A simple, convenient preparation for enantiomerically pure 1,1'-bi-2- naphthols

Article abstract of DOI:10.1016/S0957-4166(98)00396-6

A new preparative method for enantiomerically pure 1,1'-bi-2-naphthols is described. 1,1'-Bi-2-naphtholboric anhydride generated from the reaction of racemic 1,1'-bi-2-naphthol and boric acid in toluene is reacted with (S)- proline to produce 1,1'-bi-2-naphtholboric proline anhydride. Its two diastereomers were efficiently separated in THF. After treating successively with NaOH, HCl, and recrystallizing from benzene, enantiomerically pure (S)- and (R)-1,1'-bi-2-naphthol were obtained in 71-79% yield and in 62-74% yield, respectively.

Full text of DOI:10.1016/S0957-4166(98)00396-6

TETRAHEDRON:
ASYMMETRY
Pergamon
Tetrahedron: Asymmetry 9 (1998) 3985–3989
A simple, convenient preparation for enantiomerically pure
0
1
,1 -bi-2-naphthols
∗
Zixing Shan, Ying Xiong, Weizhong Li and Dejie Zhao
Department of Chemistry, Wuhan University, Wuhan 430072, China
Received 26 August 1998; accepted 25 September 1998
Abstract
0
0
A new preparative method for enantiomerically pure 1,1 -bi-2-naphthols is described. 1,1 -Bi-2-naphtholboric
0
anhydride generated from the reaction of racemic 1,1 -bi-2-naphthol and boric acid in toluene is reacted with (S)-
proline to produce 1,1 -bi-2-naphtholboric proline anhydride. Its two diastereomers were efficiently separated in
0
THF. After treating successively with NaOH, HCl, and recrystallizing from benzene, enantiomerically pure (S)-
0
and (R)-1,1 -bi-2-naphthol were obtained in 71–79% yield and in 62–74% yield, respectively. © 1998 Elsevier
Science Ltd. All rights reserved.
1. Introduction
0
It has been demonstrated that 1,1 -bi-2-naphthyl compounds possessing C chirality are very useful
2
chiral inducers in stoichiometric and catalytic asymmetric reactions. Specifically, many chiral auxiliaries
0
developed from enantiomerically pure 1,1 -bi-2-naphthols exhibited an excellent chiral induction ability
1
2
3
in asymmetric reductions, asymmetric Diels–Alder reactions, asymmetric aza Diels–Alder reactions,
asymmetric ene reactions, asymmetric Michael additions, asymmetric hydroformylations, asymmetric
alkylations, asymmetric oxidations, asymmetric epoxidations and asymmetric nitroaldol reactions.
As for the preparation of enantiomerically pure 1,1 -bi-2-naphthols, a number of approaches have been
reported. However, most preparative methods need expensive homochiral materials, and they either have
a long period for preparation, or are not easy to carry out, or have lower yields. To our knowledge,
only one research group has reported the resolution of racemic 1,1 -bi-2-naphthol using a naturally
inexpensive amino acid via an inclusion complexation. Unfortunately, they merely obtained 65% ee
4
5
6
7
8
9
10
0
11
0
0
0
(
S)-(−)- and 44% ee (R)-(+)-1,1 -bi-2-naphthol from the reaction of racemic 1,1 -bi-2-naphthol and (S)-
proline in benzene under refluxing conditions for 24 h. In order to obtain essentially enantiomerically
0
pure 1,1 -bi-2-naphthols, they either did three successive repetitions of the above procedure, or enriched
∗
Corresponding author.
0957-4166/98/$ - see front matter © 1998 Elsevier Science Ltd. All rights reserved.
