| Abstract
| - Halogenated aryl ketones (XC6H4COR: X = Cl, F; R = Me, Et, Ph) and benzyl alcohols(XC6H4CH(OH)R: X = Cl; R = Me, Et) have been reduced catalyticallyover Pt/C at 50 °C, by bubbling H2at atmospheric pressure into a multiphase system consisting of ahydrocarbon solvent (isooctane)and an alkaline aqueous phase (KOH 50%) in the presence of aphase-transfer (PT) agent (oniumsalts or polyoxyethylene monoalkyl ethers). The chemoselectivityof the reaction is sharply modifiedby the PT-agent: in its absence, a wide range of products isobserved, including those derivingfrom the complete reduction of both the aromatic ring and carbonylfunctions. Instead, the presenceof the PT-agent allows several different halo ketones to be transformedinto their correspondingbenzylic alcohols: that is, the hydrodechlorination occurs only withthe partial hydrogenation ofthe CO group to the CH(OH) one, while further reductions aretotally prevented. Under suchconditions, both ionic (onium salts) and nonionic (polyoxyethylenemonoalkyl ethers: Brij 35, 52,56, and 58) compounds have been tested, and results seem to suggestthat the higher theirhydrophilicity is, the better the chemoselectivity toward the formationof dehalogenated alcoholsis as well. Moreover, under multiphase conditions, also halo arylalcohols lead to the correspondingdechlorinated alcohols in quantitative yields although a slowerreaction is observed with respectto ketones.
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