Microwave Assisted Synthesis of Some Pyridine Derivatives Containing Mercaptotriazole and Thiazolidinone as a New Class of Antimicrobial Agents

Abstract

A fast and facile procedure for the synthesis of pyridomercaptotriazole 4a–e and pyridothiazolidinone 5a–e is being reported starting from dihydropyridine 1a–e . Subsequent oxidation with nitrating mixture (HNO ₃ /H ₂ SO ₄ ) produced the anticipated 2,6-dimethylpyridine derivatives 2a–e , which were subsequently condensed with thiosemicarbazide in ethanol to produce the key intermediate 2,2′-[4-(4-substituted phenyl)- 2,6-dimethylpyridine-3,5-diyl]dicarbonyldihydrazine carbothioamides 3a–e . In the final step pyridomercaptotriazole derivatives 4a–e were synthesized by treating 3a–e in alkaline media. In parallel pyridothiazolidinone derivatives 5a–e were obtained by the reaction of 3a–e with ClCH ₂ COOH/CH ₃ COONa. All the reactions were carried out on microwave irradiation in good yield with short time. The structures of all the compounds have been confirmed on the basis of their analytical, IR, ¹ H NMR, and Mass spectral data (Table I and Table II). The potent antimicrobial effects of the synthesized compounds were also investigated.

Keywords:

• Dihydropyridine
• dihydrazinocarbothioamide
• green chemical synthesis
• mercaptotriazole
• microwave protocol
• thiazolidinone

Acknowledgments

The authors are thankful to Head, Department of Chemistry, M. L. Sukhadia University, Udaipur (Raj.) for providing laboratory facilities. The authors are also thankful to the Director, RSIC, CDRI, Lucknow, for spectral and analytical studies. Additionally, one of the authors (SM) is thankful to CSIR-New Delhi and one of the authors (RV) is thankful to UGC-New Delhi for providing necessary financial assistance.

Notes

*Activity index = Inhibition area of the sample/inhibition area of the standard; C₁ = Ciprofloxacin; C₂ = Amphotericin B. Diameter of disc in 5 mm.