Mechanistic studies on photochemical degradation of nifedipine

Abstract

Irradiation of nifedipine in methylene chloride at 366 nm yielded 2,6-dimethyl-3,5-dimethyl-3,5-dicarbomethoxy-4-(2``nitrosophenyl)-pyridine with the quantum efficiency of 0.37, while irradiation at 254 nm initially gave nitroso compound which in turn is photooxidized to 2,6-dimethyl-3,5-dicarbomethoxy-4-(2``-nitrophenyl)-pyridine with quantum efficiency of 0.014 on further irradiation in the presence of oxygen. The intramolecular hydrogen abstraction of nifedipine appeared to proceed from the triplet excited state. The quantum yield of photo-degradation of nifedipine at 366 nm decreased as the concentration of amine increased. The quantum yields at 254 nm irradiation of nitroso compound(II) sharply increase with the decrease in polarity of the solvents. It is probably due to the strong charge transfer character in the creation state of nitroso compound(II).