Synthesis Of Noncovalent Carbon-bonding Catalysts And Their Application In The Regulation Of Catalytic Activity And Regioselectivity In Gold Catalysis

Carbon-bonding interactions(CB)are weak interactions between electrically deficient carbon centers and electron donors(ED).This type of noncovalent force widely exists in biological systems,which plays an important role in the modulation of the spatial conformation of proteins.In addition,carbon-bonding interactions have found applications in molecular recognition,drugs discovery,and material chemistry.Since carbon-bonding interactions are comparably weak,the concept of carbon-bonding interactions yet remains a subject to be explored in the field of organocatalysis.Based on relevant research on carbon-bonding interactions,we discovered a class of cyclopropane derivatives incorporated with carbonyl,ester,and cyano groups as supramolecular carbon-bonding catalysts.Among these catalysts,bidentate CB donors showed superior catalytic activity.On this basis,we developed a new strategy,carbon-bonding metal catalysis,with the purpose of improving the catalytic activity and regioselectivity of metal-catalyzed reactions.This catalysis approach was demonstrated by a range of gold-catalyzed reactions,and the experimental results showed that the catalytic activity and regioselectivity could be largely enhanced by carbon-bonding interactions.Given that no chiral carbon-bonding catalysts have been reported thus far,a series of chiral carbonbonding catalysts were synthesized based on barbituric scaffold,and their catalytic properties were preliminarily explored.Part Ⅰ:Modulation of gold catalytic activity and regioselectivity by weak carbon-bonding interactionsWeak Carbon-bonding interactions are prevalent in biological systems,providing remarkable stability for protein folding,helix,and protein-protein/ligand interactions.In this thesis,the activation of metal-halogen bond by carbon-bonding interactions was conceived and applied to the field of metal catalysis.This activation approach is capable of enhancing the catalytic activity and regioselectivity in a series of gold-catalyzed cyclization reactions,which in contrast are difficult to access by silver salts and weakly coordinated anionic salts.The experimental results showed that catalysts with a rigid framework enable a more efficient carbon bonding,thus providing higher activity than monodentate catalysts.In this thesis,the mechanism that involves the activation of metal-halogen bonds by carbon-bonding interactions was demonstrated by NMR experiments and titration experiments.The experimental results revealed that the weak carbon-bonding interactions between neutral CB donor and halogen atom plays a decisive role in controlling the regioselectivity.Carbon-bonding metal catalysis provides a distinct approach for the activation of metal catalysts and has potential application in asymmetric catalysis,thus expanding the capability of weak carbon-bonding interactions.Part Ⅱ:Design and synthesis of chiral carbon-bonding catalystsThe design and synthesis of chiral catalysts are key to asymmetric catalysis.In this thesis,chiral barbituric scaffold was incoperated into the catalysts,and six chiral catalysts were synthesized.In contrast to carbon-bonding catalyst bearing the Meldrum’s acid skeleton,its counterpart with the barbituric moeity has better solubility and catalytic activity.Moreover,a wide range of chiral sources can be introduced into this type of catalysts.The catalysts exhibited good catalytic activity in the Pictet-Spengler reaction,and preliminary results indicated that these catalysts can control stereoselectivity.This study expands the scope of carbon-bonding catalysts,and provides a new approach to asymmetric organocatalysis.