Abstract
The wavelength dependency and the mechanism of photo-oxidation of ethyl 2-[4, 5-bis(4-methoxyphenyl)thiazole-2-yl]pyrrol-1-ylacetate (KBT-3022) in solution were investigated. The wavelength contributing to the photo-degradation of KBT-3022 in a mixture of acetonitrile-H2O (1 : 1) was found to be the near ultraviolet region, between 400 and 270 nm.The photo-oxidation of KBT-3022 was enhanced by the presence of rose bengal, which generates singlet oxygen as a photosensitizer, and by the presence of D2O in which the lifetime of singlet oxygen is about 10 times longer than in H2O. On the other hand, photo-oxidation was inhibited by the presence of sodium azide, or 1, 4-diazabicyclo[2.2.2]octane, both of which are known to be singlet oxygen quenchers. These results suggest that KBT-3022 acts by itself as a photosensitizer in its own photo-oxidation. Thus, the photo-degradation of N-methylpyrrole was enhanced by the presence of KBT-3022. It is concluded from these results that KBT-3022 reacts with singlet oxygen to form KBT-3022 endo-peroxide intermediate, and then undergoes hydrolysis to afford 5-hydroxylactam (D2).
