HETEROCYCLIC SYSTEMS CONTAINING BRIDGEHEAD NITROGEN ATOMS. PART LXVIII. REACTION OF 5-FLUOROBENZIMIDAZOLYL-2-THIONE WITH CHLOROACETIC ACID: STUDIES OF ORIENTATION OF CYCLIZATION IN THE SYNTHESES OF 6-FLUORO- AND 7-FLUOROTHIAZOLOBENZIMIDAZOL-3(2H)-ONES

Article abstract of DOI:10.1016/S0022-1139(00)81001-5

4-Fluoroaniline on successive acetylation, nitration and hydrolysis affords 4-fluoro-2-nitroaniline which on reduction with Raney nickel and hydrazine hydrate followed by treatment of the resulting diamine with carbon disulphide in situ gives 5-fluorobenzimidazolyl-2-thione.The thione on condensation with chloroacetic acid yields <(5-fluoro-2-benzimidazolyl)-thio>acetic acid which on cyclization in a mixture of acetic anhydride and pyridine furnishes two isomers viz. 6-fluoro- and 7-fluorothiazolo<3,2-a>benzimidazol-3(2H)-ones.The condensation of thione with 1,2-dibromoethane affords sym-bis-(5-fluorobenzimidazo-2-yl-mercapto)ethane.The structural assignments for the 6-fluoro- and 7-fluorothiazolo<3,2-a>benzimidazol-3(2H)-ones have been made by 1H-NMR spectral data using two different methods.