Studies On Reactions Of Fluorinated Enol Silyl Ethers With Diazo Compounds Or Ketones

This thesis focuses on expanding the application of fluorinated enol silyl ethers in organic synthesis.First,an unprecedented Au?I?-catalyzed cross-coupling reaction of fluorinated enol silyl ethers with diazo reagents was developed.Second,the Mukaiyama-aldol reaction of fluorinated enol silyl ethers with ketones was reexamined with the substrate scope being effectively expanded.This thesis has accomplished the following research work:1)The Au?I?-catalyzed cross-coupling reaction of fluorinated enol silyl ethers with diazooxindoles or other donor-acceptor type diazo reagents was developed.The cross-coupling reaction of tetrasubstituted monofluorinated enol silyl ethers,difluorinated enol silyl ethers or trisubstituted monofluorinated enol silyl ethers with diazooxindoles or other donor-acceptor type diazo reagents were developed by using Ph₃PAuOTf or IPr AuSbF₆ as catalyst,providing a new method for the efficient and stereoselective synthesis of all-carbon or fluorinated tetrasubstituted alkenes and trisubstituted alkenes.The gold catalyst showed better catalytic activity than other acid catalysts in the above cross-coupling reactions.According to the control experiments,remarkable fluorine effects on the reactivity and selectivity was observed:under the standard conditions,the reaction of tetrasubstituted monofluorinated enol silyl ether with methyl phenyldiazoacetate gave high yield and Z:E>20:1,while only trace amount of products were obtained by using chlorinated or brominated enol silyl ethers as substrates.In addition,the reactivity of difluorinated enol silyl ether with diazooxindole was higher than that of dichlorinated analogue.Based on these results of experiments and DFT calculations,a possible reaction mechanism was proposed,which might involve the nucleophilic addition of fluorinated enol silyl ethers to gold carbenid intermediate,followed by the cleavage of C-F bond to give desired multisubstituted alkenes.2)A metal triflate catalyzed Mukaiyama-aldol reaction of fluorinated enol silyl ethers with ketones was developed.A highly efficient catalyst-free Mukaiyama-aldol reaction of tryptanthrin with fluorinated enol silyl ethers was developed by using methanol as solvent,affording various tryptanthrin based tertiary alcohols featuring an?-fluorinated ketone moiety.This method was successfully applied to the total synthesis of the difluoro analogue of the natural product Phaitanthrin B.In addition,the Bi?OTf?₃ or Sc?OTf?₃ catalyzed Mukaiyama-aldol reaction of difluoroenoxysilanes with unactivated ketones was further developed,providing a simple,efficient and general method for the synthesis of tertiary alcohols featuring an?,?-difluorinated ketone moiety.Bi?OTf?₃ was identified as the optimal catalyst for the reaction of aryl or alkynyl ketones,while Sc?OTf?₃ turned out to be the best for that of aliphatic ketones.In addition,Sc?OTf?₃ could achieve excellent 1,2-selectivity in the corresponding reaction of?,?-unsaturated ketones.The catalytic asymmetric reaction of difluoroenoxysilanes with acetophenone was also studied,and some preliminary results have been obtained.