Synthesis and antitubercular evaluation of amidoalkyl dibenzofuranols and 1H-benzo[2,3]benzofuro[4,5-e][1,3]oxazin-3(2H)-ones

A new class of amidoalkyl dibenzofuranols and 1H-benzo[2,3]benzofuro[4,5-e][1,3]oxazin-3(2H)-ones was synthesized in very good yields through polyphosphoric acid supported on silica (PPA–SiO2) catalyzed one-pot three component condensation of 2-dibenzofuranol; aromatic aldehydes and acetamide or benzamide or urea under solvent free conditions. At 125 °C the reaction led to the formation of amidoalkyl dibenzofuranols 5a–k where as at 160 °C cyclization take place to give oxazin-3(2H)-one analogues 6a–e. Screening all the 16 compounds for in vitro antimycobacterial activity against Mycobacterium tuberculosis H37Rv (MTB) resulted 1-((4-chlorophenyl)(2-hydroxydibenzo[b,d]furanyl)methyl)urea 5h; 1-((4-bromophenyl)(2-hydroxydibenzo[b,d]furanyl)methyl)urea 5i; 1-phenyl-1H-benzo[2,3]benzo furo[4,5-e][1,3]oxazin-3(2H)-one 6a (MIC 3.13 μg/mL) and 1-(4-chlorophenyl)-1H-benzo[2,3]benzofuro[4,5-e][1,3]oxazin-3(2H)-one 6b; 1-(4-bromophenyl)-1H-benzo[2,3]benzofuro [4,5-e][1,3]oxazin-3(2H)-one 6c (MIC 1.56 μg/mL) as most active antitubercular agents.

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