Colored complexes can be obtained from some enones on addition to ethereal Me(2)CuLi.LiI at -78 degrees C. The unreacted enone can be recovered from these mixtures in high yield by low-temperature protonation. When 2,2,5-trimethyl-4-hexen-3-one was added to Me(2)CuLi.LiI at -80 degrees C, cuprate-olefin and lithium-carbonyl complexes were formed and observed by C-13 NMR. On warming this reaction solution to -55 degrees C, only the lithium-carbonyl complex was detectable which slowly (t(1/2) approximate to 2.5 h) converted into the beta-alkylated enolate. Implications of these observations on the description of the mechanism of the 1,4-addition reaction are presented.