REACTION OF BU2CULI.LII WITH ALKYL IODIDES - EVIDENCE FOR FREE-RADICALS AND ELECTRON-TRANSFER

Treatment of iodocyclohexane with Bu2CuLi.LiI yields substantial amounts of butylcyclohexane, cyclohexane, cyclohexene, bicyclohexyl, and octane. Trapping experiments demonstrate that the bulk of these products derive from cyclohexyl radicals, indicating that an electron-transfer mechanism is operative. Some of the cyclohexane and bicyclohexyl is traced to transmetalation. Likewise, 1-methyl-1-cyclohexyl iodide and 2-heptyl iodide react via electron transfer, whereas cyclohexyl bromide, 1-heptyl iodide, and 1-heptyl bromide do not. These results are in harmony with House's hypothesis that electron transfer from organocuprates occurs when the reduction potentials of the substrates are more positive than -2.35 V.