Iron-Catalyzed Cross-Coupling Reactions

Simple iron salts such as FeCl(n), Fe(acac)(n) (n = 2,3) or the salen complex 4 turned out to be highly efficient, cheap, toxicologically benign, and environmentally friendly precatalysts for a host of cross-coupling reactions of alkyl or aryl Grignard reagents, zincates, or organomanganese species with aryl and heteroaryl chlorides, triflates, and even tosylates. An "inorganic Grignard reagent" of the formal composition [Fe(MgX)(2)] prepared in situ likely constitutes the propagating species responsible for the catalytic turnover, which occurs in many cases at an unprecedented rate even at or below room temperature. Because of the exceptionally mild reaction conditions, a series of functional groups such as…