Atropisomerism of the C-1-C′-1 axis of 2,2′,8,8′-unsubstituted 1,1′-binaphthyl derivatives

Article abstract of DOI:10.1021/jo0100289

The Suzuki coupling of optically active (S)-binaphthyl bromide 10 with (S)-binaphthyl boronic acid 11 produced a diastereomeric mixture of tetrahydroxyquaternaphthyls 4. The coupling products 4 as well as their derivatives 5-7 can be considered as members of the family of 1,1′-binaphthyl-3,3′-diols. The C-1-C′-1 axis of all these compounds was found to have an unusually high rotational barrier. Generally, the barrier is higher for derivatives having more bulky substituents at the 3 and 3′ positions.

Full text of DOI:10.1021/jo0100289

5
042
J . Org. Chem. 2001, 66, 5042-5047
Atr op isom er ism of th e C-1-C′-1 Axis of 2,2′,8,8′-Un su bstitu ted
1
,1′-Bin a p h th yl Der iva tives
Hak-Fun Chow* and Chi-Wai Wan
Department of Chemistry, The Chinese University of Hong Kong, Shatin, NT, Hong Kong, China
hfchow@cuhk.edu.hk
Received J anuary 9, 2001
The Suzuki coupling of optically active (S)-binaphthyl bromide 10 with (S)-binaphthyl boronic acid
1
1 produced a diastereomeric mixture of tetrahydroxyquaternaphthyls 4. The coupling products 4
as well as their derivatives 5-7 can be considered as members of the family of 1,1′-binaphthyl-
3
,3′-diols. The C-1-C′-1 axis of all these compounds was found to have an unusually high rotational
barrier. Generally, the barrier is higher for derivatives having more bulky substituents at the 3
and 3′ positions.
In tr od u ction
tial to become a new class of chiral auxiliaries or catalysts
in asymmetric synthesis.
1
,1′-Binaphthyl 1 and its derivatives bearing a C-1-
C-1′ chiral axis are versatile auxiliaries and ligands for
a wide range of asymmetric synthetic and catalytic
1
reactions. The high rotational barrier of the chiral axis
is mainly due to the presence of substituents at the 2,2′
2
or 8,8′ positions on the binaphthyl nucleus. In fact, 1,1′-
binaphthyl derivatives without substituents at these
locations are known to racemize at room temperature.3
For example, 1,1′-binaphthyl has a half-life for racem-
ization of 12 h at 20 °C.3b 1,1′-Binaphthyl-5,5′-dicarboxylic
acid, which has a slightly more stable C-1-C-1′ axis, has
a half-life for racemization of 4.5 h at 50 °C.3 Similarly,
the half-lives for racemization of 1,1′-binaphthyl-4,4′-
disubstituted compounds fall within a range of 2-50 h
at room temperature.3 Herein, we report a high rota-
tional barrier of the C-1-C-1′ axis in 4,4′-diaryl-1,1′-
binaphthyl-3,3′-diol derivatives 2 at room temperature.
The existence of a configurationally stable chiral axis in
such compounds at room temperature may provide an
opportunity for us to design new chiral, binaphthyl
ligands based on structure 2. As the ligating atoms are
now located at the 3 and 3′ positions of the binaphthyl
a
c
As part of our continuing program toward the con-
struction of chiral rigid rodlike oligomers, we are inter-
6
ested in preparing optically active 1,1′-binaphthyl-2,2′-
diol oligomers 3 having the C-4 and C-4′ positions directly
linked to each other. It is anticipated that a closer
packing of the chiral binaphthyl units may impose some
kind of macromolecular order along the oligomer main
axis, which in turn may lead to an amplification of their
chiroptical properties. As a result of this study, it was
found that the dimeric species 4-7 of this series of
oligomers existed as a mixture of diastereomers due to a
restricted rotation of the carbon-carbon bond joining the
two binaphthyl units. Structurally, these compounds may
be considered as 4,4′-diaryl-1,1′-binaphthyl-3,3′-diol de-
rivatives 2. However, strictly speaking, they belong to
the family of quaternaphthyls and are related to the
nucleus, such optically active, C
2
symmetrical 1,1′-
binaphthyl-3,3′-diol derivatives 2, when bound to a metal
ion, will have a torsional angle that is different from
that of the well-known 1,1′-binaphthyl-2,2′-diol (BINOL)
or 1,1′-binaphthyl-2,2′-bis(diphenylphosphino) (BINAP)
4
ligand. It has previously been demonstrated that the
torsional angle of binaphthyl-derived metal complexes
has a strong influence on the reactivity and enantiose-
lectivity in asymmetric reactions;5 hence, ligands 2
having new geometrical attributes may have the poten-
*
To whom correspondence should be addressed. Phone: 26096344.
Fax: 26035057
1) For a review, see Rosini, C.; Franzani, L.; Raffaelli, A.; Salvadori,
P. Synthesis 1992, 503.
2) Kranz, M.; Clark, T.; von Ragu e´ Schleyer, P. J . Org. Chem. 1993,
8, 3317.
3) (a) Cooke, A. S.; Harris, M. M. J . Chem. Soc. 1963, 2365. (b)
7
series of octahydroxyquaternaphthyls or hexahydroxy-
(
(
(5) (a) Mikami, K.; Motoyama, Y.; Terada, M. Inorg. Chim. Acta
1994, 222, 71. (b) Harada, T.; Takeuchi, M.; Hatsuda, M.; Ueda, S.;
Oku, A. Tetrahedron: Asymmetry 1996, 7, 2479.
5
(
Pincock, R. E.; J ohnson, W. M.; Wilson, K. R.; Haywood-Farmer, J . J .
Am. Chem. Soc. 1973, 95, 6477. (c) Hutchins, L. G.; Pincock, R. E. J .
Org. Chem. 1980, 45, 2414.
(6) (a) Ng, M.-K.; Chow, H.-F.; Chan, T.-L.; Mak, T. C. W. Tetrahe-
dron Lett. 1996, 37, 2979. (b) Chow, H.-F.; Ng, M.-K. Tetrahedron:
Asymmetry 1996, 7, 2251.
(7) Tanaka, K.; Furuta, T.; Fuji, K.; Miwa, Y.; Taga, T. Tetrahedron:
Asymmetry 1996, 7, 2199.
(
4) (a) Noyori, R.; Takaya, H. Acc. Chem. Res. 1990, 23, 345. (b)
Narasaka, K. Synthesis 1991, 1.
