Etudes sur les composés organométalliques partie XX Sélectivité de l'addition 1,4 de composés benzyliques du titane IV avec la benzylidéneacétone

o-DPPB-Directed Copper-Mediated and -Catalyzed Allylic Substitution with Grignard Reagents

The ortho-diphenylphosphanylbenzoyl (o-DPPB) group was explored as a directing leaving group in copper-mediated and copper-catalyzed allylic substitution with Grignard reagents. Complete control of chemo-, regio- and stereoselectivity with complete syn-1,3-chirality transfer was observed as a result of the directed nature of the reaction. No excess of organometallic reagent is required and the directing group can be recovered quantitatively. Coordination studies in the solid state and in solution have shown that two substrates are bound via the phosphine function of the directing group at copper. Dynamic NMR experiments in solution are in agreement with a ligand-exchange process at copper, a prerequisite for the development of a substoichiometric process.