Thesis (M.Sc.)--Chulalongkorn University, 1998

In this study, photoreactants, 3- and 5-(trimethylsilyl)-1-methylpyrazoles were synthesized and their photoreactions were investigated. Predicted by permutation pattern, 5-(trimethylsilyl)-1-methylimidazole (P4), 2-(trimethylsilyl)-1-methylimidazole (P6), and 4-(trimethylsilyl)-1-methylimidazole (P7), the three predicted photoproducts of 5-(trimethylsilyl)-1-methylpyrazole, and 2-(trimethylsilyl)-1-methylimidazole (P4&P7) and 4-(trimethylsilyl)-1-methylimidazole (P6), the two predicted photoproducts of 3-(trimethylsilyl)-1-methylpyrazole were synthesized as the authentic compounds for comparison. However, attempt to synthesize 4-(trimethylsilyl)-1-methylimidazole was unsuccessful. It was found that 5-(trimethylsilyl)-1-methylpyrazole underwent phototransposition to three photoproducts as well as photocleavage to the other product. The phototransposition products were 5-(trimethylsilyl)-1-methylimidazole as a major product of P4 process, 4-(trimethylsilyl)-1-methylimidazole as a predicted product of P7 process, and 1-methylimidazole. The last product was assumed to be the secondary product arising from 2-(trimethylsilyl)-1-methylimidazole which was a P6 photoproduct. The photocleavage product obtained as well, was identified as 3-(trimethylsilyl)-3-(N-methylamino) propenenitrile. 3-(trimethylsilyl)-1-methylpyrazole underwent phototransposition to two photoproducts as well as photocleavage to the other product. The phototransposition products were 4-(trimethylsily)-1-methylimidazole as a predicted product of P6 process and 1-methylimidazole which was assumed to be the secondary product arising from 2-(trimethylsilyl)-1-methylimidazole as a product of P4&P7 processes. The reaction also gave a photocleavage product which was identified as 3-(N-methylamino) propenenitrile. Furthermore, 4-(trimethylsilyl)-1-methylpyrazole, the other isomer of the photoreactants of this series, was also synthesized. Unfortunately its low purity was not suitable to carry out the phototransposition reaction.