Mamdouh A.M. Taha

Condensed 1,2,4-triazines. I: Fused to heterocycles with three-, four-, and five-membered rings

Publisher Summary Compounds containing the 1,2,4-triazine moieties are largely used as pharmaceuticals, dyes, pesticides, and herbicides. Great interest is directed to the synthesis of the title heterocycles having potentially useful biological properties. A large number of 1,2,4-triazines that are condensed with one or more heterocycles are well known and a wide variety of synthetic methods for their preparations are available. This chapter illustrates the triazines that are fused to heterocycles with three, four, and five-membered rings. It covers the survey of the literature of these condensed compounds from 1974 to 1992. The parent compound of this series has two Kekule structures. It can be fused with other heterocycles at its six different sites. The 1,2,4-triazine ring can also constitute a central unit in a condensed ring system, where two or more faces are included in fusions. It is noted that the heterocycles having fused benzene rings are categorized according to the heterocycle that is directly fused to the triazine ring.

Synthesis and Biological Activities of Condensed Heterocyclo[n,m-a,b, or c]Quinazolines

Publisher Summary The synthesis and biological activities of title compounds are systematically arranged according to the complexity of the heterocyclic ring directly fused to the pyrimidine ring of the quinazoline nucleus (irrespective of other rings that might be fused to it), starting with those having one nitrogen atom in a three-membered ring and going to more complex ones. The heterocycles have been arranged according to the type of their heteroatom in the following order: nitrogen, oxygen, sulfur, and selenium. Consideration has been given to the alternative nomenclature of some heterocyclo- quinazolines, also known as quinazolinoheterocycles, in order to comply with the nomenclature rules of the IUPAC. The diverse biological activities of the title compounds have certainly contributed to the extensive efforts directed towards their synthesis.

Synthesis of 1,3,4-Thiadiazole and 1,2,4-Triazole acyclo C-Nucleosides

Abstract Reaction of 4-arylthiosemicarbazides (1) with 2,3,4,5-tetra-O-acetylgalactaroyl dichloride (2) gave the corresponding 2,3,4,5-tetra-O-acetylgalactaroyl-bis(4-aryl-thiosemicarbazides (3). The latter compounds underwent dehydrative cyclization by heating with phosphoryl chloride to give 1,2,3,4-tetra-O-acetyl-1,4-bis(5-arylamino-1,3,4-thiadiazol-2-yl)galacto-tetritols (4) which afforded, upon de-O-acetylation with methanolic ammonia, the corresponding 1,4-bis(5-arylamino-1,3,4-thiadiazol-2-yl)-galacto-tetritols (5). Compounds 3 were also cyclodehydrated, in a different way, with concomitant de-O-acetylation upon treatment with ethanolic sodium ethoxide to give 1,4-bis(4-aryl-5-thioxo-1,2,4-triazol-3-yl)galacto-tetritols (6). Acetylation of 6 with acetic anhydride in the presence of pyridine afforded 1,2,3,4-tetra-O-acetyl-1,4-bis(1-acetyl-4-aryl-5-thioxo-1,2,4-triazol-3yl)galacto-tetritols (7). Compounds 3a, 3b and 6a-c showed no antibacterial activity against Bacillus subtilis, Escherichia coli, P...

Cyclization of aldonic acid aroylhydrazides to 1,3,4-oxadiazoline derivatives

Abstract d -Glucono-1,5-lactone reacts with aroylhydrazines to give the corresponding 1-aroyl-2- d -gluconylhydrazines. Condensative cyclization of these compounds using triethyl orthoformate gave the corresponding 5-aryl-2-ethoxy-3- d -gluconyl-2,3-dihydro-1,3,4-oxadiazoles.

Cyclization of 2,3,4,5-tetra-O-acetylgalactaric bis-(aroylhydrazides) to saccharide bis(1,3,4-oxadiazolyl) derivatives

Abstract Condensation of 2,3,4,5-tetra-O-acetylgalactaroyl dichloride with two equivalents of various aroylhydrazines gave the corresponding 2,3,4,5-tetra-O-acetylgalactaric bis(aroylhydrazides). Condensative and dehydrative cyclization of these bis(hydrazides) with triethyl orthoformate and phosphoryl chloride, respectively, gave the corresponding 3,3′-(2,3,4,5-tetra-O-acetylgalactar-1,6-dioyl)-bis(5-aryl-2-ethoxy-2,3-dihydro-1,3,4-oxadiazole) and 1,2,3,4-tetra-O-acetyl-1,4-bis(5-aryl-1,3,4-oxadiazol-2-yl)-galacto-tetritols. The elucidation of the structure of the compounds prepared is discussed and mechanistic pathways for their formation are proposed.

Synthesis of 3-(Tetritol-1-YL)-6-Phenyl-1,2,4-Triazolo[3,4-a]Phthalazines and Conformational Analysis of their Acetates

ABSTRACT Condensation of 1-hydrazino-4-phenylphthalazine with D-arabinose, L-arabinose, D-lyxose, and D-xylose gave the corresponding 3-(tetritol-l-yl)-6-phenyl-1,2,4-triazolo[3,4-a]phthalazines (acyclic C-nucleoside analogs). D-Ribose, on the other hand, reacted with the same hydrazine to give the corresponding aldehydo-D-ribo-(4-phenyl-1-phthalazinyl) hydrazone. Catalytic dehydrogenative cyclization of this hydrazone with palladium-on-charcoal affected its transformation into the corresponding triazolophthalazine. Acetylation of the prepared acyclic C-nucleoside analogs gave the corresponding tetra-O-acetyl derivatives, the conformational analysis of which has been studied using proton magnetic resonance spectroscopy. Results of some biological activities of the prepared compounds are reported.