1. Chiral Concave N-Heterocyclic Carbenes 3 rd International Summer School “Supramolecular Systems in Chemistry and Biology“ Tim Reimers Kiel, GER

2. N-Heterocyclic Carbenes (NHC) Different ring sizes… Different heteroatoms… Bulky groups R are needed to avoid dimerization

3. How to make NHCs? E.g. by deprotonation: First crystalline carbene (1991)! A. J. Arduengo III, R. L. Harlow, M. Kline, J. Am. Chem. Soc. 1991, 113, 361. Ad = Adamantyl

4. What can NHCs be used for? As ligands in transition metal mediated reactions: Olefin metathesis Suzuki-Miyaura reaction M. Scholl, S. Ding, C. W. Lee, R. H. Grubbs, Org. Lett. 1999, 6, 953. O. Navarro, R. A. Kelly III, S. P. Nolan, J. Am. Chem. Soc. 2003, 125, 16194.

5. What can NHCs be used for? As organocatalysts: C. Burstein, F. Glorius, Angew. Chem. Int. Ed. 2004, 43, 6205.

6. What does “concave“ mean?

7. A Concave Catalyst Concave system Reactive centre

8. A ConcaveCatalyst Concave system Reactive centre Solvent Substrate Functional group

9. Turn over number? A ConcaveCatalyst

10. Concave bimacrocyclic NHC

11. Special Effect with a Concave NHC 52 % X = (CH 2 ) 8 41 % X = (CH 2 ) 10 3 % n. o. 42 % O. Winkelmann, C. Näther, U. Lüning, Org. Biomol. Chem. 2009, 7, 553. ****

12. Chiral Concave NHC

13. Problem: Interconversion by rotation at room temperature Chiral resolution impossible!

14. NMR Experiments O. Winkelmann, D. Linder, J. Lacour, C. Näther, U. Lüning, Eur. J. Org. Chem. 2007, 3687-3607.

15. NMR Experiments CDCl 3 C 2 D 2 Cl 4 CD 2 Cl 2 C 2 D 2 Cl 2 d.e. 40 % d.e. 17 % d.e. 15 % d.e. 10 % O. Winkelmann, D. Linder, J. Lacour, C. Näther, U. Lüning, Eur. J. Org. Chem. 2007, 3687-3607. H-2 im H-8 nap

16. Chiral Concave NHC

17. Can two methyl groups avoid rotation?

18. NMR Experiments

19. H-5 nap H-4 ph H-8 nap CDCl 3 No diastereomeric excess!

20. Increasing the Temperature T = T C T < T C T > T C

21. VT-NMR Experiments No coalescence!

22. Synthesis O. Winkelmann, D. Linder, J. Lacour, C. Näther, U. Lüning, Eur. J. Org. Chem. 2007, 3687-3607. n = 3,4

23. Synthesis O. Winkelmann, D. Linder, J. Lacour, C. Näther, U. Lüning, Eur. J. Org. Chem. 2007, 3687-3607. n = 3,4

24. Synthesis n = 3,4 O. Winkelmann, D. Linder, J. Lacour, C. Näther, U. Lüning, Eur. J. Org. Chem. 2007, 3687-3607.

25. Synthesis

26. Outlook Application of the chiral concave NHC in asymmetric catalysis But first: chiral resolution!

27. Acknowledgements Lüning group Prof. U. Lüning Travel grant