TRIAZOLINES .32. SYNTHESIS OF 1-ALKYL-2-AMINOBENZIMIDAZOLES FROM 5-AMINO-1-(2-NITROARYL)-1,2,3-TRIAZOLINES

5-Amino-l-(2-nitroaryl)-1,2,3-triazolines 5 are converted into 1-alkyl-2-aminobenzimidazoles 7 in refluxing triethyl phosphite. The reaction occurs via thermal rearrangement of 5 followed by nitrogen elimination which produces N2-(2-nitroaryl)amidines 8 as intermediates. Reduction of the nitro group to nitrene, addition to the C=N bond and rearrangement of the intermediate 2,2-disubstituted benzimidazoles accounts for the formation of the end products.