| Summary: | 博士 === 國立清華大學 === 化學系 === 103 === Abstract
This dissertation describes development of new synthetic organic transformations by using gold and silver salts. The use of these soft alkynophilic metals enables mild, diastereoselective and efficient transformations of a variety of readily available substrates to wide range of synthetically useful carbocyclic and nitrogen or oxygen containing heterocyclic products. For better understanding the thesis is divided into four chapters.
The first chapter deals with the Gold-catalyzed reactions of 2-ethynylbenzyl ethers with organic oxides for synthesis of 1,3-dihydroisobenzofuran derivatives through a formal cycloaddition reaction. Such 1,3-dihydroisobenzofuran core is one of the most commonly encountering skeletons in nature and the core scaffold has a wide spread application in structural and biological importance. The core structures of the resulting products are constructed through a formal [4+1] cycloaddition among α-carbonyl carbenoids and tethered ethers. The utility of this catalysis includes various substituents on phenyl groups and different ethers.
The second chapter deals with the Gold- and Silver-catalyzed [4+2] cycloaddition reactions of ynamides with aryl-oxetanes and aryl-azetidines to form six membered heterocycles. Oxetanes function as nucleophiles whereas gold--ynamides are present as electrophiles. In the case of azetidines, silver hexafluoroantimonate was found to be more active than gold catalyst in their [4+2]-cycloadditions with ynamides. The two cycloadditions are applicable to a reasonable range of ynamides, oxetanes and azetidines, thus manifesting their synthetic utility to access six-membered heterocycles such as 6-amino-3,4-dihydro-2H-pyrans and 2-amino-1,4,5,6-tetrahydropyridines.
The third chapter describes the Gold-catalyzed cycloadditions of ynamides with azidoalkenes or 2H-azirines to give [3+2] or [4+3] formal cycloadducts of two different classes. Cycloadditions of ynamides with 2H-azirine species afford pyrrole products. For ynamides substituted with an electron-rich phenyl group, their reactions with azidoalkenes proceed through novel [4+3] cycloadditions to deliver 1H-benzo[d]azepine products instead.
The fourth chapter presents development of a oxidative cyclizations of 1,6 diynes with 8-methylquinoline N-oxides through dual activation mode to achieve 3-keto naphthols and 3-keto phenol derivatives. The value of the reaction is reflected by their applicability to a broad range of benzene- and nonbenzene-derived substrates.
|
|---|
