Alkynyliodonium salts in organic synthesis. Preparation of annelated dihydropyrroles by cascade addition/bicyclization of dienyltosylamide anions with phenyl(propynyl)iodonium triflate

The addition of simple pentadienyltosylamide derivatives to the two- carbon electrophile phenyl(propynyl)iodonium triflate initiates a sequence of transformations that furnishes complex, highly functionalized cyclopentenannelated dihydropyrrole products in moderate yields with complete stereoselection. This sequence demonstrates that diyls resulting from homolytic scission of alkylidene carbene-alkene adducts can be readily accessed under mild experimental conditions and that, in the presence of appropriate pendant functionality, these diyls can productively cyclize. The isomeric isoprene-derived tosylamides follow an abbreviated reaction course and deliver azabicyclo[3.1.0]hexanes via an isomerization that competes with diyl formation.