Showing papers by "Wafaa S. Hamama published in 2011"

Synthesis and Antioxidant Evaluation of Some New 3‐Substituted Coumarins

Abstract: 3-Acetylcoumarin (1) was utilized as a key intermediate for the synthesis of 2-aminothiazole derivative 3 via bromination of 1 to afford acetylbromide 2 followed by treatment with thiourea or via Biginelli reaction of 1. Treatment of 3 with 5-chloro-3-methyl-1-phenyl-1H-pyrazole-4-carbaldehyde, 2-methyl-4H-benzo[d][1,3]oxazin-4-one, furo[3,4-b]pyrazine-5,7-dione or 2-methyl-5,6,7,8-tetrahydro-4H-benzothieno[2,3-d][1,3]oxazin-4-one afforded diazine derivatives 4-7. Also, pyridopyrimidine 8 was obtained via a one pot reaction of 6-aminothiouracil, p-chlorobenzaldehyde and 3-acetylcoumarin. Moreover, refluxing of 6-aminothiouracil with one equivalent amount of 2 afforded the thiazolopyrimidine 9, while the pyrrolothiazolopyrimidine 10 was revealed when two equivalent amounts of 2 was used. Furthermore, treatment of enamine 11 with 2-aminobenzothiazole or 6-aminothiouracil afforded the pyrimidine derivatives 12 and 13, respectively. Transamination of enamine 11 with m-anisidine followed by cyclization of the resulting enaminone 14 gave the desired quinoline 15. Also, treatment of 11 with thiophenol in dioxane gave the mercapto derivative 16. Moreover, coupling of 11 with 4,6-dimethyl-1H-pyrazolo[3,4-b]pyridin-3-yl-diazonium chloride, followed by complete cyclization of the resulting product afforded the pyridopyrazolothiazine 19 via the intermediate 18. Furthermore, the pyrazolopyrimidine 20 was revealed via a one pot condensation of 11, 3-methyl-1-phenyl-1H-pyrazol-5(4H)-one and ammonium acetate. The thiadiazine derivatives 21-23 were obtained via treatment of 2 with the corresponding o-aminothiols. Desulphonation of 23 afforded the pyrazolotriazine 24. Finally, reaction of 2 with 2-hydroxybenzaldehyde gave benzofuran derivative 25. Representative compounds of the synthesized products were evaluated as antioxidant agents.

Synthesis and antimicrobial and antioxidant activities of simple saccharin derivatives with N-basic side chains

Abstract: A new class of N-basic side chains was obtained from 2,3-dihydro-2H-3-oxobenzo[d]isothiazole and aliphatic or aromatic aldehydes. Secondary amines (morpholine, N-methylpiperazine and ethyl isonipecotate) afforded tertiary N-basic side chains (4–6), while dibasic secondary amines (such as piperazine) gave bis-tertiary N-basic side chains (2). On the other hand, the use of mono- or dibasic primary amines namely; aniline, anisidine, phenyl hydrazine, o-hydroxy benzoic acid hydrazide, hydrazine hydrate, and ethylenediamine (instead of secondary amines) afforded secondary N-basic side chain as mono component or as bis component 7a-c, 9a-c, 11 and 12a-c. In addition, secondary Mannich base was synthesized via Michael addition to the corresponding aldimine. The new compounds were investigated for antioxidant and antimicrobial activities. Compounds 2, 7c and 12a exhibited significant antimicrobial activity, whereas compounds 7a, 7b, 9b, 9c and 11 exhibited high antioxidant activity as compared to ascorbic acid, These compounds showed the best protective effect against DNA damage induced by bleomycin.

Reactivity features of cyclododecanone

Abstract: Cyclododecanone is a highly important synthetic intermediate for macrocyclic systems. This review is the sole and comprehensive one that covers the different aspects of cyclododecanone chemistry over the period from 1950 to 2010.

Fused and spiro nitrogen heterocycles of quinuclidine and its C-nucleosides

Abstract: Quinuclidin-3-one ( 1 ) was used as a versatile intermediate for the synthesis of fused and spiro quinuclidine and its C -nucleosides. The reaction of 1 with formalin and secondary amines namely; morpholine, piperidine, and piperazine afforded the corresponding Mannich bases 2 - 4 in acid medium. Quinuclidino[3,2- b ]pyran 5 has been synthesized via a selective cyclocondensation reaction between Mannich base of quinuclidinone hydrochloride 2 and malononitrile. The transformation of 1 with formalin and methylamine in molar ratio (1:20:2) afforded the spiro compound 7 . Ring expansion of 2 under Schmidt reaction conditions gave the 1,3-diazabicyclo[3.2.2]nonanone derivative 6 . Eventually, the synthesis of C -nucleosides 10 , 12 - 14 were achieved by using aldohexoses and aldopentose catalyzed by zinc chloride, while, the bis -quinuclidine derivative 15 was obtained by using sodium carbonate. Newly synthesized compounds were characterized by IR, 1 H NMR, and mass spectral data.