Generation and reactions of arylzinc and arylmagnesium compounds
Organomagnesium and organozinc reagents contain one or two organic groups linked to a magnesium or zinc atom, respectively. Both classes of reagent are important in modern synthetic organic chemistry. For example, Grignard reagents derived from insertion of magnesium(0) into carbon–chlorine or carbon–bromine bonds are reactive carbon nucleophiles. Zinc enolates and the Simmons-Smith reagent (IZnCH2I) are important organozinc species and the Negishi cross-coupling reaction has dramatically increased the utility of a wide variety of organozinc compounds in organic synthesis. Figure 1 summarizes the most common methods for preparing these compounds.
Aryl- and heteroarylmagnesium and zinc reagents may be prepared through the insertion of the elemental metal into the corresponding organohalides, halogen/metal exchange, transmetalation, or directed magnesiation/zincation using metal amide bases. These reagents are trapped with electrophiles in a variety of addition or substitution processes, including cross-coupling reactions.