Diphenylamines, reaction with carboxylic acids

Many acridines and benzacridines have been synthesized by the Bernthsen reaction (l884LA(224)l) in which a diphenylamine is heated with a carboxylic acid and zinc chloride, with or without aluminum chloride. The reaction has been reviewed (73HC(9)141), and will be outlined here. The yields are not generally high one of the better examples is the synthesis of 2-chloro-9-methylacridine (312) (63BCJ1477). In the synthesis of the... 

In lubricating compositions, these compounds show excellent antioxidant synergy with aromatic amines such as alkylated diphenylamines [43] and sulphur compounds such as metal dihydrocarbyl dithiophosphate, a metal dithiocarbamate, sulphurised olefins, alkyl and aryl sulphides, alkyl and aryl polysulphides, sulphurised carboxylic acid esters, sulphurised alkylphenols, reaction product of an olefin and sulphurised alkylphenol, and phosphosulphurised terpenes or mixtures thereof [43],... 

Acridines are an important structural feature of many natural products and medicinally important compounds. They can be produced in a straightforward manner by a Friedel-Crafts reaction, the Bernthsen acridine synthesis, 1 9 which couples diaryl amines (such as diphenylamine) with a carboxylic acid (such as benzoic acid) in the presence of a Lewis acid (zinc chloride, ZnCl2, is a typical reagent). Heating to 260°C (10 h) gave a 48% yield of acridine 317.1 9 ... 

This reaction was first reported by Bernthsen in 1878It is one of the earliest methods for the synthesis of acridine by heating diphenylamine hydrochloride with benzonitrile. Therefore, this reaction is generally known as the Bernthsen reaction. In the modified method, the mixture of diphenylamine, an aromatic or aliphatic carboxylic acid, and zinc chloride is heated at 200-270°C for 20 Heating zinc chloride with fV-acyldiphenylamine or a mixture of diphenylamine and acyl chloride also affords acridines. ... 

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