Neighboring Group Participation In Electrophilic Cyclization And Diiodonation Of A-Alkynylol

Furans are important heterocycles and are present as key structural units in many biologically important natural products and pharmaceutical substances.Furans are (?)dely used as building blocks in organic synthesis.The development of novel and efficient approaches to furan derivatives has been an active research area over the past decades.electrophilic cyclization of heteroatomic nucleophiles with alkyne derivatives has been proven to be one of most effective methods for preparing heterocyclic compounds,particularly for poly-substituted furans.The 1,2-migration of the thio group is an important chemical transformation extensively used in the synthesis of heterocyclic compounds.Especially,1,2-migration of thio group with substitution of tethered nucleophiles to thiiranium intermediate provides a valuable synthetic tool for building expected heterocyclesWe synthesize 4-thio-but-2-yn-1-ols,which could be easily prepared via Grignard reaction of magnesium acetylides with aldehydes and study electrophilic cyclization reaction with NXS(X=I,B,Cl).We developed a facile and efficient method for the synthesis of 2,4-dihalo-3-thio-furans via the electrophilic cyclization and 1,2-migration of the thio group.The process showed considerable synthetic advantages in terms of product diversity,mild reaction conditions,the simplicity of the reaction procedure,and good-to-excellent yields.This type of reaction presented here has potential utility in organic synthesis.1,2-Diiodoalkenes are useful intermediates in organic synthesis.Earlier studies have shown that they were prepared stereospecifically,with only trans-adducts being obtained,by direct addition of iodine to alkynes.However,the reactions proceeded very slowly with low conversion.Neighboring group participation is an important mode of chemical reactivity whereby interaction of neighboring groups with reactive centers can alter rates of reactions.We demonstrated the highly stereoselective formation of(E)-diiodoalkenes using iodine through neighboring group participation. Such diiodides can be used to provide access to stereo-defined polyenes,and functionally complex tri-and tetra-substituted alkenes.