| Summary: | 博士 === 國立臺灣師範大學 === 化學系 === 99 === This dissertation is divided into four chapters. Chapter I highlights the facts, those motivated us to pursue the research, presented in this dissertation. Chapter II deals with [hydroxy(tosyloxy)iodo]benzene (HTIB) mediated “on water” synthesis of chromeno-isoxazoles and isoxazolines. Chromeno-isoxazolines and chromeno-isoxazoles are synthetically and medicinally valuable compounds. However, the reported methodologies to access these compounds are plunged either by the usage of toxic solvents, long reaction time and applicable to limited number of substrates. We attempted to overcome these limitations by developing a protocol for HTIB mediated on water synthesis of chromeno-isoxazolines and isoxazoles from α-allyloxy and α-propargyloxy benzaldoxime derivatives. A mechanism for this conversion was postulated on the basis of our experimental outcome and related literature reports. In chapter III, an unprecedented synthesis of isoxazoline N-oxide, via HTIB mediated N-O coupling is described. The effect of the mediums on N-O coupling was studied by carrying out the reaction in homogeneous and heterogeneous mediums. A mechanism was postulated on the basis of the experimental outcomes and the mechanism is supported by the related literatures. On treating the cyclohexene fused isoxazoline N-oxide derivatives with halonium ion sources, TCC and NBS, the C-C bond which connects the isoxazoline with cyclohexene ring was cleaved. The ring cleavage is happened via a nitroso intermediate. Scope of this ring cleavage protocol, mechanistic study, and thermal effect on the life time of the nitroso intermediate are discussed in chapter IV. This chapter also deals with the treatment of the nitroso intermediate with a base, to synthesize novel types of oxime derivatives.
Keywords:on water、chromeno-isoxazole、isoxazoline N-oxide、halonium ion
|
|---|