1
0.1021/jo0100289 CCC: $20.00 © 2001 American Chemical Society
Published on Web 06/21/2001

Atropisomerism in 2,2′,8,8′-Unsubstituted 1,1′-Binaphthyl Derivatives
J . Org. Chem., Vol. 66, No. 15, 2001 5043
Sch em e 1a
Sch em e 2a
a
Key: (i) Cs2CO3, n-C4H9I, acetone, 56 °C; (ii) 1-hexyne,
Pd(PPh3)2Cl2, CuI, NEt3, C6H6, 60 °C; (iii) H2, PtO2, EtOH/EtOAc;
(iv) n-BuLi, THF, B(OMe)3; (v) HCl; (vi) Pd(PPh3)4, aq Na2CO3,
EtOH/toluene, 110 °C; (vii) BBr3, CH2Cl2, 0 °C; (viii) Cs2CO3, MeI,
acetone, 56 °C; (ix) (1S)-camphor-10-sulfonyl chloride, NEt3,
CH2Cl2, 0 °C.
a
Key: (i) 4-tolylboronic acid, Pd(PPh3)4, aq Na2CO3, EtOH/
toluene, 110 °C; (ii) BBr3, CH2Cl2, 0 °C; (iii) (1S)-camphor-10-
sulfonyl chloride, NEt3, CH2Cl2, 0 °C; (vi) 4-bromotoluene, Pd(P-
Ph3)4, aq Na2CO3, EtOH/toluene, 110 °C.
quaternaphthyls8 reported by others. The latter com-
pounds are known to exhibit multiple atropisomerism
due to the chiral axes connecting the naphthyl subunits.
though the two compounds could be separated by flash
column chromatography (in less than 10 min) at 20 °C,
the minor slower running component reappeared from a
clean sample of the major faster running compound once
the sample was allowed to stand at 20 °C (∼10 h).
Likewise, the faster running component also appeared
from a clean sample of the slower running fraction after
prolonged standing at 20 °C. Hence, the two compounds
are slowly interconverting and cannot be isolated in 100%
purity. If the solvents of the two freshly separated
samples were quickly evaporated under reduced pressure
at 4 °C, one could obtain samples that were of reasonably
Resu lts a n d Discu ssion
9
The Suzuki coupling reaction was used to construct
the dimeric binaphthyl derivatives 4-7. Bis-O-butylation
of (S)-4,4′-dibromo-1,1′-binaphthyl-2,2′-diol 810 afforded
the corresponding bis-O-butyl ether 9 in 89% yield
(
Scheme 1). An n-hexyl group was then installed to one
1
1
end of the dibromide 9 via the Sonogashira coupling
with 1-hexyne, followed by saturation of the resulting
carbon-carbon triple bond by catalytic hydrogenation to
give a monobromide 10. Metalation of the bromide 10
with n-butyllithium, followed by reaction of the interme-
diate organolithium derivative with trimethyl borate,
then afforded the corresponding boronic acid 11. This
compound was not characterized but was immediately
coupled to the monobromide 10 under the Suzuki condi-
1
good homogeneity for H NMR spectral analysis. The two
spectra (in CDCl ) are nearly identical except that the
faster running compound has a sharp aromatic singlet
3
at δ 7.54. This signal, however, is presumably upfield
shifted and merged with other aromatic signals for the
slower running compound. The mass spectrum of the
sample mixture gave the most abundant peak at m/z 738,
which corresponded to the expected theoretical mass of
the tetraphenol 5. At this point, we suspected that the
diastereomerism was due to a hindered rotation of the
newly formed carbon-carbon bond joining the two chiral
binaphthyl units. However, such an unusually high
rotational barrier of the C-1-C′-1 bond at room temper-
ature of binaphthyls without substituents at 2,2′,8,8′
positions was not anticipated. Therefore, it was necessary
to confirm that the additional atropisomerism was not
the result of a racemization of the original binaphthyl
chiral axis in compounds 10 and 11 during their prepara-
tions.
Using the enantiomerically pure (S)-aryl dibromide 9
as a model compound, the stereochemical integrity of the
preexisting chiral axis during the various chemical
transformations was assessed (Scheme 2). Hence, the
dibromide 9 was coupled to 4-tolylboric acid [prepared
from 4-bromotoluene via sequential treatment of n-BuLi,
B(OMe)
give the ditolyl-substituted binaphthyl derivative 12 in
7% yield. Treatment of the bis-O-butyl ether 12 with
BBr in CH Cl then provided the 4,4′-ditolyl binaphthyl-
2,2′-diol 13 as a white solid in 80% yield. The stereo-
tions (2 M aqueous Na
2 3 3 4
CO , Pd(PPh ) , ethanol/toluene,
1
10 °C) to give an inseparable diastereomeric mixture
(
∼1:1) of the tetra-O-butyl ethers 4 in 90% yield. The
mass spectrum of the mixture had a molecular ion peak
at m/z 963 (M + H ), which was consistent with the
molecular formula of the dimeric structure. The forma-
+
1
tion of a diastereomeric mixture was suggested by H and
1
3
C NMR spectroscopy. Hence, four sets of triplet signals,
attributable to the methyl groups belonging to the
O-butyl moieties, appeared at δ 0.62, 0.64, 0.69, and 0.70
in the 1H NMR spectrum. Similarly, three C NMR
signals (δ 69.49, 69.62, and 69.73), instead of two,
belonging to the methylene carbons adjacent to the
oxygen atoms were also noted.
13
Treatment of the mixture of tetra-O-butyl ethers 4 with
BBr
3
gave tetraphenols 5 as two separable products as
revealed by thin-layer chromatography analysis. Al-
(
8) Belohradsky, M.; Budes ´ı nsky, M.; G u¨ nterov a´ , J .; Hodacov a´ , J .;
Holy, P.; Z a´ vada, J .; Cisarov a´ , I.; Podlaha, J . J . Org. Chem. 1996, 61,
205.
3
and 1 M HCl] under the Suzuki conditions to
1
(
(
9) Miyaura, N.; Suzuki, A. Chem. Rev. 1995, 95, 2457.
10) The (R)-antipole of compound 8 had been reported earlier, see
8
ref 6.
3
2
2
(
11) Sonogashira, K.; Tohda, Y.; Hagihara, N. Tetrahedron Lett.
1
975, 4467.

5
044 J . Org. Chem., Vol. 66, No. 15, 2001
Chow and Wan
chemistry of the C-1-C-1′ axis of compound 13 was then
240-245 nm and a negative second Cotton effect at 227-
229 nm of comparable molar ellipticities in their circular
dichroism (CD) spectra. This observation was consistent
with the presence of the two (S)-configurated chiral axes
in both diastereomers.14 Unfortunately, no single crystals
could be obtained for these compounds and hence the
absolute configuration of the newly constructed chiral
axis could not be ascertained due to the very similar
nature of their CD spectra.
