Synthesis and separation of the atropisomers of 2-(5-benzo[b]fluorenyl)-2′-hydroxy-1,1′-binaphthyl and related compounds

Article abstract of DOI:10.1016/j.tet.2006.06.004

Several syn and anti atropisomers of 2-(5-benzo[b]fluorenyl)-2′-hydroxy-1,1′-binaphthyl and related compounds were synthesized from 1,1′-binaphthyl-2,2′-diol (BINOL). It was possible to separate the syn and anti atropisomers by silica gel column chromatog

Full text of DOI:10.1016/j.tet.2006.06.004

Tetrahedron 62 (2006) 8133–8141
Synthesis and separation of the atropisomers of
2-(5-benzo[b]fluorenyl)-20-hydroxy-1,10-binaphthyl
and related compounds
y
*
Hua Yang, Jeffrey L. Petersen and Kung K. Wang
C. Eugene Bennett Department of Chemistry, West Virginia University, Morgantown, WV 26506-6045, USA
Received 24 March 2006; revised 28 May 2006; accepted 1 June 2006
Available online 27 June 2006
Abstract—Several syn and anti atropisomers of 2-(5-benzo[b]fluorenyl)-20-hydroxy-1,10-binaphthyl and related compounds were
synthesized from 1,10-binaphthyl-2,20-diol (BINOL). It was possible to separate the syn and anti atropisomers by silica gel column chroma-
tography. The syn atropisomers are potential hetero-bidentate ligands for complex formation with metals. By starting from enantiomerically
pure (R)-(+)-BINOL and (S)-(ꢀ)-BINOL, four optically active syn atropisomers and two anti atropisomers with high enantiomeric purity were
obtained. The structures of two syn atropisomers and one anti atropisomer were established by X-ray structure analyses.
Ó 2006 Elsevier Ltd. All rights reserved.
1. Introduction
Conversion of only one of the two hydroxyl groups to
a different functional group or conversion of both hydroxyl
groups to two different functional groups to form hetero-
bidentate binaphthyls, such as NOBIN (5),13–17 MOP
(6),18–20 and MAP (7),21 has also been investigated.22
The barriers of rotation around the carbon–carbon single
bond connecting the two C1 carbons of these 2,20-di-
substituted binaphthyls are high,1–5,23,24 giving stability
to the chiral configuration even at high temperature and
allowing the molecules to be used in a variety of synthetic
applications.
The use of 1,10-binaphthyl-2,20-diol (BINOL, 1) as a chiral
reagent for asymmetric synthesis has been extensively inves-
tigated.1–5 The design and synthesis of modified BINOLs as
ligands in asymmetric catalysis continue to be an area of in-
tense current interest.6,7 Conversion of both hydroxyl groups
of BINOL to two other identical functional groups capable
of coordinating with metals has led to the discovery of many
useful C2-symmetrical homo-bidentate ligands, including
BINAP (2),8–10 BINAM (3),11 and 2,20-bis(2-indenyl)-
binaphthyl (4).12
NH2
OH
OMe
PPh2
NMe2
PPh2
OH
OH
PPh2
PPh2
NOBIN, 5
MAP, 7
MOP, 6
BINOL, 1
BINAP, 2
We recently reported an efficient synthetic pathway using
ethynylarenes to produce the benzannulated enediynyl alco-
hols for subsequent cascade transformations to 5-aryl-11H-
benzo[b]fluorenes.25 This synthetic method was adopted
for the preparation of structurally distorted 4,5-diarylphenan-
threnes26,27 and the atropisomers of 1,2-bis[5-(11H-benzo-
[b]fluorenyl)]benzenes and related compounds.28 We now
report an additional application of this synthetic method
using 2-ethynyl-20-methoxy-1,10-binaphthyl (13), prepared
from BINOL (Scheme 1), as the starting ethynylarene for
the synthesis of 2-(5-benzo[b]fluorenyl)-20-hydroxy-1,10-bi-
naphthyl and related compounds.
NH2
NH2
BINAM, 3
4
Keywords: 2-(5-Benzo[b]fluorenyl)-20-hydroxy-1,10-binaphthyls; Atrop-
isomers; Benzannulated enyne-allenes; Cascade biradical cyclization.
* Corresponding author. Tel.: +1 304 293 3068x6441; fax: +1 304 293
4904; e-mail: kung.wang@mail.wvu.edu
To whom correspondence concerning the X-ray structures should be
addressed. Tel.: +1 304 293 3435x6423; fax: +1 304 293 4904; e-mail:
jeffrey.petersen@mail.wvu.edu.
y
0040–4020/$ - see front matter Ó 2006 Elsevier Ltd. All rights reserved.
doi:10.1016/j.tet.2006.06.004

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H. Yang et al. / Tetrahedron 62 (2006) 8133–8141
O
P
O
OMe
OMe
K2CO3
MeI
Tf2O
pyridine
NBS
OMe
R
OMe
OH
OMe
R1
Me
BINOL, 1
(racemic)
OMe
AIBN
N2
K2CO3
11: R1 = CH2Br, 90%
12: R1 = CHO, 86%
8, 86%
9: R = OTf, 91%
10: R = Me, 93%
NiCl2(dppp)
MeMgI
NaIO4
13, 90%
1. BuLi
OMe
O
I
OMe
KO-t-Bu
HO-t-Bu
2.
