Ra cem iza tion Ba r r ier s of 1,1′-Bin a p h th yl a n d
1,1′-Bin a p h th a len e-2,2′-d iol: A DF T Stu d y
Ludeˇk Meca,† David Rˇ eha,‡,§ and Zdeneˇk Havlas*,§,|
Institute of Chemical Technology, Technicka´ 5, 166 28 Prague 6, Czech Republic, J . Heyrovsky´ Institute of
Physical Chemistry, Dolejsˇkova 3, 182 23 Prague 8, Czech Republic, Institute of Organic Chemistry and
Biochemistry, Flemingovo na´m. 2, 166 10 Prague 6, Czech Republic, and Center for Complex Molecular
Systems and Biomolecules, 182 23 Prague 8, Czech Republic
havlas@uochb.cas.cz
Received March 14, 2003
Density functional theory has been applied to the study of various pathways and transition states
for the configurational inversion of 1,1′-binaphthyl (1) and 1,1′-binaphthalene-2,2′-diol (2). The
preferred pathway is found to be anti with centrosymmetric transition state. Whereas the reaction
path of 1 goes downhill from transition to ground state, in the case of 2 it contains one unexpected
local minimum. Very satisfactory agreement with available experimental values of activation Gibbs
energies is achieved.
In tr od u ction
1,1′-Binaphthyl (1) and its derivatives exhibit hindered
rotation about internuclear bonds, and their enantiomers
can be isolated at room temperature. Synthetically useful
1,1′-binaphthalene-2,2′-diol (2; BINOL) can be obtained
from simple derivatives of 1.
F IGURE 1. Possible racemization pathways of 1,1′-binaphthyl
(1).
TABLE 1. Ra cem iza tion of 1,1′-Bin a p h th yl (1) a n d
1,1′-Bin a p h th a len e-2,2′-d iol (2)
τ1/2
∆Gq
rac
rac
Enantiomerically pure BINOL is easily obtainable by
resolution1 of low-cost racemate and is one of the most
used chiral auxiliaries for asymmetric synthesis.2 Rota-
tional barriers of 1 and 2 have been measured3 (Table
1). The racemization barriers of 1,1′-binaphthyl deriva-
compd T (°C)
solvent
44 benzene
50 dimethylformamide 14.5
(min) (kJ /mol)
ref
1
1
2
2
68
100.7
98.5
155.5
158
3a
3b
195 naphthalene
220 diphenyl ether
270
60
3c,d
this work
† Institute of Chemical Technology.
tives have been computed using molecular mechanics4
and semiempirical methods.5
‡ J .Heyrovsky´ Institute of Physical Chemistry.
§ Center for Complex Molecular Systems and Biomolecules.
| Institute of Organic Chemistry and Biochemistry.
Racemization of binaphthyl is possible through a
passage of 2,8′- and 2′,8-substituents (anti route) or 2,2′-
and 8,8′-substituents (syn route). Cooke and Harris3b
suggested two kinds of anti pathways for racemization
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Asymmetry 1995, 6, 2123.
(2) (a) Ojima, I. Catalytic Asymmetric Synthesis, 2nd ed.; Wiley-
VCH: New York, 2000. (b) Rosini, C.; Franzini, L.; Raffaelli, A.;
Salvadori, P. Synthesis 1992, 503. (c) Noyori, R. Asymmetric Catalysis
in Organic Synthesis; Wiley: New York, 1994.
(3) (a) Colter, A. K.; Clemens, L. M. J . Phys. Chem. 1964, 68, 651.
(b) Cooke, A. S.; Harris, M. M. J . Chem. Soc. 1963, 2365. (c) Smrcˇina,
M. Study of racemization barriers and asymmetric transformations of
selected enantiomers. PhD Dissertation (in Czech), Charles University,
Prague, 1991. (d) Kyba, E. P.; Gokel, G. W.; de J ong, F.; Koga, K.;
Sousa, L. R.; Siegel, M. G.; Kaplan, L.; Sogah, D. Y.; Cram, D. J . J .
Org. Chem. 1977, 42, 4173.
(4) (a) Dashevsky, V. G.; Kitaygorodsky, A. I. Theor. Eksp. Khim.
1967, 3, 43. (b) Gamba, A.; Rusconi, E.; Simonetta, M. Tetrahedron
1970, 26, 871. (c) Gustav, K.; Su¨hnel, J .; Wild, U. P. Chem. Phys. 1978,
31, 59. (d) Carter, R. E.; Liljefors, T. Tetrahedron 1976, 32, 2915. (e)
Liljefors, T.; Carter, R. E. Tetrahedron 1978, 34, 1611. (f) Leister, D.;
Kao, J . J . Mol. Struct. 1988, 168, 105. (g) Tsuzuki, S.; Tanabe, K.;
Nagawa, Y.; Nakanishi, H. J . Mol. Struct. 1990, 216, 279.
(5) Kranz, M.; Clark, T.; Schleyer, P. v. R. J . Org. Chem. 1993, 58,
3317.
10.1021/jo034344u CCC: $25.00 © 2003 American Chemical Society
Published on Web 06/12/2003
J . Org. Chem. 2003, 68, 5677-5680
5677