Studies And Applications Of Several Dicarbonylative Reactions

Dicarbonylation is of great significance due to the unique 1,2-dione motif, which is not only widely existing in pharmaceutically important natural products, but also a powerful synthetic precursor toward diverse heterocycles and fluorescent materials. Based on our group’s previous research on C-C bond cleavage, this thesis applied a-hydroxyl ketone as a commonly used reagent to realized dicarbonylations of various terminal alkynes and indoles, with oxygen as a green oxidant. The dicarbonyl products were further applied in single atom implantation of chalcogen toward special heterocycles, and construction of solvatochromic fluorescent indole-substituted quinoxalines. This thesis includes the following sections:Part 1:dicarbonylation of alkynesAn efficient and mild copper-catalyzed one-pot approach toward ynediones has been established. A variety of ynediones were constructed directly through oxidative coupling of alkyne with a-hydroxy ketone. Oxygen-oxidizing and neutral condition in one-pot for a wide range of substrates including natural product derivatives make this transformation highly efficient and practical. On the basis of control experiments, in-situ IR measurements and isotopic labelling experiments, a plausible mechanism involving intermediate phenylglyoxal was drawn. Applications by synthesis of various heterocycles were also investigated.Part 2:dicarbonylation of indolesCopper-catalyzed aerobic oxidative C3-dicarbonylation of indoles has been realized directly by a-hydroxyl ketone, which served as a universal dicarbonylative reagent under this mild condition. The methodology showed powerful compatibility with various functional groups, offering a straightforward means to produce different heterocycle-substituted quinoxalines in excellent yields. These multi-type substituted fluorescent quinoxalines exhibited photophysical properties and solvatochromism in certain rules. Based on control experiments, a plausible reaction mechanism was proposed.Part 3:selective single atom implantations of chalcogenSelective single atom implantations of chalcogen have been established. As environmentally friendly and readily available atom transfer reagents, water and thiourea were used to construct a series of 3(2H)-furanones and 3(2H)-thiophenes with different ynediones under mild conditions. Tautomerism of 3(2H)-furanones, the type of catalyst, and isotopic labelling experiments were investigated. GC-MS provided powerful evidence to illuminate the transformation of thiourea during sulfur atom insertion. Based on mechanistic studies, plausible mechanisms for both two reactions were proposed respectively.