Acetic anhydride with arylamines

Direct nitration of aniline and other arylamines fails because oxidation leads to the formation of dark colored tars As a solution to this problem it is standaid practice to first protect the ammo group by acylation with either acetyl chloride or acetic anhydride... 

The required arylamine 973 was prepared starting from the aryl acetate 937. The compound 937 was also used for the palladium(II)-catalyzed total synthesis of carbazoquinocin C (274) (545) (see Scheme 5.124) and carbazomycin G (269) (652). The acetate 937 was transformed to the corresponding 5-nitro derivative 974 by reacting with fuming nitric acid in a mixture of acetic anhydride and glacial acetic... 

All the syntheses of this type give piperid-4-ones or pyrid-4-ones. Errera reported that diethyl acetonedicarboxylate condensed with triethyl orthoformate in hot acetic anhydride, and that treatment of the product with ammonia gave a poor yield of the pyrid-4-one (644) (1898CB1682). It is certain that the intermediate is the di(ethoxyvinyl) ketone (643), so that this is perhaps better classified as a [5 + 1] synthesis, but most developments from this beginning do not involve isolation of intermediates. An arylamine has been used to obtain an A-arylpyrid-4-one (645) (46JA1253). 

Any of the customary reducing agents suitable for converting aryl nitro groups to arylamines (Fe, HC1 Sn, HC1 H2, Ni) may be used. Acetylation of p-aminophenol may be carried out with acetyl chloride or acetic anhydride. The amino group of p-aminophenol is more nucleophilic than the hydroxyl group and is acetylated preferentially. 

Treatment of amine oxides containing at least one nitrogen-attached methyl group with acetic anhydride, results in the Polonovski reaction (reaction 65) product studies on which indicate the involvement of radicals . The reaction is also catalysed by Fe(ni) and by many transition-metal complexes (reaction 66) . These reactions have been studied as models for the bacterial degradation of nicotine which involves iV-oxidation as the first step . JV Arylamine oxides give considerable amounts of o-acetylarylamines on treatment with acetic anhydride, presumably via cyclisation from the N-ace-tate , and similar migrations are common for heterocyclic... 

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