Convenient methods for the synthesis organotellurium compounds derived from pyrazole derivatives: synthesis and antimicrobial evaluation

Abstract

A new series of organic tellurium compounds containing pyrazole derivatives were prepared. Initially, penta-2,4-dione-3-tellurocyanate (1) was prepared by the refluxing equimolar amounts of potassium tellurocyanate with 3-chloro-2,4-pentadione. Compound 1 was oxidized by excess bromine to obtain the corresponding tribromide (2). The cycloaddition reaction of compound 1 with phenylhydrazine formed 3,5-dimethyl-1-phenyl-4-tellurocyanatopyrazole (3 (in good yield. Treatment of compound 3 with excess bromine gave 3,5-dimethyl-1-phenylpyrazole-4-yltellurium tribromide (4) in an excellent yield. Reduction of compound 3 with a solution of 10% NaOH gave the corresponding ditelluride (5) in excellent yield. Compounds with a general formula of ArTeX₃; X = Cl (6) or I (7) were synthesized in excellent yields by reacting compound 3 with excess thionyl chloride or iodine, respectively. Refluxing ditelluride 5 with activated copper powder gave the corresponding telluride (8) in very good yield. Finally, tellurated pyrazole dihalides compounds 9–11 were prepared by reacting 8 with equimoles of the thionyl chloride, bromine and iodine, respectively. The structures of compounds 1–11 were elucidated according to their CHN elemental analyses and FTIR, ¹H- and ¹³C-NMR spectroscopies and mass spectrometry. The antibacterial activity for both Gram-positive and Gram-negative bacteria were evaluated. The tested compounds showed a good degree against the growth of fungi and bacteria. Most the antimicrobial activity of the prepared compounds was better than fluconazole.

Graphical Abstract

Keywords:

• pyrazoles
• tellurated pyrazoles organotellurium
• cycloaddition reactions
• potassium tellurocyante
• aryltellurocyanate
• antimicrobial activity