Hassan A. Etman

Synthesis and antitumor evaluation of some new 1,3,4-oxadiazole-based heterocycles

The synthetic strategies and characterization of some novel 1,3,4-oxadiazole derivatives carrying different pharmacophores and heterocyclic rings that are relevant to potential antitumor and cytotoxic activities are described. The antitumor activities of the newly synthesized compounds were evaluated according to the protocol of the National Cancer Institute (NCI) in-vitro disease-oriented human cells screening panel assay. The results revealed that five compounds, namely 2, 7a, 11a, 12b, and 17; displayed promising in-vitro antitumor activity in the 4-cell lines assay. Incorporating a thiazole ring to 1,3,4-oxadiazole skeleton resulted in better antitumor activities than those displayed by the pyrazole and thiophene ring systems. Transformation of 1,3,4-oxadiazole 2 to N-(6-amino-7H-pyrazolo[5,1-c][1,2,4]triazol-3-yl)benzamide (15) diminished the antitumor activity.

Developments in 1,2,5-triazepine chemistry: Reactions and synthetic applications

ABSTRACT The chemistry of 1,2,5-triazepines and related compounds is reported. The investigated heterocycles are monocyclic and fused 1,2,5-triazepines. The different sections cover the synthesis and reactions of monocyclic and fused heterocycles incorporating 1,2,5-triazepine ring systems. This review also covers modifications of the 1,2,5-triazepines into many useful ring systems using a host of reagents and other multistep transformations. The biological evaluation of the target compounds is described, as well as the synthetic applications. The reaction mechanisms are discussed. GRAPHICAL ABSTRACT

Thiazolidin-5-Ones: Synthesis and Reactions

Thiazolidin-5-ones and their derivatives have been long used as precursors for the synthesis of biologically active molecules. The general methods of preparations of thiazolidinones have been mentioned. The reactions of the title compounds are subdivided into groups that cover reactions to yield monoheterocycles.

SYNTHESIS OF SOME NEW THIAZOLIDIN-5-ONE DERIVATIVES OF PHARMACEUTICAL INTEREST

Condensation of thiazolidin-5-one derivative 1 with different aromatic aldehydes gave the corresponding arylidenes 2a–e. Compound 2e was reacted with urea and thiourea to give the corresponding thiazolo[5,4-d]pyrimidine derivatives 3a, b, respectively. Treatment of compound 1 with phenyl isothiocyanate in basic DMF gave the nonisolable potassium salt of the adduct 4, which underwent heterocyclization upon treatment with chloroacetyl chloride and phenacyl bromide to give the corresponding [2,4′] bisthiazolidinylidenes 5 and 8. Moreover, the reactions of compound 1 with a variety of reagents, e.g., ninhydrin and isatin, were investigated. The structures of these compounds were established by analytical and spectral data.

Synthesis and reactions of 2-cyano-2-(5-oxo-3-phenyl-thiazolidin-2-ylidene)-acetamides

The base promoted nucleophilic addition of cyanoacetamide derivatives 2a,b to equimolar amount of phenyl isothiocyanate in DMF containing potassium hydroxide afforded the corresponding potassium sulfide salts 3a,b which were not isolated but which underwent heterocyclisation upon treatment with chloroacetyl chloride to give the corresponding 2-cyano-2-(5-oxo-3-phenylthiazolidin-2-ylidene)-acetamide derivatives 4a,b. The reactions of 4a,b with aryl diazonium salts, bromine and aromatic aldehydes were studied in order to obtain compounds 5–11.

A new route for the synthesis of phenazine di-N-oxides

SummarySeveral phenazine 5,10-dioxides (7a–d) were prepared by the reaction of 2-methyl-3-acetylquinoxaline 1,4-dioxide (2) with different aromatic aldehydes or by direct cyclization of the quinoxaline cinnamoyl derivatives3 in basic medium. In addition, the phenazine derivatives8 and9–12 were synthesized by a one-pot reaction of substitutedo-nitroanilines with different hydroxy compounds in the presence of sodium hypochlorite solution.ZusammenfassungMehrere Phenazin-5,10-dioxide (7a–d) wurden durch Reaktion von 2-Methyl-3-acetylchinoxalin-1,4-dioxid (2) mit verschiedenen aromatischen Aldehyden oder durch direkte Cyclisierung der Chinoxalinderivate3 in basischem Milieuhergestellt. Zusätzlich wurden die Phenazinderivate8 und9–12 in einer Eintopfreaktion von substituierteno-Nitroanilinen mit verschiedenen Hydroxyverbindungen in Gegenwart von Natriumhypochloritlösung synthetisiert.

