Studies On Phosphine-catalyzed Addition Reactions Of Propiolates And Acid Anhydrides

As an important branch of organocatalysis,nucleophilic phosphine catalysis has developed rapidly in the past two decades,providing an important access to various organic molecules under metal-free conditions.The activated alkynes,a class of substrates frequently encountered in nucleophilic phosphine catalysis,have exhibited rich reactivity patterns such as self-isomerization reactions,addition and dipolar cyclization reactions with either nucleophiles or electrophiles.A plethora of synthetic methodologies have therefore been established on nucleophilic phosphine catalysis involving activated alkynes.Remarkably,the electrophiles encountered in the phosphine-catalyzed transformations of activated alkynes are mainly centered on the polarizedπ-type bonds such as C（28）C,C（28）O,and C（28）N bonds,which leads to cascade cyclizations or addition reactions,and the reactions involving the cleavage of theσ-type bonds of the electrophiles are still undeveloped.Therefore,the investigation of the reactivity patterns of activated alkynes withσ-type bonds of electrophiles will not only enriches the chemistry of organophosphine catalysis involving activated alkynes,but also provides new avenues to 1,2-difunctionalization of alkyne moiety.This thesis has systematically explored the phosphine-catalyzed chemoselective acylesterification,tandem addition,and Michael type reaction between alkynoates and acid anhydrides,enabling stereoselective synthesis of either the polysubstituted olefines or the multifunctional dienes.Using P（3-CH₃OC₆H₄）₃as the catalyst in toluene at room temperature,the acylesterification of alkynoate could be achieved in high yields and good to excellent stereoselectivity.Under the catalysis of P（2-CH₃OC₆H₄）₃,using THF as the solvent and H₂O as the additive at 60 ℃,the tandem addition of alkynoates with acid anhydrides was chemoselectively realized,leading to multifunctional dienes in high yield and excellent stereoselectivity.In the presence of a catalytic amount of P（2,4,6-（CH₃O）₃C₆H₂）₃in THF with H₂O as the additive,the Michael type reaction of alkynoate and acid anhydrides proceeded smoothly at room temperature,affording vinyl esters.These reactions exhibit a wide substrate scope,and both electron-rich and electron-poor aryl anhydrides and alkyl anhydrides were well accommodated.The structure assignments of the products were established on ¹H NMR,¹³C NMR,high-resolution mass spectrometry as well as X-ray single crystal diffraction measurements.On the basis of the experimental results and a series of control experiments,reasonable mechanistic elaborations were proposed for the three types of reactions.This study unveils for the first time the divergent reactivity of alkynoates toward C-Oσbond of electrophiles under organophosphine catalysis,which further expands the reactivity modes of alkynoates.It also provides a new synthetic method for stereoselective synthesis of polysubstituted olefines and conjugated dienes under mild and metal-free conditions.