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.