Studies On Gold(?)-Catalyzed Cycloisomerization Reactions Enabled By Bifunctional Phosphine Ligands

In past two decades,homogeneous gold catalysis has developed rapidly.Cationic gold species are regarded as the most powerful catalysts for the electrophilic activation of alkynes toward a variety of nucleophiles.As strong yet air-and moisture-tolerant carbophilic Lewis acids,gold complexes show unparalleled mildness and selectivity in the formation of carbon-carbon and carbon-hetero bonds.With the gradually understanding of gold-catalyzed reactions,it has been discovered that ligands play an important role in achieving mild reaction conditions,creating new reactivity,and realizing ideal selectivity.This thesis studies specially designed phosphine ligands containing a remote basic functional group,which enable gold(I)catalysts to activate the propargyl C-H bond and in situ generate allene intermediates which may undergo a series of nucleophilic addition reactions upon the activation by bifunctional gold(I)catalysts.The research is mainly divided into the following two parts:1.The first part focuses on the bifunctional gold(I)complex-catalyzed direct cycloisomerization of alkynyl ketone compounds to 2,5-disubstituted furan derivatives.By using alkynyl ketones as the starting materials and gold(I)as catalyst,the protocol provides an efficient and mild synthesis of furan derivatives which have potential applications in medicinal chemistry.The reaction has advantages of good generality of substrates,broad compatibility of functional groups,high atom-economy and no need to use excessive amount of additional bases.2.The second part focuses on the bifunctional gold(I)complex-catalyzed cycloisomerization of 1,3-enynes to in situ generate cyclopentadiene intermediates,which are further trapped by dienophiles via Diels-Alder reactions to deliver stable norbornene derivatives in one-pot manner.The reaction has advantages of simple operation,mild reaction conditions,and high atom-economy.