Activated Selenoxide-Mediated Electrophilic Cyclization Of Alkynes

Benzobicyclic structure not only widely exists in many important biological and medical compounds,but also can be used as chiral ligands,catalysts and other compounds,which has good application value.Alkyne is one important type of compound in organic synthesis.The electrophile-mediated cyclization of internal alkynes has become one of the most effective method for synthesizing carbocycles and heterocycles,which provides cyclic structures with different substituents,such as halogen,phosphorus,sulfur,and so on.Organic selenium compounds have very good research value due because of their unique chemical and biological properties.For example,selenoxide can be activated by acid anhydride to obtain a strong electrophilic substance like sulfur sulfoxide to functionalize the compound.But compared with sulfoxide,activated selenoxide system has not been much developed and the related methodologies need further research.This study proposes the internal alkyne electrophilic cyclization reaction involving selenium-containing electrophiles,and develops a new method for the synthesis of seleno-substituted dihydronaphthalene derivatives.The key to this reaction is to use trifluoromethanesulfonic anhydride to activate selenium sulfoxide to form a strong electrophilic reagent and react with alkynes to obtain vinyl intermediates.Then the aromatic ring is used as a nucleophile to form a new six-membered ring,followed by aromatization and demethylation with triethylamine.This metal-free one-pot reaction has a good functional group tolerance and the reaction yield is high,up to 98%,which allowed us to afford 2-phenylselenyl-3,4-dihydronaphthalene and other derivatives easily,including selenium-substituted phenanthrene,dihydroquinoline,2H-chromene,and coumarin.And the obtained products could be further converted into various valuable aryl-aryl compounds in simple steps,which well reflects the application potential of this reaction.