No abstract

A series of bis-compounds (2) were synthesized by condensing dihydro-1,3-(disubstituted)phenyl-2-thioxopyrimidine-4,6(1H,5H)-dione with hippuric acid in presence of acetic anhydride. The compound (2) on further treatment with aromatic amine afforded dihydropyrimidine (3) through an eco-friendly procedure by sonication. The sonication method reduces time and gives higher yields, and also the effluent produced is free from hazardous contamination and organic by-products. The novel pyrimidines were also synthesized by traditional methods for comparison purposes and sonication method was found to be superior. Structures of the synthesized compounds have been elucidated on the basis of elemental analysis and spectral data.

A simple and efficient method has been developed for the synthesis of 2,4,7-tri(substituted) phenyl-2,4,8,10-tetraza-3,9-dithioxo-5-oxobicyclo-[4.4.0]dec-1(6)-ene (4) and 2,4,7-tri(substituted)phenyl-2,4,8,10-tetraza-3-thioxo-5,9-dioxobicyclo[4.4.0]dec-1(6)-ene (5), by a one-pot, three-component cyclocondensation reaction of a 1,3 dicarbonyl compound (thiobarbituric acid), an aromatic aldehyde, and urea/thiourea using catalytic a amount of concentrated HCl in refluxing ethanol. Representative samples were screened for their anti-microbial activity against the Gram-negative bacteria, Escherichia coli and Proteus aeruginosa, and the Gram-positive bacteria, Staphyllococcus aureus and Corynebacterium diphtheriae using the disc diffusion method. The structures of the products were confirmed by IR, 1 H-and 13 C-NMR spectroscopy, as well as by elemental analysis.

New potent antibacterials, fused isoxazole and pyrazole derivatives, were synthesized using 5,5-dimethylcyclohexane-1,3-dione (1) and 3-[(4-chlorobenzylidene) amino]-2-thioxoimidazolidin-4-one (2) as synthons. Aromatic aldehydes on condensation with 1 and 2 gave 2-arylidene-5,5-dimethylcyclohexane- 1,3-dione (3) and 5-arylidene-3-[(4-chlorobenzylidene)amino]-2-thioxoimidazolidin-4-one (4), respectively. Compounds 3 and 4 were forced to undergo heterocyclization reaction with nucleophilic reagents to give the title compounds. The newly synthesized heterocyles (5-8) were characterized based on their chemical properties and spectroscopic data, and were found to inhibit Staphylococcus aureus and Corynebacterium diphtheriae.

A series of 1-(3,4-dihydro-3-oxo-2H-1,4-benzoxazine-2-carbonyl)-3-methyl-4-(substituted phenylhydrazono)-2-pyrazolin-5-ones have been synthesized by the reaction of 2H-3,4-dihydro-3-oxo-1,4-benzoxazine-2-carboxylic acid hydrazide with substituted acetoacetic ester derivatives using acetic acid as solvent under microwave irradiation (MWI), as well as by conventional methods. The reaction rate is enhanced tremendously and the yields are improved under MWI as compared to conventional methods.