1
determined by an H NMR method reported previously
by us.12 On the basis of our previous findings, the
1
difference of the H NMR chemical shift values of the two
diastereotopic methylene protons adjacent to the sulfonyl
moiety of the bis[(1S)-camphor-10-sulfonate] derived from
an (S)-binaphthyl-2,2′-diol was known to be consistently
smaller than 0.5 ppm, while that of the bis-sulfonate
derived from an (R)-binaphthyl-2,2′-diol was larger than
1
.0 ppm. This observation had also been independently
The tetraphenols 5 were also reacted with excess (1S)-
camphor-10-sulfonyl chloride to give a mixture of dia-
stereomeric tetrasulfonates 7 that could not be cleanly
separated by column chromatography. However, enriched
samples of the faster (∼90% purity) and slower (∼80%
purity) running diastereomers could be obtained and they
were shown to be configurationally stable at 20 °C. The
1
3
confirmed by another group. Hence, treatment of the
diol 13 with (1S)-camphor-10-sulfonyl chloride and NEt
afforded the corresponding bis[(1S)-camphor-10-sul-
3
1
fonate] 14 in 77% yield. Examination of the H NMR
spectrum of the bis-sulfonate 14 showed the presence of
only one AB system (δ 2.52, 2.95) due to the relevant
methylene groups. As the chemical shift difference was
less than 0.5 ppm, no racemization of the chiral axis had
occurred in both the Suzuki coupling and BBr
tection reactions.
To show that the absolute configuration of the binaph-
thyl chiral axis also remained intact during the prepara-
tion of the aryl boronic acid 11 from the aryl bromide
1
H NMR spectra of both diastereomers showed two AB
systems arising from the diastereotopic methylene groups
adjacent to the sulfonyl moiety. In both cases the chemi-
cal shift differences were less than 0.5 ppm, thus further
confirming that no racemization occurred at the two
original chiral axes. The specific rotations of the two
compounds are slightly different from one another. Again
we were unable to assign the absolute configuration of
the newly formed carbon-carbon axis because of the poor
crystallinity of the tetrasulfonates 7.
In summary, we reported here an unexpected atropi-
somerism of the C-1-C′-1 axis of some 4,4′-diaryl-1,1′-
binaphthyl-3,3′-diol derivatives. The configurational sta-
bility of the chiral axis was dependent on the steric size
of the substituents at the 3 and 3′ positions. In general,
compounds with more bulky substituents are configura-
tionally more stable.
3
depro-
1
0, the absolute configuration of the boronic acid 11 was
also determined. The boronic acid 11 was coupled to
-bromotoluene under the Suzuki conditions to produce
the unsymmetrical binaphthyl ether 15 in 92% yield.
Deprotection (BBr , CH Cl ) of the two butyl ether groups
4
3
2
2
produced a 1,1′-binaphthyl-2,2′-diol 16, which was simi-
larly converted to the corresponding bis-[(1S)-camphor-
1
exhibited two AB systems arising from the two different
methylene groups adjacent to the sulfonyl moieties.
Again, both the chemical shift differences were less than
1
0-sulfonate] 17. The H NMR spectrum of compound 17
1
1
0
.5 ppm (correlation determined by H- H 2D-COSY
Exp er im en ta l Section
experiment); hence, there was no racemization of the
binaphthyl chiral axis during the preparation of the
boronic acid 11. Therefore, it was concluded that the
diastereomerism in the tetra-O-butyl ethers 4 must be
due to the hindered rotation of the newly formed carbon-
carbon axis.
Gen er a l Meth od s. All reactions were conducted under a
nitrogen atmosphere. Melting points were taken on a hot-plate
microscope apparatus and were uncorrected. All physical
measurements were performed at 20 °C unless otherwise
stated. 1H (300 MHz) and C (75 MHz) NMR spectra were
13
3
recorded in CDCl unless otherwise stated. Mass spectra were
As the fast interconversion between the two diastere-
omeric binaphthyl tetraphenols 5 at room temperature
prevented us from conducting a thorough study of their
individual spectroscopic and chiroptical properties, some
configurationally stable derivatives of the tetraphenols
obtained either by fast atom bombardment (FAB), liquid
secondary ion mass spectrometry (L-SIMS) or electron ioniza-
tion (EI) method. The reported molecular mass values (m/z),
unless otherwise specified, were the most abundant monoiso-
topic mass. Optical rotations were measured at 589 nm. CD
spectra were recorded in 1,2-dichloroethane as the solvent.
Elemental analyses were carried out at MEDAC Ltd., Depart-
ment of Chemistry, Brunel University, Uxbridge, U.K. All
chemicals were purchased from commercial suppliers and used
without further purification.
5
with more bulky substituents were prepared. Treat-
ment of the diastereomeric tetraphenols 5 with excess
methyl iodide in the presence of Cs CO in acetone
2
3
afforded a separable mixture of the diastereomeric tetra-
O-methyl ethers 6 in 72% yield. The two compounds were
configurationally stable at 20 °C for 24 h but were rapidly
equilibrated in boiling toluene. The half-life for racem-
ization of the newly formed axis was determined to be
approximately 0.5 h at 56 °C in chloroform solution by
(S)-4,4′-Dibr om o-2,2′-d ibu toxy-1,1′-bin a p h th yl (9). A
1
0
mixture of (S)-4,4′-dibromo-1,1′-binaphthyl-2,2′-diol 8 (6.0 g,
3.5 mmol), n-butyl iodide (5.0 mL, 43.9 mmol), and cesium
1
carbonate (10.0 g, 30.7 mmol) in dry acetone (50 mL) was
stirred under reflux for 5 h. The mixture was filtered through
a short pad of silica gel and washed with ethyl acetate (50
mL). The filtrate was concentrated on a rotary evaporator and
the crude product chromatographed on silica gel (hexane/
EtOAc ) 50/1) to give the product 9 (6.7 g, 89%) as a white
1
1
H NMR spectroscopic measurement. The H NMR
spectral data of the two diastereomers were slightly
different from one another. Hence, for the faster running
diastereomer, one of the aromatic singlets had a chemical
shift value of δ 7.61, while that of the slower running
diastereomer was downfield shifted to δ 7.64. Both
compounds showed a positive first Cotton effect at around
2
5
solid: mp 70-71 °C; R
-79.7 (c ) 1.24, CHCl
0
7
7
f
0.74 (hexane/CH
2
Cl
2
) 5/1); [R]
D
)
1
3
); H NMR 0.65 (t, J ) 7.2 Hz, 6 H),
.93-1.04 (m, 4 H), 1.34-1.44 (m, 4 H), 3.86-3.99 (m, 4 H),
.12 (d, J ) 8.4 Hz, 2 H), 7.22 (ddd, J ) 0.9, 7.5, 7.7 Hz, 2 H),
.39 (ddd, J ) 1.2, 7.5, 7.7 Hz, 2 H), 7.72 (s, 2 H), 8.22 (d, J )
(
12) Chow, H.-F.; Wan, C.-W.; Ng, M.-K. J . Org. Chem. 1996, 61,
712.
