Catalytic Dehalogenation of Aryl Chlorides Mediated by Ruthenium(II) Phosphine Complexes

The catalytic dechlorination of aryl chlorides performed by RuHCl(H 2 ) 2 (PCy 3 ) 2 and RuH 2 (H 2 ) 2 (PCy 3 ) 2 in alcohols is rapid and complete within 1 h. The mechanism involves a transfer hydrogenation step with participation of the alcohol. The system exhibits significant functional group tolerance. The catalyst can be generated in situ from [RuCl 2 (COD)] x (COD = cyclooctadiene) and 2 equiv of phosphine (PCy 3 or P i Pr 3 ). Catalytic conversions are similar to those observed when an isolated precatalyst is used. Mechanistic considerations and the scope of the process are discussed.