N-Nitrosoacylarylamines

Abstract

The decompositions of N-nitrosoacylarylamines in benzene and in carbon tetrachloride have been investigated. The reaction products of N-nitrosobenzanilldes parallel those of N-nitrosoacetanilides, carboxylic acids being the major products from almost all reactions carried out in both benzene and carbon tetrachloride. Carboxylic anhydrides, hitherto unreported products, have been isolated from reactions in carbon tetrachloride. The observed displacement of a bromo or uitro substituent in o- or p-positions in the amino moiety of the nitrosoamide by a chloride or benzoate ion during the formation of aryl halides and substituted phenyl benzoates is in contrast to Suschitsky's results. In general, the major part of the reaction appears to be abstraction by a carboxylate anion of hydrogen from the o-position in the amino moiety of the nitrosoamide to form the carboxylic acid. However, when both o-positions in the amino moiety of the nitrosoamide are substituted, the reaction proceeds primarily by nucleophilic displacement of a substituent by the carboxylate anion. The decomposition of N-nitrosoacetanilide in carbon tetrachloride gives a benzynoid-type adduct with 2,3,4,5-tetraphenylcyclopentadienone, with consequent suppression of the formation of chlorobenzene, which is a major product from a reaction carried out in the absence of the above diene. Appropriate benzynoid-type adducts are also formed in reactions of N-nitrosobenzanilides with 2,3,4,5 tetraphenylcyclopentadienone and with anthracene, but not with furan. By the use of substituted N-nitrosobenzanilides, it has been shown that, for appreciable adduct formation with 2,3,4,5-tetraphenylcyclopentadienone, a substituent must be in the m-position in the amino moiety, i.e. o- or p- to the hydrogen which is being removed in the formation of the carboxylic acid. The nature of the acyl moiety of the molecule has some influence on the formation of the adduct, but the nature of the solvent appears to have little influence on the yield of adduct formed. In reactions in which high yields of benzynoid-type adducts are obtained, the only other major product isolated is the appropriate carboxylic acid. True aryne intermediates are discounted, and it is suggested that the intermediate is dipolar in nature. A reaction scheme involving radicals, previously suggested by Riichardt et al. can be modified to account for the reaction in benzene. The reaction in carbon tetrachloride, however, appears to follow a different reaction path, and probably involves radicals to a slight extent only, the main reaction being ionic.