Iron-catalysed cross-couplings

Fiirstner reported the iron-catalysed crosscoupling of aryl-halides or aryl-pseudohalides with allgrl-Grignard reagents. Iron-catalysed biaryl bond formation could also be achieved from the coupling of aryl-halides or aryl-pseudohalides with aryl-Grignard reagents.  

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Iron-catalysed cross-coupling and olefin hydrofunctionalisation reactions have emerged that operate well in the absence of the more commonly required noble metals. Similarly, operationally simple and practical iron-catalysed carbonyl and olefin hydrogenation procedures are now available, providing inexpensive routes for molecule construction. 

Scheme 13.1 Iron-catalysed cross-coupling reactions of aryl halides with benzene.

Scheme 13.25 Iron-catalysed cross-coupling between JV-Boc-protected azetidines and aryl magnesium bromides.

The iron(m)-catalysed cross-coupling of MeMgBr with 1-bromopropene (Scheme 17) has been found to proceed stereospecifically. The reaction rate is virtually... 

Iron-catalysed direct Suzuki-Miyaura cross-coupling between Af-het-erocyclic amines and aryl boronic acids. 

Initially, this field was pioneered by Li who reported in 2007 on the formation of new carbon-carbon bonds directly starting from diarylmethanes and 1,3-dicarbonyl compounds under mild reaction conditions (80-100 °C, 5-36 h) in the presence of catalytic quantities of an inexpensive iron precursor (iron(ii) chloride, 20 mol%) and stoichiometric quantities of an oxidant (DTBP). The overall reaction can be regarded as an iron(ii) chloride-catalysed oxidative activation of a benzylic carbon-hydrogen bond followed by a cross-coupling reaction to form a carbon-carbon bond (Scheme 13.7, bottom). The mechanistic proposal is based on a single-electron transfer pathway as shown in Scheme 13.7. Initial homolysis of DTBP in the presence of the iron(ii) salt forms both tert-butoxyl radical and an iron(iii) species. Then, proton abstraction from the diarenemethane generates the two key... 

Scheme 7.5 Plausible mechanism for iron-catalysed Kumada cross-coupling.

The reactivity of A-heterocyclic carbenes (NHC) with iron has been presented through the various types of complexes that have been described. Their catalytic applications in cross-coupling, allylation, aziridination, hydrosilylation, and as hydrogenase mimics are detailed. A report on cross-coupling reactions catalysed by complexes of iron group metals with NHC features the reaction mechanisms. ... 

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