N N Me N OH O Ph N N Me N O OH Ph N N Me N OEt O Ph N N Me Ph O N Me N N Br H Me Ph O N N Me Ph OH Br N N Me Ph N Me OH OH N N Me Ph Cl Br N N Me Ph 1b 1a MeCH2I, K2CO3, –HI N Me 5 OH Cl –H2O, –HI 2 MeCONH2, pyridine, –HBr MeCONH2, pyridine, –HBr –H2O –HCl 4 3b 3a N N O N Me Me Ph N N O N OHC CHO Ph N N O N Ph N N Et Et Me N Et –2 H2O +2 N N O N OHC CHO Ph 7 N N O N Ph 9a-b N Et + N Et + I– H2O + 5 A 6 Me + A = 1-ethylpyridinium-2-yl A = 1-ethylquinolinium-2-yl A = 1-ethylpyridinium-4-yl 8,9a bc +2 SeO2 8a-c +1 SeO2 + 1,4-Dioxane A A 2 I– I– I– + A A Me 128 J.CHEM. RESEARCH (S), 1997 J. Chem. Research (S), 1997, 128–129 J. Chem. Research (M), 1997, 0850–0865 Synthesis and Electronic Absorption Spectra of Some Five-membered Bisheterocyclic Polymethine Cyanine Dyes Reda Mahmoud Abd El-Aal Chemistry Department, Aswan-Faculty of Science, Aswan, Egypt 3,5-Dimethyl-1-phenyl-1H-pyrazolo[4,3-d]oxazole 5 was prepared and used as starting material in the synthesis of some new polymethine cyanine dyes incorporating a bisheterocyclic system.Polymethine cyanine dyes1 including mono-, di- and trimethine types have found various applications as photographic sensitisers for both colour and black and white films2 and textile dyes.3 They are also useful as photosensitisers in blue green light4–6 and as analytical reagents.7 In the present paper, a new synthesis of 3,5-dimethyl- 1-phenyl-1H-pyrazolo[4,3-d]oxazole 5 is developed and con- firmed by the interaction between 4-bromo-3-methyl- 1-phenyl-1,4-dihydropyrazol-5-one (3ak3b)8 and/or 4- bromo-5-chloro-3-methyl-1-phenylpyrazole 4 with pyridine as catalyst and ethanol as solvents, Scheme 1.Selective oxidation of 5 with an equi- or bi-molar ratio of SeO2 17 in boiling 1,4-dioxane afforded the corresponding 3 - m e t h y l - 1 - p h e n y l - 1 H- p y r a z o l o [ 4 , 3 - d] o x a z o l e - 5 - c a r b a l d e - hyde 6 or its 3,5-dicarbaldehyde 7, respectively.The 1H NMR spectra of the aldehydes 6 and 7 show characteristic absorptions at d 10.2 and 10.0, respectively, for the CHO groups and other signals which, along with the IR spectra, are presented in Table 4 (full text). The condensation of compounds 6 and 7 with 2(4)-methylsubstituted heterocyclic quaternary salts (equi- or bi-molar) in refluxing ethanol in the presence of piperidine as catalyst afforded the corresponding asymmetric 3-methyl-1-phenyl- 1H-pyrazolo[4,3-d]oxazol-5-yl [2(4)]-dimethine (8a–c) and symmetric 1-phenyl-1H-pyrazolo[4,3-d]oxazole-3,5-diyl [2(4)]- bis(dimethine) cyanine dyes (9a–c), Scheme 3.Quaternisation of 3,5-dimethyl-1-phenyl-1H-pyrazolo[4,3- d]oxazole 5 using iodoethane afforded the corresponding b i s q u a t e r n a r y - 2 , 4 - d i e t h y l - 3 , 5 - d i m e t h y l - 1 - p h e n y l - 1 H- p y r a - zolo[4,3-d]oxazole-2,4-diium bis(iodide) 10. Interaction of 10 with 1-methyl-pyridinium (-quinolinium or -isoquinolinium) iodide (equi- or bi-molar) afforded the corresponding asym- Scheme 1 Scheme 3N N O N