REACTION OF ORGANOMERCURIC HALIDES WITH DICOBALT OCTACARBONYL . A NEW KETONE SYNTHESIS

Many organomercuric halides react with dicobalt octacarbonyl in tetrahydrofuran solution at room temperature to give the ketone (R2C=0) derived from R in RHgX, Hg[Co(CO)4]2, Co(II) halide, and carbon monoxide. The reaction proceeds rapidly and is of good preparative utility. The scope and limitations of this new ketone synthesis have been defined and the probable mechanism involves the following steps: solvent-induced redox disproportionation of dicobalt octacarbonyl to give THFCo(CO)4+ and Co(CO)4¯; nucleophilic displacement of halide ion from mercury by the latter; electrophilic cleavage of the C-Hg bond in the RHgCo(CO)4 formed (or in its disproportionation product, R2Hg) by THFCo(CO)4+, forming RCo(CO)4; organic group migration in the latter, producing RCOCo(CO)3; and reaction of the latter with RCo(CO)4 to give the ketone and cobalt carbonyl. Diphenylmercury also reacts with dicobalt octacarbonyl in THF to give benzophenone and Hg[Co(CO)4]2. © 1969, American Chemical Society. All rights reserved.