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 degrees C the reaction led to the formation of amidoalkyl dibenzofuranols 5a-k where as at 160 degrees 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) me thyl) 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 mu g/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 mu g/mL) as most active antitubercular agents. (C) 2011 Elsevier Ltd. All rights reserved.