Studies On Functionalization Of Aryl Ethers And Oxidation Of Alkynylborates

As an important transformation in organic synthesis,C(sp~2)-O bond cleavage and formation have been widely used in synthetic chemistry and materials science.Among C-O bonds,C(sp~2)-O bond cleavage of the aryl ether has become a hot topic in organic synthesis methodology in recent years.However,due to the inertia of C-O bond,the conversion of C-O bond has some problems,such as harsh reaction conditions or the use of transition metal.In addition,the oxidation of organic borides was one of the main methods to construct C-O bond,the corresponding alcohols,phenols and carbonyl compounds have been prepared through the mature oxidation of C(sp~3)-B and C(sp~2)-B bond,but the development of the oxidation of C(sp)-B bond was slow.Therefore,it is of great significance to explore and develop new methods of C-O bond cleavage and formation.The research is mainly focused on the cleavage and formation of C-O bond.It was realized the functionalization of aryl ethers C(sp~2)-O bond and terminal alkyne through the new methods of C-O bond cleavage and C-B bond oxidation,which were constructed efficiently the C-O bond and C-P bond with the synthesis of aryl ethers,aryl phosphines and carboxylic acid derivatives.The new methods also would used in the synthesis and modification of drug,ligand and peptides.This dissertation is divided into four chapters as follows.Chapter 1 commenced with a review on the development of C-O bond cleavage and formation,specifically emphasizing the research status of aryl ethers C(sp~2)-O bond conversion and C-B bond oxidation.Chapter 2 was studied the etherification o f aryl methyl ethers.A general and efficient protocol was developed for the synthesis of aryl alkyl ethers through transition-metal-free C-OMe bond cleavage and C-OR bond formation,which was ocured between aryl methyl ethers and various commercially avai lable primary,secondary and tertiary alcohols in the presence of alkali.The protocol is also applicable to a series of natural products and drugs.The great utility of our methodology has been demonstrated by the gram-scale reaction,the iterative C-O bond,and diversified product derivatization as well as its application in the synthesis of butoxycaine.In addition,DFT calculations and experimental results simultaneously confirm that a potassium ion plays a critical role in the activation of methoxy gro up via binding with the nitrile and provide support for an S _NAr mechanism.Chapter 3 was established the phosphination of arylethyl ethers.The method realized the gram scale synthesis of organic aryl phosphines through the activation of C(sp~2)-O bond by coordination of cyano group and potassium ion,which was based on o-ethoxyaromatic nitriles as raw materials and disubstituted phosphines as nucleophiles.This method is easy to operate and can be scaled up to 10 grams without transition metals.Chiral phosphino-oxazolines,sulfinamide and imine ligands can be prepared from cyano arylphosphines by cyano functionalization.It also provides a new method for the synthesis of chiral phosphine ligands.Chapter 4 was developed the oxidation of C(sp)-B bond.Starting from terminal alkynes,the method realized the transition-metal-free direct functionalization of terminal alkynes by boronization,oxone oxidation and nucleophilic reagent attack.Amino acids and peptides can be used as effective nucleophiles,and the corresponding carboxylic acid derivatives have been successfully obtained.In addition,the oxidation of C(sp)-B bond provides a new method for the modification of drugs and peptides.