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.
格氏试剂 2(其中含
镁碳原子是唯一的立构中心)在 Pd(0) 或 Ni(0) 催化下与
乙烯基溴偶联,得到完全保留构型的化合物 3。使用 Fe(acac)3 或 Co(acac)2 作为催化剂的偶联伴随着相当大的外消旋作用。这些发现是针对协同极性和逐步
SET
金属转移途径之间的二分法进行讨论的。