Elham Sayed Darwish

Facile Synthesis of Heterocycles via 2-Picolinium Bromide and Antimicrobial Activities of the Products

The 2-picolinium N-ylide 4, generated in situ from the N-acylmethyl-2-picolinium bromide 3, underwent cycloaddition to N-phenylmaleimide or carbon disulfide to give the corresponding cycloadducts 6 and 8, respectively similar reactions of compound 3 with some electron-deficient alkenes in the presence of MnO2 yielded the products 11 and 12. In addition, reaction of 4 with arylidene cyanothioacetamide and malononitrile derivatives afforded the thiophene and aniline derivatives 15 and 17, respectively. Heating of picolinium bromide 3 with triethylamine in benzene furnished 2-(2-thienyl)indolizine (18). The structures of the isolated products were confirmed by elemental analysis as well as by 1H- and 13C-NMR, IR, and MS data. Both the stereochemistry and the regioselectivity of the studied reactions are discussed. The biological activity of the newly synthesized compounds was examined and showed promising results.

SYNTHESIS AND ANTIMICROBIAL EVALUATION OF SOME NEW PYRIDINE BASED HETEROCYCLES

A facile and convenient synthesis of pyridine, pyridazine, 2(3H)-1,3,4-thiadiazole and pyrazole derivatives incorporating a pyridine-2-ylcarboxamido moiety via the versatile, readily accessible 3-oxo-N-(pyridin2-yl)butanamide is described. Antimicrobial evaluation of some selected examples from the synthesized products was carried out and showed moderate activity.

SYNTHESIS AND ANTIMICROBIAL EVALUATION OF SOME ISOXAZOLE BASED HETEROCYCLES

The versatile hitherto unreported 2-cyano-N-(4-{[(5-methylisoxazol3-yl)amino]sulfonyl}phenyl)acetamide (3) was utilized for the synthesis of a variety of heterocycles incorporating sulfamoyl moiety. The 2-pyridone derivatives were obtained via reaction of cyanoacetamide with pentane-2,4-dione, arylidenes malononitrile, or terephthalaldehyde and malononitrile upon heating under reflux in the presence of a catalyst. Condensation of the cyanoacetamide 3 with salicylaldehyde furnished the corresponding chromene derivatives. Coupling of 3 with arene diazonium chlorides gave the hydrazone derivatives 13a-c, which upon treatment with hydrazine hydrate and ethyl chloroformate furnished the corresponding pyrazole and triazine derivatives, respectively. Reaction of 3 with carbon disulfide and 1,2-dibromoethane, 1,3-dibromopropane or dimethyl sulfate afforded 2-cyano-2-(1,3-dithiolan-2-ylidene)-N-(4-{[(5-methylisoxazol-3yl)amino]sulfonyl}phenyl)acetamide (18), 2-cyano-2-(1,3-dithian-2-ylidene)-N4-{[(5-methylisoxazol-3-yl)amino]sulfonyl}phenyl)acetamide (19), and 2-cyanoN-(4-{[(5-methylisoxazol-3-yl)amino]sulfonyl}phenyl)-3,3-bis(methylthio)acrylamide (20). The newly synthesized compounds were evaluated for their in vitro antibacterial and antifungal activities, and showed promising results. INTRODUCTION Cyanoacetamides are highly reactive bifunctional compounds. The carbonyl and the cyano functions of these compounds are suitably situated to enable reactions with common reagents to form a variety of heterocycles. Also, the active methylene of cyanoacetamide can take part in a variety of condensation and substitution reactions. Moreover, cyanoacetamides and their related heterocyclic derivatives have attracted great attention due to their interesting biological, therapeutic value and pharmaceutical activities HETEROCYCLES, Vol. 89, No. 6, 2014 1393

Synthesis, Acidity Constants and Tautomeric Structure of the Diazonium Coupling Products of 2-(Benzylsulfanyl)-7H-purin-6- one in Its Ground and Excited States

A series of new 8-arylhydrazono-2-(benzylsulfanyl)-7H-purin-6-ones 6 were synthesized, their electronic absorption spectra in different organic solvents of varying polarities were investigated and their acid dissociation constants in both the ground and excited states were determined spectrophotometrically. The tautomeric structures of such products were elucidated by spectral analyses and correlation of their acid dissociation constants with the Hammett equation. The results indicated that the studied compounds 6 exist predominantly in the hydrazone tautomeric form 6A in both the ground and excited states.

Synthesis, Characterization, Tautomeric Structure and Solvatochromic Behavior of Novel 4-(5-Arylazo-2-Hydroxystyryl)-1-Methylpyridinium Iodide as Potential Molecular Photoprobe

A novel series of the title compound 4-(5-arylazo-2-hydroxystyryl)-1-methylpyridinium iodide 6 has been synthesized via condensation reactions of the arylazosalicylaldehyde derivatives 4a–i with 1-methyl-picolinium iodide 5. The structures of the new arylazo compounds were characterized by 1H NMR, IR, mass spectroscopy, as well as spectral and elemental analyses. The electronic absorption spectra of arylazomerocyanine compounds 6 were measured in different buffer solutions and solvents. The pK′s and pK*′s in both the ground and excited states, respectively, were determined for the series and their correlations with the Hammett equation were examined. The results indicated that the title arylazomerocyanine dyes 6 exist in the azo form 6A in both ground and excited states. The substituent and solvent effects (solvatochromism) of the title compound arylazomerocyanine dyes were determined using the Kamlet-Taft equation and subsequently discussed.

Enamines in Heterocyclic Synthesis: A Novel Simple and Efficient Route to Condensed Pyridazines

An efficient and easy preparation of enamine derivatives, via active methyl and methylene compounds by in situ-generated 1-(diethoxymethyl)piperidine, produced from the mixture of triethyl orthoformate/piperidine/DMF, are described. Some new pyridazinone derivatives have been synthesized from the reaction of enamines with hydrazine hydrate and cyanoacid hydrazide. Graphical Abstract Enamines in Heterocyclic Synthesis: A Novel Simple and Efficient Route to Condensed Pyridazines