Isopropylmagnesium chloride

Isopropylmagnesium chloride is an organometallic compound with the general formula ₂HCMgCl. This highly flammable, colorless, and moisture sensitive material is the Grignard reagent derived from isopropyl chloride. It is commercially available, usually as a solution in tetrahydrofuran.

Synthesis and reactivity

Solutions of isopropylmagnesium chloride by treating isopropyl chloride with magnesium metal in refluxing ether:
This reagent is used to prepare other Grignard reagents by transmetalation. An illustrative reaction involves the generation of the Grignard reagent derived from bromo-3,5-bisbenzene:
Addition of one equivalent of LiCl to isopropylmagnesium chloride gives "Turbo Grignard" solutions, named so due to the increased rate and efficiency for transmetalation reactions.
Isopropylmagnesium chloride is also used to prepare isopropyl compounds, such as chlorodiisopropylphosphine:
This reaction exploits the bulky nature of the isopropyl substituent.

Turbo-Grignard reagents

As initially reported by Knochel et al., lithium chloride enhances the ability of isopropylmagnesium chloride toward transmetalation reactions. The more reactive species, a LiCl-iPrMgCl complex, is called a Turbo-Grignard reagent. These species are related to Turbo-Hauser bases, a family of magnesium amido compounds containing also LiCl. "Turbo-Grignards", as they are often called, are aggregates with the formula ₂. These species promote formation of aryl and heteroaryl Grignard reagents by halogen-magnesium exchange:
The traditional method for generating the aryl Grignard reagent proceeds less predictably:
Furthermore, traditional routes to Grignard reagents has limited functional group compatibility, whereas the Turbo-Grignard method tolerates other halides, some ester groups, and nitriles.
Studies suggest that the enhanced reactivity towards electrophiles by "Turbo-Grignard" reagents in comparison to their "classic" equivalent can be attributed to a greater concentration of nucleophilic magnesate complexes in the solution due to the presence of LiCl.