39998-52-2Relevant articles and documents
Supercritical methanol as solvent and carbon source in the catalytic conversion of 1,2-diaminobenzenes and 2-nitroanilines to benzimidazoles
Sun, Zhuohua,Bottari, Giovanni,Barta, Katalin
, p. 5172 - 5181 (2015/12/08)
Benzimidazoles and N-methylbenzimidazoles were synthesized by simply heating 1,2-diaminobenzenes in supercritical methanol over copper-doped porous metal oxides. These catalysts were derived from synthetic hydrotalcites that only contain earth-abundant starting materials. The carbon equivalents needed for the construction of the benzimidazole core originated from the solvent itself, which is known to undergo reforming to hydrogen and carbon monoxide through the formation of a formaldehyde intermediate. A variety of 1,2-diaminobenzenes were converted to the corresponding mixtures of benzimidazoles and N-methylated analogues in good yields. Interestingly, the more challenging, but readily available 2-nitroanilines, which require an additional reduction step prior to cyclization, could also be successfully converted to benzimidazoles in high selectivity. Furthermore, various other alcohols were applied besides methanol, to obtain 2-alkyl- and 1,2-dialkylbenzimidazoles. Preliminary mechanistic insights into the origins of N-alkylation as well as the reactivity of the nitro derivatives are discussed.
Photoinduced Double Proton Tautomerism in 4-Azabenzimidazole
Chou, Pi-Tai,Wu, Guo-Ray,Wei, Ching-Yen,Cheng, Chung-Chih,Chang, Chen-Pin,Hung, Fa-Tsai
, p. 10042 - 10052 (2007/10/03)
The proton-transfer tautomerism of 4-azabenzimidazole (4ABI) mediated by hydrogen bonding formation has been studied in the ground as well as in the excited state by means of absorption and emission spectroscopies. Thermodynamics of self-association and hydrogen-bonded complexes in nonpolar solvents were obtained. Proton-transfer isomers of 4ABI have been determined by syntheses and spectral characterization of various 4ABI methyl derivatives. The 4ABI dimer and 1:1 4ABI/acetic acid complex possessing cyclic dual hydrogen bonds undergoes a fast excited-state double proton-transfer reaction, resulting in a proton-transfer tautomer emission. Surprisingly, however, the ESDPT is prohibited in the 4ABI/2-azacyclohexanone cyclic hydrogen-bonded complex. The results render the conclusion that photoinduced double proton transfer in the 4ABI hydrogen-bonded complex can be fine-tuned by its associated guest molecule, as further supported by the molecular modeling as well as ab initio calculations.
