Iron-Containing Ionic Liquid as Catalyst for Cross-Coupling of Grignard Reagents with Alkyl Halides

Significance

Iron-catalyzed cross-coupling reactions recently have attracted great attention due to the low price and non-toxic properties of iron salts. Despite the large amounts of published methods, they are not general and often are not sufficiently practical. This protocol uses a cheap and easily recyclable ionic liquid, which successfully catalyzes the cross-coupling of primary, secondary and benzylic chlorides and bromides with arylmagnesium reagents. The reactions require only ten minutes at 0 °C. Tertiary halides are not reactive. The catalyst can be recycled up to four times. The required amount of the catalyst is as low as 0.5 mol%. Heterocyclic compounds like 4-bromo-1-methylpiperidine can be used successfully for the coupling reaction.