Boron Reagents/Transition Metals Co-catalyzed New Reaction By Trapping Ylides With Allene/Propargyl Carbocations

Active intermediates are important chemical species in organic reactions.By exploring the interactions of different active intermediates,the transforamtions or new reactions may be discovered in this process.Our group have been devoted to researching the diverse transformations of active ylide intermediates.By developing various electrophilic reagents to capture the active ylide intermediates in situ generated,a series of new multi-component reactions in one-pot were developed to construct complex structural function molecules in one-step reaction.In this thesis,we expanded the capture reagents from stable electrophiles to active carbocation intermediates.Through designing and developing of novel allene carbocations,the coupling of dual active intermediates was achieved in this case.Furthermore,by regulated the substrates,the controllable conversion of classical allene carbocations and their isomer propargyl carbocations was achieved,a series of structural diversity molecules of conjugated olefins,dihydrofurans and alkynes were constructed well.Relevant studies have been achieved a new reaction of allene carbocations to capture the active ylide intermediates successfully.Through regulated selectively of allene intermediates/propargyl carbocations,providing a new fashion for the diverse transformations of allene compounds.Five sections are included as following:In chapter 1,we briefly summarized the one-pot multi-component reactions via active ylide intermediates captured and the diverse transformations of allenes,proposed the necessity of developing new chemical transformations of ylides/allenes including the corresponding research ideas.In chapter 2,we developed an Rh（II）/B（C₆F₅）₃ co-catalyzed unprecedent transformation,in which the allene carbocations raised from propargyl alcohols to captured the active oxonium ylides in situ generated from diazo compounds and nucleophiles（benzyl alcohols,alkyl alcohols）selectively,the formed allene intermediates transformed to multi-substituted conjugated dienes derivatives efficiently.The synthesis of polysubstituted conjugated dienes has been a challengeable issue due to the steric hindrance effection of the substituents.In this fashion,it can be constructed efficiently in one step under mild reaction conditions.In chapter 3,we developed the tandem cycloaddition reaction of allene carbocation with active ylide intermediates which generated from aryl diazoketone and water under the co-catalysis of Rh（II）/p-FC₆H₄B（OH）₂.Through the intramolecular cyclization ofα-hydroxy-substituted allene intermediates formed by multi-component captured,the polysubstituted dihydrofuran derivatives containing oxygen-containing heterocycles were efficiently constructed in one pot.The developed method provides a green and economic manner for constructing heterocyclic compounds.In chapter 4,through the electrical regulation of the substrates,we achieved an Rh（II）/B（C₆F₅）₃ co-catalyzed selective capture process of propargyl carbocations with active ylides by employing alkyl alcohols with strong electron-withdrawing substituents.This fashion enables the rapidly and efficiently construction of complex substituted alkynes,showing favorable synthetic application prospects.It also provides a strategy for diversity-oriented synthesis via allene/propargyl carbocations.In chapter 5,we summarized and prospected this topic,proposed a feasibility strategy to construct tetrasubstituted conjugated olefins via allene carbocations/ylide intermediates in the future.