N-Monobenzoylation (acetylation, arylsulfonation), N-, C- di- and N-, C-, O- tribenzoylation of 5H(chloro, nitro)-2-methyl(ethyl)benzimidazoles
Khusnutdin M. Shakhidoyatov
Department of Organic Synthesis, Institute of the Chemistry of Plant Substances, Academy of Sciences of the Republic of Uzbekistan, Tashkent 100170, Uzbekistan
Tozagul U. Dzhumatanova
Comprehensive Institute of Natural Sciences of Karakalpakstan Branch, Academy of Sciences of Uzbekistan, Nukus 230100, Karakalpakstan, Uzbekistan
Ubaydullo M. Yakubov
Department of Organic Synthesis, Institute of the Chemistry of Plant Substances, Academy of Sciences of the Republic of Uzbekistan, Tashkent 100170, Uzbekistan
Azimjan A. Mamadrahimov *
Department of Organic Synthesis, Institute of the Chemistry of Plant Substances, Academy of Sciences of the Republic of Uzbekistan, Tashkent 100170, Uzbekistan
Gulsara E. Berdimbetova
Comprehensive Institute of Natural Sciences of Karakalpakstan Branch, Academy of Sciences of Uzbekistan, Nukus 230100, Karakalpakstan, Uzbekistan
*Author to whom correspondence should be addressed.
Abstract
The interaction of 2-methyl(ethyl)-5H(chloro, nitro)benzimidazoles with benzoyl (acetyl) chloride, and p-toluenesulfonyl chloride in the presence of triethylamine in tetrahydrofuran or chloroform was studied. It was found that the reaction proceeds in three stages with the formation of N-monobenzoyl (acetyl, p-toluenesulfonyl), N-, C-dibenzoyl- and N-, C-, O-tribenzoyl benzimidazoles depending on the ratio of reagents, the nature of the substituent in the aromatic ring, α-methylene group, and acid chlorides. It was revealed that in the case of acetyl, p-toluenesulfonyl chloride reaction is stopped at the first stage with formation of N-monoacetyl (p-toluenesulfonyl) derivatives. The method for HPLC analysis for separation, identification and determination of the ratio of obtained compounds was developed. It was found that 1-acetyl (benzoyl)-2-methylbenzimidazoles were decomposed at the standing. The crystalline form of 1-acetyl-2-methylbenzimidazole is decomposed to the 2-methylbenzimidazole: 25% (7 days), 50% (15 days), 100% (30 days) and decomposition of 1-benzoyl-2-methylbenzimidazole to the 2-methylbenzimidazole (50%) occurs within 2 months.
Keywords: 1H-2-methyl-, ethyl-, 1-benzoyl-, p-toluenesulfonyl-, 2-acetyl-, methyl-, 5H-, -chloro, -nitrobenzoyl benzimidazoles, benzoyl chloride, p-toluenesulfonyl chloride, acylation, N-mono -, N, C-di-, N-, C-, O-tribenzoylation