METAL IONS AND COMPLEXES IN ORGANIC REACTIONS .9. COPPER(1)-CATALYSED CONVERSION OF ARYL HALIDES INTO ALKYL ARYL ETHERS

Whereas sodium alkoxides reduced aryl halides (ArHal → ArH) under heterogeneous catalytic conditions, e.g., in solutions containing a suspension of copper(I) oxide,1 reaction could in some cases be diverted to nucleophilic sustitution (ArHal → ArOAlk) by operating with a substantially homogeneous liquid medium containing copper(I) salts as catalysts. In a suitably chosen reaction system, e.g., ArHal-NaOAlk-AlkOH-Cul-2,4,6-collidine, at ∼100-120°, high yields of ethers resulted with alkoxides derived from normal monohydric alkanols, but reduction usually predominated with alkoxides from other types of alcohols. The process is exemplified by preparations of methyl or ethyl ethers (∼80-100%) from monocyclic or polycyclic aryl bromides or iodides, including those containing Me, OMe, or CO2H groups as nuclear substituents. Lower yields (∼35-50%) resulted when OH or NH2 were substituents, probably because of their participation in competing reactions, and no ethers were obtained when NO2, CHO, or COMe were substituents.