GB602334A - Improvements in or relating to the manufacture of 2:7-disubstituted acridones and reduction products thereof - Google Patents

Abstract

2 : 7-Disubstituted acridones in which the substituents each contain a nitrogen atom directly linked to a nuclear carbon atom, e.g. 2 : 7-diaminoacridone of the formula <FORM:0602334/IV(b)/1> are prepared by heating a 31 : 4-disubstituted diphenylamine-2-carboxylic acid of the general formula <FORM:0602334/IV(b)/2> wherein R1 represents an amino group, a mono- or dialkylamino group, an acylamido or a nitro group and R2 represents an amino group, a mono- or dialkylamino group or an acylamido group with sulphuric acid. Preferably concentrated sulphuric acid of at least 98 per cent concentration is used and, if desired, phosphoric and/or anhydrous boric acid may be present. When R1 and/or R2 represents an acylamino group or groups, the cyclisation of the diphenylamine-2-carboxylic acid is usually accompanied by simultaneous deacylation. When R1 represents a nitro group, the resulting 2 : 7-substituted-acridone may be reduced by standard methods to yield 2 : 7-diaminoacridone, e.g. by the action of tin and hydrochloric acid or stannous chloride and hydrochloric acid and decomposing the stannichloride formed with aqueous alkali. The resulting 2 : 7-diaminoacridone may be reduced with an alkali metal amalgam in neutral or alkaline solution, e.g. sodium amalgam may be used, to yield 2 : 7-diaminoacridone which may be oxidized with oxygen in the presence of a ferric salt, e.g. ferric chloride, to yield 2 : 7-diaminoacridine. In examples: (1) 2 : 7-diaminoacridone is prepared by heating 31-amino-4-acetylamino-diphenylamine-2-carboxylic acid with concentrated sulphuric acid; (2) 2-amino-7-nitroacridone is similarly prepared from 31-amino-4-nitrodiphenylamine-2-carboxylic acid and is reduced to 2 : 7-diaminoacridone with stannous chloride and hydrochloric acid; (3) 2-amino-7-nitroacridone is prepared as in (1) from 31-acetamido-4-nitro-diphenylamine-2-carboxylic acid. 31-Amino- and 31-acetamido-4-nitro-diphenylamine-2-carboxylic acids are obtained by condensing 2-chloro-5-nitrobenzoic acid with metaphenylene diamine and if necessary acylating with acetic anhydride. 31 - Amino - 4 - acetylamino - diphenylamine - 2 - carboxylic acid is prepared by condensing metaphenylene diamine with 5-acetylamino-2-chlorobenzoic acid which may be prepared by reducing 5-nitro-2-chlorobenzoic acid and acylating. Specification 602,331 is referred to.