Preparation of Amines by Reduction

Three of the following amines can be prepared by the Gabriel synthesis three cannot. Write equations showing the successful applications of this method. 

Almost any nitrogen-containing organic compound can be reduced to an amine. The synthesis of amines then becomes a question of the availability of suitable precursors and the choice of an appropriate reducing agent. 

Alkyl azideSy prepared by nucleophilic substitution of alkyl halides by sodium azide, as shown in the first entry of Table 21.3, are reduced to alkylamines by a variety of reagents, including lithium aluminum hydride. 

In its overall design, this procedure is similar to the Gabriel synthesis a nitrogen nucleophile is used in a carbon-nitrogen bond-forming operation and then converted to an amino group in a subsequent transformation. 

The same reduction methods may be applied to the conversion of nitriles to primary amines. 

Since nitriles can be prepared from alkyl halides by nncleophilic substitntion with cyanide ion, the overall process RX RC=N RCH2NH2 leads to primary amines that have one more carbon atom than the starting alkyl halide. 

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This procedure illustrates a general method for the preparation of amines by reductive cleavage of sulfonamides by hydrobromic acid in the presence of phenol.9 The present synthesis makes 1,3-dihydroisoindole readily accessible and is superior in certain respects to the other two practical methods of preparation. Thus the method here described is shorter and gives a higher overall yield than the three-step synthesis of Neumeyer,7 and obviates the special apparatus and careful control required by the electrochemical process of Dunet, Rollet, and Willemart.4... 

Alkyl groups may be introduced into ammonia, a primary amine, or a secondary amine by means of an aldehyde or ketone in the presence of a reducing agent, such as molecular hydrogen and a catalyst, active metals and acids, or formic acid or one of its derivatives. When the reducing agent is formic acid or a derivative, the reaction is known as the Leuckart reaction and is discussed elsewhere (method 432). An excellent review of the preparation of amines by reductive alkylation has been presented. This article includes a discussion of the scope and utility of the reaction, a selection of experimental conditions, illustrative preparations, and a tabulation of primary, secondary, and tertiary amines prepared thereby. ... 

The Preparation of Amines by Reductive Alkylation William S. Emerson... 

Preparation of the N-H bond by exchange a. Preparation of amines by reduction of nitro compounds (RN02 ------------------> RNH2)... 

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