Patent GB-828847-A (GB)
Title: Improvements in or relating to cyanine dyes
Inventor: DUFFIN GEORGE FRANK
IPC: C09B23/10
Filed: 1956-12-14
Abstract: Compounds of the general formula <FORM:0828847/IV (b)/1> wherein R1 is hydrogen or an aryl group, R2 is hydrogen or a carboxylic acyl or arylsulphonyl group, and R3 is an aryl or substituted aryl group, are prepared by the base-catalysed rearrangement of tetronic acid aryl hydrazones of the formula <FORM:0828847/IV (b)/2> to give compounds wherein R2 is H, followed by acylation, if required, to give compounds wherein R2 is carboxylic acyl or arylsulphonyl.  An example is given of the preparation of 3-a -hydroxybenzyl-1-phenyl-5-pyrazolone from g -phenyltetronic acid phenylhydrazone using sodium ethoxide. 3-a -Hydroxymethyl- and 3-a -hydroxybenzyl - 1 - p - chlorophenyl - 5 - pyrazolones are similarly prepared.  An example also is given of the treatment of tetronic acid phenyl hydrazone with sodium ethoxide to give 3-hydroxymethyl-1-phenyl-5-pyrazolone which is not isolated. Tetronic acid phenylhydrazone is prepared by dissolving a -ethoxycarbonyl-tetronic acid in aqueous caustic soda, acidifying with conc.  HCl whereupon CO2 is evolved, and treating the product at 0 DEG  C. with phenylhydrazine in the presence of sodium acetate and acetic acid.  Tetronic acid - p - chlorophenylhydrazone is similarly prepared.  g -Phenyltetronic acid phenylhydrazone is prepared by dissolving g -phenyltetronic acid in aqueous acetic acid and adding phenylhydrazine.  g  - Phenyltetronic acid - p - chlorophenylhydrazine is similarly prepared.  According to the Provisional Specification, R1 may be alkyl or aralkyl.ALSO:Merocyanine dyes of the general formula <FORM:0828847/IV(c)/1> wherein R1 is hydrogen or an aryl group, R2 is hydrogen or a carboxylic acyl or arylsulphonyl group, R3 is an aryl or substituted aryl group, R4 is hydrogen or an alkyl group, R5 is an alkyl, hydroxyalkyl or aryl group, m and n are 0 or 1 and D completes a 5- or 6-membered heterocyclic nucleus, are prepared (i) for dyes wherein R4 is methyl or ethyl; by reacting an ortho ester of the formula R4C(OC2H5)3 with a compound of the formula <FORM:0828847/IV(c)/2> and a compound of the formula <FORM:0828847/IV(c)/3> wherein X is an anion; (ii) for dyes wherein R2 is H ; by reacting a base such as sodium ethoxide with a tetronic acid aryl hydrazone of the formula <FORM:0828847/IV(c)/4> whereby a pyrazolone of formula 1 above is formed in situ (or by starting with a compound of formula I), and then reacting this with a compound of formula <FORM:0828847/IV(c)/5> wherein Y is an alkylthio, alkylthiovinyl, alkylthiopropenyl or higher homologous group, or an acetanilidovinyl group; (iii) for dyes wherein R2 is acyl or arylsulphonyl ; by treating a dye wherein R2 is H with an acylating agent such as acetic anhydride or benzoyl chloride or an arylsulphonyl chloride such as toluene-p-sulphonyl chloride. Examples are given of the preparation of dyes wherein R1 is H or phenyl, R2 is H, acetyl, benzoyl or toluene-p-sulphonyl, R3 is phenyl or p-chlorophenyl, R4 is H or methyl, R5 is methyl or ethyl, and D completes an indole, benzthiazole, 5-methyl-benzthiazole, benzoxazole, 6 - methoxy - benzoxazole, 5,6-dimethyl - benzoxazole, 5 - phenyl - benzoxazole, 2 - quinoline or 4 - quinoline nucleus. According to the Provisional Specification, R1 may be alkyl or aralkyl.