13) Lustenberger, P.; Martinborough, E.; Denti, T. M.; Diederich,
F. J . Chem. Soc., Perkin Trans. 2, 1998, 747.
8
(14) Harada, N.; Nakanishi, K. Circular Dichroic Spectroscopy -
(
Exciton Coupling in Organic Stereochemistry; Oxford University
Press: Oxford, 1983.

Atropisomerism in 2,2′,8,8′-Unsubstituted 1,1′-Binaphthyl Derivatives
J . Org. Chem., Vol. 66, No. 15, 2001 5045
8
1
1
.4 Hz, 2 H); 13C NMR 13.48, 18.67, 31.14, 69.43, 119.63,
13C NMR 13.55, 13.59, 13.69, 13.72, 14.15, 18.73, 18.77, 18.83,
18.96, 22.73, 29.58, 29.69, 30.92, 31.47, 31.58, 31.75, 31.84,
33.60, 69.49, 69.62, 69.73, 116.47, 116.51, 117.83, 118.07,
119.16, 120.84, 123.19, 123.24, 123.41, 123.50, 123.86, 125.62,
125.72, 125.92, 126.48, 126.66, 127.88, 127.91, 128.79, 134.60,
134.81, 134.83, 139.64, 139.75, 140.41, 140.44, 154.01, 154.05,
19.73, 123.31, 124.81, 125.65, 126.94, 127.04, 127.66, 134.61,
+
54.06; MS (EI, m/z) 556 (M , 68). Anal. Calcd for C28
28 2
H O -
Br
2
: C, 60.45; H, 5.07. Found: C, 60.42; H, 5.06.
(
S)-4-Br om o-2,2′-d ibu toxy-4′-h exyl-1,1′-bin a p h th yl (10).
A mixture of the dibromide 9 (2.3 g, 4.1 mmol), 1-hexyne (0.47
mL, 4.1 mmol), Pd(PPh Cl (0.29 g, 0.41 mmol), and CuI (0.04
g, 0.21 mmol) in dry benzene (30 mL) and triethylamine (6
mL) was stirred under nitrogen at 60 °C for 12 h. The mixture
was filtered through a short pad of silica gel and washed with
ethyl acetate (75 mL). The solution was washed with 1 M HCl
+
3
)
2
2
154.21, 154.26; MS (EI, m/z) 963 (M + H , 100). Anal. Calcd
for C68
Tetr a p h en ols (5). BBr
mmol) was added to a solution of the tetra-O-butyl ethers 4
2
(0.23 g, 0.24 mmol) in anhydrous CH Cl (10 mL) under N .
82 4
H O : C, 84.78; H, 8.58. Found: C, 85.10; H, 8.88.
3
2 2
(1.5 mL, 1.0 M in CH Cl , 1.50
2
2
and saturated NaCl solution, dried (Na
solvents were removed in vacuo and the crude product purified
by flash chromatography on silica gel (hexane/CH Cl ) 18/1)
to give the monoacetylene compound (1.23 g, 54%) as a yellow
2
SO
4
), and filtered. The
The mixture was stirred at 0 °C for 2 h, quenched with 1 M
HCl solution (20 mL), and extracted with ethyl acetate (50
mL). The organic layer was washed with saturated NaCl
2
2
4
solution, dried (MgSO ), and filtered. The filtrate was concen-
2
5
oil: R
f
0.51 (hexane/CH
2
Cl
); H NMR 0.65 (t, J ) 7.5 Hz, 6 H), 0.95-1.04 (m, 7 H),
.36-1.40 (m, 4 H), 1.57-1.64 (m, 2 H), 1.70-1.77 (m, 2 H),
2
) 5/1); [R]
D
) -73.0 (c ) 1.13,
trated in vacuo and the residue purified by flash chromatog-
raphy on silica gel (hexane/EtOAc ) 6/1) to give the tetraphe-
nols 5 as a mixture of diastereomers (0.16 g, 90%): mixed mp
1
CHCl
3
1
2
.63 (t, J ) 6.9 Hz, 2 H), 3.87-3.98 (m, 4 H), 7.11 (t, J ) 8.1
123-125 °C; R
f
0.50 (faster running diastereomer) and 0.23
2
5
Hz, 2 H), 7.19-7.24 (m, 2 H), 7.34-7.41 (m, 2 H), 7.54 (s, 1
H), 7.72 (s, 1 H), 8.21 (d, J ) 8.4 Hz, 1 H), 8.34 (d, J ) 8.4 Hz,
1
3
1
1
1
(slower running diastereomer) (hexane/EtOAc ) 3/1); [R]
D
1
3
) -52.5 (c ) 0.63, CHCl ) (diastereomeric mixture); H NMR
1
3
H); C NMR 13.44, 13.66, 18.65, 19.42, 22.13, 30.98, 31.13,
1.17, 68.98, 69.36, 78.82, 95.54, 118.88, 119.68, 120.10,
20.29, 122.88, 123.05, 123.98, 124.71, 125.45, 125.77, 126.19,
(faster running isomer) 0.95 (t, J ) 7.2 Hz, 6 H), 1.36-1.50
(m, 8 H), 1.50-1.63 (m, 4 H), 1.90 (quintet, J ) 7.8 Hz, 4 H),
3.18 (t, J ) 7.8 Hz, 4 H), 5.20 (s, 2 H), 5.22 (s, 2 H), 7.19-7.24
(m, 3 H), 7.28-7.45 (m, 11 H), 7.54 (s, 2 H), 7.60 (d, J ) 8.1
Hz, 2 H), 8.12 (d, J ) 8.1 Hz, 2 H); (slower running isomer)
0.95 (t, J ) 7.2 Hz, 6 H), 1.34-1.50 (m, 8 H), 1.50-1.63 (m, 4
H), 1.90 (quintet, J ) 7.8 Hz, 4 H), 3.18 (t, J ) 7.8 Hz, 4 H),
5.23-5.29 (m, 4 H), 7.20-7.49 (m, 16 H), 7.60 (d, J ) 8.1 Hz,
2 H), 8.13 (d, J ) 7.8 Hz, 2 H); 13C NMR (mixture) 14.16, 22.69,
29.64, 30.53, 31.79, 33.23, 108.67, 111.34, 117.51, 119.36,
119.65, 123.87, 124.19, 124.47, 124.69, 125.01, 127.20, 127.53,
26.48, 126.77, 126.92, 127.64, 129.37, 133.83, 134.73, 153.67,
54.10; MS (EI, m/z) 558 (M , 100). Anal. Calcd for C34
+
37 2
H O -
Br: C, 73.24; H, 6.69. Found: C, 73.21; H, 6.91. A sample of
this internal acetylene (1.10 g, 1.97 mmol) was stirred under
hydrogen in the presence of PtO (0.08 g) in ethanol-ethyl
2
acetate (20 mL, 1:1) mixture at room temperature for 1.5 h.
