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 tran sformations that furnishes complex, highly functionalized cyclopentenannela ted dihydropyrrole products in moderate yields with complete stereoselectio n. This sequence demonstrates that diyls resulting from homolytic scission of alkylidene carbene-alkene adducts can be readily accessed under mild exp erimental conditions and that, in the presence of appropriate pendant funct ionality, these diyls can productively cyclize, The isomeric isoprene-deriv ed tosylamides follow an abbreviated reaction course and deliver azabicyclo [3.1.0]hexanes via an isomerization that competes with diyl formation.