York: Wiley, ISBN 0-471-85472-7
  3. ↑ Karsten, Eller; Henkes, Erhard; Rossbacher, Roland; Höke, Hartmut (2000). "Amines, Aliphatic". Ullmann's Encyclopedia of Industrial Chemistry. doi:10.1002/14356007.a02_001.
  4. ↑ Biggs, B. S.; Bishop., W. S. (1947). "Decamethylenediamine". Organic Syntheses 29: 18. doi:10.15227/orgsyn.027.0018.
  5. ↑ Allen, C. F. H.; Wilson, C. V. (1947). "2,4-Diphenylpyrrole". Organic Syntheses 27: 33. doi:10.15227/orgsyn.027.0033.
  6. ↑ Robinson, John C.; Snyder, H. R. (1943). "β-Phenylethylamine". Organic Syntheses 23: 71. doi:10.15227/orgsyn.023.0071.
  7. ↑ J. Barrault, Y. Pouilloux "Catalytic Amination Reactions Synthesis of fatty amines. Selectivity control in presence of multifunctional catalysts" Catalysis Today 1997 Volume Pages 137–153. doi:10.1016/S0920-5861(97)00006-0
  8. ↑ Musser, Michael Tuttle (2000). "Adipic Acid". Ullmann's Encyclopedia of Industrial Chemistry. doi:10.1002/14356007.a01_269.
  9. ↑ Ookawa, Atsuhiro; Soai, Kenso (1986). "Mixed solvents containing methanol as useful reaction media for unique chemoselective reductions within lithium borohydride". The Journal of Organic Chemistry 51 (21): 4000–4005. doi:10.1021/jo00371a017.
  10. ↑ Hutchins, R. O.; Maryanoff, B. E. (1973). "2-tert-Butyl-1,3-diaminoproane". Organic Syntheses 53: 21. doi:10.15227/orgsyn.053.0021.
  11. ↑ Suter, C. M.; Moffett, Eugene W. (1934). "The Reduction of Aliphatic Cyanides and Oximes with Sodium and n-Butyl Alcohol". Journal of the American Chemical Society 56 (2): 487–487. doi:10.1021/ja01317a502.
  12. ↑ van Es, T.; Staskun, B. (1971). "4-Formylbenzenesulfonamide". Organic Syntheses 51: 20. doi:10.15227/orgsyn.051.0020.
  13. ↑ V. Krishnan, A. Muthukumaran, H. V. K. Udupa (1979). "The electroreduction of benzyl cyanide on iron and cobalt cathodes". Journal of Applied Electrochemistry 9 (5): 657–659. doi:10.1007/BF00610957.
  14. ↑ V. Krishnan, A. Muthukumaran, H. V. K. Udupa (1983). Process for Electrochemical Preparation of beta phenylethylamine using cobalt black cathode (PDF). Calcutta: India Patent Office.
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