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Paper | Regular issue | Vol 48, No. 1, 1998, pp.113-121
Published online, 1st January, 1970
DOI: 10.3987/COM-97-8020
Alkyl-substituted Benzo[1,2-d:3,4-d' ]diimidazoles. Preparation and Annular Tautomerism

Shuntaro Mataka,* Kazuchika Isomura, Tsuyoshi Sawada, Takehito Tsukinoki, Masashi Tashiro, Kazufumi Takahashi, and Akiyoshi Tori-i

*Instituete of Advanced Material Study, Kyushu University, 6-1, Kasuga-koen, Kasuga 816-8580, Japan


The treatment of 4-nitro-5-amino-2,1,3-benzothiadiazole (3) with tin/hydrochloric acid in the presence of a carboxylic acid having a C1-C3 chain gave the corresponding 2,5-dialkylbenzo[1,2-d:3,4-d’]diimidazoles (1). When the amount of tin was reduced to a half, 3 afforded only 5-alkylimidazolo[4,5-d]benzothiadiazoles (2). Unsymmetrical dialkyldiimidazoles (1) were obtained from 2 in a second step. Annular tautomers due to NH-proton exchange of the imidazole rings of 1 and 2 could be observed in 1H NMR spectra in DMSO-d6 at a low concentration (ca. 5 x 10-4M).