Synthesis and antibacterial evaluation of benzazoles tethered dihydro[1,3]oxazines

Abstract

Synthesis of various benzazoles tethered 1,3-oxazines such as 1<i style="">H</i>-benzo[<i style="">d</i>]azolophenyl-3,4-dihydro-2<i style="">H</i>-benzo­[<i style="">e</i>][1,3]oxazines <b style="">2a-j</b>, 2-(3-(1<i style="">H</i>-benzo[<i style="">d</i>]oxazol-2-yl)phenyl)-2,3-dihydro-1<i style="">H</i>-naphtho[1,2-<i style="">e</i>][1,3]oxazine <b style="">3</b>, 2-(3-(1<i style="">H</i>-benzo-[<i style="">d</i>]imidazol-2-yl)phenyl)-2,3-dihydro-1<i style="">H</i>-naphtho[1,2-<i style="">e</i>][1,3]oxazine <b style="">4</b> and 3-(3-(benzo[<i style="">d</i>]oxazol-2-yl)phenyl)-7-(benzo[<i style="">d</i>]thiazol-2-yl)-3,4-dihydro-2<i style="">H</i>-benzo[<i style="">e</i>][1,3]oxazine <b style="">5</b> has been accomplished through three-component one-pot Mannich type condensation-cyclization reaction of substituted phenols or β-naphthol with formaldehyde and benzazolo­phenyl amines at 80-90°C. All the newly synthesized compounds have been characterized on the basis of elemental and spectral analyses. Moreover, these compounds have been evaluated for their <i style="">in vitro</i> antibacterial efficacy against two Gram-positive bacteria <i style="">viz</i> <i style="">S. epidermidis </i>and<i style=""> S. aureus</i> and two Gram-negative bacteria <i style="">viz</i> <i style="">E. coli </i>and<i style=""> P. aeruginosa</i>. Interestingly, the compounds, <b style="">2f-i</b> have displayed significant antibacterial efficacy with IC₅₀ (0.208-1.106 µg/mL).