Iron-Catalyzed Reductive Radical Cyclization of Organic Halides in the Presence of NaBH4: Evidence of an Active Hydrido Iron(I) Catalyst

Iron made'em: Iron(II) complexes such as FeCl 2 and [FeCl 2(dppe) 2] (dppe=1,2-bisdiphenylphosphinoethane) are efficient precatalysts for the radical cyclization of unsaturated iodides and bromides in the presence of NaBH 4 (see scheme). Cyclic voltammetry studies suggests that the reaction occurs through a radical mechanism via an anionic hydrido iron(I) species as the key intermediate for the activation of the substrates by electron transfer. Copyright © 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.