Carbocupration Reactions of Acetylenes and Olefins

In the addition of Me2CuLi reagents to electron-deficient acetylenes [85-88], DCD-type complexes have been identified by NMR [84, 89]. As shown below, an ynoate affords a vinylcopper intermediate, while an ynone instead affords an allenolate (Eq. 10.9). The origin of this diversity remains unclear. A related carbocupration mechanism has also been proposed for the reaction with allenylphosphme oxide [53]. Olefin carbocupration of dienes [90] and cyclopropenes [34, 36] is known, but these mechanisms also remain unclear. 

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