Active-iron-promoted hydrodehalogenation of organic halides

Under very mild reaction conditions, the active-iron-based reducing system composed of FeCl2·4H2O, an excess of lithium powder and a catalytic amount (5 mol%) of 4,4′-di-tert-butylbiphenyl (DTBB) as electron carrier, efficiently performed the hydrodehalogenation of alkyl and aryl halides in tetrahydrofuran at room temperature. The reaction of a series of alkyl and aryl chlorides, bromides, and iodides with this reducing combination led to the formation of the corresponding products resulting from a halogen/hydrogen exchange. Interestingly, the reducing system was efficient in the hydrodehalogenation of aryl fluorides and polychlorinated aromatics. The use of deuterium oxide instead of water in the iron salt allowed the preparation of the corresponding deuterated products. A reaction mechanism has been proposed on the basis of different experiments.