The Grignard reagent 6, in which the magnesium-bearing carbon 
 atom is the sole stereogenic centre has been added to CO2, 
 PhNCO, PhNCS and certain aldehydes with full retention of configuration. 
 Reaction with benzophenone, electron-deficient aldehydes and several allyl 
 halides proceeded with partial or complete racemization. The findings are 
 discussed with respect to a dichotomy between concerted polar and stepwise 
 SET reaction pathways.
                                    格氏试剂 6 中的含
镁碳原子是唯一的立体中心,该试剂已加入 
CO2、PhNCO、Ph
NCS 和某些醛中,并完全保留了构型。 
 与
二苯甲酮、缺电子醛和几种烯丙基卤化物反应时,会发生部分或完全消旋化。这些发现与协同极性反应途径和逐步 
SET 反应途径之间的二分法有关。