Studies On The Deoxygenation/Borylation Of Ketones And The Oxidation Of C(sp)-B Bonds

The versatility and availability of ketones make them important raw materials in organic chemistry and they are used in a variety of synthetic transformations.Alkenylboronates and alkynylboronates are very important synthetic building blocks in organic chemistry,which play a very significant role in many fields such as organic synthesis,functional materials,pharmaceuticals,and biologically active molecules.Therefore,the synthesis of alkenylboronates and the transformation of alkynylboronates have attracted extensive attention.The general strategies of synthesizing alkenylboronates from alkynes and alkenes have been well established.In view of the fact that alkynes and alkenes are difficult to obtain in some cases,the synthesis of alkenylboronates from ketones is prospective.In this context,we have developed rhodium-catalyzed deoxygenation and borylation of ketones to synthesize valuable alkenes,vinylboronates and vinyldiboronates in the presence of B₂pin₂.We have also developed an efficient and practical method for one-pot synthesis of carboxylic acids,esters and amides form1,1-dibromoalkenes.The 1,1-dibromoalkenes were converted into alkynylboronates through Corey-Fuchs reaction and borylation in the presence of ⁿBu Li and ⁱPr OBpin.Finally,the carboxylic acids and their derivatives were derived from alkynylboronates through C(sp)-B bond oxidation.The dissertation is divided into four chapters:(1)The deoxygenation of ketones,the synthesis of alkenylboronates and the transformation of alkynylboronates are reviewed.It mainly includes the development of deoxygenative alkylation and olefination of ketones,the development of synthesis of alkenylboronates and 1,1-diboration products,and the research status of transformation of alkynylboronates.(2)Using[RhCl(cod)]₂ as the catalyst and B₂pin₂ as the oxygen-abstraction reagent,a novel rhodium-catalyzed deoxygenative olefinations reaction involving carbonyl?-carbon of ketones was developed.A series of olefin pr oducts with high selectivity(E/Z>20:1)were obtained,which enriched the methods of deoxygenative olefination of ketones.The reaction conditions for the deoxygenative olefination of ketones are optimized.The protocol has mild conditions,wide substrate applicability and good functional group compatibility.The synthetic application of a leukotriene B ₄receptor specific inhibitor LY223982 precursor illustrates the practicality of this strategy.(3)Based on the deoxygenative olefinations of keto nes,a novel rhodium-catalyzed deoxygenation and borylation of ketones with B ₂pin₂ have been developed.A series of vinylborates and vinyldiboronates with regioselectivity and stereoselectivity were obtained,which expanded the synthetic methods of alkenyl boronates and enriched the applications of ketones.Under mild reaction conditions,this strategy has broad substrate applicability and good functional group compatibility.Through mechanism experiments,a possible dual catalytic cycle for the deoxygenation and borylation was proposed.Mechanistic studies support that rhodium-catalyzed ketone dehydrogenation of ketones to get alkenes through boron enolate intermediates,followed by rhodium-catalyzed dehydrogenative borylation of alkenes to afford alkenyl boronates.The process of deoxygenation and borylation has also been verified by the DFT calculation s.A series of synthetic applications,the synthesis of functional molecules and isomers of temarotene demonstrated the practicability of this method.(4)An effective and practical method for the synthesis of carboxylic acids,esters and amides from 1,1-dibromoalkenes derived from aldehydes has been developed,which enriched the synthetic methods of carboxylic acids and their derivatives.The key process of the reaction is the formation of alkynylboraonate intermediates and the oxidation of C(sp)-B bonds.After simple operation under mild reaction conditions,the target carboxylic acid,ester and amide can be obtained in one step.The protocol has broad substrate scope,good efficiency and functional group compatibility.A series of synthetic applications such as the modification of peptides,the synthesis of diclofenac,the carbon chain extension of carboxylic acids and the synthesis of esmolol have expanded the transformation of the C(sp)-B bond,which also shows that the method has a certain practical significance.