PII: S0957-4166(98)00396-6

3986
Z. Shan et al. / Tetrahedron: Asymmetry 9 (1998) 3985–3989
the excess enantiomer from the product with a lower ee in a system consisting of boric acid and
tetramethylethylenediamine. Even so, the overall yields of (S)-(−)- and (R)-(+)-isomer were only 43.7%
0
and 31.5% (calcd. from racemic 1,1 -bi-2-naphthol), respectively. Although the authors utilized a cheaper
amino acid as the resolving agent in those preparations, owing to a long preparative period and a
complicated reaction, these methods still are not economical from the preparative point of view. In the
0
course of looking for a practical preparation of enantiomerically pure (S)-(−)- and (R)-(+)-1,1 -bi-2-
12
naphthol, we invented a cyclic borate ester method on the basis of examining, extensively, the reactions
of racemic 1,1 -bi-2-naphthol with boron compounds and chiral auxiliaries. Recently, we published the
resolution of racemic 1,1 -bi-2-naphthol utilizing an alkaloid as the resolving agent via the formation of a
0
0
13
cyclic borate ester. We wish to report herein the preparative method for enantiomerically pure (S)-(−)-
0
0
and (R)-(+)-1,1 -bi-2-naphthol from racemic 1,1 -bi-2-naphthol, boric acid and (S)-proline (Scheme 1).
Scheme 1.
2. Results and discussion
0
Racemic 1,1 -bi-2-naphthol 1 was allowed to react with boric acid in toluene under reflux for several
hours. The resulting water during the course of the reaction was removed by azeotropic distillation. The
reaction mixture was cooled to room temperature and filtered. The solid was washed successively with
0
freshly dried toluene and diethyl ether and dried under reduced pressure to give 1,1 -bi-2-naphtholboric
anhydride 2. 2 was allowed to reflux with (S)-proline 3 in a 1:2–2.3 molar ratio in tetrahydrofuran for 3
0
h to produce, almost quantitatively, a white precipitate of (S)-1,1 -bi-2-naphtholboric acid (S)-proline
anhydride 4A. The precipitate was filtered, and the filtrate was evaporated to dryness to give solid
0
(
R)-1,1 -bi-2-naphtholboric acid (S)-proline anhydride 4B. 4A and 4B, thus obtained, were separately
dissolved in a dilute NaOH, and, followed by the treatment with a dilute HCl and diethyl ether, offered
0
(
‘
R)-(+)- and (S)-(−)-1,1 -bi-2-naphthol of over 90% ee from the corresponding organic phase. After
kinetic’ crystallization14 from benzene, enantiomerically pure (S)-(−)- and (R)-(+)-1,1 -bi-2-naphthol
0
were obtained in ca. 80% overall yield, respectively.

Z. Shan et al. / Tetrahedron: Asymmetry 9 (1998) 3985–3989
3987
0 0
,1 -Bi-2-naphtholboric anhydride 2 generated from the reaction of racemic 1,1 -bi-2-naphthol and
1
boric acid in toluene did not need to be separated. To the reaction system was directly added with constant
stirring solid (S)-proline 3 in a 1:2–2.3 molar ratio (‘one pot’ reaction), then heated for an additional
3
h under reflux. The reaction mixture was cooled to room temperature and filtered. The solid was
washed successively with toluene and diethyl ether and dried under reduced pressure. Tetrahydrofuran
was then added, and stirred for 2 h at room temperature. The solid and the mother liquor were separated,
0
0
from which 4A and 4B were obtained. This was followed by working up by the basification, the
acidification and ‘kinetic’ crystallization as with the above procedure, obtaining (S)-(−)- and (R)-(+)-
0
1
,1 -bi-2-naphthol with enantiomeric purity in 71% and 62% yield, respectively.
0
In summary, a novel convenient method to prepare enantiomerically pure (R)-(+)- and (S)-(−)-1,1 -
0
bi-2-naphthol through the reaction of racemic 1,1 -bi-2-naphthol, boric acid and (S)-proline has been
0
developed. The above results indicate that by using isolated 1,1 -bi-2-naphtholboric anhydride in the
preparative reaction, products with high enantiomeric excess and high yield are obtained; a ‘one-pot’
method is easier to carry out, although it gave products with slightly lower ee and yield. Our methods
presented here not only made use of a readily available chiral pool material, but are also operationally
simple. We believe this route is one of the most practical approaches for preparing enantiomerically pure
0
1
,1 -bi-2-naphthols in high yield at present.