Ph Et Et Me N N O N Ph N Et N N O N Ph Me Me N+ N O N Ph Me Me Et Et N Et +2 N Et Et Et N+ N O N Ph N Et Et Et Me N+ N O N Ph Et Et H2C (EtO)2CH CH2 CH(OEt)2 N Et +2 N Et 12a–c + 11,12 N Et + A = 1-ethylpyridinium-4-yl A = 1-ethylquinolinium-4-yl A = 1-ethylisoquinolinium-1-yl N+ N O N Ph Et Et a bc 2 I– A 5 10 + 2 I– A 2 I– + A + + 11a–c + 2 I– 2 I– 14 16a–c N+ N O N Ph A Et Et A Me + CH2CH(OEt)2 +2 CH(OEt)3 N Et + 13 15,16 N Et I– + 15a–c + CH(OEt)3 A = 1-ethylpyridinium-2-yl A = 1-ethylisoquinolinium-2 -yl A = 1-ethylpyridinium-4-yl a bc A EtI Me + A 2 I– A 2 I– + A + A 2 I– N Et + Me 2 I– + J.CHEM. RESEARCH (S), 1997 129 metric and symmetric monomethine cyanines 11a–c and 12a–c, Scheme 4. Treatment of 10 with ethyl orthoformate (equi- or bimolar) in the presence of piperidine afforded compounds 13 and 14 respectively. These compounds are key intermediates in the synthesis of asymmetric and symmetric trimethine cyanine dyes 15a–c and 16a–c via condensation with 2(4)-methyl-substituted heterocyclic quaternary salts (equior bi-molar).The electronic absorption spectra of the asymmetric and symmetric dimethine (8a–c, 9a–c), monomethine (11a–c, 12a–c) and trimethine (15a–c, 16a–c) cyanine dyes in 95% ethanol were dependent on the nature of the heterocyclic quaternary salts (A) and on the type of cyanine molecules, i.e. whether asymmetric or symmetric.The structures of all new compounds were confirmed by elemental analysis as well as by IR and 1H NMR spectral data. I am grateful to Professor Dr A. I. M. Koraiem, Professor of organic chemistry, Aswan-Faculty of Science, for his help and guidance in the preparation of the manuscript. Techniques used: IR, 1H NMR, GCMS, UV–VIS References: 17 Schemes: 4 Table 1: Characterisation data for 6, 7, 8a–c and 9a–c Table 2: Characterisation data for 10, 11a–c and 12a–c Table 3: Characterisation data for 13, 14, 15a–c and 16a–c Table 4: IR and 1H NMR data of selected cyanine dyes Received, 13th June 1996; Accepted, 3rd January 1997 Paper E/6/04155H References cited in this synopsis 1 N.Tyutyuikov, J. Fabian, A. Mehlhorm, F. Dietz and A. Tadjer, Polymethine Dyes – Structure and Properties, St. Kliment Ohridski University Press, Sofia, Bulgaria, 1991. 2 A. M. Osman and Z. H. Kalil, J. Appl. Chem. Biotechnol., 1975, 25, 633. 3 G. D. Kandel and G. F. Duffin, Br. Pat., 797 144, 1930. 4 L. G. S. Brooker and G. H. Keyes, J. Am. Chem. Soc., 1935, 57, 2488. 5 M. S. Fujiravara, T. K. Masukawe and M. Kawasaki, Ger. Offen., 2 734 335, 1978 (Chem. Abstr., 1978, 88, 161 442c). 6 S. Baba, B. Okubo and E. Sakamato, Ger. Offen., 260 968, 1976 (Chem. Abstr., 1977, 86, 49 175a). 7 A. S. Fakhonov, A. A. Anisimova, K. N. Bagdasarov and M. S. Chernovyant, Zh. Anal. Khim., 1984, 39, 1040. 13 L. Smith, Kgl. Fysiograf. Sallskab, Lond., Forh., 18 No. 1, 3, 1948 (Chem. Abstr., 1950, 44, 490. 17 Z. H. Khalil, A. I. M. Koraiem, M. A. El-Maghraby and R. M. Abu El-Hamd, J. Chem. Tech. Biotechnol., 1986, 36, 379. Scheme 4