Synthesis of some new 4-[P-heterocyclo-substituted aniline] -2,7-dimethyl-l,8-naphthyridines of expected antimicrobial activity

The reaction of 4-chloro-2,7-dimethyl-l,8-naphthyridine [1] with benzocaine and/or aminophenol gives the corresponding ethyl naphthyridineaminobenzoate derivative 2a and/or p-hydroxy-anilinonaphthyridine derivative 2b depending upon the nature of the reactants used. The reaction of compound 2a with hydrazine hydrate gives the corresponding acid hydrazide 3 which was allowed to react with CS[2] at different conditions giving the oxadiazole 4 and / or the dithiocarbazate 5, and with a beta-diketone and a [3-dikctoester to give the corresponding pyrazole 9 and/or the pyrazolone 10. As well as, the reaction of the acid hydrazide 3 with different aromatic aldehydes afforded the Schiff bases 11a-d. which upon cyclization with thioglycolic acid afforded the thiazolidinones 12. On the other hand, the reaction of 1 with different amines, afforded 4-substituted 1,8-naphthyridines 13a-c, which gave the 2,7- distyrylnaphthyridines 14a-d upon reaction with different aromatic aldehydes. Moreover, reaction of 1 with p-hydroxy- acetophenone and/or p-aminophenol gave the corresponding 4-[p-acetylphenoxy] and/or 4-[p-aminophenoxy]-1,8-naphthyndine derivatives 15a and/or 15b, respectively. Reaction of 15a with different aldehydes afforded the chalcones 16a-d, 2-[lH] oxopyridines 17a-f, 2-[lH]iminopyndmes 19a,b, 2-[lH] thioxopyndincs 20a-c, while reaction of 15b with aromatic aldehydes gave the 1,8-naphthyridine-p-phenoxy Schiff bases 21a-c and other related compounds have been synthesized. Furthermore, some 1,8-naphthyridine Mannich bases 24a-d were produced by treatment of 2b with p-formaldchyde and secondary amines. In addition, reaction of 4 with ethanolic solution of paraformaldehyde and the appropriate secondary amine, afforded the corresponding 1,3,4-oxadiazole Mannich bases 25a-c. Some of the new compounds were evaluated for their antimicrobial activity

Spectrophotometric determination of oxytetracycline by coupling with diazonium salts

Diazotized p-nitroaniline [I], sulfanilic acid [II] and sulfanilamide [III] were used for the spectrophotometric determination of oxytetracycline [OTC]. The procedure is based on the observation of that in slightly alkaline medium OTC reacts with I, II and III. A stable azo dye is formed and show maximum absorption at 550, 560, and 575 nm, respectively. The variable affecting development of the color have been investigated and the conditions optimized. Beer's law is obeyed for up to 25, 90 and 90 mug/ml on using I, II and III, respectively. Molar absorptivities [L mol-1 cm-1] and Sandell's sensitivities [mug cm-2 per 0.001 absorbance unit] are respectively; 0.83 x 104 and 57.8 x 10-3, 0.14 x 104 and 200 x 10-3 and 0.12 x 104 and 176.5 x 10-3. The mean percentage accuracies were 99.9 +/- 1.75, 99.95 +/- 0.71. The results obtained either in pure form or in pharmaceutical formulations are accurate and precise. The nature of the dye was discussed and the structure of a mono azo dye was suggested

Spectrophotometric studies on some azo compounds derived from tetracycline and oxytetracydine

The absorption spectra of some azo compounds derived from aniline, p- nitroaniline, sulfanilic acid and sulphanilamide coupled with tetracycline [TC] and oxytetracycline [OTC] in organic solvents and buffer solutions of different pH values have been investigated. The results have been utilized for the determination of pKa. The spectra of the compounds were discussed in relation to molecular structure