3. Experimental
0
3
.1. Reaction of the separated 1,1 -bi-2-naphtholboric anhydride with (S)-proline
0
5
.72 g (20 mmol) racemic 1,1 -bi-2-naphthol refluxed with 1.40 g (22.58 mmol) boric acid in 120
0
ml toluene with the liberation of water to give 5.92 g of powdery white solid of 1,1 -bi-2-naphtholboric
anhydride 2, yield, 98%. It does not melt at up to 300°C. Elemental analysis: found (%), B, 3.36; C,
−
8.86; H, 3.90. Calcd for B C H O : B, 3.51; C, 79.25; H, 3.99. IR (KBr, cm ): 1620 m, 1594 m,
2 40 24 5
509 m, 1466 ms (naphthalene ring framework); 1360 s (ν B–O); 1307 vvs (νB–O–B); 1228 s (ν C–O);
1
7
1
8
as
as
18 vs, 751 vs (δC–H).
0
3
.0 g (5 mmol) 1,1 -bi-2-naphtholboric anhydride 2 prepared as stated above was allowed to mix
with 1.15 g (10 mmol) (S)-proline 3 in 50 ml dried tetrahydrofuran and was refluxed for 3 h; a
great deal of white solid precipitated out of the reaction system. After the reaction mixture was
cooled to room temperature, the solid was filtered out, washed successively with tetrahydrofuran and
0
diethyl ether and dried under reduced pressure to afford 2.33 g 1,1 -bi-2-naphtholboric acid (S)-proline
derivative 4A, yield, 96% (based on C H BNO ·C H O). It does not melt at up to 260°C. IR (KBr,
2
5
20
4
4
8
−
1
as
cm ): 1750 sh, 1742 ms (ν
); 1619 m, 1593 m, 1506 m, 1467 m (naphthalene ring framework);
C_O
as
as
†
as
); 1080 vs (νsB–O); 1050
N-→B
1
368 m, 1333 ms (ν
); 1251 vs (ν
) ; 1230 sh, ms (ν
Naph–H
B–O
Naph–O–B
s
s
s (ν Naph–O–B); 1020 vs (ν
); 824 ms, 754 s (δ
). After recrystallization from acetonitrile, it
C–O
1
lost the associated tetrahydrofuran. H NMR (DMSO-d +MeCN-d , ppm, TMS=0): 1.66–2.30 (4H, m,
6
3
‡
CH CH ); 2.75–3.38 (3H, m, NHCH ); 4.54 (1H, t, NCHCOO); 6.97–7.53 (8H, m, 8×Binaph-H);
2
2
2
+
7
2
.80–8.04 (4H, m, 4×Binaph-H). MS (EI, 70 ev): m/z, 409 (44.3, M ), 364 (2.8), 312 (13.2), 297 (5.7),
68 (15.1), 239 (14.2), 70 (100), 44 (3.3). The solid 4A was treated successively with 30 ml 2N NaOH
and 30 ml 2 N HCl at room temperature with stirring, followed by the addition of 30 ml diethyl ether
†
‡
‘
‘
Naph’ is an abbreviation of naphthalene ring.
Binaph-H’ represents a proton of binaphthyl group.

3988
Z. Shan et al. / Tetrahedron: Asymmetry 9 (1998) 3985–3989
to give a clear two-phase solution. The organic layer was collected and the water layer was extracted
with diethyl ether (10 ml×2). The organic phases were then combined and washed with saturated brine,
0
dried over anhydrous sodium sulfate, filtered and the filtrate was evaporated to dryness. (S)-(−)-1,1 -Bi-
25
2
-naphthol (1.22 g) was obtained, yield, 85.3%, m.p. 206–208°C, [α] =−33.73 (c=1, THF), 94% ee.
