Kumada-Corriu coupling of Grignard reagents, probed with a chiral Grignard reagent.
The Grignard reagent 2, in which the magnesium-bearing carbon atom is the sole stereogenic centre has been coupled with vinyl bromide under Pd(0) or Ni(0)-catalysis to give compound 3 with full retention of configuration. Coupling using Fe(acac)3 or Co(acac)2 as catalyst was accompanied by considerable racemisation. These findings are discussed with respect to a dichotomy between concerted polar and stepwise SET transmetallation pathways.
Hölzer
Bettina
B
Fachbereich Chemie, Philipps-Universität Marburg, Hans-Meerwein-Strasse, D-35032 Marburg, Germany.
Hoffmann
Reinhard W
RW