Polyethylene glycol-400 (PEG-400) is a recyclable and rapid reaction medium for synthesizing a new series of 4-(3-[substitutedphenyl]-4,5-dihydro-1-phenyl-1H-pyrazol-5-yl)-1H-imidazoles in two-step procedures by condensation of 1H-imidazole-4-carbaldehyde and various acetophenones to form chalcones followed by base-catalyzed cyclization employing phenyl hydrazine in a catalyst-free approach. The way of projected approach provides easy work-up, less reaction time, avoids metal-based and toxic catalysts, high yield, and reduces the use of carcinogenic organic solvents. The synthesized scaffolds have been screened for their anti-microbial and anti-tubercular activity against a set of pathogens.

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Background: Several strategies have been reported for the synthesis of thiazole derivatives. Methods: However, many of these methods suffer from several drawbacks. Several modifications have been made to counter these problems. Here, we have synthesized a new series of 2-(2-((1HImidazol- 4-yl)methylene)hydrazinyl)-4-(4-substitutedphenyl)thiazoles without using the catalyst at room temperature. Results: The structures of synthesized compounds have been confirmed by spectral analysis, such as Mass, IR, 1H NMR and 13C NMR. All synthesized compounds were screened for in vitro antibacterial activity against some gram-positive and gram-negative bacteria. Conclusion: The thiazole derivatives, with a pharmacologically potent group, discussed in this article may provide valued therapeutic important in the treatment of microbial diseases, especially against bacterial and fungal infections.

The tetrazole fused pyrimidine system possesses a broad spectrum of biological activities. So, we have synthesized 5-(substitutedphenyl)-7-(1Himidazol-4-yl)-4,7-dihydrotetrazolo [1,5-a]pyrimidine derivatives (5a-n) by reaction of chalcones with 5-aminotetrazole without catalyst in appropriate solvent. The structural elucidation of these compounds is based on MS, IR, 1 H-NMR and 13 C-NMR spectral data. The in vitro anti-microbial activity was investigated against Gram-positive and Gram-negative bacterial and fungal strains.It was found that the compounds 5a, 5b, 5c, 5d, 5e showed significant activities against tested organisms as compared to standard drugs (Ampicillin and Griseofulvin) while compounds 5a, 5c, 5i, and 5k showed good percentage of average inhibition in the dormant and active stage of tuberculosis.We carried out the synthesis of tetrazolo [1,5-a]pyrimidines in the acidic and basic catalytic amount at reflux temperature, but there was not much satisfied with the yield and reaction time of obtained products.Again the same reaction was carried out without any solvent or catalyst in fused condition but yield was very low. So from the above conclusion, we have chosen, an alcoholic solvents such as methanol, n-propanol, isopropanol, n-butanol and polar solvent like dimethylformamide (DMF) and 1,4-dioxane.After doing various optimizations in the experimental conditions, it was concluded that, when the reaction was carried out in n-butanol solvent showed better yield (87%) in less reaction time.All the newly synthesized compounds were characterized using IR, 1 H-NMR, 13 C-NMR, and mass spectroscopy. The IR spectrum of synthesized compounds exhibited characteristic absorption band at 3075 cm -1 for aromatic C=C stretching vibration band. Characteristic absorption band observed at 1315 cm -1 for C-N stretching in imidazole ring and at 1605 for C=N of the pyrimidine ring system and all other general frequency band are in good agreement with the structure. 1 H-NMR spectra of the compound 5b showed characteristic singlet signals at 12.16 ppm due to the proton of imidazole-NH and at 10.44 ppm due to the proton of fused pyrimidine-NH. Chiral carbon proton was observed doublet at 5.28 ppm with 2.80 Hz coupling constant value. The 1 H-NMR spectrum of compound 5c exhibited two doublets, arising from the two equivalent phenyl ring protons at 7.54 and 7.24 ppm. The 13 C-NMR spectrum of compound 5c showed signal at 53.23 ppm for the chiral carbon while at 96.00 ppm for the pyrimidine ring C=C carbon and at 21.12 ppm for the methyl carbon attached to phenyl ring. Molecular ion peak was observed in agreement with molecular weight of respective compound i.e. the molecular formula of compounds 5c and 5m by displaying molecular ion peaks at m/z 279 (M + ) and 325 (M + ) respectively. Scheme 1 PLAUSIBLE REACTION MECHANISM: Scheme 2The examination of the data of the Table 2 revealed that many of the compounds shown good activity against bacterial strain when compared with the standard drugs like Ampicillin, Chloramphenicol, and...