Polymethine dyes, process of making them and photographic elements containing them

摘要

1-Phenacylpyridinium bromide is prepared by allowing a mixture of a -bromo-acetophenone and pyridine to stand at room temperature and then adding ether to precipitate the product. 1-Cyanomethylpyridinium chloride is prepared by allowing a mixture of chloro-acetonitrile and pyridine to stand at room temperature followed by heating on a steam bath. The pyridine used may be substituted by a bromine atom or a methyl group in the 3-position or by a phenyl group, or quinoline may be used to give the corresponding quinolinium compounds.ALSO:Polymethine dyes having the general formula I wherein R is an alkyl or substituted alkyl group of 1 to 6 carbon atoms or an aralkyl or allyl group, Z completes a 5- or 6-membered heterocyclic nucleus, d is 0 or 1, n is 1, 2 or 3, Q is a pyridinium or quinolinium group, substituted or not, and joined to the carbon atom through its nitrogen atom, W is a benzoyl or cyano group and X is an anion, are prepared by condensing a cyclammonium salt of the formula II wherein R2 is an acyl group, R3 is an aryl group and Y is an anion, with a pyridinium or quinolinium salt of the formula III wherein Y1 is an anion. Examples are given of the preparation of dyes wherein Z completes a benzthiazole, benzoxazole or 4-quinoline nucleus. The pyridinium group Q may carry a bromine atom or methyl group in the 3-position or a phenyl substituent.