SYNTHESIS OF SUBSTITUTED PHENYL KETONES VIA PD-CATALYZED HYDRODECHLORINATION OF THEIR POLYCHLORINATED DERIVATIVES

The following compounds, 2- and 3-methylacetophenones, 2- and 3-methyl benzophenones, and 2,2'-, 2,3'- and 3,3'-dimethylbenzophenones have be en synthesized through a Pd-catalysed hydrodechlorination of the corre sponding dichlorinated derivatives. The reaction has been carried out under multiphase conditions at 30-50 degrees C, by bubbling H-2 at atm ospheric pressure into a biphasic system constituted by an organic sub strate solution (isooctane solvent) and an aqueous alkaline solution ( 50% aq KOH), in the presence of Pd/C (5% wt) and Aliquat 336 (tricapry lylmethylammonium chloride). Likewise, fluorinated aceto- and benzophe nones (4-fluoro-3-methylacetophenone and 4-fluoro-3-methylbenzo-, 4-fl uoro-2',3-dimethylbenzo-, 4-fluoro-3,3'-dimethylbenzophenones) have be en prepared starting from the corresponding chlorinated methylfluoro- and dimethyfluoro ketones. Under such conditions, the presence of the onium salt allows the reaction to proceed with a high chemoselectivity : chlorine is removed while both the reduction of the carbonyl group a nd/or fluorine removal are prevented.