Synthesis and antimicrobial activity of novel bis-azaphenothiazines

Abstract

N-alkylation of azaphenothiazines using dibromoalkanes or dibromoalkenes did not result in the formation of bis-azaphenothiazines under known conditions such as refluxing, for more than 100 h, with NaNH2/xylene or NaH/toluene. However, when the same reaction was tried with NaH/DMF at −5 °C to r.t., it yielded the desired product in 68–71 % yield. These novel bis-azaphenothiazines containing a suitable alkyl or alkenyl spacer were found to possess moderate to significant antimicrobial activities against three gram positive bacteria (Staphylococcus aureus, Bacillus subtilis, and Staphylococcus epidermis), four gram negative bacteria (Escherichia coli, Pseudomonas aeruginosa, Salmonella typhi, and Klebsiella pneumoniae) as well as four fungi (Aspergillus niger, Aspergillus fumigatus, Aspergillus flavus, and Candida albicans). Compounds 2b–d were found to exhibit strong antifungal activity, comparable to the standard drug miconazole against A. niger and A. fumigatus.