Kamal F. M. Atta

Synthesis and Antibacterial Activities of Novel Imidazo[2,1-b]-1,3,4-thiadiazoles

2-Amino-5-(2-aryl-2H-1,2,3-triazol-4-yl)-1,3,4-thiadiazoles 2-4 have been synthesized by the reaction of 2-aryl-2H-1,2,3-triazole-4-carboxylic acids 1 with thiosemicarbazide. Their reaction with phenacyl (p-substituted phenacyl) bromides led to formation of the respective 6-aryl-2-(2-aryl-2H-1,2,3-triazol-4-yl)imidazo[2,1-b]-1,3,4-thiadiazoles 5. Reactivity of the latter fused ring towards reaction with different electrophilic reagents afforded the corresponding 5-substituted derivatives 6-8. The structure of the above compounds was confirmed from their spectral characteristics. Some of these compounds were found to possess slight to moderate activity against the microorganisms Staphylococcus aureus, Candida albicans, Pseudomonas aeruginosa, and Escherichia coli.

MAOS of Quinoxalines, Conjugated Pyrazolylquinoxalines and Fused Pyrazoloquinoxalines from l‐Ascorbic and d‐Isoascorbic Acid

Microwave‐assisted organic synthesis (MAOS) has been used to accelerate the conversion of L‐ascorbic acid (1) and D‐isoascorbic acid (2) to the title heterocycles by conversion to 3‐(L‐threo‐ or D‐erythro‐glycerol‐1‐yl)quinoxaline‐2‐carboxylic acid o‐aminoanilides (7 and 8), which were transformed to lactones 9 and 10, respectively, under acidic condition. The acetylation of compounds 9 and 10 afforded 3‐(L‐threo‐ or D‐erythro‐2,3‐di‐O‐acetyl‐glycerol‐1‐yl)quinoxaline‐2‐carboxylic‐γ‐lactones (11 and 12). Treatment of 10 with phenylhydrazine gave the hydrazides 13. 3‐[1‐Phenylhydrazono‐L‐threo‐2,3,4‐trihydroxybutyl]‐1H‐quinoxalin‐2‐one (14) and its D‐erythro‐analog 15 were prepared from 1 and 2. Subsequent cyclizations gave the respective pyrazolylquinoxalines 16 and 17 and pyrazolo[3,4‐b]quinoxalines 26 and 27. The regioselectivities of allylation and epoxypropylation of 16 and 17 were investigated and could be interpreted by the semiempirical AM1 method. Degradation of 26 or 27 gave 1‐phenylpyrazolo[3,4‐b]quinoxaline‐3‐carboxaldehyde (28). Degradation of 14 or 15 gave aldehyde 29. The combination of using microwave (MW) and bentonite, as a support, has improved the yields in less reaction times in addition to performing the reactions under environmentally clean conditions

MAOS of Sugar Phenylosazones and their Derived Pyrazoles and Triazoles

Microwave‐assisted organic synthesis (MAOS) has proven to be practical to provide heterocycles from sugar osazones; an efficient method was developed for the characterization of sugars via their osazones 1–4 using microwave irradiation. The microwave‐assisted organic synthesis irradiation technique has been applied to convert d‐arabino‐hexose phenylosazone to 2‐phenyl‐4‐(d‐arabinotetrahydroxybutyl‐1,2,3‐triazole (5), which was then oxidized to the corresponding aldehyde whose oxime 9 was transformed to 4‐cyano‐2‐phenyltriazole 10. The condensation of 7 with thiosemicarbozide gave 10. Degradation of 1 afforded mesoxaldehyde 1,2‐bisphenylhydrazone 11, which cyclized to 1‐phenyl‐4‐phenylazo‐pyrazole (12) under acidic conditions. Irradiation of 6 in HBr/AcOH afforded 4‐(d‐arabino‐2′,3′‐di‐O‐acetyl‐1′,4′‐dibromobutyl)‐2‐phenyl‐2H‐1,2,3‐triazole. The acetylated phenylosazone was converted to furopyridazine 14. The irradiation of phenylosazone with acetic anhydride in pyridine gave the respective O‐acetyl derivative, whereas with boiling acetic anhydride gave the pyrazole 14, which afforded 15 and 16.

Chemistry of Pent-4-yne-1,3-diones (Acetylenic β-diketones) as Precursors for Heterocyclic Compounds

Abstract The pent-4-yne-1,3-diones (acetylenic β-diketones) have different reactive functionalities which let them attractive, particularly as precursors for heterocyclic compounds. This chapter surveyed the chemistry of their synthesis, which has started with the appropriate propiolic acid derivatives or acetylenic aldehydes. They have been converted to five-, six-, and seven-membered heterocyclic rings in addition to fused bicyclic compounds such as dithiepine, pyrrolo[1,2,3]triazole, thiathiophthene, pyrazolo[1,3]thiazines, pyrazolo[1,5-c]pyrimidines, and metal complexes. The spectroscopic properties have also been reviewed.