The mixture was filtered through a short pad of Celite and
the filtered cake washed with ethyl acetate (20 mL × 2). The
filtrate was concentrated under reduced pressure and the
residue purified by flash chromatography on silica gel (hexane/
128.26, 128.80, 133.79, 133.89, 141.10, 143.38, 152.21, 152.38,
+
152.48; MS (EI, m/z) 738 (M , 50). Anal. Calcd for C52
50 4
H O :
CH
2
Cl
2
) 16/1) to give the titled compound 10 as a colorless
C, 84.52; H, 6.82. Found: C, 84.09; H, 6.36.
2
5
oil (0.80 g, 73%); R
f
0.54 (hexane/CH
2
Cl
); H NMR 0.61 (t, J ) 7.5 Hz, 3 H), 0.65 (t,
J ) 7.5 Hz, 3 H), 0.88-1.03 (m, 7 H), 1.32-1.57 (m, 10 H),
2
) 5/1); [R]
D
) -62.8
Tetr a -O-m eth yl Eth er s (6). A mixture of the tetraphenols
5 (100 mg, 0.14 mmol), methyl iodide (50 µL, 0.80 mmol), and
cesium carbonate (260 mg, 0.80 mmol) in dry acetone (10 mL)
was stirred under reflux for 2 h. The mixture was filtered
through a short pad of Celite and washed with ethyl acetate
(20 mL × 2). The filtrate was concentrated on a rotary
evaporator and the crude compound chromatographed on silica
gel (hexane/CH Cl ) 5/1) to give the faster running (50 mg,
2 2
45%) and slower running diastereomer (30 mg, 27%) of 6 as
white solids. Data for the faster running diastereomer 6: mp
1
(c ) 1.89, CHCl
3
1
7
8
1
6
1
1
1
.78-1.88 (m, 2 H), 3.08-3.23 (m, 2 H), 3.82-3.98 (m, 4 H),
.11-7.40 (m, 7 H), 7.72 (s, 1 H), 8.03 (d, J ) 8.4 Hz, 1 H),
.21 (d, J ) 8.4 Hz, 1 H); 13C NMR 13.50, 13.56, 14.15, 18.65,
8.75, 22.72, 29.55, 30.91, 31.24, 31.40, 31.82, 33.61, 69.16,
9.69, 115.74, 117.71, 120.22, 121.36, 122.74, 123.15, 123.84,
24.73, 125.74, 125.98, 126.12, 126.68, 126.91, 127.64, 127.80,
+
34.47, 135.06, 140.70, 153.94, 154.30; MS (EI, m/z) 562 (M ,
00). Anal. Calcd for C34
2
5
H
41
O
2
Br: C, 72.72; H, 7.36. Found:
257-258 °C dec; R
f
0.22 (hexane/CH
); H NMR 0.96 (t, J ) 6.9 Hz, 6 H), 1.35-
2
Cl
2
) 2/1); [R]
D
) -99.5
1
C, 73.14; H, 7.62.
(c ) 1.47, CHCl
3
Tetr a -O-bu tyl Eth er s (4). n-BuLi (0.78 mL, 1.6 M in
hexane, 1.25 mmol) was added to a solution of the binaphthyl
bromide 10 (0.35 g, 0.62 mmol) in dry THF (10 mL) at -78 °C
1.50 (m, 8 H), 1.52-1.64 (m, 4 H), 1.92 (quintet, J ) 7.2 Hz,
4 H), 3.14-3.30 (m, 4 H), 3.82 (s, 6 H), 3.87 (s, 6 H), 7.16-
7.40 (m, 14 H), 7.61 (s, 2 H), 7.62-7.66 (m, 2 H), 8.10 (d, J )
8.4 Hz, 2 H); 13C NMR 14.16, 22.73, 29.74, 30.93, 31.83, 33.77,
56.93, 57.03, 114.63, 116.32, 117.71, 119.67, 123.27, 123.54,
124.02, 125.69, 125.91, 126.12, 126.23, 126.86, 127.81, 128.70,
2
under N . After 15 min, trimethyl borate (0.14 mL, 1.23 mmol)
was added in one portion to the reaction mixture. The solution
was then warmed to room temperature for 1 h and quenched
with diluted HCl solution. The mixture was extracted with
ethyl acetate (50 mL), washed with water and saturated NaCl
134.41, 134.57, 139.92, 140.95, 154.41, 154.65; MS (FAB, m/z)
+
795 (M + H , 50); HRMS (EI) calcd for C56
58 4
H O 794.4332,
solutions, dried (Na
2
SO
4
), and filtered. The solvent was
found 794.4328. Data for the slower diastereomer 6 (0.03 g,
28%): mp 257-258 °C dec; R 0.06 (hexane/CH Cl ) 2/1);
[R]25
) -55.2 (c ) 0.52, CHCl ); H NMR 0.96 (t, J ) 6.9 Hz,
removed in vacuo, and the crude boronic acid 11 was used
immediately in the Suzuki coupling reaction without charac-
terization.
f
2
2
1
D
3
6 H), 1.35-1.50 (m, 8 H), 1.52-1.65 (m, 4 H), 1.92 (quintet, J
) 7.2 Hz, 4 H), 3.17-3.28 (m, 4 H), 3.81 (s, 6 H), 3.86 (s, 6 H),
7.18-7.27 (m, 6 H), 7.32-7.43 (m, 8 H), 7.56-7.61 (m, 2 H),
7.64 (s, 2 H), 8.11 (d, J ) 8.4 Hz, 2 H); 13C NMR 14.17, 22.74,
29.76, 30.95, 31.84, 33.79, 56.90, 57.11, 114.56, 116.27, 117.72,
119.48, 123.37, 123.60, 124.03, 125.68, 126.06, 126.14, 126.23,
126.77, 127.87, 128.74, 134.32, 134.55, 139.90, 140.99, 154.37,
A heterogeneous mixture of the above boronic acid 11, the
binaphthyl bromide 10 (0.22 g, 0.39 mmol), and Pd(PPh
g, 0.04 mmol) in ethanol/toluene (20 mL, 1:1) and aqueous Na
CO solution (2 M, 2 mL) was refluxed for 12 h. The mixture
was cooled to room temperature and diluted with ethyl acetate
50 mL). The mixture was washed with 1 M HCl and saturated
NaCl solutions, dried (Na SO ), and filtered. The crude product
was then purified by flash chromatography on silica gel
hexane/CH Cl
tetra-O-butyl ethers 4 as a colorless oil (0.34 g, 90%): R
3 4
) (0.05
2
-
3
(
+
2
4
154.64; MS (FAB, m/z) 795 (M + H , 35); HRMS (EI) calcd for
56 58 4
C H O 794.4332, found 794.4329.
