Microwave assisted synthesis of novel spiro diarylidenes and their antimicrobial assay

A rapid and high yield microwave assisted synthesis of a series of novel 7,9-bis-(arylidene)-4-methyl-2,6,10-triphenyl-2,3-diazaspiro[4,5]dec-3-ene-1,8-dione has been explored. The spiro diarylidene derivatives having nitrogen atom and alpha,beta-unsaturated ketone moiety were synthesized by aldol condensation between 4-methyl-2,6,10-triphenyl-2,3-diazaspiro[4,5]dec-3-ene-1,8-dione and corresponding aryl aldehydes followed by dehydration. The synthesized series of novel spirodiarylidene derivatives were characterized using IR, H-1- and C-13-NMR and mass spectra. Density functional theory (DFT) study was performed by Gaussian 09 software. The antimicrobial activities of the synthesized derivatives were evaluated against two pathogenic Gram-positive and Gram-negative bacterial strain and three pathogenic fungal species by disk diffusion method. The minimum inhibitory concentration was determined by the microbroth dilution technique. The results of the present study demonstrated that the examined compounds marked 5a and 5c, possessing 4-NO2 and 5-Br-2-OH substituents, are found to be more active against Gram-positive bacterium Staphylococcus aureus, 8 and 16 mu g mL(-1), respectively, and moderately active against Gram-negative bacteria Pseudomonas aeruginosa and Escherichia coli, compared to other synthetic derivatives. However, none of the synthesized derivatives showed any activity against Streptococcus pyrogenes. Compound 5e, possessing 2,4,6-(OCH3)(3)C6H3 moiety, exhibited broad spectrum activity against all fungal strains under study, but showed no antibacterial activity.