Intramolecular [3 + 2] Annulation of Olefin-Tethered Cyclopropylamines

Starting from readily available olefin-tethered tertiary aminocyclopropanes, we have developed a convenient [3 + 2] annulation reaction by means of one-electron oxidation which can be induced photochemically or chemically, followed by two sequential 5-exo radical cyclizations. The rate constants for the competing 1,5-hydrogen transfer in the β-immonium carbon radical intermediate have been estimated to fall between 1000 (6-exo) and 100 (7-exo and/or 8-endo) s -1 at room temperature.