ORTHO-NITROANILINE DERIVATIVES .79 SYNTHESIS OF 2-ALKOXYBENZIMIDAZOLE N-OXIDES (2-ALKOXY-N-HYDROXYBENZIMIDAZOLES) FROM ORTHO-NITROANILINES

N-Phenacyl-N-p-tolylsulphonyl-o-nitroanilines (8) are cyclised to 2-alkoxybenzimidazole N-oxides (⇌ 2-alkoxy-N-hydroxybenzimidazoles) (13)-(16) by sodium alkoxides in the appropriate alcohol. N-Phenacyl-o- nitroanilines themselves undergo cleavage, or at best give low yields of 2-benzoylbenzimidazole N-oxides, by reaction with alkoxides under similar conditions. N-Acetonyl-N-p-tolylsulphonyl-o-nitroanilines (9) are also cyclised to 2-alkoxybenzimidazole N-oxides by sodium alkoxides. When the ketonic functions of (8) and (9) are replaced by ester or cyano groups, however, cleavage occurs in alcoholic base in preference to cyclisation. N-Phenacyl- (8f) and N-acetonyl-N-p-tolylsulphonyl-6-methy-2-nitroaniline (9f) are anomalous in that they are cyclised by alkoxides to 1-hydroxy-4-methylbenzimidazolone (21).