2-Amino-5-(3-fluoro-4-methoxyphenyl)thiophene-3-carbonitrile have been synthesized from 1-(3-fluoro-4-methoxyphenyl)ethanone, malononitrile, a mild base and sulfur powder using Gewald synthesis technique and the intermediate was treated with 1,3-disubstituted pyrazole-4-carboxaldehyde to obtain the novel Schiff bases. 1,3-disubstituted pyrazole-4-carboxaldehyde derivatives have been synthesized by Vilsmeier-Haack reaction in the course of a multi-step reaction. The structure of novel compounds were established on the basis of their elemental analyses IR, 1 H NMR, 13 C NMR, and mass spectral data and then screened for their in vitro antimicrobial activity. Among them 5a, 5c, 5f and 5h showed excellent activity when compared to other derivatives. Remaining derivatives showed moderate activity.

The aim of this study was to synthesize newer potent Schiff bases by condensing 2-amino-5-(2,4-dichlorophenyl)thiophene-3-carbonitrile and 1,3-disubstituted-1Hpyrazole-4-carbaldehydes, and to investigate their biological activity. The compounds were synthesized via Gewald synthesis and characterized by spectral data and elemental analyses. They were screened for their in vitro antibacterial and antiinflammatory activities. The synthesized compounds were also evaluated for in vitro antitubercular activity against Mycobacterium tuberculosis H37Rv using the microplate Alamar Blue assay. Compounds 8b, 8c, 8f, 8g, 8k, 8n, and 8o showed promising antibacterial activity. The interactions between the substituted pyrazoles and bovine protein showed promising anti-inflammatory activity. The experimental results revealed compound 8a as a promising antitubercular agent. Hemolytic assays confirmed that the compounds are nontoxic, with percentage hemolysis ranging from 3.6 to 20.1, at a concentration of 1 mg/ml. The results suggest that the pyrazole ring and the substitution pattern on the heterocyclic moiety have an effect on the bioactivity.

Pursuing our recent interest regarding the antimicrobial activity of Schiff bases derivatives, we have synthesized a series of 6-(substitutedphenyl)- N' -(( E )-(substitutedphenyl)methylidene)-2-methylpyridine-3-carbohydrazides ( 5a-n ) and evaluated their antibacterial activity. Structures of these compounds were confirmed by standard studies of FTIR, 1 H NMR, 13 C NMR, MS and elemental analysis. Antibacterial activity of synthesized molecules was tested against Gram-positive ( S. aureus and E. faecalis ) and Gram-negative ( E. coli and P. aeruginosa ) bacterial strains. Synthesized compounds showed good antibacterial activity at a lower concentration than standard. Most of the compounds ( 5a , 5c , 5i , 5j and 5n ) are potent against all the tested bacterial strains with MIC values ranging from 1.56-12.5 μg/mL.

Abstract2‐amino‐5‐(3‐fluoro‐4‐methoxyphenyl)thiophene‐3‐carbonitrile derivatives have been synthesized from 1‐(3‐fluoro‐4‐methoxyphenyl)ethanone, malononitrile, mild base, and sulfur powder using the Gewald method through a multistep reaction sequence. The structures of newly synthesized compounds were established on the basis of their elemental analyses, IR, 1H NMR, 13C NMR, and mass spectral data, and then synthesized compounds were screened for their in vitro antimicrobial activity. Among them, derivatives 3b (thiphene), 3f (pyrazole), and 3d (halogen) showed good activity and remaining derivatives exhibited moderate activity.

Heterocyclic chemistry is the interesting area for the effective approach and for the invention of biologically active 1,3,4-oxadiazole cores. 1,3,4-Oxadiazole is a five membered heterocyclic ring which plays key role in the development of new medicinal species for the treatment of numerous diseases. Hence, nowadays researchers have developed the innovative methods for the synthesis of 1,3,4-oxadiazole derivatives and their medicinal applications. Therefore, results of recent developments in the synthesis and biological applications of 1,3,4-oxadiazole candidates over the past 15 years (2005-2019) are reviewed in the present article. The information in the present article may be useful to many researchers which lead to exploration of new therapeutic species for the society.

In aim of obtaining novel bio‐active compounds, a new series of 5‐(3,5‐difluorophenyl)‐2‐(2‐imino‐5‐arylidene)‐4‐oxothiazolidin‐3‐yl)thiophene‐3‐carbonitrile (6a–d) and N‐(3‐cyano‐5‐(3,5‐difluorophenyl)thiophen‐2‐yl)‐2‐(substitutedamino)acetamide (7a–f) were synthesized via Gewald's method and characterized by 1H/13C nuclear magnetic resonance, Fourier‐transform infrared, mass spectrometry, and elemental analyses. All the newly prepared compounds were screened for their in vitro anti‐tubercular activity against virulent strain M. tuberculosis (H37Rv) at different concentrations ranging from 0.2 to 100 μg/ml. Most of the compounds were potent showing better inhibition at concentrations 6.25, 12.5, 25, 50, and 100 μg/ml. The anti‐inflammatory activity of the compounds was studied using inhibition of albumin denaturation technique. Tested compounds exhibited remarkable anti‐inflammatory activity. Hemolytic assay also confirmed that compounds are non‐toxic with a percentage hemolysis ranging from 1.81 to 14.94 at a concentration of 1 mg/ml. The results suggest that amino‐substituted acetamide and thiazolidin‐4‐one moiety, as well as the substitution pattern on the heterocyclic ring, have an effect on bioactivity.

A new series of 1‐(9‐benzylidene‐2,7‐dichloro‐9H‐fluoren‐4‐yl)‐2‐(methylselanyl)ethanol was synthesized by a simple Knoevenagel condensation of 1‐(2,7‐dichloro‐9H‐fluoren‐4‐yl)‐2‐(methylselanyl)ethanol with different substituted aromatic aldehydes in basic media. These synthesized compounds were confirmed on the basis of their elemental analyses, infrared (IR), 1H NMR, 13C NMR, and mass spectral data and screened for the antibacterial and antifungal activity. The preliminary antibacterial and antifungal screening revealed that the compounds 8c (dichloro), 8d (fluoro), 8e (chloro), 8i (methoxy), and 8l (methyl) displayed moderate to good activity. The antibacterial results of these compounds were further supported by in silico molecular docking studies, for the inhibition of Escherichia coli MurB enzyme (PDB code: 2MBR), wherein they showed higher binding energy and good affinity towards the active pocket of the enzyme compared with that of the standard drug Ciprofloxacin. Thus, the plausible mechanism of their antibacterial activity was owed to their inhibitory action of the bacterial MurB enzyme.

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