Hydrogen-transfer hydrodehalogenation of aromatic halides with alcohols in the presence of noble metal catalysts

Catalytic hydrodehalogenation of aromatic halides was carried out in an 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-trichlorobenzene was dechlorinated to give benzene containing D atoms with high yield, indicating that the hydrodechlorination reaction includes hydrogen-transfer from 2-propanol to chlorobenzenes. Iodo-, bromo-and fluoro-benzenes were also readily dehalogenated in the catalytic system. (C) 1997 Elsevier Science B.V.