Click 1,4-regioselective synthesis, characterization, and antimicrobial screening of novel 1,2,3-triazoles tethering fluorinated 1,2,4-triazole and lipophilic side chain

Abstract

Base-catalyzed alkylation of 5-(4-fluorophenyl)-2,4-dihydro-1,2,4-triazole-3-thione (3) with one or two equivalents of propargyl bromide in presence of triethylamine as catalyst selectively produced the thiopropargylated 1,2,4-triazole 7 in 90 % yield. Under the same reaction conditions, 4-ethyl-5-(4-fluorophenyl)-3-(prop-2-yn-1-ylthio)-1,2,4-triazole (8) was produced. Conversely, when the propargylation was carried out in presence of sodium bicarbonate, a mixture of S,N 4- (24) and S,N 2-bis(propargylated) triazoles (25) was obtained in 85 % overall yield. The click 1,3-dipolar cycloaddition reaction of the mono- (7, 8) and/or bis(propargylated)-1,2,4-triazoles (24) with a variety of long-chain alkyl azides, conducted in t-BuOH:H2O (10:1) in presence of sodium ascorbate and copper(II) sulfate at room temperature, afforded the regioselective 1,4-disubstituted mono- (14–18) and bis(1,2,3-triazole) derivatives (26–30) containing a fluorinated 1,2,4-triazole moiety and a lipophilic side chain. The structures of the new products were elucidated by infrared (IR), 1H and 13C nuclear magnetic resonance (NMR), and mass spectrometry. They were also assessed in vitro for their antimicrobial potency against six bacteria (Bacillus subtilis, Streptococcus pneumonia, Staphylococcus aureus, Escherichia coli, Pseudomonas aeruginosa, and Klebsiella pneumonia) and two fungi (Aspergillus fumigatus and Candida albicans). The bioassay results revealed that some of the tested compounds displayed promising antimicrobial activity.