BINOL: A Versatile Chiral Reagent

Introduction

The aim of enantioselective synthesis or catalysis is to produce chiral products starting from achiral substrates by exploiting the presence of chiral reagents. The enantiomeric atropisomers of 1,1′-binaphthyl-2,2′-diol (BINOL) are the best-known representatives of axially chiral molecules and were first prepared as racemate in 1873 by von Richter. [1] BINOL is used for both stoichiometric and ­catalytic asymmetric reactions. [2] The chiral atropisomers (R)-1 ([α]²⁰ _D +35.5 THF, c 1), mp 205-211 °C and (S)-1 ([α]²⁰ _D -34.5, THF, c 1), mp 205-211 °C are stable at high temperature and allow numerous asymmetric reactions under various experimental conditions (Figure 1). [3] BINOL-mediated asymmetric oxidation, reduction and C-C bond-forming reactions are well-established reactions in ­organic synthesis. BINOL (1) can be easily prepared from 2-naphthol using Cu-amine complexes to give racemic BINOL which can be converted into (R)-BINOL [(R)-1] or (S)-BINOL [(S)-1] by enzymatic resolution [4] or via chemical resolution (Scheme 1). [5]

Figure 1

Scheme 1

References

• 1 von Richter V. Chem. Ber.  1873,  6:  1252 
• 2 For a recent review on BINOL, see: Brunel JM. Chem. Rev.  2005,  105:  857 
• 3 Meca L. Reha D. Havlas Z. J. Org. Chem.  2003,  68:  5677 
• 4a Lin G. Liu SH. Chen SJ. Wu FC. Sun HL. Tetrahedron Lett.  1993,  34:  6057 
• 4b Cavazza M. Zandomeneghi M. Ouchi A. Koga Y. J. Am. Chem. Soc.  1996,  118:  9990 
• 4c Juarez-Hernandez M. Johnson DV. Holland HL. McNulty J. Capretta A. Tetrahedron: Asymmetry  2003,  14:  289 
• 5a Brunel JM. Buono G. J. Org. Chem.  1993,  58:  7313 
• 5b Wang M. Liu SZ. Liu J. Hu BF. J. Org. Chem.  1995,  60:  7364 
• 5c Li Z. Liang X. Wu F. Wan B. Tetrahedron: Asymmetry  2004,  15:  665 
• 6 Schiffers R. Kagan HB. Synlett  1997,  1175 
• 7 Nishikori H. Yoshihara R. Hosomi A. Synlett  2003,  561 
• 8a Bougauchi M. Watanabe S. Arai T. Sasai H. Shibasaki M. J. Am. Chem. Soc.  1997,  119:  2329 
• 8b Kakei H. Nemoto T. Ohshima T. Shibasaki M. Angew. Chem. Int. Ed.  2004,  43:  317 
• 9a Sakane S. Fujiwara J. Maruoka K. Yamamoto H. J. Am. Chem. Soc.  1983,  105:  6154 
• 9b Sakane S. Fujiwara J. Maruoka K. Yamamoto H. Tetrahedron  1986,  42:  2193 
• 10 Bertozzi F. Olson R. Frejd T. Org. Lett.  2000,  2:  1283 
• 11 Gao G. Wang Q. Yu X.-Q. Xie R.-G. Pu L. Angew. Chem. Int. Ed.  2006,  45:  122