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Anion radical coupling

Anion radical coupling. Anita Kożuch 19 IV 2011. Plan. methods for the formation of aryl-aryl bonds anionic cyclohydrogenation history mechanism applications. Selective formation of aryl-aryl bonds between reaction partners (no functionality other than C-H bonds at the carbon atom):

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Anion radical coupling

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  1. Anion radical coupling Anita Kożuch 19 IV 2011

  2. Plan • methods for the formation of aryl-aryl bonds • anionic cyclohydrogenation • history • mechanism • applications

  3. Selective formation of aryl-aryl bonds between reaction partners (no functionality other than C-H bonds at the carbon atom): • transition metal catalyzed cross-coupling reactions • oxidative dimerization of electron-rich arenes (Scholl, Kovacic and others) • intramolecular oxidative dimerization (Müllen) • oxidative photocyclization of stilbenes to phenanthrenes (Mallory reaction) • thermal cyclodehydrogenations by flash vacuum pyrolysis • anionic cyclodehydrogenation of aromatic hydrocarbons

  4. Classic example of anionic cyclodehydrogenation: Oxidative cyclization of 1,10-binaphthyl (1) to perylene (2) M. Rickhaus, A.P. Belanger, H. A. Wegner, L.T. Scott,J.Org.Chem. 2010,75, 7358

  5. Anion radical coupling as an unique method • the highest efficiency in conversion 1,1’-binaphthyl to perylene • alkali metals are used to induce oxidation

  6. Classic example of anionic cyclodehydrogenation: Oxidative cyclization of 1,10-binaphthyl (1) to perylene (2) M. Rickhaus, A.P. Belanger, H. A. Wegner, L.T. Scott,J.Org.Chem. 2010,75, 7358

  7. History • first isolated by Miller • mechanism discovered by accident in 1967 by Solodovnikov et al. H.Gilman, C.G.Brennen, J. Am. Chem. Soc. 1949, 71, 657 M. Rickhaus, A.P. Belanger, H. A. Wegner, L.T. Scott, J.Org.Chem. 2010,75, 7358

  8. Definition Aromatic radical anion Ar + e- → Ar●- Ar●- + e- → Ar2- N. L. Holy, Chem. Rev.1974, 74, 243

  9. General types of anion reactions

  10. General types of anion reactions

  11. Reactivity of a radical anion N. L. Holy, Chem. Rev.1974, 74, 243

  12. Mechanism M +Ar → Ar●- + M+ • The equilibrium constatnt depends on: • nature of the metal • hydrocarbon • solvent • temperature M. Rickhaus, A.P. Belanger, H. A. Wegner, L.T. Scott, J.Org.Chem. 2010, 75, 7358

  13. M. Rickhaus, A.P. Belanger, H. A. Wegner, L.T. Scott, J.Org.Chem. 2010, 75, 7358

  14. M. Rickhaus, A.P. Belanger, H. A. Wegner, L.T. Scott, J.Org.Chem. 2010, 75, 7358

  15. M. Rickhaus, A.P. Belanger, H. A. Wegner, L.T. Scott, J.Org.Chem. 2010, 75, 7358

  16. M. Rickhaus, A.P. Belanger, H. A. Wegner, L.T. Scott, J.Org.Chem. 2010, 75, 7358

  17. M. Rickhaus, A.P. Belanger, H. A. Wegner, L.T. Scott, J.Org.Chem. 2010, 75, 7358

  18. Examined conditions K (in an excess), THF, at 80 ºC gave 73% yield Other conditions examined (metal, solvent, temperature) gave yelds of 10% or less: a) K, 1,2-dimethoxyethane, 80 ºC b) K, diglyme, 80 ºC c) K, toluene, 80 ºC d) Na, THF, 66 ºC e) Na, diglyme, 80 ºC f) Na, TMEDA, 120 ºC g) Na, toluene, 110 ºC M. Rickhaus, A.P. Belanger, H. A. Wegner, L.T. Scott, J.Org.Chem. 2010, 75, 7358

  19. Oxidative agent • exposure to oxygene (small scale) • elemental iodine • Na2S2O5 • SO2 S.H.Bossmann, H.Durr, M.R. Pokhrel, Synthesis 2005, 6, 907

  20. SO2 as an oxidative agent S. Hunig, I. Wehner, Synthesis 1989, 552

  21. Applications P. Schlichting, U. Rohr, K. Müllen, J. Mater. Chem. 1998, 8, 2651

  22. Applications

  23. Applications Reductive ring closure of helicenes A. Ayalon, M. Rabinovitz, Tetrahedron Lett. 1992,33, 17, 2395

  24. Applications Terrylene synthesis U.Scherf, K. Müllen, Synthesis 1992,23

  25. Summary • formation of aryl-aryl bonds • efficiency • unique method • oxidazing agent • obscure mechanism Betterunderstanding of anioniccyclohydrogenation will encouragetheirwideruse inorganicsynthesis.

  26. Thank you !!!Questions ???

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