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A variety of new pyridopyrimidine derivatives are synthesized based on one-pot three-component reactions of 6-amino-2-thiouracil derivatives (I) and (XIII).

The reaction of 2,3-dichloro-1,4-naphthoquinone with alkoxides, primary amines, and phenols was shown to proceed chemoselectively rather to the corresponding 2-substituted 3-chloro-naphthoquinones or 2,3-disubstituted quinones than to brazanquinone derivatives. Difunctional reagents like mercaptobenzimidazole, methyl urea, or guanidine lead to the corresponding heterocyclic system. The chemoselectivity of these reactions was found to be critically dependent on the reagents and reaction conditions used. These reaction parameters can thus be used to govern the synthesis of distinct compounds.

Dodecahydro-3a,9a-diazaperylene (DHDAP) was prepared in one step from p-phenylenediamine and 1-bromo-3-chloropropane, and its first redox potential is 292 mV more negative than the first redox potential of N,N,N′,N′-tetramethyl-p-phenyl enediamine (TMPD), thus becoming the most easily oxidized p-phenylenediamine homologue.

3-Cyano-6-methyl-5,6,7,8-tetrahydro[1,6]naphthyridine-2(1H)-thione (3a) and 3-cyano-6-methyl-4-(2'-thienyl)-5,6,7,8- tetrahydro[1,6]naphthyridine-2(1H)-thione (3b) were reacted with α-halo compounds to give the intermediates 4a-j which upon refluxing in ethanolic sodium ethoxide afforded the thieno[2,3-b][1,6]naphthyridine derivatives 5a-1. Further annellation of pyridine and pyrimidine rings to the remaining free bond of the fused thiophene ring was achieved, providing tetrahydro-pyrido[2',3':4,5]- and -pyrimido[4',5':4,5]-thieno[2,3-b][1,6]naphthyridines. Some of the synthesised compounds were screened against different strains of bacteria.

Fatma K. Abdel-Wadood, Maisa I. Abdel-Monem, Atiat M. Fahmy, and Ahmed A. Geies Chemistry Department, Faculty of Science, Assiut University, Assiut 71516, Egypt Reprint requests to Prof. Dr. Ahmed Geies. Fax: 0020882342708. E-mail: geies@aun.edu.eg Z. Naturforsch. 2008, 63b, 303 – 312; received August 19, 2007 A one-step synthesis of [1,6]naphthyridine-2(1H)-thione (3a), pyrano[3,4-b]pyridine-2(1H)thione (3b), thiopyrano[3,4-b]pyridine-2(1H)-thione (3c) and 6-oxoquinoline-2(1H)-thione (3d) through the reaction of benzylidene-cyanothioacetamide (1) with cyclic ketones 2a – d is described. The reaction of 3a – d with organyl chlorides yielded the 2-alkylthio-3-cyanopyridines 4a – p which upon refluxing in ethanolic sodium ethoxide afforded the thieno[2,3-b]pyridine derivatives 5a –n. Some of the synthesized compounds were screened for the activity against bacteria and fungi.

Syntheses of fused heterobicyclic systems containing 1,2,4-triazolo/1,2,4-triazinopyridinone moieties were accomplished by heterocyclization of 4-(4-chlorophenyl)-1,6-diamino-2-oxo-1,2-dihydropyridine-3,5-dicarbonitrile (III ) or 6-amino-4-(4-chlorophenyl)-2-oxo-1-(5,6-diphenyl-1,2,4-triazin-3-ylamino)-1,2-dihydropyridine-3,5-dicarbonitrile (XII) with α,β-bifunctional oxygen and halooxo compounds in different media in order to establish a relation between structure and their activities. Compounds III and XII which contain 1,2-biamino group are more favoured to the ringclosure reactions. Structure assignments of new products have been established on the basis of elemental analysis and spectral data. The antimicrobial activity of the products has been also evaluated where some compounds showed a better activity against selected tested microbes in comparison with control.

N,N'-Bis(2-propenyl)-2,7-diazapyrenium salts are synthesized in good yield from the reaction of 1,4,5,8-naphthalenetetracarboxylic dianhydride with allylamine, followed by LiAlH(4) reduction and subsequent oxidation with 2,3-dichloro-5,6-dicyano-1,4-benzoquinone (DDQ). The nature of the counteranion depends on the solvent system used for recrystallization of the crude product from the final DDQ-oxidation step. X-ray analysis shows that if recrystallization is carried out in boiling CH(3)OH/H(2)O (1:1, v/v), the counteranion in the resulting deep-red crystals is always the alkoxy anion of 2-cyano-5,6-dichloro-3-hydroxy-1,4-benzoquinone, whether the final DDQ oxidation ends with addition of HClO(4) or HCl; on the other hand, if recrystallization is carried out with anhydrous acetonitrile, the product is N,N'-bis(2-propenyl)-2,7-diazapyrenium diperchlorate or dichloride depending on whether the DDQ oxidation is followed by addition of concd HClO(4) or concd HCl, respectively. Importantly, if the DDQ oxidation is quenched with HBr, Br(-) is oxidized to Br(2) by unreacted DDQ, and the resulting product is N, N'-bis(2,3-dibromopropyl)-2,7-diazapyrenium dibromide. Comparative absorption and time-resolved emission studies provide evidence for possible dimerization of N,N'-bis(2-propenyl)-2,7-diazapyrenium diperchlorate in CH(3)CN.