Synthesis of 2,5-disubstituted 1,3,4-oxadiazoles as biologically active heterocycles

2-(Benzimidazol-2'-yl) benzoyl hydrazide 1 when condensed with aromatic acids in the presence of POCl3 afforded 2- aryl-5-[2'-benzimidazol-2 "-yl) phenyl]-1, 3, 4-oxadiazoles 2a-o. The acid hydrazide 1 on cyclisation with CNBr yield 2-amino-5-[2'-(benzimidazol-2 "-yl-phenyl) 1, 3, 4-oxadiazole 3 which on reaction with aryl sulphonyl chlorides and substituted benzoyl chloride give the corresponding sulphonamides 4a-o and amides 5a-o, respectively. ail the products have been evaluated in vitro for their antimicrobial activity against several microbes and antitubercular activity against Mycobacterium tuberculosis H37Rv.