Ph
t-Bu
16
3. H2O
refluxing
toluene
SiMe3
R
Ph
Pd(PPh3)4
CuI, i-Pr2NH
R
t-Bu
17: R = OH, 92%
18: R = H, 89%
Et3SiH
CF3CO2H
14: R = SiMe3, 90%
15: R = H, 94%
NaOH
t-Bu
OMe
t-Bu
OMe
OH
OH
BBr3
+
+
19a (racemic)
19b (racemic)
20a, 39% (racemic)
20b, 42% (racemic)
Scheme 1.
2. Results and discussion
to 19b occurred upfield at d 4.00 (J¼21.0 Hz) and 3.89
(J¼21.0 Hz). On the other hand, the 1H NMR signal of the
methoxyl group of 19b at d 3.20 is downfield from that of
19a at d 2.58.
Racemic BINOL was converted to 2-hydroxy-20-methoxy-
1,10-binaphthyl (8)29 for the subsequent transformation
to the corresponding triflate 930 as reported previously.
The NiCl2(dppp)-catalyzed (dppp¼Ph2PCH2CH2CH2PPh2)
cross-coupling reaction31,32 between 9 and methylmag-
nesium iodide led to 2-methoxy-20-methyl-1,10-binaphthyl
(10),33 which was brominated to give 2-(bromomethyl)-
Presumably, the transformation from 18 to 19a and 19b
involved an initial 1,3-prototropic rearrangement to form
the benzannulated enyne-allene 21 as proposed previously
(Scheme 2).25 A subsequent Schmittel cyclization reac-
tion41–44 then generated biradical 22 for an intramolecular
radical–radical coupling to produce 23 and, after a second
prototropic rearrangement, 19a and 19b.
20-methoxy-1,10-binaphthyl (11).34,35 Oxidation of 11 with
36
NaIO4
then produced 2-formyl-20-methoxy-1,10-bi-
naphthyl (12).37,38 Treatment of 12 with dimethyl (1-di-
azo-2-oxopropyl)phosphonate in the presence of potassium
carbonate39 then gave the requisite 2-ethynyl-20-methoxy-
1,10-binaphthyl (13). Attempts to convert 9 to 13 directly
by the Sonogashira reaction with (trimethylsilyl)ethyne
followed by desilylation were unsuccessful. However, the
Sonogashira reaction between 13 and 1-iodo-2-[(trimethyl-
silyl)ethynyl]benzene40 furnished 14, which was then desi-
lylated to produce the benzannulated enediyne 15.
KO-t-Bu
HO-t-Bu
OMe
18
refluxing
toluene
Ph
C
t-Bu
21
Condensation between 15 and pivalophenone (16) gave the
benzannulated enediynyl alcohol 17 as an essentially 1:1
mixture of two diastereomers. Reduction of 17 with triethyl-
silane in the presence of trifluoroacetic acid then led to the
benzannulated enediyne 18. Treatment of 18 with potassium
tert-butoxide in refluxing toluene for 5 h then produced an
essentially 1:1 mixture of the two atropisomers of 2-(5-
benzo[b]fluorenyl)-20-methoxy-1,10-binaphthyl, the syn
atropisomer 19a (racemic) with the methoxyl group and
the five-membered ring of the benzo[b]fluorenyl moiety
syn to each other and the corresponding anti atropisomer
19b (racemic). An AB quartet 1H NMR signals attributable
to the methylene hydrogens of 19a occurred at d 4.44 (J¼
21.7 Hz) and 4.36 (J¼21.8 Hz), whereas those attributable
OMe
H
OMe
t-Bu
t-Bu
22
23
19a
+
19b
Scheme 2.
Compared to the dianion of 4 in which the indenyl anions
possess a C2 symmetry and the two faces are homotopic,
the 5-benzo[b]fluorenyl substituent in 19a and 19b lacks

H. Yang et al. / Tetrahedron 62 (2006) 8133–8141
8135
such a symmetry element and its two faces are heterotopic,
making it possible to form the two atropisomers 19a and
19b. Treatment of the mixture of 19a and 19b with BBr3
for demethylation then produced the corresponding syn
atropisomer of 2-(5-benzo[b]fluorenyl)-20-hydroxy-1,10-bi-
naphthyl (20a, racemic) and the corresponding anti atrop-
isomer 20b (racemic) also as a 1:1 mixture. The tert-butyl
group was also removed under the reaction conditions. Pre-
sumably, the loss of the tert-butyl group occurred because
of the presence of trace amount of acid in the reaction mix-
ture, which protonated the C10 carbon of the benzofluorenyl
substituent followed by the loss of a tert-butyl cation as
observed in other aromatic systems.45–48 It was possible to
separate 20a and 20b by silica gel chromatography and to
obtain single crystals of these two atropisomers for X-ray
structure analyses.
HO
HO
HO
HO
+
(R)-(+)-BINOL
(R)-20b
(R)-20a
24
24
O
SO2Cl
(R)-20b-camphorsulfonate
(R)-20a-camphorsulfonate
OH
OH
OH
The X-ray structures of 20a and 20b (Fig. 1) revealed that
the benzofluorenyl substituent is essentially perpendicular
to the central naphthyl ring onto which it is attached, and
the other naphthyl ring bearing the hydroxyl group is also
essentially perpendicular to the central naphthyl ring. The
fact that 20a and 20b could be separated as atropisomers
indicates that the rates of rotation around the carbon–carbon
single bond connecting the C2 carbon of the binaphthyl sys-
tem and the C5 carbon of the benzo[b]fluorenyl substituent
and around the C1–C10 single bond are slow at room temper-
ature. Heating 20a and 20b in refluxing toluene (110 ꢁC) for
5 h showed no interconversion between the two atrop-
isomers. The AB quartet 1H NMR signals of the methylene
hydrogens of 20a occurred at d 4.14 (J¼22.2 Hz) and 4.08
(J¼21.6 Hz), downfield from those of 20b at d 3.87
(J¼21.6 Hz) and 3.68 (J¼21.6 Hz).
