1. 1 Chiral Anion-Mediated Asymmetric Ion Pairing Chemistry Reporter: Zhi-Yong Han 2010-12-31

2. Background and Introduction Ion Pair ( by Bjerrum in 1926) A pair of oppositely charged ions held together by Coulomb attraction without formation of a covalent bond. contact (tight or intimate) ion pair solvent separated ion pair solvent-shared ion pair “Strict” electrostatic ion pair H-bonded charge-assisted supramolecular entity Ion Pairing Chemistry Brønsted acid catalysis

3. Structure and properties of anionic counterions Chiral Anions Carboxylate and sulfonate anions Borate anions phosphate anions Hexacoordinated phosphorus anions Other anionic structures

4. Carboxylate and sulfonate anions Application: enantiomeric resolutions Water-soluble sulfonated resorcarenes commercially available cyclic polyacids

5. Borate anions Mariappan Periasamy, J. Org. Chem. 1999, 64, 7643-7645

6. Up to 34% ee B. A. Arndtsen, Org. Lett., 2000, 2, 4165–4168. Borate anions

7. ee < 26% Bruce A. Arndtsen Organometallics 2004, 23, 2838-2840

8. Borate anions A. Nelson, Tetrahedron: Asymmetry, 2003, 14, 1995–2004. A + : Ag, Na, Et 2 NH 2 +, Et 3 NH +

9. Borate anions Up to 84% ee Walter Leitner Angew. Chem. Int. Ed. 2006, 45, 3689 –3692

10. Borate anions Hisashi Yamamoto J. Am. Chem. Soc. 1998, 120, 6920-6930

11. Borate anions Gary B. Schuster J. Am. Chem. Soc. 1998, 120, 1705-1717

12. B. List, Angew. Chem., Int. Ed., 2006, 45, 4193–4195 B. List, Angew. Chem., Int. Ed., 2008, 47, 1119–1122.

13. F. D. Toste, Science, 2007, 317, 496–499.

14. E. N. Jacobsen, J. Am. Chem. Soc., 2007, 129, 13404–13405.

15. E. N. Jacobsen, J. Am. Chem. Soc., 2008, 130, 7198–7199.

16. VAPOL-Boron Lewis Acid? Up to 98% ee Jon C. Antilla and William D. Wulff* J. Am. Chem. Soc. 1999, 121, 5099-5100 Catalyst structure not determined

17. Wulff, W. D. Eur. J. Org. Chem. 2007, 206, 8–2071. VAPOL-Boron Lewis Acid?

18. Scope and Mechanistic Studies Wulff, W. D. Chem.sEur. J. 2008, 14, 3785–3803.

19. Catalyst structure determination No non-linear effect. The results suggest that it is likely that only one molecule of the ligand is involved in the active catalyst. Wulff, W. D. Chem.sEur. J. 2008, 14, 3785–3803.

20. Catalyst structure determination Wulff, W. D. Chem.sEur. J. 2008, 14, 3785–3803.

21. Evidence: Boroxinate Based Brønsted Acid

22. William D. Wulff J. AM. CHEM. SOC. 2009, 131, 15615–15617 To form catalyst 10, >3 fold of borane was needed