(
2
2
) 6/1) to give a diastereomeric mixture of the
Tetr a su lfon a tes (7). A mixture of the binaphthol dimer 5
(0.20 g, 0.27 mmol) and (1S)-camphor-10-sulfonyl chloride (0.27
g, 1.08 mmol) in dry CH Cl (10 mL) and triethylamine (1.0
mL) was stirred at 0 °C for 3 h. The reaction mixture was
diluted with water and extracted with CH Cl (50 mL). The
combined extracts were washed with saturated NaCl solution,
dried (Na SO ), and filtered. The filtrate was concentrated in
vacuo and purified by flash chromatography on silica gel
f
0.26
2
5
1
(
hexane/CH
2
Cl
2
) 2/1); [R]
D
) -73.7 (c ) 0.55, CHCl
3
); H
2
2
NMR 0.62 (t, J ) 7.8 Hz, 3 H), 0.64 (t, J ) 7.8 Hz, 3 H), 0.69
(
H), 1.31-1.60 (m, 20 H), 1.89 (quintet, J ) 7.2 Hz, 4 H), 3.15-
3
7
t, J ) 7.2 Hz, 3 H), 0.70 (t, J ) 7.2 Hz, 3 H), 0.88-1.11 (m, 14
2
2
.25 (m, 4 H), 3.89-4.09 (m, 8 H), 7.11-7.45 (m, 14 H), 7.46-
.51 (m, 2 H), 7.59-7.63 (m, 2 H), 8.09 (d, J ) 8.4 Hz, 2 H);
2
4

5
046 J . Org. Chem., Vol. 66, No. 15, 2001
Chow and Wan
(
hexane/EtOAc ) 4/1) to give a 1:1 mixture of the diastereo-
meric tetrasulfonates 7 (0.37 g, 87%). Data for the faster
running diastereomer 7: mp 110-111 °C; R 0.34 (hexane/
vacuo and purified by flash chromatography on silica gel
(hexane/EtOAc ) 4/1) to give the product 14 as a white solid
f
(0.31 g, 77%): mp 121-122 °C; R 0.16 (hexane/EtOAc ) 5/1);
f
2
5
1
25
1
EtOAc ) 2/1); [R]
(
6
2
H), 2.80 (d, J ) 15 Hz, 2 H), 2.99 (d, J ) 15 Hz, 2 H), 3.12-
3
(
1
3
1
1
2
D
) +17.1 (c ) 0.46, CHCl
3
); H NMR 0.50
[R]
D
3
) +7.2 (c ) 0.73, CHCl ); H NMR 0.51 (s, 6 H), 0.77 (s,
s, 6 H), 0.55 (s, 6 H), 0.76 (s, 6 H), 0.79 (s, 6 H), 0.95 (t, J )
.6 Hz, 6 H), 1.20-1.50 (m, 16 H), 1.50-1.62 (m, 4 H), 1.75-
.35 (m, 24 H), 2.46 (d, J ) 15 Hz, 2 H), 2.56 (d, J ) 15 Hz, 2
6 H), 1.24-1.35 (m, 4 H), 1.75-2.28 (m, 10 H), 2.49 (s, 6 H),
2.52 (d, J ) 15 Hz, 2 H), 2.95 (d, J ) 15 Hz, 2 H), 7.35-7.53
(m, 14 H), 7.73 (s, 2 H), 8.04-8.07 (m, 2 H); 13C NMR 19.22,
19.33, 21.23, 24.77, 26.65, 42.16, 42.60, 47.51, 48.95, 57.57,
122.05, 122.13, 126.27, 126.50, 126.94, 127.36, 129.13, 129.97,
130.16, 133.74, 136.08, 137.71, 143.16, 145.24, 213.10; MS
.28 (m, 4 H), 7.38-7.61 (m, 12 H), 7.68 (s, 2 H), 7.68-7.73
m, 2 H), 7.87 (s, 2 H), 8.18 (d, J ) 8.4 Hz, 2 H); 13C NMR
+
4.11, 19.18, 19.30, 22.62, 24.85, 25.02, 26.66, 29.60, 30.53,
1.70, 33.18, 42.20, 42.62, 47.61, 49.12, 57.61, 120.75, 121.02,
23.68, 123.90, 124.22, 126.20, 126.68, 126.94, 127.07, 127.31,
27.73, 130.45, 131.08, 133.62, 139.22, 142.83, 145.17, 145.53,
(FAB, m/z) 917 (M + Na , 10); HRMS (L-SIMS) calcd for
54 54 8 2
C H O S 894.3257, found 894.3274.
(S)-2,2′-Dibu toxy-4-h exyl-4′-(4-tolyl)-1,1′-bin aph th yl (15).
A heterogeneous mixture of the boronic acid 11 [prepared from
10 (0.30 g, 0.53 mmol)] and 4-bromotoluene (0.10 g, 0.58
+
13.07, 213.23; MS (FAB, m/z) 1596 (M + H , 60). Anal. Calcd
for C92
H
106
O
16
S
4
: C, 69.23; H, 6.69. Found: C, 69.37; H, 6.76.
