1 Chiral Anion-Mediated Asymmetric Ion Pairing Chemistry Reporter: Zhi-Yong Han

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

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

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

Borate anions Mariappan Periasamy, J. Org. Chem. 1999, 64,

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

ee < 26% Bruce A. Arndtsen Organometallics 2004, 23,

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

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

Borate anions Hisashi Yamamoto J. Am. Chem. Soc. 1998, 120,

Borate anions Gary B. Schuster J. Am. Chem. Soc. 1998, 120,

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

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

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

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

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

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

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

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.

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

Evidence: Boroxinate Based Brønsted Acid

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