2-Arylbenzoxazoles, 2-arylbenzimidazoles and 2-arylbenzothiazoles were directly synthesized from substituted 2-aminophenols and aldehydes in the presence of activated carbon (Darco® KB or Shirasagi KL) in xylene under an oxygen atmosphere. Hantzsch 1,4-dihydropyridines and 1,3,5-trisubstituted pyrazoles were also oxidized to the corresponding aromatic compounds by the aid of activated carbon in both acetic acid and xylene. Furthermore, oxidative aromatization of 9,10-dihydroanthracenes using molecular oxygen was also promoted by activated carbon.
Keywords: 2-aminophenols, Darco KB-B, 2-arylbenzimidazole, aromatization, pyrazole derivatives
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