Photcatalytic green system for reduction of nitroarenes under sunlight and violet LED irradiation

Heterogeneous photocatalysis by semiconductor materials has been gaining increasing interest in organic synthesis1.TiO2, because of its unique chemical and physical properties, such as high efficiency, low cost, physical and chemical stability, widespread availability, and noncorrosive property is broadly used in the fields of solar energy conversion and photocatalysis2.Li et al. first reported a photoinduced reduction of nitro compounds to the corresponding amines using TiO2 -P25 as a catalyst under UV light, they used 2 ml of a 0.01M solution of nitrobenzene in the reaction3.An important problem of heterogeneous photocatalytic reactions is low amount of substrate. Also there aresome limitations for using semiconductors in water, associated with the low solubility of substrates and over-oxidation of organic compounds which are a result of the oxidant species produced (such as ˙OH and O2 ˙/HO2 ˙) in a photocatalytic process. Photocatalytic reduction of nitroarenes to amines under sun light and violet LED irradiation in water has been taken in to consideration. To overcome the solubility problem of nitro compounds in water polyethylene glycol-400 was used as cosolvent. The reaction was done using a TiO2/PEG-400 system in water as solvent. Under sunlight irradiation 0.1 mmol of nitro benzene was used. Very interestingly under violet LED irradiation, 1 mmol of nitro benzene was used in reaction as starting material in water. For other Derivatives of nitrobenzene 0.5 mmol of nitro compound was used.