Synthesis of Some New 5-Arylazothiazole Derivatives as Disperse Dyes for Dyeing Polyester Fibers

A series of 5-arylazo-2-(arylidenehydrazino)-2-th iazo lin -4-one dyes 3 and 4 was prepared by cyclocondensation of hydrazonoyl bromides 2 with various thiosemicarbazone derivatives 1. While the synthesis of 3-amino-N-(5-arylazo-2-thiazo lyl)-thieno[2,3-b]pyrid ine-2-carboxamide dyes 8 was achieved by the reaction of 2-(N-chloroacetyl)-5-ary lazo-thiazo le derivatives 5 with 4,6-dimethyl-2-mercaptonicotinonitrile fo llowed by heterocyclizat ion of the obtained sulfide derivatives 7 in a solution of ethanol containing sodium ethoxide. These dyes were applied as disperse dyes for dyeing polyester fibers and their characteristics and fastness properties have been measured. The dyed fibers exh ibit very good to excellent washing, perspiration and sublimat ion fastness properties, with little variation in good to excellent rubbing and light fastness.


Introduction
The chemistry of 2-th iazo lines, including new methodologies for their preparation, and recent applicat ions, such as their growing use in organic synthesis in the biological field and asymmetric catalysis as ligands has been recently reviewed [1]. 2-A minothiazo les are known main ly as biologically active co mpounds with a broad range of activity and as intermed iates in the synthesis of antibiotics and dyes [2]. Several papers have been published on the use of these compounds as antimicrobial [3], antifungal [4], anti-inflammatory activity [5], anesthetic [6] and antiviral drugs [7]. 2-A minothiazoles and their derivatives are also used in the syntheses of various types of dyes [8][9][10][11]. In continuation of our previous studies [9,[12][13][14][15] on the synthesis of a variety of thiazole derivatives fro m the readily obtainable cheapest starting materials for dyeing polyester fabrics, we focused on the synthesis of several new S/N heterocyclic azo dyes and their applications as azo-disperse dyes for dyeing polyester fibers. These sulfur and/or nit rogen heterocyclic a zo dyes provide strong shades that range from yellow, orange, red, and brown colors.

Results and Discussion
Heating of thiosemicarbazones 1 with ethyl arylhydrazonobromoacetates 2 in ethanol containing anhydrous sodium acetate afforded the format ion of the corresponding 2-(benzylidenehydrazino)-5-arylazo-thiazolidin -4-one derivatives 3 and 4 (Scheme 1). The chemical structure of dyes 3 and 4 was based on their elemental analyses and spectral data. The IR spectra of the synthesized dyes 3 and 4 displayed absorption bands corresponding to NH in the region 3260-3189 cm -1 in addition to the characteristic absorption frequencies in the region 1712-1697 cm -1 corresponding to the carbonyl group. The 1 H NM R spectrum of 3b revealed a singlet signal at δ 2.4 for the methyl protons (Ar-Me), mu ltip let in the region δ 7.1-7.9 for the aro mat ic and NH protons, singlet at δ 8.5 fo r the methine proton (CH=N), in addit ion to singlet for the hydrazono proton (C=N-NH) at δ 11.5 pp m. The 2-(N-ch loroacetyl)-5-ary la zo-thiazole derivatives 5 [15] were reacted with 4,6-d imethyl-2-mercaptonicotinoni trile 6 by reflu xing in acetone containing sodium carbonate to yield the corresponding sulfide derivatives 7, which underwent cyclization on heating in a solution of ethanol containing sodium ethoxide to afford the corresponding thieno- [2,3-b]pyridine derivatives 8 (Sche me 2). The chemical structures of 7 and 8 were established on the basis of their elemental analyses and spectral data. The IR spectrum of 7a is characterized by the presence of strong absorption bands at 3333 cm -1 for the NH stretching, 2221 cm -1 corresponding to the nitrile group and 1699 cm -1 corresponding to the carbonyl group. The IR spectrum of 8a clearly indicated the lack of cyano absorption band and revealed the characteristics of NH 2 absorption bands at 3177, 3280 cm -1 in addition to the carbonyl absorption band at 1632 cm -1 . The strong decrease in the carbonyl absorption frequencies is attributed to the highly chelated intramolecular H-bond structure. The 1 H NMR spectrum of 7b is characterized by the presence of three singlet signals at δ 2.4, 2.5 and 2.6 corresponding to three methyl protons, singlet at δ 4.2 for the methylene protons, singlet at δ 7.0 for pyridine C 5 -H proton and multip let at δ 7.2-7.9 for aro mat ic protons. The 1 H NMR spectrum o f 8b confirmed the lack of the singlet signal that characterized the methylene protons and showed three singlet signals corresponding to the three methyl protons at δ 2.4, 2.8 and 3.0, in addit ion to the singlet signal at δ 7.3 for the pyridine C 5 -H proton and multip let signal at δ 7.4-7.9 for the aro matic p rotons.    The visible absorption data for the synthesized dyes were measured in d ichloro methane and are listed in table (1). The absorption ma xima of the synthesized dyes ranged from 390 to 524 n m. Within the series of azo dyes investigated, the relation between the shift observed in the absorption maxima and polar characteristics of substituent, may be su mmarized as follows:

Abs or pti on S pectral Characteristics
1. The introduction of an electrondonating group in the para position in the arylhydrazono mo iety gives a bathochromic shift relative to the unsubstituted compound. 2. The bathochromic shift acco mpanying the substituents in the diazo co mponent was in the following order H → CH 3 → OCH 3 ~ Br → NO 2

Dyeing and Fastness Properties
The synthesized disperse dyes under investigation were applied to polyester fibers at 2% shade by high-temperature pressure technique (130℃) where a range of color shades has been obtained as the visual color shades varied fro m yellow, golden yellow, orange, reddish brown to brown. Generally, variat ion in co lor o f these dyes results fro m the alternation in the diazoniu m and coupling components. The dyes on polyester fibers were evaluated in terms of their fastness properties using standard method [16] and given in table (2), where fastness to light, sublimation and perspiration was assessed in accordance with AATCC-15 (1985), rubbing fastness test was carried out with a crockmeter (Atlas) in accordance with AATCC-88 (1988) and wash fastness test in accordance with IS: 765-1979.