+
OH
(S)-(-)-BINOL
(S)-20a
(S)-20b
24
24
(S)-20b-camphorsulfonate
(S)-20a-camphorsulfonate
Scheme 3.
(1S)-(+)-10-camphorsulfonyl chloride (24), were found to
be of high diastereomeric purity (>99% de) by H NMR
1
analysis of the methyl signals recorded on a 600 MHz
NMR spectrometer. The 1H NMR signals of the two methyl
groups in (R)-20a-camphorsulfonate occurred at d 0.82 and
0.51, clearly separated from those of (S)-20a-camphor-
sulfonate at d 0.84 and 0.49, from those of (R)-20b-
camphorsulfonate at d 0.88 and 0.57, and from those of
(S)-20b-camphorsulfonate at d 0.85 and 0.66. The noise
By starting from enantiomerically pure (R)-(+)-BINOL with
[a]2D5 +36.1 (c 1, THF) to prepare (R)-(+)-15 with [a]2D5 +102
(c 0.90, THF) for condensation with 16, the synthetic se-
quence led to (R)-20a and (R)-20b, which were separated
by silica gel chromatography and were found to exhibit
specific rotations of [a]2D5 +124 (c 0.53, THF) and [a]D25
+44.4 (c 0.49, THF), respectively (Scheme 3). Similarly,
by starting from (S)-(ꢀ)-BINOL with [a]2D5 ꢀ36.8 (c 1,
THF) to prepare (S)-(ꢀ)-15 with [a]2D5 ꢀ102 (c 1.1, THF),
(S)-20a with [a]2D5 ꢀ126 (c 0.76, THF), and (S)-20b with
[a]2D5 ꢀ44.9 (c 0.72, THF) were produced.
1
levels of the H NMR spectra of these four camphorsulfo-
nates were low, allowing the 13C-satellites (0.55% each) of
the methyl signals to be clearly discerned. As a result, it
was possible to detect the presence of minute quantities
(0.55%) of the three other isomers. For example, in the
case of (R)-20a-camphorsulfonate, the 13C-satellites of the
most upfield shift methyl signal occurred at d 0.62 and
0.41 with peak heights significantly taller than any other
signals that could be attributed to the methyl groups of the
three other isomers at d 0.49, 0.57, and 0.66. The ability to
The four corresponding sulfonic esters, derived from the
reactions of (R)-20a, (R)-20b, (S)-20a, and (S)-20b with
20a
20b
Figure 1. X-ray structures of the syn atropisomer 20a and the anti atropisomer 20b.

8136
H. Yang et al. / Tetrahedron 62 (2006) 8133–8141
Table 1. Synthesis of benzannulated enediynyl alcohols and enediynes
ring originated from aryl ketone 25 to produce 31a and 31b
as observed previously.28 Attacking the b-position to form
the corresponding indeno-fused anthracene derivatives did
not appear to occur. The higher reactivity of the a-position
than the b-position of naphthalene in the homolytic addition
may be responsible for the regioselectivity.51,52
Aryl ketones
Enediynyl alcohols
and enediynes
OMe
O
The 1H NMR signals of the methylene hydrogens of 31a oc-
curred as an overlapping singlet at d 4.40, whereas those of
31b occurred upfield as an AB quartet at d 3.83 (J¼20.5 Hz)
and 3.54 (J¼21.3 Hz), similar to those of 19b. On the other
hand, the 1H NMR signal of the methoxyl hydrogens of 31b
occurred at d 2.44, downfield from that of 31a at d 2.29. A
single crystal of 31a suitable for X-ray structure analysis
was obtained by recrystallization of the mixture from a
mixture of methylene chloride/hexanes solution. Because
of non-bonded steric interactions, the indeno-fused phen-
anthrene moiety in 31a is non-planar with the phenanthrene
unit showing a bend in the direction away from the
2-methoxynaphthyl ring system. Treatment of a mixture of
31a and 31b with BBr3 for demethylation allowed the
separation of 32a from the resulting mixture by silica gel
chromatography.
t-Bu
25
R
27: R = OH, 89%
29: R = H, 90%
t-Bu
OMe
O
t-Bu
26
R
28: R = OH, 92%
30: R = H, 89%
t-Bu
achieve high optical purity also suggests that no rotation
occurred around the C1–C10 single bond during the entire
synthetic sequence.