Synthesis and antioxidant evaluation of some new 2-benzoylamino-5-hetaryl-1,3,4-oxadiazoles

A series of new functionalized 2-benzoylamino-5-hetaryl-1,3,4-oxadiazoles were efficiently synthesized via the reaction of the versatile key intermediates, 2-benzoylamino-5-cyanomethyl-1,3,4-oxadiazole (1) and N-(5-(5-amino-3-phenylamino)-1H-pyrazol-4-yl)-1,3,4-oxadiazol-2-yl)-benzamide (13), with some appropriate electrophilic reagents. The structures of the newly synthesized compounds were established on the basis of elemental analyses, spectral data, and by alternative synthesis wherever possible. The mechanisms of the studied reactions are discussed. Also, we evaluate the antioxidant activity of some representative examples of the newly prepared compounds. Among the synthesized compounds, 2-benzoylamino-5-cyanomethyl-1,3,4-oxadiazole (1) and N-(5-(7-methyl-5-oxo-2-(phenylamino)-4,5-dihydropyrazolo[1,5-a]pyrimidin-3-yl)-1,3,4-oxadiazol-2-yl)benzamide (17) showed excellent antioxidant activity and exhibited high protection against DNA damage induced by the Bleomycin iron complex.

Synthesis of Novel 1,2,3,4-Tetrahydrocarbazole Derivatives of Biological Interest

2-Cyano-N-(tetrahydrocarbazole)acetamide (1) was utilized for the synthesis of several new arylazocarbazole derivatives (2a–e). Compound (1) reacted with phenyl isothiocyanate to yield the corresponding non-isolable intermediate (3), which gave, upon treatment with dilute hydrochloric acid, thiocarbamoyl derivative (4). Compound (3) reacted with chloroacetone, chloroacetic acid, chloroacetyl chloride, ethyl bromoacetate, and phenacyl bromide to afford thiazolone derivatives (6), (8), and (10), respectively. Compound (1) was heated in the presence of pyridine and/or hydrazine hydrate and/or isatine to give the corresponding tetrahydrocarbazole derivatives (13), (14), and (18), respectively. Supplemental materials are available for this article. Go to the publishers online edition of Phosphorus, Sulfur, and Silicon and the Related Elements to view the free supplemental file.

Chemistry of 2-Cyanomethylbenzothiazole

This review article includes the methods for the preparation of 2-cyanomethylbenzothiazole, its chemical reactivity towards different electrophiles and nucleophiles, and its use for the synthesis of heterocyclic compounds. Its biological activity and applications are also reported. This review includes 159 references.

Co-sensitization of Ru(II) complex with terthiophene-based D–π–π–A metal-free organic dyes for highly efficient dye-sensitized solar cells: influence of anchoring group on molecular geometry and photovoltaic performance

In this work, we studied the photovoltaic performance of two novel metal-free organic dyes (MR-3 and MR-4) with the molecular motif D–π–π–A carrying the same donor (trimethoxy benzene) and terthiophene (π) units but with different anchoring moieties. MR-3 and MR-4 displayed PCE of 4.54% and 2.38%, respectively. Furthermore, MR-3 co-sensitized with NCSU-10 exhibited improved efficiency of 9.09% than NCSU alone (8.74%). One of the merits in the studied structure motif D–π–π–A was modulating the molecular geometry of the sensitizers and eliminating the steric effect between the donor and π-spacer (terthiophene) to furnish a coplanar molecular structure and to maximize electronic conjugation. In addition, coupling-steric effect precludes effective conjugation and reduces light harvesting as it increases the band gap. To eliminate the steric effect of the aryl moiety at ortho position of 2,4,6-trimethoxyphenyl donor, another conjugated spacer, alkene (CHCH), was inserted between the donor and the π-spacer (terthiophene), which maximized the electron conjugation throughout the coplanar system; the optimized molecular geometry of the dyes was calculated using DFT. Another molecular geometry feature that was studied was the influence of different anchoring groups on coplanarity of the dye structure and consequently the photovoltaic performance. In the case of MR-3, where the anchoring group is based on the cyanoacrylic group, the optimized geometry was found coplanar. However, when rhodanine moiety was used as an anchoring group, the calculated optimized geometry of the dye (MR-4) was not coplanar, which resulted in weak electronic coupling and inferior electronic injection into TiO2 conduction band edge. The inter-relationship between the optimized geometry of the dyes and their photovoltaic performance is discussed.