Mechanistic Studies Of The Gold(Ⅰ) Catalyzed Activation Of Glycosyl Ortho-alkynylben Zoates And The Related Chemical Processes

This thesis focuses on mechanistic studies of the gold(Ⅰ)catalyzed activation of glycosyl ortho-alkynylbenzoates and related chemical processes,which contains four major sections.The first section is an introduction of our research strategy:"new chemical information targeted chemical research tool development" based approach to realize chemical breakthrough.Many of the research advances in this thesis were achieved via this strategy.The second section is mechanistic investigations of the gold(Ⅰ)catalyzed anomerization of glycosyl ortho-alkynylbenzoates.Anomerization,which involves cleavage and formation of the anomeric C-O bond,is of fundamental importance in the carbohydrate chemistry.Glycosyl ortho-alkynylbenzoates can readily undergo anomerization in the presence of gold(Ⅰ)catalyst,a process which contains new anomerization mechanism.We have performed kinetic analysis,reaction intermediate characterization and quantitative analysis of this chemical process via our newly developed HPLC kinetic analysis system,NMR analysis,and single crystal X-ray analysis,after which a mechanistic model was proposed.The model involves a nucleophilic addition of vinyl gold(Ⅰ)complex onto sugar oxocarbenium(or dioxolenium)intermediate and an elimination of LAu+ from the vinyl gold(Ⅰ)complex,an equilibrium between mono-and di-gold(Ⅰ)complexes and a transient glycosyloxypyrylium species,which provides guide for further development of the gold(Ⅰ)catalyzed glycosidation methodology.The third section is studies of the gold(Ⅰ)catalyzed recombination of glycosyl ortho-alkynylbenzoates.In gold(Ⅰ)catalyzed activation of glycosyl ortho-alkynylbenzoates,addition of vinyl gold(Ⅰ)complex onto sugar oxocarbenium intermediate from the opposite face of the sugar ring(compared to the cleave pathway)leads to "visible" anmerization while from the same face leads to "invisible"recombination.In some cases,the later is in fact the major activation pathway in the reaction system.We have designed and developed a chemical labeling method,which makes the "invisible" recombination process "visible",combined with our newly developed HPLC kinetic analysis system,kinetics of the anomerization/recombination pathway in crossover reaction system in the presence of the labeled substrates have been investigated,the ratio of the initial rates of the two pathways has been achieved,and the "mechanistic implication" of these data has been discussed in details.This research furthers our understanding of the mechanism of the gold(Ⅰ)catalyzed activation of glycosyl ortho-alkynylbenzoates.The last section is studies of the hydration process of arylphosphine gold(Ⅰ)cations.Arylphosphine gold(Ⅰ)cations are widely used as catalyst in gold catalysis,their hydration process are important for understanding the mechanistic details of gold(Ⅰ)-catalyzed transformations.We have conducted research on this process via single crystal X-ray anaylsis and NMR analysis,characterized two new types of arylphosphine coordinated gold(Ⅰ)hydrates and investigated their interconversions.Based on these results,we proposed a hydration equilibrium,discussed its influencial factors,and applied it to explain some phenomena in gold(Ⅰ)catalysis.This work is helpful for the further development of gold chemistry and mechanistic understandings of gold catalysis.