D
After ‘kinetic’ crystallization from benzene, 1.13 g massy crystals of (S)-(−)-isomer was obtained, m.p.
25
2
06–207°C, [α]D =−35.3 (c=1, THF), 100% ee, overall yield, 79%.
The mother liquor removed 4A was evaporated to dryness to give a yellowish solid residue which was
washed with a small amount of benzene and dried under vacuum, to afford 2.45 g solid 4B, yield, 101%.
It did not melt at up to 260°C. Its IR and MS resembled those of 4A in shape. 4B was worked up by the
basification, the acidification and ‘kinetic’ crystallization according to the same procedure as above; 1.06
0
25
g (R)-(+)-1,1 -bi-2-naphthol was afforded, m.p. 206–207°C, [α]D =+35.2 (c=1, THF), 100% ee, overall
yield, 74%.
0
3
.2. ‘One-pot’ preparation of enantiomerically pure 1,1 -bi-2-naphthols
0
2
.86 g (10 mmol) racemic 1,1 -bi-2-naphthol and 0.70 g (11.3 mmol) boric acid were allowed to mix
in 70 ml toluene and reflux with constant stirring for several hours. The liberated water was distilled off
to produce a white solid precipitate. The reaction mixture was cooled to about 50°C; 1.30 g (11.3 mmol)
(S)-proline was added and reflux was continued, with stirring, for an additional 3 h. The mixture was
then cooled to room temperature. The resulting large amount of white solid was separated by filtration,
washed successively with fresh toluene and diethyl ether, and dried under reduced pressure to give 4.0
g product. The product was transferred to a 100 ml flask and 50 ml tetrahydrofuran was added. The
mixture was stirred magnetically for 2 h at ambient temperature, filtered, the solid was washed with fresh
0
tetrahydrofuran and then dried under reduced pressure; 2.1 g 4A was obtained. It did not melt at up to
1
2
95°C. After recrystallization from acetonitrile, its IR, H NMR and MS were the same as those of 4A.
The mother liquor removed 4A was evaporated to dryness to give 2.45 g yellowish solid residue 4B . It
0
0
−
1
as
did not melt at up to 260°C. IR (KBr, cm ): 1756 ms, br (ν
); 1619 m, 1592 m, 1506 m, 1467 m
C_O
as
as
as
): 1079 s (νsB–O);
N-→B
(
1
naphthalene ring framework); 1339 ms (ν
); 1248 s (ν Naph–O–B); 1232 s (ν
B–O
s
0
0
019 vs (ν C–O); 821 ms, 752 ms (δNaph–H). 4A and 4B , thus obtained, were treated separately by the
basification, the acidification and ‘kinetic’ crystallization as per the above procedure, and afforded 1.02
0
25
g transparent massy crystals of (S)-(−)-1,1 -bi-2-naphthol, m.p. 206–207°C, [α] =−35.5 (c=1, THF),
D
0
1
2
00% ee, overall yield, 71.3%, and 0.90 g transparent massy crystals of (R)-(+)-1,1 -bi-2-naphthol, m.p.
20
06–207°C, [α]D =+35.4 (c=1, THF), 100% ee, overall yield, 62%, respectively. Additionally, in the
course of ‘kinetic’ crystallization from benzene for (R)-(+)-isomer with lower ee, 0.3 g light white solid
was separated, m.p. 216–218°C, [α]D =+0.6 (c=1, THF), 2% ee. It is obvious that this was racemic
20
0
1
,1 -bi-2-naphthol contaminated by (R)-isomer.
Acknowledgements
Financial support by the National Natural Science Foundation of China and the Natural Science
Foundation of Hubei Province are gratefully acknowledged.

Z. Shan et al. / Tetrahedron: Asymmetry 9 (1998) 3985–3989
3989
References
1
2
3
4
. (a) Noyori, R. Chem. Soc. Rev. 1989, 18, 187. (b) Suzuki, M.; Morite, Y.; Koyano, H.; Koga, M.; Noyori, R. Tetrahedron
990, 46, 4809.
