New Method for the Preparation of Activated Nickel and Cobalt Powders and Their Application in Biaryl Synthesis

Article abstract of DOI:10.1021/jo00173a024

An activated nickel powder has been prepared by the procedure of electrolysis of a NiSO4 aqueous solution with Hg as the cathode to form a nickel amalgam followed by the removal of the mercury from the amalgam at 150 deg C and 10^-3 torr.The nickel powder, similar to Cu in Ullmann's biaryl synthesis, has been found to react with aryl iodide and aryl bromide at 140 deg C to give biaryls in good yields and with dibrombenzene to yield a number of interesting products including triphenylene, tetraphenylene, and polyphenyls, depending on the relative position of the dibromo groups.In the presence of KI, the powder also induces, unprecedentedly, the homo coupling of an aryl chloride to a biaryl.The activity of the activated nickel powder was further demonstrated by the reaction with benzyl bromide to give 1,2-diphenylethane and with α,α-dichlorotoluene to afford mainly trans-stilbene.