Preparations and selectivities of magnesium-based mixed cuprates

The reactions of magnesium-based cuprates ‘R2CuMg’ (prepared from 2RMgX+CuI) with methyl cinnamate furnish conjugate addition products in 60–82% yields. The mixed cuprates ‘PhBuCuMg’, ‘BuPhCuMg’ or [‘Ph2CuMg’+‘Bu2CuMg’], prepared in three different ways, conjugatively add to methyl cinnamate to produce butylated adduct selectively. Another set of mixed cuprates ‘BuMeCuMg’, ‘MeBuCuMg’ or [‘Bu2CuMg’+‘Me2CuMg’] also selectively transfers butyl groups toward conjugate addition reactions. These results reflect to the fact that Cu–Bu bond is more reactive than Cu–Ph or Cu–Me bonds present in the mixed cuprates.