Transition Metal-catalyzed Borylation Of Ketones And Their Derivatives

Ketones and their derivatives are extremely important intermediates in organic synthesis,their carbonyl groups can be converted into other functional groups through various reactions.So they are widely used in the fields of biomedicine,pesticides,biomaterials,and new materials.Ketones can be deoxyborylated into alkylborates,which is a valuable synthetic method for alkylborates.Diaryl structures are important functional structures of drugs,dyes,and advanced materials,therefore the development of synthetic methods for diarylalkyl borate esters is of great significance.Although the traditional synthetic methods of diaryl geminal diborates have been reported,the synthesis of using cheap diaryl ketones as starting materials has not yet been realized.The research of this paper mainly focuses on the boronation reaction of carbonyl and its derivative enol silyl ether.Firstly,cheap cobalt acetylacetonate/terpyridine was used as the catalytic system and pinacol borate ester was used as the deoxygenating reagent to develop the diaryl ketone of deoxyhydroboration reaction and its deoxygediboration reaction,which successfully prepared diarylmethylborate and gemodiarylgediboronate.Additionally,asymmetric hydroboration of alkyl ketone-derived enol silyl ethers was achieved using metal rhodium/phosphine ligands as catalysts,providing a new method for the synthesis of chiral β-hydroxyboronic acid ester derivatives.This paper is divided into five chapters.The main contents are summarized as follows:Firstly,overview of the synthesis of alkyl borate esters and the deoxygenative borylation reaction of ketones,including the deoxygenative borylation of ketones catalyzed by transition metals(copper,iron,rhodium,platinum,etc.),and the research progress and mechanism of the deoxygenative borylation of ketones without the participation of transition metals.Then,the research progress of asymmetric catalytic hydroboration of olefins by transition metals(rhodium,iridium,copper,iron,cobalt,etc.)in recent years has been summerised,and the context of transition metal types,ligand types,and substrate types have been detailedly classified and reviewed,briefly introducing the research progress and reaction mechanisms in related fields.In the first part of study,a method that uses the cheap metal cobalt/terpyridine as the catalytic system to catalyze the deoxygenation of diaryl ketones and synthesize diarylmethylborates was developed,which has the merits of fast reaction rate,high efficiency,and good functional group compatibility.Furtherly,the practicality of the reaction in the field of organic synthesis has been proved through gram-level preparation and a series of carbon-boron bond transformations of the product.Mechanistic research has shown that cobalt acetylacetonate firstly reacts with pinacolborane/bipinacolborane to form an active cobalt intermediate(Co-Bpin),which then reacts with diaryl ketones to form diaryloxyboron intermediate,which then reacts with the pinacol borate to form1,1-gediborate,which then under the action of water and alkali is converted into a diaryl ketone hydroboration product.In the second part of study,an approach that through a cheap metal cobalt/terpyridine-based catalytic system to catalyze the deoxygenation of diaryl ketones and acquire 1,1-gemdiaryl 1,1-gemodiborates was developed.For the first time,this way contributes to the cheap metal-catalyzed geminal diboration reaction of diaryl ketones and directly synthesize diaryl geminal diborates,with fast reaction and good functional group compatibility,which provides a new choice for the synthesis of diaryl geminal diborates.Mechanistic studies show that the diaryl ketone is firstly catalyzed by cobalt to form the diaryl oxyboron intermediate,which then the oxyboron intermediate reacts with another molecule of pinacol borate to obtain the diaryl geminal diborate.In the third part of study,using rhodium/chiral phosphine ligand as the catalytic system obtained the enantioselective hydroboration of alkyl ketone-derived enol silyl ethers.With the method of mild reaction conditions and wide substrate adaptability,the preparation of a series of chiral β-hydroxyborates and their silicon-containing protected chiral diol derivatives was achieved.And through the product β-hydroxyborates,a series of molecules with structural diversity were constructed,providing a new method for the enantioselective construction of β-hydroxyboronic acid esters and their derivatives.