. (a) Kagan, H. B.; Riant, O. Chem. Rev. 1992, 92, 1007. (b) Kobayashi, M.; Araki, M.; Hachiya, I. J Org. Chem. 1994, 59,
758. (c) Ishihama, K.; Yamamoto, H. J. Am. Chem. Soc. 1994, 116, 1561.
. (a) Ishitani, H.; Kobayashi, S. Tetrahedron Lett. 1996, 37(41), 7357. (b) Hattori, K.; Yamamoto, H. J. Org. Chem. 1992,
7, 3264.
. (a) Mikami, K.; Matsukawa, S.; Sawa, E.; Harada, A.; Koga, N. Tetrahedron Lett. 1997, 38(11), 1951. (b) Mikami, K.;
Terada, M. Tetrahedron 1992, 48, 5671. (c) Corey, E. J.; Barnes-Seeman, D.; Lee, T. W.; Goodman, S. N. Tetrahedron
Lett. 1997, 38(37), 6513.
1
3
5
5. Kobayashi, S.; Suda, S.; Yamada, M.; Mukaiyama, T. Chem. Lett. 1994, 97, 1.
6. (a) Sakai, N.; Mano, S.; Nozaki, K.; Takaya, H. J. Am. Chem. Soc. 1993, 115, 7033. (b) Nozaki, H.; Sakai, N.; Nanno,
T.; Higashijima, T.; Mano, S.; Horiuchi, T.; Takaya, H. J. Am. Chem. Soc. 1997, 119, 4413. (c) Horiuchi, T. Tetrahedron
1997, 53(23), 7795.
7. Chan, A. S. C.; Zhang, F. Y.; Yip, C. W. J. Am. Chem. Soc. 1997, 119, 4080.
8
. (a) Komatsu, N.; Hashizuma, M.; Sugita, T.; Uemura, S. J. Org. Chem. 1993, 58, 4529. (b) Reetz, M. T.; Merk, C.;
Naberfeld, G.; Rudolph, J.; Griebenow, N.; Goddard, R. Tetrahedron Lett. 1997, 38(30), 5273.
. Bougauchi, M.; Watanabe, S.; Arai, T.; Sasai, H.; Shibasaki, M. J. Am. Chem. Soc. 1997, 119, 2329.
9
10. (a) Shibasaki, M.; Sasai H. Pure Appl. Chem. 1996, 68(3), 523. (b) Sasai, H.; Suzuki, T.; Arai, T.; Shibasaki, M. J. Am.
Chem. Soc. 1992, 114, 4418.
11. (a) Periasamy, M. Pure Appl. Chem. 1996, 68, 663. (b) Periasamy, M.; Bhanu Prasad, A. S.; Bhaskar Kanth, J. V.; Kishan
Reddy, Ch. Tetrahedron: Asymmetry 1995, 6(2), 341. (c) Periasamy, M.; Venkatraman, L.; Thomas, K. R. J. J. Org. Chem.
1
997, 62(13), 4302.
2. Shan, Z. X.; Wang, G. P.; Duan, B.; Zhao, D. J. Faming Zhuanli Shenqing Gongkai Shuomingshu CN1097728, 25 January
995. Appl. No: CN93103325, 1993.
3. (a) Shan, Z. X.; Wang, G. P.; Duan, B.; Zhao, D. J. Tetrahedron: Asymmetry 1996, 7(10), 2647. (b) Shan, Z. X.; Cheng, F.
Y.; Huang, S. W.; Zhao, D. J.; Jing, Z. Z. Tetrahedron: Asymmetry 1997, 8(8), 1175.
1
1
1
1
4. Smrcina, M.; Lorene, M.; Hanus, V.; Sedmera, P.; Kocovsky, P. J. Org. Chem. 1992, 57(6), 1917.