GB896219A - Process for the manufacture of 2:5-disubstituted oxdiazoles - Google Patents

Abstract

1 : 3 : 4-Oxdiazoles substituted in the 2 : 5 position are prepared by condensing in the presence of meta-, pyro-or polyphosphoric acid a hydrazine salt of a meta-, pyro-, or polyphosphoric acid with a monocarboxylic acid or ester having one or two non condensed rings and in which any amino group present in a benzene residue in a para-position with respect to the carboxyl group is a primary amino group. The carboxylic acids may be heterocyclic, for example, furancarboxylic, thiophenecarboxylic, coumalic, picolinic, nicotinic, and isonicotinic, or aromatic, e.g. benzoic, or the carboxyl group may be bound to such a ring directly or through a -CH2- or -CH=CH- group, e.g. phenyl acetic, cinnamic and methylcinnamic acids. Monocarboxylic acids may be of general formula <FORM:0896219/IV (b)/1> X represents hydrogen, or an alkyl or phenyl radical or an H2N group, Y hydrogen, an alkyl group, or a hydroxyl group in o-position to the carboxyl, and Z, hydrogen, alkyl or alkylamino group or a nitro group in o-position to X, and acids preferred are benzoic and alkyl benzoic, and hydroxy benzoic or alkyl benzoic. The "polyphosphoric acids" are of general formula, Hn+2PnO3n+1, where n is at least 3, and they are derived from orthophosphoric acid and phosphorus pentoxide. The condensation may be carried out in an excess of polyphosphoric acid with the excess serving as a solvent or solvents such as benzene, trichlorobenzene, nitrobenzene or tetrahydrofuran may be used and the reaction is performed between 80 DEG C. and 200 DEG C. Examples describe the preparation of 2 : 5-bis-[phenyl-(11)], 2 : 5-bis-[41-aminophenyl-(11)], 2 : 5 - bis - [51 - methyl - 21 - hydroxyphenyl(11)], 2 : 5-bis-[21-hydroxyphenyl-(11)]-1 : 3 : 4 oxdiazoles and other compounds with methyl, dimethyl, t-butyl, methoxy, hydroxy, hydroxymethyl, monochloro or bromo and dichloro or dibromo hydroxy, nitro, dimethylamino phenyl, diphenyl, hydroxyphenylyl, styryl, benzyl, and pyridyl substituents in the bis-2 : 5 positions. The compounds may be employed as U.V. light absorbers, optical brighteners, bactericides, dyestuffs or dyestuff or dyestuff and plastic intermediates.