Some substituent interactions of substituted o-nitroanilines

Abstract

An introduction to the methods of preparation and some general properties of benzimidezele-N-oxidec are discussed in Chapter 1. In Chapter 2, the reaction of N-P-nitrobenzyl-N-P-tolylsulphonyl-o-nitroaniline with sodium methoxide in methanol to give 2-p-nitrophenylbenzimidazole-3-oxide is discussed. With the aid of reaction kinetics a mechanism which involves cyclisation prior to detosylation is established. The corresponding reactions of N-methylsulphonyl, N-acetyl and N-benzoyl-N-P-nitrobenzyl-o-nitroaniline with sodium methoxide similarly involve cyclisation prior to deacylation, For the corresponding cyclisations of N-acetyl and N-benzoyl-N-banzylo-nitroaniline to 2-phenylbenzimidazole-3-oxide, a mechanism involving deacylation prior to cyclisation is proposed, The reaction of N-p-nitrobenzyl-N-p-tolylsulphonyl-2 ,4-di- nitroanilina and K"benzyl-N-p-tolylsulphonyl-2 , 4-dinitroaniline with sodium methoxide does not give expected cyclised product, but gives instead N-p-tolylsulphonyl-2,4-dinitroaniline. Various mechanisms to account for these results are discussed The reaction of ethyl N-o-nitrophenylcarbamate with base and p-nitrobenzy 1bromide gives along with the expected product N-ethoxycarbony1-N-p-nitrobenzyl-o-nitroaniline, l-p-nit robenzyloxy-2-p-nitrophenylbenzimidazole. In Chapter 3, the reaction of N-phenacyl-N-p-tolylsulphony1-o-nitroaniline and various substituted analogues with a selection of bases is discussed. The major product of these reactions in which the base is methoxide, ethoxide, and n-propoxide is the corresponding a-2-alkoxybensimidazole-3-oxide. A mechanism for this reaction is proposed and the steps taken to verify it discussed. The scope and limitations of this type of reaction are considered. Chapter 4 deals with the attempted synthesis of a reaction intermediate, namely l-p-tolylsulphonylbenzimidazole-3-oxcide, postulated in the reaction scheme used to explain the formation of the 2-alkoxybenzimidazole-3-oxides.