Treatment of 30 with potassium tert-butoxide in refluxing
toluene for 5 h produced a more complex mixture of prod-
ucts with the 1H NMR spectrum showing four sets of methyl-
ene AB quartets in an approximately 6:1:1:1 ratio with the
major AB quartet signals attributable to 33a occurred at
d 4.51 (J¼21.5 Hz) and 4.42 (J¼21.0 Hz) (Scheme 5). The
other three methylene AB quartets occurred between
d 4.60 and 3.91 could be tentatively attributed to 33b, 33c,
and 33d. As in the case of 31a and 31b, attacking the C4 car-
bon of the phenanthryl system originated from aryl ketone
Similarly, the use of aryl ketone 25, readily prepared from
coupling between 2-naphthoyl chloride and tert-butylcopper
in quantitative yield,28,49 for condensation with 15 produced
enediynyl alcohol 27 (Table 1). The use of aryl ketone 26,
likewise prepared by treatment of 3-phenanthrenecarboxylic
acid50 with thionyl chloride followed by tert-butylcopper
(95% yield), for condensation with 15 produced 28. Subse-
quent reduction of 27 and 28 with triethylsilane in the pres-
ence of trifluoroacetic acid then provided the benzannulated
enediynes 29 and 30, respectively. Treatment of 29 with po-
tassium tert-butoxide in refluxing toluene for 5 h furnished
the syn atropisomer 31a and the anti atropisomer 31b in
a 1.5:1 ratio (Scheme 4). It is worth noting that the intra-
molecular radical–radical coupling reaction of the biradical
derived from 29 involved only the a-position of the naphthyl
t-Bu
OMe
t-Bu
OMe
KO-t-Bu
HO-t-Bu
30
+
refluxing
toluene
33a (racemic)
33b (racemic)
t-Bu
OMe
t-Bu
OMe
t-Bu
OMe
t-Bu
OMe
KO-t-Bu
HO-t-Bu
+
29
+
refluxing
toluene
+
31b (racemic)
31a + 31b (1.5 : 1) = 58%
31a (racemic)
33c (racemic)
33d (racemic)
33a + 33b + 33c + 33d (6 : 1 : 1 : 1) = 94%
OH
OH
BBr3
BBr3
32a, 29% (racemic)
34a, 53% (racemic)
Scheme 4.
Scheme 5.

H. Yang et al. / Tetrahedron 62 (2006) 8133–8141
8137
26 during the intramolecular radical–radical coupling re-
action could lead to 33a and 33b, whereas attacking the
C2 carbon of the phenanthryl system could account for the
formation of 33c and 33d. Treatment of the mixture with
BBr3 allowed the isolation of the syn atropisomer 34a by
silica gel chromatography.
tetrahydrofuran (THF) were distilled from benzophenone
ketyl prior to use. (R)-(+)-BINOL with [a]2D5 +36.1 (c 1,
THF), (S)-(ꢀ)-BINOL with [a]2D5 ꢀ36.8 (c 1, THF), n-butyl-
lithium (1.6 M) in hexanes, tert-butyllithium (1.7 M) in
pentane, triethylsilane, trifluoroacetic acid, potassium tert-
butoxide (1.0 M) in 2-methyl-2-propanol, 1-bromo-2-
[(trimethylsilyl)ethynyl]benzene, Pd(PPh3)4, copper(I)
iodide, CuBr$SMe2, diisopropylamine, pivalophenone
(16), 2-naphthoyl chloride, boron tribromide, and (1S)-(+)-
10-camphorsulfonyl chloride (24) with [a]2D2 +33 (c 1,
CHCl3) were purchased from chemical suppliers and were
used as received. Compounds 829 and 930 were prepared
according to the reported procedures. The NiCl2(dppp)-
catalyzed (dppp¼Ph2PCH2CH2CH2PPh2) cross-coupling
reaction31,32 between 9 and methylmagnesium iodide was
employed for the synthesis of 1033 in 93% yield. Bromina-
tion of 10 with NBS produced 1134,35 in 90% yield. The sub-
sequent oxidation of 11 with NaIO436 then furnished 1237,38
in 86% yield. 1-Iodo-2-[(trimethylsilyl)ethynyl]benzene40
was prepared by treatment of 1-bromo-2-[(trimethylsilyl)-
ethynyl]benzene in THF with n-butyllithium at ꢀ78ꢁ C
followed by iodine. Aryl ketone 25 was prepared in quan-
titative yield by coupling of 2-naphthoyl chloride with
tert-butylcopper as described previously.28,49 Aryl ketone
26 (95% yield) was likewise prepared by treatment of 3-phe-
nanthrenecarboxylic acid with thionyl chloride followed
by tert-butylcopper. 3-Phenanthrenecarboxylic acid was
prepared from commercially available 3-acetylphenan-
threne as reported previously.50 1H (270 MHz) and 13C
(67.9 MHz) NMR spectra were recorded in CDCl3 using
CHCl3 (1H d 7.26) and CDCl3 (13C d 77.0) as internal stan-
dards unless otherwise indicated for those recorded on
a 600 MHz NMR spectrometer.
Optically active (R)-34a with [a]2D0 ꢀ735 (c 1.2, THF) and
(S)-34a with [a]2D0 +722 (c 0.92, THF) were also prepared
from (R)-(+)-BINOL and (S)-(ꢀ)-BINOL, respectively
1
(Scheme 6). The H NMR spectra of the corresponding
sulfonic esters, (R)-34a-camphorsulfonate and (S)-34a-cam-
phorsulfonate, showed that these two binaphthyl derivatives
were also of high diastereomeric purity (>97% de).
HO
HO
HO
(R)-(+)-BINOL
(R)-34a
24
(R)-34a-camphorsulfonate
OH
OH
OH
4.1.1. 2-Ethynyl-20-methoxy-1,10-binaphthyl (13). To a
solution of 0.420 g (1.35 mmol) of 12 and 0.373 g of potas-
sium carbonate in 20 mL of anhydrous methanol was added
0.311 g (1.62 mmol) of dimethyl (1-diazo-2-oxopropyl)-
phosphonate,39 and the reaction mixture was stirred at
room temperature for 24 h. The analysis of the reaction mix-
ture by TLC indicated that 12 was completely consumed at
this stage. The reaction mixture was then diluted with diethyl
ether, washed with a 5% aqueous sodium bicarbonate solu-
tion, dried over sodium sulfate, and concentrated. Purifica-
tion of the residue by flash column chromatography (silica
gel/25% CH2Cl2 in hexanes) afforded 0.376 g of 13
(1.22 mmol, 90%) as a white solid: IR 3282, 1508, 1262,
(S)-(-)-BINOL
(S)-34a
24
(S)-34a-camphorsulfonate
Scheme 6.
