Sulfur Mediated Functionalization Of Alkenens And Alkynes

As important functional groups in organic compounds,alkenes and alkynes have been wildly studied.In recent years,transition-metal catalyzed functionalization of allylic carbon-hydrogen bond,carbon-carbon double bond and triple bond is a major research direction.However,their functionalization under transition-metal-free condition attracted less attention.This thesis mainly focuses on the functionalization of allylic carbon-hydrogen bond and carbon-carbon triple bond with triflic anhydride activated sulfoxides.In the first chapter,the recent research about anhydride activated sulfoxides is introduced.Anhydride activated sulfoxide intermediates are strong electrophiles and have been applied to functionalization of many kinds of compounds such as alkenes,alkynes,phenols,anilines,nitriles and carbonyl compounds.All these reaction process are similar.Firstly,the activated sulfoxide intermediates react with substrates to generate tri-substituted sulfonium salts through a Swem-type Pummerer reaction.Then,different substituted sulfonuim salts can be transformed to corresponding products under appropriate conditions.In the second chapter,an anti-Markovnikov rearrangement in sulfur mediated allylic C-H amination of olefins is reported.The thermodynamic driving force for the rearrangement of secondary carbocations to primary carbocations could be the result of the intramolecular electrostatic repulsion in dicationic intermediates.Besides,the influence of the substrates'functional groups,reaction concentration and reaction temperature were investigated.This reaction can also constitutes as a new method for the preparation of allylic amines and azetidines from terminal alkenes.In the third chapter,synthesis of a-heterosubstituted ketones through sulfur mediated difunctionalization of internal alkynes is reported.With different nucleophiles containing nitrogen,oxygen,sulfur or halogen,a-amino ketones,a-acyloxy ketones,a-thio ketones,a-halo ketones,a-hydroxy ketones,and related heterocyclic structures can be prepared in one-pot,respectively.The reaction mechanism was proposed,based on the isolation of reaction intermediates.We also tried a chiral Br(?)nsted acid catalyzed reaction to prepare enantioenriched a-substituted ketones directly from alkynes.In the fourth chapter,the sulfur mediated electrophilic cyclization of aryl substituted internal alkynes was realized.A series of 3-thio-4-aryl-1,2-dihydronaphthalene was synthesized from 4-aryl-1-yne in one-pot.Althrough electrophilc cyclization of internal alkynes have been wildly researched for many years,the sulfenylating reagents applied in the electrophilic cyclization remains rare.We realized this transformation with the triflic anhydride activated methyl substituted sulfoxides.First,the carbon-carbon triple bond reacted with electrophilic sulfur reagents to generate the vinyl cation which can be captured by tethered aryl ring.The desired products can be obtained after demethylation with Et3N.By changing the alkyne substrates,sulfenyl substituted phenanthrene,dihydroquinoline,2H-chromene,and coumarin were synthesized,respectively.In summary,sulfur mediated functionalizations of alkenes and alkynes were researched.A new anti-Markovnikov rearrangement was reported in the allylic carbon-hydrogen amination.Methods for synthesis of a-substituted ketones and 3-thio-4-aryl-1,2-dihydronaphthalene from alkynes in one-pot were developed through Swern-type Pummerer reactions.