HYDROGEN-TRANSFER HYDRODEHALOGENATION OF AROMATIC HALIDES WITH ALCOHOLS IN THE PRESENCE OF NOBLE-METAL CATALYSTS

Catalytic hydrodehalogenation of aromatic halides was carried out in a n alcohol solution containing base compounds in the presence of carbon -supported noble metal catalysts. It was found that dechlorination of 1,2,4-trichlorobenzene to benzene effectively occurred in a 2-propanol solution of a base compound such as NaOH or KOH in the presence of Rh /C or Pd/C at temperatures below 65 degrees C. When deuterium-labeled 2-propanol, CD3CD(OD)CD3, was used as a solvent, 1,2,4-trichlorobenzen e was dechlorinated to give benzene containing D atoms with high yield , indicating that the hydrodechlorination reaction includes hydrogen-t ransfer from 2-propanol to chlorobenzenes. Iodo-, bromo-and fluoro-ben zenes were also readily dehalogenated in the catalytic system. (C) 199 7 Elsevier Science B.V.