Reductions of nitrogen containing functional groups:

• reduction of azides, yields primary amines
• reduction of nitriles, yields primary amines
• reduction of nitro groups, yields primary amines
• reduction of amides, yields primary, secondary or tertiary amines

Reduction of Azides

Summary

• Azides, R-N₃, can be reduced to primary amines, R-NH₂
• Reagents : either lithium aluminum hydride (LiAlH₄) / ether solvent or catalytic hydrogenation (e.g. H₂/Pd)
• Alkyl azides are prepared by nucleophilic substitution (S_N2) by azide ion, N₃^-, of primary or secondary alkyl halides.

• Reduction of Nitriles
• Reduction of Nitro compounds
• Reduction of Amides

Reduction of Nitriles

Summary

• The nitrile, RCºN, is reduced to the 1^o amine by conversion of the CºN to R-CH₂-NH₂
• Reagents : either lithium aluminum hydride (LiAlH₄) / ether solvent or catalytic hydrogenation (e.g. H₂/Pd).
• Alkyl nitriles are prepared by nucleophilic substitution (S_N2) by cyanide ion, CN^-, of primary or secondary alkyl halides.
• Aryl nitriles can also be reduced to aryl amines.

Questions
What is the oxidation state of the nitrile C in acetonitrile, CH₃CN  ?  
What is the oxidation of the same C atom in acetonitrile, CH₃CN after reaction with LiAlH₄ ?  

Related reactions

• Reduction of Azides
• Reduction of Nitro compounds
• Reduction of Amides
  

Reduction of Nitro Compounds

Summary

• Nitroarenes can be reduced to primary aryl amines (see scheme).
• Typical reducing agents include, Fe / H⁺, Sn / H⁺ or catalytic hydrogenation (e.g. H₂ / Pd)
• Nitroarenes are prepared by the nitration of aromatics.
• This is probably the most important method for the synthesis of anilines (Ar-NH₂)  and, therefore, accessing the chemistry of diazonium compounds.

• Reduction of Azides
• Reduction of Nitriles
• Reduction of Amides

Reduction of Amides

Reactions usually in Et₂O or THF followed by H₃O⁺ work-ups

Summary

• Amides, RCONR'₂, can be reduced to the amine, RCH₂NR'₂ by conversion of the C=O to -CH₂-
• Amides can be reduced by LiAlH₄ but NOT the less reactive  NaBH₄
• Typical reagents :  LiAlH₄  / ether solvent followed by aqueous work-up.
• Note that this reaction is different to that of other C=O compounds which reduce to alcohols
• The nature of the amine obtained depends on the substituents present on the original amide.

ook at the N substituents in the following examples (those bonds don't change !)

• R, R' or R" may be either alkyl or aryl substituents.
• In the potential mechanism shown below, note that it is an O system that leaves. This is consistent with O systems being better leaving groups that the less electronegative N systems.

     Reduction of Azides
     Reduction of Nitriles
     Reduction of Nitro compounds
     Reduction of Carboxylic acids and Esters
 
 

REACTION OF LiAlH4 WITH AN AMIDE
Step 1: The nucleophilic H from the hydride reagent adds to the electrophilic C in the polar carbonyl group of the ester. Electrons from the C=O move to the electronegative O creating an intermediate metal alkoxide complex.
Step 2: The tetrahedral intermediate collapses and displaces the O as part of a metal alkoxide leaving group, this produces a highly reactive iminium ion an intermediate.
Step 3:  Rapid reduction by the nucleophilic H from the hydride reagent as it adds to the electrophilic C in the iminium system. p electrons from the C=N move to the cationic N neutralizing the charge creating the amine product.

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