Convenient synthesis of benzothiazinoisoindol-11-ones and benzoindenothiazin-11-ones, and antimicrobial testing thereof

Abstract

Benzo[5,6][1,4]thiazino[3,4-a]isoindol-11-ones 5a-t and benzo[b]indeno[1,2-e][1,4]thiazin-11(10aH)-ones 6a-e were synthesized conveniently via cyclocondensation of 2-bromo-2-(2/3-substitutedphenyl)-1H-indene-1,3(2H)-diones and 2-aminobenzenethiols in freshly dried ethanol with 70-85% yields. The synthesized derivatives were well characterized by employing different spectral techniques (FTIR, ¹H & ¹³C NMR and HRMS) and X-ray crystallographic analysis. Further, all the reported compounds were tested for their antibacterial and antifungal activities using Ciprofloxacin and Fluconazole as standard drugs, respectively. The results of antimicrobial evaluation revealed that compounds 5o and 5t displayed remarkable inhibitory activity against B. subtilis, S. aureus, P. aeruginosa and A. niger with MIC values in the range of 0.0141-0.0283 µmol/mL, whereas 5j was found active against E. coli and C. albicans with MIC values of 0.0286 µmol/mL and 0.0143 µmol/mL, respectively. Additionally, among all the benzo[b]indeno[1,2-e][1,4]thiazin-11(10aH)-ones, 6c exhibited excellent inhibition against all the tested bacterial and fungal strains with MIC values ranging from 0.0143 to 0.1145 µmol/mL. Structure activity relationships were also established for all the tested benzo[5,6][1,4]thiazino[3,4-a]isoindol-11-ones 5a-t.

Keywords: Antibacterial; Antifungal; Benzothiazine; Isoindolone; SAR.