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Iron-catalyzed Cross Coupling reactions: From Rust to a Rising Star

Iron-catalyzed Cross Coupling reactions: From Rust to a Rising Star. Weijun Liu. Transition metal catalyzed cross couplings have seen incredible advances and applications, have wide scope and compatibility. But…..typically use palladium and nickel which are generally toxic and expensive.

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Iron-catalyzed Cross Coupling reactions: From Rust to a Rising Star

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  1. Iron-catalyzed Cross Coupling reactions: From Rust to a Rising Star Weijun Liu

  2. Transition metal catalyzed cross couplings have seen incredible advances and applications, have wide scope and compatibility. But…..typically use palladium and nickel which are generally toxic and expensive. Expensive and/or sensitive ancillary ligands are required. Alkyl iodides, bromides and triflates are best. With special ligands alkyl chlorides may be used.

  3. Iron: A More Practical Alternative • Iron is one of the most abundant metals on earth. (5.6% of earth’s crust. 4th most abundant element after oxygen, silicon, and aluminum. Nickel is 0.0084%, palladium is 0.0000015%, gold is 0.0000004% of Earth’s continental crust.) • 2. Cheap • •PdCl2: $4005/150g $26.70/g • •NiCl2: $98.40/250g $0.39/g • •FeCl3: $30.40/1kg $0.03/g • 3. nontoxic • •Prevalent in biological systems

  4. Content: • Early Examples • 2. Alkenyl Derivatives as Substrates • 3. Aryl Derivatives as Substrates • 4. Alkyl Derivatives as Substrates • 5. O, N, S-Arylation • 6. Oxidative Cross-coupling

  5. Early Examples J. Kochi, J. Am. Chem. Soc.1971, 93, 1487

  6. Kochi, J. J. Org. Chem.1976, 41, 502

  7. 2. Alkenyl Derivatives as Substrates NMP as cosolvent Cahiez, G. Synthesis1998, 1199

  8. Cahiez, G.Synthesis1998, 1199

  9. 60% 60% Cahiez, G.; Knochel, P.Synlett2001, 1901

  10. 3. Aryl Derivatives as Substrates Furster, A.Angew. Chem., Int. Ed.2002, 41, 609

  11. Proposed Formal Catalytic Cycle

  12. 4. Alkyl Derivatives as Substrates Furster, A.Angew. Chem., Int. Ed.2004, 43, 3955

  13. Furster, A.Angew. Chem., Int. Ed.2004, 43, 3955

  14. Furster, A.Angew. Chem., Int. Ed.2004, 43, 3955

  15. Only tertiary halides and alky chlorides were found be inert.

  16. Nakamura, E. J. Am. Chem. Soc.2004, 126, 3686

  17. Hayashi, T. Org. Lett.2004, 6, 1279

  18. Cossy, J.Angew. Chem., Int. Ed.2007, 46, 6521

  19. 51% Chai, C.L.L.Adv. Synth., Catal.2007, 349, 1015

  20. 5. O, N, S-Arylation Bolm, C.Angew. Chem., Int. Ed.2007, 46, 8862

  21. Bolm, C.Angew. Chem., Int. Ed.2007, 47, 586 Bolm, C.Angew. Chem., Int. Ed.2008, 47, 2880

  22. 6. Oxidative Cross-coupling Iron-Catalyzed Homo-Coupling FeI/FeIII or Fe0/FeII Fe-II/Fe0 Cahiez, G. Org. Lett.2005, 7, 1943

  23. Cahiez, G. J. Am. Chem. Soc.2007, 129, 13788

  24. Oxidative Heterocoupling Cahiez, G.Angew. Chem., Int. Ed.2009, 43, ASAP

  25. Iron-Catalyzed Direct Arylation through Directed C-H Bond Activation

  26. Nakamura, E. J. Am. Chem. Soc.2008, 130, 5858

  27. Iron-Catalyzed Chemoselective ortho Arylation of Aryl Imines by Directed C-H Bond Activation Nakamura, E.Angew. Chem., Int. Ed.2009, 48, ASAP

  28. Li, Z.-P.; Li, C.-J.Angew. Chem., Int. Ed.2007, 46, 6505

  29. X = N, O, S Li, Z.-P.Angew. Chem., Int. Ed.2008, 47, 7497

  30. Summary 1. Iron catalysts activate alkenyl, aryl, and alkyl derivatives. 2. Iron catalysts activate aryl chlorides, triflates and tosylates under ligand free conditions. 3. Iron-catalyzed cross-coupling shows excellent functional group tolerance. 4. Iron-catalyzed cross-coupling needs only short reaction (typically 5-30 min) time and are performed at low temperatures (typically -20 oC to 0 oC). 6. Iron salts has been successfully applied in the C-H bond activation and oxidative coupling reactions But the iron-catalyzed cross coupling is not nearly as mature as its palladium and nickel counterparts. And the reaction mechanisms are needed to be proved.

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