Synthesis and biological study of newly synthesized AZO appended thiadiazolin heterocycles

Abstract

Pathogens are causative agents that are responsible for different types of infectious diseases. Despite improvements in antibiotics, bacterial infections carry on with problems in health care. The random use of antibiotics makes bacteria become resistant to antibiotics. Therefore, new antibiotics with excellent efficacy are urgently needed to fight infections. In this regard, thiadiazol rings containing compounds having a wide variety of biological activities are considered as promising candidates. The nitrogen atoms of 1, 3, 4-thiadiazole ring is shown to be very electron underprovided due to the electron-withdrawing effect but susceptible to nucleophilic attack. The present work demonstrates the synthesis of derivatives of 5-phenyl- 1,3,4-thiadiazole-2-amine by single step reaction. In addition, a series of azo appended thiadiazol is synthesized by diazotization of 5-phenyl-1,3,4-thiadiazole-2-amines by coupling with different coupling compounds such as dimedone, acetylacetone and ethyl acetoacetate. Herein, we report a method for forming hydrazinylidene group by condensation reaction of azo appended thiadiazol compounds with dimedone, acetylacetone and ethyl aceto acetate. These compounds are characterized by spectroscopic analyses utilizing Infrared (IR) and Nuclear Magnetic Resonance (1H-NMR, 13C-NMR) spectra and also screened for antibacterial property.

Table-1: Synthesis of azo appended thiadiazols

SI. No . Starting Materials Products Melting Point (℃) % Yield

01

118- 120 55%

02

76-78

50%

SI. No. Starting Materials Products Melting Point (℃) % Yield

03

202-205

50%

04

115-117

55%

05

112-115

58%

06

102-105 53%

07

215-218 50%

08

121-124 50%

Antibacterial Test The synthesized compounds S-5, S-6 & S-9 were evaluated for their in vitro antibacterial activity against two Gram-positive (Staphylococcus Aureus, Bacillus megaterium), three Gram-negative (Escherichia coli, Pseudomonas aeruginosa, Shigella boydii) bacteria and S- 11,S-12 were evaluated for their in vitro antibacterial activity against two Gram-positive, two Gram-negative bacteria, where standard disc of Ciprofloxacin is used. Compounds S-5, S-6 & S-9 showed moderate activity against E.coli and S.aureus. Compound S-11 and S-12 showed good activity against Bacillus megaterium and S-11 and S-12 showed moderate result against Staphylococcus aureus.