3. Conclusion
A synthetic pathway leading to the atropisomers of 2-(5-
benzo[b]fluorenyl)-20-hydroxy-1,10-binaphthyl and related
compounds was developed. The structures of syn atrop-
isomers 20a and 31a and anti atropisomer 20b were estab-
lished by X-ray structure analyses. The presence of a
hydroxyl group and a benzo[b]fluorenyl or a related group
in these 2,20-disubstituted 1,10-binaphthyls could allow the
formation of useful complexes with metals. The enantio-
merically pure syn atropisomers, (R)-20a, (S)-20a, (R)-
34a, and (S)-34a, hold potential as hetero-bidentate ligands
for asymmetric catalysis.
1
1082 cmꢀ1; H d 8.01 (1H, d, J¼8.9 Hz), 7.93–7.86 (3H,
m), 7.72 (1H, d, J¼8.4 Hz), 7.51–7.44 (2H, m), 7.37–7.19
(4H, m), 7.02 (1H, d, J¼8.7 Hz), 3.80 (3H, s), 2.76 (1H,
s); 13C d 154.8, 138.8, 133.6, 133.3, 132.7, 129.8, 129.0,
128.0, 127.9, 127.7, 126.59, 126.54, 126.48, 125.0, 123.6,
121.5, 120.6, 114.0, 83.3, 79.8, 57.0; MS m/z 331 (MNa+),
239, 204; HRMS calcd for C23H16ONa (MNa+) 331.1099,
found 331.1096.
Enantiomerically pure (R)-13 with [a]2D5 +48.6 (c 1.2, THF)
and (S)-13 with [a]2D5 ꢀ49.5 (c 1.3, THF) were prepared from
(R)-(+)-BINOL and (S)-(ꢀ)-BINOL, respectively.
4.1.2. 2-Methoxy-20-[2-[(trimethylsilyl)ethynyl]phenyl]-
ethynyl-1,10-binaphthyl (14). To a mixture of 1-iodo-2-
[(trimethylsilyl)ethynyl]benzene (0.126 g, 0.813 mmol),40
4. Experimental
4.1. General
All reactions were conducted in oven-dried (120 ꢁC)
glassware under a nitrogen atmosphere. Diethyl ether and

8138
H. Yang et al. / Tetrahedron 62 (2006) 8133–8141
Pd(PPh3)4 (0.104 g, 0.090 mmol), and copper(I) iodide
(0.052 g, 0.272 mmol) in 10 mL of toluene was added via
cannula a solution of 0.209 g of 13 (0.679 mmol) in 3 mL
of diisopropylamine. After 13 h of stirring at 70 ꢁC, 20 mL
of a saturated ammonium chloride solution and 20 mL of
diethyl ether were added. The organic layer was separated,
and the aqueous layer was back extracted with diethyl ether.
The combined organic layers were washed with brine and
water, dried over sodium sulfate, and concentrated. Purifica-
tion of the residue by flash column chromatography (silica
gel/25% methylene chloride in hexanes) afforded 0.292 g
of 14 (0.608 mmol, 90%) as a white solid: IR 2157, 1249,
mixture of two diastereomers) as a yellow liquid: IR 3568,
1
1265 cmꢀ1; H d 8.03 (2H, dd, J¼8.9, 1.5 Hz), 7.93–7.74
(8H, m), 7.59 (1H, d, J¼7.2 Hz), 7.56 (1H, d, J¼6.9 Hz),
7.51–7.44 (4H, m), 7.36–7.20 (16H, m), 7.17–7.06 (4H,
m), 6.99 (2H, dt, J¼7.6, 1.8 Hz), 6.26 (1H, dd, J¼7.7,
0.7 Hz), 6.21 (1H, dd, J¼7.7, 0.7 Hz), 3.78 and 3.76 (6H,
two singlets), 2.46 and 2.43 (2H, two singlets), 1.13 (18H,
s); 13C d 154.9, 142.1, 138.61, 138.57, 133.8, 133.1, 132.8,
132.2, 131.81, 131.77, 129.7, 129.1, 128.26, 128.20, 128.1,
127.84, 127.78, 127.68, 127.61, 127.4, 127.3, 127.1,
126.51, 125.9, 125.3, 124.2, 123.6, 122.1, 122.0, 121.6,
114.14, 114.07, 96.0, 93.6, 91.8, 91.7, 84.5, 79.5, 57.0,
56.9, 39.7, 25.6; MS m/z 593 (MNa+), 437, 381; HRMS calcd
for C42H34O2Na (MNa+) 593.2457, found 593.2454.