mmol), Pd(PPh
mL, 1:1), and aqueous Na
3
)
4
(0.08 g, 0.07 mmol) in ethanol/toluene (20
CO (2 M, 2 mL) was refluxed for
Data for the slower running diastereomer 7: mp 111-112 °C;
2
3
2
5
R
f
0.27 (hexane/EtOAc ) 2/1); [R]
D
) -6.4 (c ) 0.76, CHCl
3
);
12 h. The mixture was cooled to room temperature and
extracted with ethyl acetate (50 mL). The mixture was washed
1
H NMR 0.58 (s, 6 H), 0.65 (s, 6 H), 0.80 (s, 6 H), 0.95 (t, J )
6
2
)
.6 Hz, 6 H), 0.97 (s, 6 H), 1.18-1.62 (m, 20 H), 1.74-2.00 (m,
0 H), 2.17-2.32 (m, 4 H), 2.60 (d, J ) 15 Hz, 2 H), 2.88 (d, J
with 1 M HCl and saturated NaCl solutions, dried (Na
and filtered. The crude product was purified by flash chroma-
tography on silica gel (hexane/CH Cl ) 10/1) to afford the
product 15 as a colorless oil (0.28 g, 92%): R 0.37 (hexane/
2 4
SO ),
15 Hz, 2 H), 2.93 (d, J ) 15 Hz, 2 H), 3.15-3.26 (m, 4 H),
2
2
3
7
1
3
4
1
1
2
.25 (d, J ) 15 Hz, 2 H), 7.36-7.68 (m, 14 H), 7.70 (s, 2 H),
.95 (s, 2 H), 8.17 (d, J ) 8.4 Hz, 2 H); 13C NMR 14.11, 19.30,
9.39, 19.47, 19.61, 22.63, 24.91, 25.08, 26.67, 26.74, 29.59,
0.56, 31.70, 33.22, 42.20, 42.27, 42.63, 42.74, 47.54, 47.65,
8.74, 49.09, 57.66, 57.73, 120.59, 120.78, 123.37, 123.85,
24.11, 126.20, 126.51, 126.88, 127.02, 127.34, 127.48, 127.61,
30.40, 131.11, 133.71, 133.78, 139.24, 142.78, 144.99, 145.47,
f
25
1
CH
2
Cl
2
) 5/1); [R]
D
3
) -55.2 (c ) 2.17, CHCl ); H NMR 0.76
(t, J ) 7.5 Hz, 3 H), 0.79 (t, J ) 7.2 Hz, 3 H), 1.04-1.21 (m, 4
H), 1.09 (t, J ) 7.2 Hz, 3 H), 1.46-1.73 (m, 10 H), 2.03 (quintet,
J ) 7.2 Hz, 2 H), 2.60 (s, 3 H), 3.24-3.40 (m, 2 H), 4.01-4.17
(m, 4 H), 7.28-7.52 (m, 10 H), 7.67 (d, J ) 8.1 Hz, 2 H), 8.03-
8.08 (m, 1 H), 8.19-8.22 (m, 1 H); 13C NMR 13.53, 13.59, 14.13,
18.70, 18.74, 21.21, 22.71, 29.54, 30.89, 31.40, 31.48, 31.81,
33.56, 69.38, 69.56, 116.40, 117.01, 119.07, 120.36, 123.14,
123.30, 123.75, 125.57, 125.78, 125.98, 126.39, 127.58, 127.80,
128.93, 130.03, 134.78, 134.82, 136.86, 138.15, 140.28, 141.22,
+
12.95, 213.19; MS (FAB, m/z) 1595 (M , 30). Anal. Calcd for
C
92
H
106
O
16
S
4
: C, 69.23; H, 6.69. Found: C, 69.62; H, 6.68.
(
S)-2,2′-Dibu toxy-4,4′-bis(4-tolyl)-1,1′-bin a p h th yl (12).
A heterogeneous mixture of 4-tolylboronic acid [prepared from
4
0
+
-bromotoluene (0.50 g, 2.9 mmol)], the dibromide 9 (0.28 g,
.50 mmol), and Pd(PPh (0.10 g, 0.09 mmol) in ethanol/
CO (2 M, 2 mL) was
154.00, 154.11; MS (EI, m/z) 572 (M , 100); HRMS (EI) calcd
3
)
4
for C41
(S)-4-Hexyl-4′-(4-tolyl)-1,1′-bin aph th yl-2,2′-diol (16). BBr
(1.8 mL, 1.0 M in CH Cl , 1.8 mmol) was added to a solution
of the bis-O-butyl ether 15 (0.34 g, 0.59 mmol) in CH Cl (10
mL) under N at 0 °C. After 2 h, the mixture was quenched
48 2
H O 572.3652, found 572.3655.
toluene (20 mL, 1:1) and aqueous Na
2
3
3
refluxed for 12 h. The mixture was cooled to room temperature
and extracted with ethyl acetate (50 mL). The mixture was
washed with 1 M HCl and saturated NaCl solutions, dried
2
2
2
2
2
(
Na
2
SO
4
), and purified by flash chromatography on silica gel
Cl ) 10/1) to give the target compound 12 (0.25
with 1 M HCl solution (20 mL) and extracted with ethyl
acetate (50 mL). The solution was washed with saturated NaCl
solution, dried (MgSO ), and filtered. The organic layer was
4
(hexane/CH
2
2
2
5
g, 87%) as an oil: R
(
f
1
0.28 (hexane/CH
2
Cl
); H NMR 0.64 (t, J ) 7.5 Hz, 6 H), 0.90-
.03 (m, 4 H), 1.33-1.45 (m, 4 H), 2.49 (s, 6 H), 3.90-4.02 (m,
2
) 5/1); [R]
D
) -54.8
c ) 1.79, CHCl
3
concentrated under reduced pressure and purified by flash
1
4
7
1
1
5
chromatography on silica gel (hexane/EtOAc ) 15/1) to give
H), 7.17-7.38 (m, 12 H), 7.53 (d, J ) 7.8 Hz, 4 H), 7.88-
.93 (m, 2 H); C NMR 13.59, 18.75, 21.27, 31.44, 69.53,
17.04, 120.13, 123.36, 125.87, 125.98, 126.05, 127.62, 128.97,
30.07, 134.73, 136.98, 138.15, 141.37, 154.00; MS (FAB, m/z)
78 (M , 100); HRMS (L-SIMS) calcd for C42
the titled compound 16 (0.25 g, 91%) as a white solid: mp 139-
1
3
25
140 °C; R
f
0.31 (hexane/EtOAc ) 5/1); [R]
D
) -30.4 (c ) 0.39,
1
CHCl ); H NMR 0.94 (t, J ) 6.9 Hz, 3 H), 1.35-1.65 (m, 6 H),
3
1.90 (quintet, J ) 7.2 Hz, 2 H), 2.49 (s, 3 H), 3.16 (t, J ) 7.5
Hz, 2 H), 5.09 (br s, 2 H), 7.21-7.43 (m, 10 H), 7.49 (d, J )
+
42 2
H O 578.3183,
1
3
found 578.3196.