Color Assessment
The color on polyester fibers is exp ressed in terms of CIELA B values (table 3) and the following CIELAB coordinates are measured, lightness (L*), chro ma (C*), hue angle fro m 0º to 360º (h), (a*) value represents the degree of redness (positive) and greenness (negative) and (b*) represents the degree of yellowness (positive) and blueness (negative). A reflectance spectrophotometer (Gretag Macbeth CE 7000a) was used for the colorimetric measurements on the dyed samples. K/S values given by the reflectance spectrometer are calculated at λ max and are directly correlated with the dye concentration on the dye substrate according to the Kubelka-Munk equation: K/S = (1-R) 2 /2R, where K = absorbance coefficient, S = scattering coefficient, R = reflectance ratio. The application of the dyes 3, 4 and 8 on polyester fibers has shown that such dyes have good affinity to polyester fibers. As shown in table 3, the color hue of the applied dyes 3 and 4 on polyester fibers is shifted to the greenish direction on the red-green axis as indicated fro m the negative value of a*, whereas the dyes 3, 4 and 8 represent degrees of redness to yellowness color hue as indicated from the positive values of a* and b*. These results are in line with the previously reported by Műller [17] on the effect of substituent in the dye structure and hue.

Conclusions
A set of 15 disperse dyes 3, 4 and 8 were synthesized by azo coupling. All o f them were investigated for their dyeing characteristics on polyester fibers. The electronic absorption spectra give variable hues fro m yellow to brown on polyester fibers. The dyed fibers exh ibit very good to excellent washing, perspiration and sublimation fastness properties with little variation in the good to excellent rubbing fastness. The degree of levelness after washing is indicative of good penetration and the excellent affinity of these dyes for polyester fiber. This in co mbination with the ease of preparation ma kes them particularly valuable.

Materials and Instrumentation
Microanalysis of the elements: carbon and hydrogen were determined at Microanalytical Laboratories, Facu lty of Science, Mansoura, Cairo and Alexandria Universities. A ll melting points are in degree centigrade and are uncorrected. Infrared spectra were recorded on a Perkin Elme r 14 spectrometer using potassium bro mide Waffer technique. 1 H NMR spectra were measured on a Bruker WP 300 in CDCl 3 , DMSO or CF 3 COOD as solvent, using TMS as an internal standard. Mass spectra were recorded on a Finnigan MAT 212 instrument. The substrate used for dyeing (100% polyester fiber) was kindly provided by Misr Beida Dyers company, Alexandria, Egypt, a product of Misr For Synthetic Fibers Co mpany, Kafr El-Dawar, Egypt. The colorimet ric measurements for the dyed polyester fibers were carried out using a reflectance spectrophotometer (GretagMacbeth CE 7000a). Fastness to washing was carried out using the automatic launder Rotadyer (sponsored by the British Standard Institute -Society of Dyers and Co lourists, fastness to perspiration was assessed according to the test sponsored by the (BSS), fastness to rubbing was carried out according to the standard method of testing (BSS) using Crockmeter of Electric Hungarian FD-17 type, fastness to sublimat ion was carried out using the Electric Japanese Thermotester T-10 type and fastness to light was carried out using the " Weather-o-meter" (Atlas Electric Devices Co. USA), AATCC standard test method.

Preparation of Dye Dispersion
Dispersion of the dye was produced by dissolving the appropriate amount of dye (0.1g dye/ 5g fiber, 2% shade) in 1 ml acetone and then added dropwise with stirring to a solution of Setamol WS (0. 5 -1.5), an anionic dispersing agent of BASF (sodium salt of a condensation product of naphthalene sulfonic acid and formaldehyde). The dyestuff dispersion was added to the dyebath at 60℃ through a fine mesh sieve or filter cloth.

Dyeing Procedure
The dye bath was prepared with liquor rat io 20:1 using sealed stainless steel dye pots of 250 ml capacity in "Galvanin-Marino VI-Italy" dyeing machine. Addit ional dispersing agent (0.5-1.0 g/l Seta mol WS of BASF) was added and the pH of the bath adjusted to 5.5 using glacial acetic acid. The polyester fibers was imme rsed and dyeing carried out by raising the dye bath temperature fro m 20 to 130℃ at a rate of 3℃ / min and holding at this temperature for 60 min before rapidly cooling to 50℃ at 9.9℃/ min. The dyed fibers was then rinsed with cold water, reduction-cleared using 2 cc/l caustic soda solution 32.5% (71ºTw), 2 g/l sodium hydrosulphite and 0.5 g/l Hostapal CV conc. non-ionic wetting agent of Clariant at 75-85℃ for 15-30 minutes and soaped with 2% nonionic detergent and ammon ia (p H 8.5) at 50 ℃ for 30 minutes to improve washing fastness then drying in a pre-drier without contact, up to a residual moisture of appro ximately 30% followed by final drying which be carried out on a hot flue.