Abstract
A new application of chiral oxazaborolidines in asymmetric transformation, namely the hydrocyanation of imines, is described. The effect of protonation of these catalysts on the reactivity and enantioselectivity of hydrocyanations is studied. Significant increase in reaction rate is observed upon protonation of the catalysts, along with the reversal of the sense of stereoinduction.
Key words
oxazaborolidine - asymmetric catalysis - hydrocyanation - imine - protonation
References and Notes
1 Corey EJ.
Helal CJ.
Angew. Chem. Int. Ed.
1998,
37:
1986
2 Hirao A.
Itsuno S.
Nakahama S.
Yamazaki N.
J. Chem. Soc., Chem. Commun.
1981,
314
3a Corey EJ.
Shibata T.
Lee TW.
J. Am. Chem. Soc.
2002,
124:
3808
3b Ryu DH.
Lee TW.
Corey EJ.
J. Am. Chem. Soc.
2002,
124:
9992
3c Zhou G.
Hu Q.-Y.
Corey EJ.
Org. Lett.
2003,
5:
3979
3d Ryu DH.
Corey EJ.
J. Am. Chem. Soc.
2003,
125:
6388
3e Ryu DH.
Zhou G.
Corey EJ.
J. Am. Chem. Soc.
2004,
126:
4800
3f Hu Q.-Y.
Zhou G.
Corey EJ.
J. Am. Chem. Soc.
2004,
126:
13708
3g Ryu DH.
Zhou G.
Corey EJ.
Org. Lett.
2005,
7:
1633
3h Corey EJ.
Angew. Chem. Int. Ed.
2002,
41:
1650
4a Ryu DH.
Corey EJ.
J. Am. Chem. Soc.
2004,
126:
8106
4b Ryu DH.
Corey EJ.
J. Am. Chem. Soc.
2005,
127:
5384
5a Sigman MS.
Jacobsen EN.
J. Am. Chem. Soc.
1998,
120:
4901
5b Sigman MS.
Jacobsen EN.
J. Am. Chem. Soc.
1998,
120:
5315
5c Corey EJ.
Grogan MJ.
Org. Lett.
1999,
1:
157
5d Krueger CA.
Kuntz KW.
Dzierba CD.
Wirachun WG.
Gleason JD.
Snapper ML.
Hoveyda AH.
J. Am. Chem. Soc.
1999,
121:
4284
5e Vachal P.
Jacobsen EN.
Org. Lett.
2000,
2:
867
5f Sigman MS.
Vachal P.
Jacobsen EN.
Angew. Chem. Int. Ed.
2000,
39:
1279
5g Takamura M.
Hamashima Y.
Usuda H.
Kanai M.
Shibasaki M.
Angew. Chem. Int. Ed.
2000,
39:
1650
5h Josephsohn NS.
Kuntz KW.
Snapper ML.
Hoveyda AH.
J. Am. Chem. Soc.
2001,
123:
11594
5i Vachal P.
Jacobsen EN.
J. Am. Chem. Soc.
2002,
124:
10012
5j Wenzel AG.
Lalonde MP.
Jacobsen EN.
Synlett
2003,
1919
5k Masumoto S.
Usuda H.
Suzuki M.
Kanai M.
Shibasaki M.
J. Am. Chem. Soc.
2003,
125:
5634
5l Huang J.
Corey EJ.
Org. Lett.
2004,
6:
5027
6a Gröger H.
Chem. Rev.
2003,
103:
2795
6b Yet L.
Angew. Chem. Int. Ed.
2001,
40:
875
6c Spino C.
Angew. Chem. Int. Ed.
2004,
43:
1764
6d Berkessel A.
Gröger H.
Asymmetric Organocatalysis
Wiley-VCH;
Weinheim:
2005.
4 were determined by comparing the sense of optical rotation with literature data:
7a Hassan NA.
Bayer E.
Jochims JC.
J. Chem. Soc., Perkin Trans. 1
1998,
3747
7b See ref. 5f.
8 Oxazaborolidines 1b and 1c were synthesized according to the literature procedure (see ref. 3).
9 Crystal data of 1b·HCN has been deposited at the Cambridge Crystallographic Data Centre with the allocated deposition number CCDC-281060: C24 H23 BN2 O, M = 366.25, colorless needles, 0.18 × 0.12 × 0.08 mm, monoclinic, a = 10.588 (1), b = 6.950 (1), c = 14.249 (2) Å, β = 105.07°(1), V = 1012.5 (2) Å3 , T = 293 (2) K, space group P 21 , Z = 2, ρ
calcd = 1.201 g/cm3 , µ = 0.073 mm-1 .
10a Trost BM.
Fettes A.
Shireman BT.
J. Am. Chem. Soc.
2004,
126:
2660
10b Casey CP.
Martins SC.
Fagan MA.
J. Am. Chem. Soc.
2004,
126:
5585
10c Arseniyadis S.
Subhash PV.
Valleix A.
Mathew SP.
Blackmond DG.
Wagner A.
Mioskowski C.
J. Am. Chem. Soc.
2005,
127:
6138
