Efficient synthesis, spectral analysis and antimicrobial studies of nitrogen and sulfur containing spiro heterocycles from 2,4-diaryl-3-azabicyclo[3.3.1]nonan-9-ones

Acetyl and propionyl group substituted thiadiazole derivatives (4a–4h, 5a–5h, 6a, 6b, 7a and 7b) have been synthesized by the cyclization of 2,4-diaryl-3-azabicyclo[3.3.1]nonan-9-one thiosemicarbazones (2a–2h, 3a and 3b) with acetic anhydride/propionic anhydride and were characterized by Elemental analysis, IR, 1H NMR and 13C NMR spectral analysis. Single crystal X-ray diffraction has also been recorded for compounds 4c and 5a. From the NMR and Single crystal X-ray diffraction analysis, compounds 4b–4d, 4f–4h, 5b, 5c, 5f–5h, 6a, 7a and 7b were found to adopt twin-chair conformations whereas compounds 4a, 4e, 5a, 5d, 5e and 6b adopt chair and boat conformation of cyclohexane and piperidine rings, respectively. Besides, the synthesized compounds were screened for antibacterial and antifungal activities using serial dilution method. The microbiological analysis showed that the electron withdrawing function substituted phenyl group at C-2 and C-4 of azabicyclononane based thiadiazoles 4c/4h and 5c/5h exposed significant antimicrobial activity against Salmonella typhi, Escherichia coli, Klebsiella pneumoniae, Aspergillus flavus, Aspergillus niger and Candida albicans at MIC of 6.25 μg/ml.

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