Alkyl Group Transfer Reactions Based On Sulfonium Ion Intermediates

As important S(IV)motifs,sulfonium ions have been widely involved in biology and chemistry research.In organisms,S-adenosyl-L-methionine(SAM)bearing sulfonium structure serves as the major methyl group donor.Such methylation process proceeds through nucleophilic substitution or radical reactions,assisting the completion of various metabolic activities.In fact,sulfonium salts,as a class of important reactants and intermediates,have been extensively reported to enable a wide array of organic transformations.Recently,developing approaches to construct sulfonium intermediates efficiently and expanding their synthetic applications have become an important research topic.This thesis presented our recent efforts in applying sulfonium intermediates formed from aryne and sulfide on methyl,ethyl,benzyl and allyl group migration reaction.The nucleophilic addition of arynes with various sulfides could lead to the formation of sulfonium intermediates in high efficiency,and enabled versatile unique reactions.Inspired by SAM’s function that the alkyl groups attached to sulfonium center could undergo nucleophilic substitution reaction,we herein reported an aryne-induced alkyl group transfer reaction through sulfonium intermediates.Mechanistically,the nucleophilic NH-indoles could undergo N-substitution reaction with sulfoniums derived from arynes and thioethers,accomplishing the alkyl group transfer from sulfur to nitrogen center.In addition,sulfides with other nucleophilic motifs(including carboxylic acids,phenols and amides)could undergo such transformations,providing facile access to structurally diverse organosulfur compounds.In general,this strategy allowed precise activation of sulfides and promote efficient group transfer reaction under mild conditions,which could be effectively employed for latestage modification of highly elaborated molecules.Mechanistic studies supported the potential intermediacy of sulfonium ions,and the intramolecular nature of our protocol.Competition experiment further suggested that the order of group transfer speed to be methyl > benzyl > allyl.