The Influence of Main Group Metallic Lewis Acids on the Formation and Reactivity of Grignard Reagents

The significance of main group metallic Lewis acids such as LiCl, MgCl2, AlCl3 on the formation and reactivities of Grignard reagents are best demonstrated by recent quick development of their diverse synthetic techniques and versatile reactivities towards various electrophiles. Although substantial progress has been made especially on the selective formation of carbon-metal bonds employing lithium chloride as the activator, novel protocols especially these for regioselective metalation of highly functionalized substrates are continuously developed and thus occupy a hot research spot in organometallic chemistry. This mini-review provides a concise overview mainly on the behavior of main group metallic salts derived from lithium, magnesium and aluminum as a powerful tool for regioselective metalation of C-X (X = Cl, Br, I) and C-H bonds. The diverse functions of these metallic salts on the reactivities of Grignard reagents are exemplified primarily choosing aldehyde as the electrophile.