J. Chem. Research (S), 1997, 44–45 J. Chem. Research (M), 1997, 0375–0384 Synthesis of Some Coumarin Derivatives as Potential Laser Dyes Mohamed H. Elnagdi,a Sanaa O. Abdallah,*a Khadiga M. Ghoneim,b Elzeni M. Ebiedc and Kawser N. Kassabd aChemistry Department Faculty of Science, Cairo University, Egypt bChemistry Department Faculty of Pharmacy, Cairo University, Egypt cChemistry Department Faculty of Science, Tanta University, Egypt dNational Institute of Laser Science, Cairo University, Egypt With a view to extend the tunability range and maximum output of the coumarin series of dyes, 15 new 3-substituted 7-hydroxycoumarins emitting in the blue-green region of the visible spectrum are synthesized, some of which show laser activity.Several 3-substituted 7-hydroxycoumarins rank among the most efficient photostable laser dyes emitting in the bluegreen region of the visible spectrum. The lasing range covered by coumarin dyes is appreciably extended when the 3-substituent is a heterocyclic moiety.1,2 Therefore it seemed relevant to design and synthesize 7-hydroxycoumarins bearing different heterocycles at the 3-position with the aim to obtain a new photostable laser dyes having rigid structures that are tunable over a wide wavelength range within the visible spectrum.This approach was also stimulated by the assumption that the introduction of biologically active heterocycles at the 3-position of 7-hydroxycoumarin may lead to physiologically active fluorescent compounds of general and analytical biological interest.The syntheses of the new 3-substituted 7-hydroxycoumarins from b-resorcylaldehyde (2,4-dihydroxybenzaldehyde; 1) are outlined in the Scheme. The 3-benzothiazolyl, 3-benzimidazolyl and 3-benzoxazolyl derivatives of 7-hydroxycoumarin 3a–c were synthesized via condensation of b-resorcylaldehyde (1) with benzothiazol- 2-ylacetonitrile (2a),3 1H-benzimidazol-2-ylacetonitrile (2b)4 and benzoxazol-2-ylacetonitrile (2c),5 respectively.Solutions of these 7-hydroxycoumarins in different organic solvents were found to be strongly fluorescent. In order to investigate the effect of introducing an acetoxy group at position 7 on the fluorescence properties of these compounds, the 3-(benzazol-2-yl)-7-acetoxycoumarins 3d–f were prepared by acetylating compounds 3a–c. The strongly fluorescent 3-thiazolyl-7-hydroxycoumarins 6a–c were obtained by the reaction of 1 with 4-aryl-2-cyanomethyl- 1,3-thiazoles 5a–c. 2-Cyanomethyl-4-phenyl-1,3-thiazole (5a)6 was obtained by the reaction of w-bromoacetophenone (4a) with cyanothioacetamide. Likewise, the same method was adopted for the preparation of the novel 2-cyanomethyl-4-p-tolyl-1,3-thiazole (5b) and 4-p-chloro- 44 J. CHEM. RESEARCH (S), 1997 *To receive any correspondence. Schemephenyl-2-cyanomethyl-1,3-thiazole (5c), using w-bromo- 4-methylacetophenone (4b) and w-bromo-4-chloroacetophenone (4c), respectively.Condensing 1 with ethyl (5-aryl-1,3,4-oxadiazol-2-yl)acetate 8a–b in ethanol containing piperidine as a catalyst afforded the 3-(5-aryl-1,3,4-oxadiazol-2-yl)-7-hydroxycoumarins 9a–b. Compound 8a7 was obtained by the reaction of ethyl 3-ethoxy-3-iminopropanoate hydrochloride with benzoylhydrazine (7a). The same method was used to prepare the unreported ethyl (5-p-anisyl-1,3,4-oxadiazol-2-yl)acetate (8b) utilising p-anisoylhydrazine (7b). Many dicoumarins show intensive anticoagulant activity and are used in the therapy of thromboembolisms.Hence it seemed worth synthesizing the dicoumarin 11, which was accomplished by condensing 1 with ethyl (5-cyanomethyl- 1,3,4-oxadiazol-2-yl)acetate (10)8 in a 2 :1 molar ratio in ethanol in presence of piperidine as a catalyst. The preparation of the 3-thiadiazolyl-7-hydroxycoumarins 14a–c was achieved by reacting 1 with the appropriate 2-acylamino- 5-cyanomethyl-1,3,4-thiadiazoles 13a–c. The thiadiazoles 13a9 and 13b10 were synthesized by treating 2-cyanoacetohydrazide with acetyl isothiocyanate (12a) and benzoyl isothiocyanate (12b), respectively.The novel 2-p-anisoylamino-5-cyanomethyl-1,3,4-thiadiazole (13c) was prepared in a similar manner using p-anisoyl isothiocyanate (12c). With a view to standardize the parameters to make the present dyes effective in the field of lasers, a study of their electronic absorption emission and excitation spectra in different organic solvents was carried out.The effects of acidity and temperature as well as dye concentration on their optical properties were also explored. The fluorescence quantum yields (ff) of these dyes are high and some showed lasing activity upon pumping with an N2 laser. The newly synthesized compounds showed variable antibacterial activities against some Gram positive, Gram negative and acid fast bacteria. Only the thiazole and the thiadiazole derivatives 3a, 6a–c and 14a–c showed significant activity against the acid fast Mycobacterium phlei, probably due to their ability to penetrate the lipid-rich cell wall which is resistant to acids, alkalis and chemical disinfectants.However, all compounds showed no significant activity against Pseudomonas fluorescence which is resistant to most antimicrobial agents. Techniques used: 1H NMR, IR, UV–VIS, MS References: 10 Scheme: 1 Received, 29th May 1996; Accepted, 5th October 1996 Paper E/6/03731C References cited in this synopsis 1 K. H. Drexhage, Topics in Applied Physics, Springer-Verlag, New York, 1973, vol. 1. 2 G. Jones II, W. R. Jackson, C. Choi and W. R. Bergmark, J. Phys. Chem., 1985, 89, 294. 3 K. Saito, S. Kambe, Y. Nakano, A. Sakurai and H. Midowkawa, Synthesis, 1983, 210. 4 J. Sawlewicz and B. Milczarska, Pol. J. Pharmacol. Pharm., 1974, 26, 639. 5 H. Moeller and C. Gloxhuber, Ger. Offen., 2 327 959 (Cl. CO 7D, A 6lK), 1975; Appl. 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