Nitrile reduction#Catalytic hydrogenation

The catalytic hydrogenation of nitriles is often the most economical route available for the production of primary amines.{{cite journal|last1=Karsten|first1=Eller|last2=Henkes|first2=Erhard|last3=Rossbacher|first3=Roland|last4=Höke|first4=Hartmut|title=Amines, Aliphatic|journal=Ullmann's Encyclopedia of Industrial Chemistry|date=2000|doi=10.1002/14356007.a02_001|isbn=3527306730}} Catalysts for the reaction often include group 10 metals such as Raney nickel,{{cite journal|last1=Biggs|first1=B. S.|last2=Bishop|first2=W. S.|title=Decamethylenediamine|journal=Organic Syntheses|date=1947|volume=29|page=18|doi=10.15227/orgsyn.027.0018}}{{cite journal|last1=Allen|first1=C. F. H.|last2=Wilson|first2=C. V.|title=2,4-Diphenylpyrrole|journal=Organic Syntheses|date=1947|volume=27|page=33|doi=10.15227/orgsyn.027.0033}}{{cite journal|last1=Robinson|first1=John C.|last2=Snyder|first2=H. R.|title=β-Phenylethylamine|journal=Organic Syntheses|date=1943|volume=23|page=71|doi=10.15227/orgsyn.023.0071}} palladium black, or platinum dioxide. However, other catalysts, such as cobalt boride, also can be regioselective for primary amine production:

: R-C≡N + 2 H₂ → R-CH₂NH₂

A commercial application of this technology includes the production of hexamethylenediamine from adiponitrile, a precursor to Nylon 66.{{cite journal|last1=Musser|first1=Michael Tuttle|title=Adipic Acid|journal=Ullmann's Encyclopedia of Industrial Chemistry|date=2000|doi=10.1002/14356007.a01_269|isbn=3527306730}}

Depending on reaction conditions, reactive 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.{{cite journal | doi = 10.1016/S0920-5861(97)00006-0 | volume=37 | title=Synthesis of fatty amines. Selectivity control in presence of multifunctional catalysts | year=1997 | journal=Catalysis Today | pages=137–153 | last1 = Barrault | first1 = J.| issue=2 }} The most important reaction condition for selective primary amine production is catalyst choice. Other important factors include solvent choice, solution pH, steric effects, temperature, and the pressure of hydrogen.

Reducing agents for the non-catalytic conversion to amines include lithium aluminium hydride, lithium borohydride,{{cite journal|last1=Ookawa|first1=Atsuhiro|last2=Soai|first2=Kenso|title=Mixed solvents containing methanol as useful reaction media for unique chemoselective reductions within lithium borohydride|journal=The Journal of Organic Chemistry|date=1986|volume=51|issue=21|pages=4000–4005|doi=10.1021/jo00371a017}} diborane,{{cite journal|last1=Hutchins|first1=R. O.|last2=Maryanoff|first2=B. E.|title=2-tert-Butyl-1,3-diaminoproane|journal=Organic Syntheses|date=1973|volume=53|page=21|doi=10.15227/orgsyn.053.0021}} or elemental sodium in alcohol solvents.{{cite journal|last1=Suter|first1=C. M.|last2=Moffett|first2=Eugene W.|title=The Reduction of Aliphatic Cyanides and Oximes with Sodium and n-Butyl Alcohol|journal=Journal of the American Chemical Society|date=1934|volume=56|issue=2|pages=487|doi=10.1021/ja01317a502}}

Nitriles can also be converted to aldehydes by reduction and hydrolysis. The Stephen aldehyde synthesis uses Tin(II) chloride and hydrochloric acid to yield an aldehyde via the hydrolysis of a resulting iminium 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{{cite journal|last1=van Es|first1=T.|last2=Staskun|first2=B.|date=1971|title=4-Formylbenzenesulfonamide|journal=Organic Syntheses|volume=51|page=20|doi=10.15227/orgsyn.051.0020}} or metal hydrides, which are used to add one mol of hydrogen to the nitrile. For example, sodium borohydride reduces nitriles in alcoholic solvents with a CoCl₂ catalyst or Raney nickel.{{Cite book|title=March's advanced organic chemistry : reactions, mechanisms, and structure.|last=Smith|first=Michael|date=October 2001|publisher=Wiley|last2=March|first2=Jerry|isbn=9780471585893|edition= 5th|location=New York|oclc=43936853}}

File:DIBAL_mechanism_.tif

The hydride reagent Diisobutylaluminium hydride, or DIBAL-H, is commonly used to convert nitriles to the aldehyde.Carey, F. A.; Sundberg, R. J.; Advanced Organic Chemistry, Part B: Reactions and Synthesis Regarding the proposed mechanism, DIBAL forms a Lewis acid-base adduct with the nitrile by formation of an N-Al bond. The hydride is then transferred to the carbon of the nitrile. Aqueous workup produce the desired aldehyde and ammonia.Solomons, T W. G, Craig B. Fryhle, and S A. Snyder. Organic Chemistry. , 2014. Print.

Benzyl nitriles can also be reduced electrochemically.{{cite journal|author1=V. Krishnan |author2=A. Muthukumaran |author3=H. V. K. Udupa|author3-link=H.V.K. Udupa |title=The electroreduction of benzyl cyanide on iron and cobalt cathodes|journal=Journal of Applied Electrochemistry|year=1979|volume=9|issue=5|pages=657–659|doi=10.1007/BF00610957|s2cid=96102382 }}{{cite book|author1=V. Krishnan |author2=A. Muthukumaran |author3=H. V. K. Udupa |title=Process for Electrochemical Preparation of beta phenylethylamine using cobalt black cathode|year=1983|publisher=India Patent Office|location=Calcutta|url=http://cecri.csircentral.net/2305/1/151691.pdf}}

• Urushibara cobalt
• Imine

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Category:Organic reduction reactions