Process for the preparation of triphenylmethane dyes

Details Process for the preparation of triphenylmethane dyes Process for the preparation of triphenylmethane dyes

C - Chemistry, Metallurgy

09

B

C09B 11/14 (2006.01) C09B 11/18 (2006.01)

Patent

CA 2057841

A process for the preparation of triphenylmethane dye of the formula: (see formula I) wherein R1 and R2 each denote hydrogen, C1-C4 alkyl, benzyl or sulfobenzyl, R3 and R4 each denote hydrogen, C1-C4 alkyl or sulfonic acid R5 denotes a phenyl, sulfophenyl, dialkylaminophenyl, C1-C4 alkylphenyl, C1-C4 alkyl-dialkylaminophenyl, halogenophenyl, naphthyl, sulfonaphthyl, disulfonaphthyl, or alkyldisulfonaphthyl comprising I. oxidation of the leuco compound of the corresponding triphenylmethane dye with manganese dioxide in the presence of an aqueous phosphoric acid at a temperature of about 20°C to about 100°C, 19 II. adding a sa~ of phosphoric acid and a base selected from the group consisting of ammonia, amines, aminoalcohols, metal hydroxides of Groups IA, IIA, IIIA and mixtures thereof in an amount sufficient to neutralize the aqueous solution, III. filtration from the precipitate and IV. isolation of said triphenylmethane dye.

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