Aniline derivatives reaction with nitrous acid

Aniline reacts with nitrous acid to give benzenediazonium salts, which react with a variety of reagents via a substitution reaction. These reagents include cuprous salts, aqueous acid, iodide, hypophosphorous acid, and activated benzene derivatives. Nucleophilic substitution at the sp carbon of a halo-benzene derivative does not occur unless high heat and pressure are used. Electron-withdrawing substituents on the benzene ring significantly lower the temperature required for the reaction. Nucleophiles for this nucleophilic aromatic substitution reaction include water, hydroxide, alkoxide, and amines. 

Hydrolyses of aminopyridopyrimidines to the corresponding pyridopyrimidones by means of acid, base, and nitrous acid have been reported. 4-Amino compounds are stable to nitrous acid, but are much more labile than the 2-amino derivatives toward acid- or base-catalyzed hydrolysis. The aminochloro-pyrido[2,3-d]pyrimidine (160) has been converted into the 2,4-dianilino analog (161) by reaction with aniline." ... 

These reactions involve a diazonium ion (see 12-47) and are much faster than ordinary hydrolysis for benzamide the nitrous acid reaction took place 2.5 x lo times faster than ordinary hydrolysis. Another procedure for difficult cases involves treatment with aqueous sodium peroxide. In still another method, the amide is treated with water and f-BuOK at room temperature. " The strong base removes the proton from 107, thus preventing the reaction marked k j. A kinetic study has been done on the alkaline hydrolyses of A-trifluoroacetyl aniline derivatives. Amide hydrolysis can also be catalyzed by nucleophiles (see p. 427). 

---