By Dehydration of Amides

Dehydration of carbamoylpyrazines to cyanopyrazines has been described in Section 3C(1). 

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Both alkyl and aryl nitriles are accessible by dehydration of amides... 

Section 20 18 Nitnles are prepared by nucleophilic substitution (8 2) of alkyl halides with cyanide ion by converting aldehydes or ketones to cyanohydrins (Table 20 6) or by dehydration of amides... 

Eatty amines are made by dehydration of amides to nitriles at 280—330°C, followed by hydrogenation of the nitrile over nickel or cobalt catalysts ... 

Nitriles contain the cyano group, —C=N. Although nitriles lack the carbonyl group of carboxylic acids, they are classified as acid derivatives because they hydrolyze to give carboxylic acids and can be synthesized by dehydration of amides. 

Another widely used method involves hydrolysis of cyanopyrida-zines. These are usually obtained from cyclizations of open-chain cyano compounds (synthesis of 4-cyano-3(2/7)-pyridazinone and its methyl analogs ), since replacement of a halogen atom by cyano group proceeds with pyridazines in low yields or not at all. Many cyanopyridazines have been obtained by dehydration of amides, such as 3- or 4-cyanopyridazine, 3-chloro-6-cyanopyridazine or 6-cyano-2-methyl-3(2.ff)-pyridazinone, and 3-chloro-4-cyano-... 

Dehydration of amides. Nitriles are conveniently prepared by dehydration of amides with PPE.7 The amide (1 part) and PPE (5 parts) are refluxed in chloroform for about two hours. Yields are in the range 35-90%. 

FIGURE 18.57 Nitriles are usually made through Sn2 reactions using cyanide as the nucleophile. Nitriles can also be formed by dehydration of amides. 

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