GB563691A - Improvements relating to phenazinium salts and their use in photographic emulsions and developers - Google Patents

Abstract

Azine dyes, which are 1 : 3-diamino-N-alkyl (or substituted alkyl) phenazinium salts, and are suitable for use as desensitizers in photographic silver salt emulsions and in photographic developers, are obtained by reducing the corresponding dinitro-N-alkyl (or substituted alkyl) 5 : 10-dihydrophenazines in presence of an acid. Such reduction may be effected with a reducing metal salt of the acid present. Specified dinitro compounds used as starting materials are the 5-methyl-, 5-ethyl-, 5-benzyl-and 5 - b - hydroxyethyl - 1 : 3 - dinitro - 5 : 10-dihydrophenazines. In examples, (1) to (4), 5-methyl-, 5-ethyl-, 5-b -hydroxyethyl- and 5-benzyl - 1 : 3 - dinitro - 5 : 10 - dihydrophenazines respectively are heated with stannous chloride and hydrochloric acid in alcohol under reflux to obtain the correspondingly 5-substituted 1 : 3-diamino-phenazinium chlorides. In examples (5) and (6), 5 - methyl - 1 : 3 - dinitro - 5 : 10 - dihydrophenazine is heated with (5) iron powder, (6) tin, and hydrochloric acid in alcohol under reflux to obtain 5-methyl-1 : 3-diamino-5 : 10-dihydrophenazinium chloride. 5 - Alkyl (or substituted alkyl) - 1 : 3 - dinitro - 5 : 10-dihydrophenazines are obtained by heating the corresponding N-alkyl (or substituted alkyl)-o-picrylaminoaniline with sodium hydroxide in methyl alcohol under reflux. N-alkyl (or substituted alkyl)-o-picrylaminoanilines are obtained by condensation of picryl chloride with the corresponding o-amino-N-alkyl-aniline, obtained by condensation of o-nitrochlorobenzene with the corresponding alkylamine and reduction of the nitro group with sodium hydrosulphite.