Preparations and selectivities of magnesium-based mixed cuprates

The reactions of magnesium-based cuprates 'R2CuMg' (prepared from 2RMgX + C uI) with methyl cinnamate furnish conjugate addition products in 60-82% yie lds. 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 'BuMeCu Mg', 'MeBuCuMg' or ['Bu2CuMg' + 'Me2CuMg'] also selectively transfers butyl groups toward conjugate addition reactions. These results reflect to the f act that Cu-Bu bond is more reactive than Cu-Ph or Cu-Me bonds present in t he mixed cuprates. (C) 2001 Elsevier Science B.V. All rights reserved.