1
865 cmꢀ1; H d 8.04 (1H, d, J¼9.1 Hz), 7.96–7.89 (3H,
m), 7.80 (1H, d, J¼8.4 Hz), 7.52–7.45 (2H, m), 7.37–7.27
(4H, m), 7.23 (1H, td, J¼6.7, 1.2 Hz), 7.13 (1H, d,
J¼7.9 Hz), 7.07 (1H, td, J¼7.3, 1.2 Hz), 6.98 (1H, td,
J¼7.7, 1.4 Hz), 6.24 (1H, dd, J¼7.9, 1.4 Hz), 3.80 (3H, s),
0.32 (9H, s); 13C d 155.0, 138.3, 133.8, 133.1, 132.8,
131.92, 131.85, 129.7, 129.0, 128.5, 128.1, 127.84,
127.77, 127.63, 127.3, 126.5, 126.4, 126.1, 125.4, 124.6,
123.6, 121.92, 121.85, 103.5, 98.2, 93.8, 91.5, 57.0, 0.1.
4.1.5. Benzannulated enediyne 18. To a mixture of 17
(0.162 g, 0.284 mmol) and triethylsilane (0.102 g,
0.875 mmol) in 15 mL of methylene chloride was added
0.20 mL of trifluoroacetic acid (0.309 g, 2.69 mmol). After
5 min of stirring at room temperature, 0.480 g of sodium car-
bonate (4.6 mmol) was added followed by 10 mL of water
and 40 mL of diethyl ether. The organic layer was separated,
dried over sodium sulfate, and concentrated. Purification of
the residue by flash column chromatography (silica gel/10%
CH2Cl2 in hexanes) provided 0.140 g (0.253 mmol, 89%) of
18 (essentially a 1:1 mixture of two diastereomers) as a
4.1.3. 2-(2-Ethynylphenyl)ethynyl-20-methoxy-1,10-
binaphthyl (15). To 0.292 g (0.608 mmol) of 14 in 10 mL
of diethyl ether were added 4 mL of a 10% sodium hydrox-
ide solution and 10 mL of methanol. After 30 min of stirring
at room temperature, the organic solvent was removed in va-
cuo, and 20 mL of water and 20 mL of diethyl ether were
added to the residue. The organic layer was separated, and
the aqueous layer was back extracted with diethyl ether.
The combined organic layers were washed with brine and
water, dried over sodium sulfate, and concentrated. Purifica-
tion of the residue by flash column chromatography (silica
gel/25% methylene chloride in hexanes) afforded 0.232 g
of 15 (0.569 mmol, 94%) as a white solid: IR 3282, 2205,
1
yellow liquid: IR 2226, 1248, 726 cmꢀ1; H d 8.03 (2H, d,
J¼9.2 Hz), 7.92 (4H, d, J¼7.9 Hz), 7.85 (2H, d,
J¼8.4 Hz), 7.55 (2H, d, J¼8.4 Hz), 7.52–7.44 (9H, m),
7.37–7.20 (15H, m), 7.16–7.11 (2H, m), 7.07 (2H, td,
J¼7.7, 1.5 Hz), 6.95 (2H, t, J¼7.7 Hz), 6.21 (2H, t, J¼
6.9 Hz), 3.79 (3H, s), 3.76 (3H, s), 3.70 (1H, s), 3.69 (1H,
s), 1.09 (18H, s); 13C d 155.0, 139.2, 138.4, 133.8, 133.1,
132.8, 132.2, 131.8, 131.7, 129.8, 129.7, 129.1, 128.4,
128.0, 127.8, 127.6, 127.5, 127.3, 127.0, 126.7, 126.5,
126.4, 125.7, 125.4, 123.6, 122.1, 121.9, 114.1, 95.3, 93.2,
92.1, 82.4, 57.0, 50.6, 35.5, 27.8; MS m/z 577 (MNa+),
437, 381; HRMS calcd for C42H34ONa (MNa+) 577.2507,
found 577.2506. The sample of 18 contains about 3% of
residual hexanes as determined by the 1H NMR spectrum.
1507, 1267, 1082 cmꢀ1
;
1H d 8.02 (1H, d, J¼8.9 Hz),
7.95–7.88 (3H, m), 7.82 (1H, d, J¼8.4 Hz), 7.50–7.43
(2H, m), 7.38–7.20 (5H, m), 7.15–7.08 (3H, m), 6.82–6.78
(1H, m), 3.77 (3H, s), 2.67 (1H, s); 13C d 155.0, 138.1,
134.1, 133.2, 132.9, 132.1, 131.9, 129.7, 129.06, 128.96,
128.1, 127.8, 127.7, 127.4, 126.5, 125.5, 123.9, 123.5,
121.9, 121.7, 114.2, 93.7, 90.9, 81.5, 80.8, 57.0; MS m/z
431 (MNa+), 381; HRMS calcd for C31H20ONa (MNa+)
431.1412, found 431.1409.
4.1.6. syn and anti Atropisomers of 2-(5-benzo[b]fluo-
renyl)-20-hydroxy-1,10-binaphthyl (20a and 20b). To
0.089 g of 18 (0.161 mmol) in 5 mL of anhydrous toluene
under a nitrogen atmosphere was added 0.2 mL of a 1.0 M
solution of potassium tert-butoxide (0.2 mmol) in 2-methyl-
2-propanol. The reaction mixture was then heated under
reflux for 5 h. After the reaction mixture was allowed to
cool to room temperature, 10 mL of water and 30 mL of
methylene chloride were introduced, and the organic layer
was separated, dried over sodium sulfate, and concentrated.
