New ring systems derived from 4,5-diaminobenzo[b]thiophen and its 3-methyl derivative

Abstract

4,5-Diaminobenzo[b]thiophen and its 3-methyl derivative have been prepared. Condensation of these diamines with 9,10-phenanthraquinone gave dibenzo[a,c]thieno[3,2-h]phenazine and its 14-methyl derivative, and with butane-2,3-dione gave 2,3-dimethylthieno[3,2-f]quinoxaline and its 9-methyl derivative. Treatment of the diamines with thionyl chloride gave thieno[3,2-e][2,1,3]benzothiadiazole and its 8-methyl derivative, whereas treatment with boiling formic acid yielded 1H-(or 3H-) thieno[3,2-e]benzimidazole and its 8-methyl derivative. The n.m.r. spectra of these compounds are reported. Nitration of thieno[3,2-e][2,1,3]benzothiadiazole gave the 7-nitro-derivative; n.m.r. evidence is provided in favour of the structure of the latter.