Abstract
One-pot photocatalytic synthesis of 2-substituted benzimidazoles from 2-nitroanilines with different alcohols by combined redox cyclization reaction using TiO2-P25 is reported. The reaction, when performed with ethanol, gives 2-methylbenzimidazole as a single product. However, in a mixture of ethanol and water (1:1), it gives both 2-methylbenzimidazole and 1-ethyl-2-methylbenzimidazole. The products have been characterized by Fourier transorm–infrared, 1H NMR, 13CNMR, and gas chromatography–mass spectrometry analysis. TiO2-P25 behaves as a combined redox photocatalyst by reducing 2-nitroaniline and oxidizing alcohols simultaneously under ultraviolet light. Easy product isolation under mild conditions and good yield make this one-pot synthesis ecofriendly.
GRAPHICAL ABSTRACT
ACKNOWLEDGMENTS
K. Selvam is thankful to the Council of Scientific and Industrial Research, New Delhi, for the award of a senior research fellowship. The authors thank the Ministry of Environment and Forests (MOEF), New Delhi, for the financial support through Research Grant Nos. 315-F-36 and 19/9/2007-RE.
Notes
Notes. [o-nitroaniline] = 14 mg / 30 mL; catalyst = 50 mg/30 mL; time of irradiation = 3 h; I = 1.381 × 10−6 Einstein L−1 s−1.
Notes. [o-nitroaniline] = 14 mg/30 mL; catalyst = 50 mg/30 mL; acetonitrile–ethanol (1:1); time of irradiation = 3 h; I = 1.381 × 10 −6 Einstein L−1 s −1..
Notes. [o-nitroaniline] = 14 mg/30 mL; catalyst suspended = 50 mg/30 mL; time of irradiation = 3 h; I = 1.381 × 10 −6 Einstein L−1 s −1 .
Notes. [Substituted o-nitroaniline] = 14 mg/30 mL; catalyst suspended = 50 mg/30 mL; acetonitrile-ethanol (1:1); time of irradiation = 3 h; I = 1.381 × 10 −6 Einstein L−1 s−1.