The residue was purified by flash column chromatography
(silica gel/10% methylene chloride in hexanes) to provide
0.070 g of a 1:1 mixture of 19a and 19b (0.126 mmol,
78%) as a pale yellow solid. The AB quartet 1H NMR signals
of the methylene hydrogens of 19a occurred at d 4.44
(J¼21.7 Hz) and 4.36 (J¼21.8 Hz), whereas those of 19b
occurred at d 4.00 (J¼21.0 Hz) and 3.89 (J¼21.0 Hz). The
signal of the methoxyl hydrogens of 19a occurred at
d 2.58 and that of 19b occurred at d 3.20.
Enantiomerically pure (R)-15 with [a]2D5 +102 (c 0.90, THF)
and (S)-15 with [a]2D5 ꢀ102 (c 1.1, THF) were prepared from
(R)-(+)-BINOL and (S)-(ꢀ)-BINOL, respectively.
4.1.4. Benzannulated enediynyl alcohol 17. To 0.125 g
(0.306 mmol) of 15 in 10 mL of anhydrous diethyl ether
under a nitrogen atmosphere at 0 ꢁC was added 0.20 mL of
a 1.6 M solution of n-butyllithium (0.32 mmol) in hexanes.
After 30 min of stirring, a solution of 0.055 g of 16
(0.340 mmol) in 4 mL of diethyl ether was introduced via
cannula, and the reaction mixture was allowed to warm to
room temperature. After an additional 2 h, 15 mL of water
was introduced, and the reaction mixture was extracted
with diethyl ether. The combined organic extracts were
washed with brine and water, dried over sodium sulfate,
and concentrated. Purification of the residue by flash column
chromatography (silica gel/5% diethyl ether in hexanes) pro-
vided 0.160 g (0.281 mmol, 92%) of 17 (essentially a 1:1
To a mixture of 19a and 19b (0.073 g, 0.13 mmol) in 10 mL
of methylene chloride was added dropwise 0.2 mL of boron

H. Yang et al. / Tetrahedron 62 (2006) 8133–8141
8139
tribromide at 0 ꢁC. The reaction mixture was stirred at 0 ꢁC
for 4 h before 10 mL of water and 20 mL of methylene chlo-
ride were introduced. The organic layer was separated, dried
over sodium sulfate, and concentrated. The residue was
purified by flash column chromatography (silica gel/5%
ethyl acetate in hexanes) to provide 0.024 g (0.050 mmol,
39%) of 20a and 0.026 g (0.054 mmol, 42%) of 20b as yel-
Purification of the residue by flash column chromatography
(silica gel/25% methylene chloride in hexanes) afforded
0.015 g of (R)-20a-camphorsulfonate (0.021 mmol, 91%)
as a light yellow solid: IR 1739, 1366, 1218 cmꢀ1 1H
;
(600 Hz) d 8.27 (1H, d, J¼8.4 Hz), 8.15 (1H, d,
J¼8.4 Hz), 7.84 (1H, dd, J¼8.4, 2.4 Hz), 7.71 (1H, s),
7.59 (1H, t, J¼7.5 Hz), 7.55 (1H, d, J¼8.4 Hz), 7.53–7.50
(2H, m), 7.48 (1H, d, J¼8.4 Hz), 7.44 (1H, dd, J¼9.0,
2.4 Hz), 7.39 (1H, t, J¼7.5 Hz), 7.36 (1H, d, J¼9.0 Hz),
7.29–7.26 (2H, m), 7.23 (1H, t, J¼7.2 Hz), 7.20 (1H, t,
J¼8.4 Hz), 7.11 (1H, t, J¼7.2 Hz), 7.02 (1H, td, J¼8.4,
3.0 Hz), 6.99 (1H, d, J¼8.4 Hz), 6.92 (1H, d, J¼7.2 Hz),
6.58 (1H, t, J¼7.8 Hz), 4.13 (1H, d, J¼21.6 Hz), 4.03 (1H,
d, J¼21.0 Hz), 2.91 (1H, d, J¼14.4 Hz), 2.22 (1H, d,
J¼18.0 Hz), 2.10 (1H, t, J¼12.6 Hz), 1.97 (1H, d, J¼
14.4 Hz), 1.94 (1H, br t), 1.88–1.83 (1H, m), 1.79 (1H, d,
J¼18.6 Hz), 1.42–1.36 (1H, m), 0.82 (3H, s), 0.51 (3H, s);
13C (150 MHz) d 213.5, 145.1, 144.0, 141.6, 140.9, 138.3,
137.8, 133.9, 133.11, 133.06, 132.7, 132.0, 131.9, 131.2,
130.9, 129.5, 129.2, 129.0, 128.4, 127.9, 127.7, 127.3,
127.1, 126.98, 126.96, 126.93, 126.73, 126.65, 126.3,
125.7, 125.3, 125.2, 124.7, 124.6, 123.7, 122.6, 121.1,
57.8, 48.7, 47.5, 42.7, 42.3, 36.4, 26.7, 24.9, 19.5, 19.4.
