Chinese Journal of Chemistry, 2009, 27, 1359—1364 Full Paper * E-mail: m_elborai@yahoo.com Received September 9, 2008; revised and accepted March 4, 2009. © 2009 SIOC, CAS, Shanghai, & WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim Synthesis and Application of Some Azo and Azomethine Dyes Containing Pyrazolone Moiety RIZK, Hala F. El-BORAI, Mohamed A.* El-HEFNAWY, Gad B. El-SAYED, Hatem F. Department of Chemistry, University of Tanta, 31527 Tanta, Egypt 3-Amino-1-phenyl-4,5-dihydro-1H-pyrazol-5-one (1) was used as starting material for the synthesis of a num- ber of azo compounds 3a—3c and azomethine derivative 4. The deblocking of 3a—3c and 4 gave rise to 5a—5c and 6 in which a free amino was revealed. The diazonium salts of 5a—5c and 6 were coupled with several phenols to produce a number of bis azo compounds 7a—7c and 8a—8c with azomethine in position 4 and azoic group in position 3. The prepared dyes were structurally confirmed by elemental analysis, spectral methods and applied to different fibers (wool, polyester and blend of wool/polyester) as disperse dyes and their fastness properties were measured. Keywords 3-aminopyrazolone, azomethine dye, disperse dye, fastness property, diazonium salt Introduction The biological activities have made synthesis of the pyrazolone ring system attractive over the years. Syn- thesis of pyrazolone provides many compounds with various biological activities. 1a-1c Azodyes containing heterocyclic rings lead to brighter and deeper shades than their benzene ana- logues. 2 They are still very important for application as disperse dyes for polyester fibers. 3a-3g Many azo pyra- zolones dyes have been utilized as chromogenic re- agents for colorimetric determinations 4a-4e and as indi- cators for complexometric titration. 5 Also, some aryl azo pyrazolone dyes have potent antimicrobial activi- ties. 6 On the other hand, pyrazolone azomethine dyes are important for the production of magenta dye images in various color photographic processes. 7a-7c As part of our continuing interest in pyrazolone chemistry, we synthesized a number of such com- pounds. 8a,8b We now report on the successful synthesis of a series of dyes containing pyrazolone moiety and their application as disperse dyes to dye different fibers. Results and discussion 3-Amino-1-phenyl-4,5-dihydro-1H-pyrazol-5-one (1) was prepared by the reaction of ethyl cyanoacetate with phenyl hydrazine in sodium methoxide. 9 Acylation of 1 was carried out with acetic anhydride to produce N-(5-oxo-1-phenyl-4,5-dihydro-1H-pyrazol-3-yl)aceta- mide (2). The coupling of 2 with a variety of aromatic diazonium salts in pyridine produced N-(5-hydroxy-1- phenyl-4-arylazo-1H-pyrazol-3-yl)acetamide (3a —3c). Also, the reaction of 2 with p-nitoso-N,N-dimethyl- aniline gave N-[4-(4-dimethylamino phenylimino)- 5-oxo-1-phenyl-4,5-dihydro-1H-pyrazol-3-yl] acet- amide (4). The basic hydrolysis of 3a—3c and 4 yielded the free amino group in position 3, which were coupled with several phenols to produce 3-(2-hydroxy-arylazo)- 4-arylazo-1-phenyl-1H-pyrazol-5-ols (7a —7c) and 4- [4-(dimethyl amino)phenylimine]-3-(2-hydroxy-aryl- azo)-1-phenyl-4,5-dihydro-1H-pyrazol-5-ones (8a—8c) (Scheme 1). The structures of the prepared compounds were con- firmed by spectroscopic techniques including UV, IR, 1 H NMR, mass data and microanalysis. The IR spectra of compounds 3a—3c, 5a—5c and 7a—7c are charac- terized by the presence of absorption bands for C＝N groups within the range 1592—1660 cm －1 , and for OH group of the pyrazolone moiety 3055—3087 cm －1 . The absorption bands for the symmetric stretching vibrations of azo N＝N groups are in the 1550—1593 cm －1 region. The IR spectra of compounds 5a—5c showed the pres- ence of absorption bands in the region of ν 3423—3430 cm －1 attributed to the free NH 2 group. Also, the IR spectra of dyes 4, 6 and 8a—8c showed absorption bands for the azomethine C＝N— groups within the range 1630—1683 cm －1 , for C＝O group of the pyra- zolone moiety 1590—1597 cm －1 . While the week broad band appearing in the 3311—3377 cm －1 region can be attributed to the presence of an associated NH group. Compound 6 showed a band at 3430 cm －1 for the free NH 2 group and compounds 8a—8c showed bands of azo N＝N groups in the 1557—1590 cm －1 region. The electronic spectra for compounds 3a—3c, 5a— 5c and 7a—7c show the absorption band of the π-π* transition of the —N＝N— group within the range of