Radical Boration And Oxyamination Of Unsaturated Compounds

The construction of carbon-heteroatom bonds represents one of most important transformations in organic chemistry,medicinal chemistry,natural product synthesis,and functional material synthesis.Thus,the development of highly efficient methods to construct carbon-heteroatom bonds is always a hot topic in synthetic chemistry.Especially,the addition reactions of carbon-carbon unsaturated bonds has attracted great attention,because of its high efficiency,easy availability of starting materials,and high atom economy.In this thesis,the author reported a couple of new methods for the formation of carbon-heteroatom bonds through the functionalization of carbon-carbon unsaturated bonds.Firstly,the author disclosed new reactivities of N-heterocyclic carbene-boryl radicals(NHC-boryl radicals)for the radical addition to alkenes and alkynes,which has provided a new pathway to create versatile carbon-boron bonds.Moreover,a Cu(?)-catalyzed direct intermolecular oxyamination of electron deficient alkenes was discussed.This method has offered a high efficient way to construct carbon-nitrogen bonds and carbon-oxygen bonds.This thesis comprises the following four chapters:In chapter one,the author described the application of Lewis base-boranes in organic synthesis with a focus on free radical reactions and the construction of carbon-boron bonds.In chapter two,a synthetic method to construct boron-handled cyclic molecules was developed based on a radical borylation/cyclization cascade of 1,6-enynes.Using a radical cascade strategy and the utlization of a thiol as the polarity reverse catalyst are the key to achieve this transformation.Control experiments and mechanisitic studies showed that the addition of NHC-boryl radicals to unsaturated carbon-carbon double bonds or triple bonds was highly dependant on the character of alkenes and alkynes.Namely,the addition reaction could only proceed when alkenes and alkynes bearing a radical stablizing groups,such as aryl and ester groups.In contrast,no reaction occurred for simple alkenes and alkynes.Such a reactivity bias ensured a initial chemoselective radical addition reaction in the radical cascade.Further transforamtion of the resulted boryl functionality to other useful building blocks was demonstrated as well.The third chapter introduces a radical regioselective hydroboration of ???-unsaturated carbonyl compounds to form stable ?-borylcarbonyl compounds using an N-heterocylic carbene borane as the boryl radical precursor.?,?-Unsaturated esters,amides,ketones and acids could be applied to afford various ?-borylcarbonyl molecules.This method features mild reaction conditions and wide substrates scope.In the last chapter,a Cu(?)-catalyzed difunctionalizaiton of electron deficient alkenes and N-acyloxyamines was developed to access ?-amino alcohols,wherein N-acyloxyamines served as both nitrogen and oxygen donors.The reaction was characterized by oxyamination of a variety of ?,?-unsaturated ketones with good yields and high regioselectivity.Mechanism studies suggested the involvement of alkyl radical intermediates in the reaction sequence.