D. Simov

Diazotization of 2-amino-6-methoxybenzothiazole at elevated temperature

Abstract The diazotization at elevated temperature of the weakly basic heterocyclic amine 2-amino-6-methoxybenzothiazole, which is used in the production of basic dyes was investigated. The results showed that the yields and purity of the dyes, produced by this method were comparable with those reported in the literature. The conclusion is drawn that the diazotization of 2-amino-6-methoxybenzothiazole at elevated temperature can result in technological improvement and simplification of the process.

Preparation of cationic azo dyes derived from 2-amino-6-(2-chloroethoxy)benzothiazole and 2-amino-4-(2-hydroxyethoxy)benzothiazole

Abstract Azo dyes derived from 2-amino-6-(2-chloroethoxy)benzothiazole and 2-amino 4-(2-hydroxyethoxy)-benzothiazole were prepared by diazotization and coupling with different N , N -disubstituted anilines. The dyes were then quaternized with various alkylating agents, re. dimethyl sulphate, benzene-sulfonic acid methyl ester, acrylamides and epoxy compounds. Some parameters of the quaternization reaction are critically evaluated. The new benzothiazolic cationic dyes absorb in the region of 606–636 nm and have molar absorptivity of 40 000–80 000 Lmol −1 cm −1 .

Preparation of 2-(N-alkyl-N-arylamino) ethyl trimethylammonium salts

Abstract The N-alkylation of 2-(N-arylamino)ethyl trimethylammonium salts with allyl chloride, benzyl chloride, epichlorohydrin, ethylene chlorohydrin and acrylonitrile was studied and the preparation of 2-(N-allyl-, -benzyl-, -2-hydroxyethyl-, 3-chloro-2-hydroxypropyl-and 2-cyanoethyl-N-arylamino)-ethyl trimethylammonium salts is described. A method is proposed for obtaining a series of differently N-substituted derivatives of these salts from the same 2-(N-arylamino)ethyl trimethylammonium salts.

One-pot synthesis of 1,3-dimethyl-2-[4-N(N,N-disubstitutedamino)phenylazo]imidazolium cationic dyes

Abstract Starting from 4-chloro- or 4-fluoroaniline, the four reaction steps — diazotization, coupling with imidazole, quaternization with dimethyl sulphate and substitution with dialkylamines, piperidine derivatives or hexamethyleneimine — were carried out as a one-pot preparation of 1,3-dimethyl-2-[4-(N,N-disubstitutedamino)phenylazo]imidazolium cationic dyes. The reaction procedure shortened considerably the overall reaction time and avoided some technical operations, such as filtration and drying.

Method for quaternization of nitrogen-containing heterocyclic azo dyes

Abstract A method is described for the quaternization of nitrogen-containing heterocyclic azo dyes using dimethyl sulphate and arylsulphonic acid methyl esters as alkylation agents in a two-phase liquid medium. The method is distinguished by fully competed quaternization at high reaction rates and moderate reaction temperatures.

The preparation of 5-nitro-2-aminophenol and some derivatives

Abstract A facile method for the preparation of 5-nitro-2-aminophenol and its derivatives is described. Starting from isatins, through Bayer-Villiger oxidation and nitration of the intermediate 2,3-dioxo-4H-1.4-benzooxazines and hydrolysis of the corresponding nitro compounds to 5-nitro-2-aminophenols, the procedure is shown to be an effective and reliable route to these compounds. From two new 5-nitro-2-aminophenols thus prepared, azo dyes from 2-naphthol and 1-phenyl-3-methylpyrazolone-5 were obtained.

Properties of azo dyes derived from 2-(N-substituted alkyl-N-arylamino)ethyltrimethyi-ammonium Salts: Part II. 3-Toluidino and 3-anisidino derivatives

Abstract The influence of 2-hydroxy ethyl, allyl and benzyl substituents at the nitrogen atom of the arylamino group on the properties of azo dyes derived from 2-(3-toluidino-, or 3-anisidmo)ethyl-N,N,N-trimethylammonium salts as coupling components and 3-nitro-, 4-nitro-, 2-chloro-4-nitro- and 2,6-dichloro-4-nitro-aniline as diazo components was studied. Electronic spectra data for the dyes in 20% ethanol and in sulphuric acid (0.1 and 4 mol litre −1 ), together with some coloristic properties, are reported. Relationships previously established for dyes derived from 2-phenylaminoethyl-N,N,N-trimethylammonium salts with respect to the effect of the substituent at the nitrogen atom and dye properties are valid for these dyes also. Methyl and methoxyl substituents in the azo component (in an ortho position with respect to the azo group) affect not only the colour, but also the rate of dyebath exhaustion, and thus the dyebath exhaustion properties of these dyes can be varied for specific end-use by appropriate structural modifications of the dyes.

Properties of Azo Dyes Derived from 2-(N-substituted alkyl-N-arylamino)ethyltrimethyl-ammonium Salts: Part I: Phenylamino Derivatives

Abstract Results are presented on the properties of azo dyes derived from 2-(N-2-hydroxyethyl-, allyl- or benzyl- N-phenylamin)ethyltrimethyl-ammonium salts as coupling components and 3-nitro-, 4-nitro-, 2-chloro-4-nitro- and 2,6-dichloro-4-nitroanilines as diazo components. The electronic spectra of the dye are discussed and a qualitative evaluation is given of their pH-stability and acid-base equilibria. It is shown that with the conjugated acids obtained, the tautomeric equilibrium is shifted almost entirely to the azonium tautomer. The nature of the substituent at the nitrogen atom of the coupling component is of importance for the combination characteristics and reserving capacity of the dyes. The compatibility value, the rate of dye-bath exhaustion and reserving capacity decrease in the order benzyl, allyl, hydroxyethyl. The colour, light-fastness and other fastness properties are not significantly influenced by the substituent.