S)-4,4′-Bis-(4-tolyl)-1,1′-bin a p h th yl-2,2′-d iol (13). BBr
1.5 mL, 1.0 M in CH Cl , 1.5 mmol) was added to a solution
of the bis-O-butyl ether 12 (0.28 g, 0.48 mmol) in CH Cl (10
mL) under N at 0 °C. The resulting mixture was stirred at 0
C for 2 h, quenched with 1 M HCl solution (20 mL), and
extracted with ethyl acetate (50 mL). The solution was washed
with saturated NaCl solution, dried (MgSO ), and filtered. The
7.8 Hz, 2 H), 7.93-7.98 (m, 1 H), 8.10 (d, J ) 8.1 Hz, 1 H); C
(
3
NMR 14.13, 21.28, 22.67, 29.60, 30.50, 31.77, 33.18, 108.83,
110.38, 117.45, 118.44, 123.74, 123.88, 124.38, 124.63, 125.02,
126.74, 127.04, 127.21, 128.01, 128.17, 129.09, 129.81, 133.94,
134.07, 137.01, 137.43, 143.17, 143.71, 152.20, 152.39; HRMS
(
2
2
2
2
2
°
32 2
(L-SIMS) calcd for C33H O 460.2401, found 460.2405.
(S)-2,2′-Di[(1S)-ca m p h or -10-su lfon yloxy]-4-h exyl-4′-(4-
tolyl)-1,1′-bin a p h th yl (17). A mixture of the binaphthol 16
(0.12 g, 0.26 mmol) and (1S)-camphor-10-sulfonyl chloride (0.26
4
organic layer was concentrated in vacuo, and the residue was
purified by flash chromatography on silica gel (hexane/EtOAc
g, 1.04 mmol) in dry CH
mL) was stirred at 0 °C for 3 h. The reaction mixture was
diluted with water and extracted with CH Cl (50 mL). The
combined extracts were washed with saturated NaCl solution,
dried (Na SO ), and filtered. The filtrate was concentrated in
2 2
Cl (10 mL), and triethylamine (1.0
)
15/1) to give the target compound 13 (0.18 g, 80%) as a white
solid: mp 224-225 °C; R
f
0.40 (hexane/EtOAc ) 5/1); [R]25
D
)
2
2
1
-
7
35.8 (c ) 0.24, CHCl
.28-7.37 (m, 12 H), 7.49 (d, J ) 6 Hz, 4 H), 7.95-7.98 (m, 2
3
); H NMR 2.49 (s, 6 H), 5.16 (s, 2 H),
2
4
1
3
H); C NMR 21.29, 110.22, 118.52, 123.96, 124.62, 126.79,
vacuo and purified by flash chromatography on silica gel
1
1
27.31, 128.03, 129.11, 129.81, 133.98, 136.96, 137.46, 143.84,
52.17; MS (FAB, m/z) 466 (M , 75); HRMS (L-SIMS) calcd
(hexane/EtOAc ) 4/1) to give the product 17 as a white solid
+
(0.17 g, 74%): mp 72-73 °C; R 0.18 (hexane/EtOAc ) 5/1);
f
[R]25
1
for C34
S)-2,2′-Di-[(1S)-ca m p h or -10-su lfon yloxy]-4,4′-b is-(4-
tolyl)-1,1′-bin a p h th yl (14). A mixture of the binaphthol 12
0.21 g, 0.45 mmol) and (1S)-camphor-10-sulfonyl chloride (0.45
g, 1.79 mmol) in dry CH Cl (10 mL) and triethylamine (1.0
mL) was stirred at 0 °C for 3 h. The reaction mixture was
diluted with water and extracted with CH Cl (50 mL). The
combined extracts were washed with saturated NaCl solution,
dried (Na SO ), and filtered. The filtrate was concentrated in
H
26
O
2
466.1931, found 466.1930.
D
3
) +28.3 (c ) 1.53, CHCl ); H NMR 0.49 (s, 3 H), 0.50
(
(s, 3 H), 0.76 (s, 6 H), 0.94 (t, J ) 6.9, 3 H), 1.19-1.47 (m, 8
H), 1.50-1.58 (m, 2 H), 1.72-2.26 (m, 12 H), 2.41 (d, J ) 15
Hz, 1 H), 2.47 (d, J ) 15 Hz, 1 H), 2.48 (s, 3 H), 2.84 (d, J )
15 Hz, 1 H), 2.91 (d, J ) 15 Hz, 1 H), 3.10-3.27 (m, 2 H),
7.34-7.57 (m, 10 H), 7.63 (s, 1 H), 7.69 (s, 1 H), 8.04 (d, J )
6 Hz, 1 H), 8.14 (d, J ) 6 Hz, 1 H); 13C NMR 14.11, 19.21,
19.27, 19.32, 19.37, 21.27, 22.63, 24.84, 26.71, 29.59, 30.55,
31.71, 33.17, 42.23, 42.66, 47.56, 48.89, 120.96, 122.17, 124.15,
(
2
2
2
2
2
4

Atropisomerism in 2,2′,8,8′-Unsubstituted 1,1′-Binaphthyl Derivatives
J . Org. Chem., Vol. 66, No. 15, 2001 5047
1
1
1
26.13, 126.26, 126.49, 127.05, 127.17, 127.32, 127.42, 129.16,
30.02, 130.20, 130.44, 133.68, 133.84, 137.72, 142.66, 143.07,
the data using a simple equilibrium model provided by a
TableCurve 2D (version 5) program.
45.32, 213.04, 213.14; HRMS (L-SIMS) calcd for (C53
60 8 2
H O S
+
+
H ) 889.3804, found 889.3839.
Deter m in a tion of th e Ra cem iza tion Ha lf-Life of th e
Ack n ow led gm en t. We thank the Research Grants
Council, HKSAR, for the financial support (CUHK4203/
Cen tr a l Ch ir a l Axis of Com p ou n d 6. A solution of a freshly
purified faster running diastereomer of the tetra-O-methyl
9
7P).
ether 6 in CDCl
3
(∼0.02 M) was placed in a sealed NMR tube.
Su p p or tin g In for m a tion Ava ila ble: Selected spectro-
The tube was then immersed in a constant-temperature bath
at 56 °C. The sample tube was removed at suitable times, and
1
13
1
1
scopic data ( H and C NMR, H- H 2D-COSY, and CD) of
the quaternaphthyl derivatives 4-7 and compounds 12-17
and a kinetic plot of the racemization of the central chiral axis
of compound 6. This material is available free of charge via
the Internet at http://pubs.acs.org.
1
the H NMR spectrum was recorded at 20 °C (acquistion time
∼
1 min). The relative amount of the faster and slower running
diastereomers was then determined by the relative integration
of the signals at δ 7.61 and 7.64. The half-life for the
racemization of the central chiral axis was estimated by fitting
J O0100289