METAL IONS AND COMPLEXES IN ORGANIC REACTIONS .8. COPPER-CATALYSED REDUCTION OF ARYL HALIDES BY ALKOXIDES

With a suitably chosen copper catalyst and solvent [e.g., a suspension of copper(I) oxide in 2,4,6-collidine], the reduction of aryl halides, ArHal → ArH, was achieved in substantial yield by means of sodium alkoxides derived from a variety of primary, secondary, and tertiary alcohols; the corresponding aldehyde or ketone was in some cases also isolated. In the absence of catalyst, reduction occurred, though less effectively, with some of the alkoxides. The corresponding alcohols had little or no reactivity. Effects of varying the halide (including the use of an α-bromo-ketone), solvent, and copper species are reported, together with comparative experiments involving hydride-ion donors (sodium hydride, borohydride, formate) as reductants.