1
low solids. 20a: H (600 MHz) d 8.28 (1H, d, J¼8.4 Hz),
8.16 (1H, d, J¼7.8 Hz), 7.79 (1H, d, J¼7.8 Hz), 7.77
(1H, s), 7.64 (1H, ddd, J¼7.8, 6.6, 1.2 Hz), 7.57 (1H, d,
J¼7.2 Hz), 7.55 (1H, d, J¼7.8 Hz), 7.52–7.50 (2H, m),
7.40–7.38 (2H, m), 7.35 (1H, d, J¼7.8 Hz), 7.26 (1H, t,
J¼7.2 Hz), 7.20–7.14 (3H, m), 7.08 (1H, ddd, J¼8.4, 6.6,
1.2 Hz), 7.03 (1H, t, J¼7.8 Hz), 6.75 (1H, ddd, J¼8.4, 6.6,
1.2 Hz), 6.69 (1H, d, J¼9.0 Hz), 6.51 (1H, d, J¼7.8 Hz),
4.82 (1H, s), 4.14 (1H, d, J¼22.2 Hz), 4.08 (1H, d,
J¼21.6 Hz); 13C (150 MHz) d 151.6, 144.5, 141.5, 140.5,
138.5, 137.3, 134.5, 133.54, 133.45, 132.3, 132.1, 131.6,
131.1, 130.0, 129.8, 129.5, 128.5, 128.4, 127.7, 127.4,
127.3, 127.2, 127.1, 126.9, 126.8, 126.7, 126.3, 125.9,
125.5, 125.1, 124.2, 123.0, 122.7, 121.5, 117.2, 116.6,
36.4; MS m/z 484 (M+), 313; HRMS calcd for C37H24O
484.1827, found 484.1829. Recrystallization from a mixture
of ethanol and methylene chloride produced a crystal suit-
1
able for X-ray structure analysis. 20b: H (600 Hz) d 8.29
4.1.8. (S)-20a-Camphorsulfonate. The same procedure was
repeated as described for (R)-20a-camphorsulfonate except
that 0.014 g of (S)-20a (0.029 mmol) was used to afford
0.018 g of (S)-20a-camphorsulfonate (0.026 mmol, 90%)
(1H, d, J¼8.4 Hz), 8.18 (1H, J¼8.4 Hz), 7.92 (1H, dd,
J¼8.4, 0.6 Hz), 7.67 (1H, t, J¼7.2 Hz), 7.59 (1H, d,
J¼7.8 Hz), 7.57 (1H, d, J¼8.0 Hz), 7.56 (1H, s), 7.54 (1H,
d, J¼8.4 Hz), 7.47 (1H, t, J¼7.2 Hz), 7.43 (1H, d,
J¼7.2 Hz), 7.36 (2H, t, J¼7.8 Hz), 7.30 (1H, t, J¼7.5 Hz),
7.25–7.23 (2H, m), 7.16 (1H, d, J¼8.4 Hz), 7.10 (1H, t,
J¼7.8 Hz), 6.98 (1H, d, J¼8.4 Hz), 6.84 (1H, t, J¼
7.5 Hz), 6.79 (1H, dd, J¼9.0, 1.2 Hz), 6.22 (1H, t,
J¼7.5 Hz), 4.78 (1H, s), 3.87 (1H, d, J¼21.6 Hz), 3.68
(1H, d, J¼21.6 Hz); 13C (150 MHz) d 150.6, 144.0, 141.6,
140.5, 138.7, 137.8, 133.6, 133.4, 133.1, 132.3, 132.2,
131.9, 131.6, 130.3, 129.3 (two carbons), 128.7, 128.1,
127.5, 127.3, 126.91, 126.86, 126.79, 126.5, 126.24,
126.21, 125.9, 125.0, 124.7, 124.5, 124.34, 124.32, 122.7,
122.5, 117.4, 117.1, 36.0; MS m/z 484 (M+), 215; HRMS
calcd for C37H24O 484.1827, found 484.1821. Recrystalliza-
tion from a mixture of ethanol and methylene chloride pro-
duced a crystal suitable for X-ray structure analysis. The
sample of 20b contains about 5% of residual hexanes as
determined by the 1H NMR spectrum.
as a light yellow solid: IR 1739, 1366, 1217 cmꢀ1 1H
;
(600 MHz) d 8.25 (1H, d, J¼8.4 Hz), 8.14 (1H, d,
J¼8.4 Hz), 7.82 (1H, dd, J¼7.8, 1.8 Hz), 7.72 (1H, s),
7.60–7.54 (3H, m), 7.52 (1H, d, J¼7.2 Hz), 7.48 (1H, d,
J¼8.4 Hz), 7.44 (1H, d, J¼8.4 Hz), 7.39 (1H, t, J¼
7.2 Hz), 7.36 (1H, d, J¼8.4 Hz), 7.32 (1H, t, J¼7.5 Hz),
7.26–7.19 (3H, m), 7.02 (1H, t, J¼7.5 Hz), 7.00–6.95 (2H,
m), 6.85 (1H, d, J¼7.8 Hz), 6.49 (1H, t, J¼7.5 Hz), 4.14
(1H, d, J¼22.2 Hz), 4.05 (1H, d, J¼21.6 Hz), 2.71 (1H,
dd, J¼15.0, 1.2 Hz), 2.31 (1H, dd, J¼15.0, 1.2 Hz), 2.21
(1H, d, J¼18.0 Hz), 1.97–1.92 (2H, m), 1.82 (1H, t,
J¼11 Hz), 1.76 (1H, d, J¼18.6 Hz), 1.26–1.11 (2H, m),
0.84 (3H, s), 0.49 (3H, s); 13C (150 MHz) d 213.3, 145.1,
144.1, 141.7, 140.9, 138.4, 137.8, 133.9, 133.2, 133.0,
132.6, 132.1, 131.8, 131.4, 130.7, 129.6, 129.2 (two car-
bons), 128.3, 127.9, 127.8, 127.6, 127.4, 127.0, 126.84,
126.81, 126.62, 126.60, 126.3, 125.8, 125.4, 125.0, 124.7,
124.6, 123.6, 122.6, 121.2, 57.8, 48.3, 47.3, 42.9, 42.2,
36.4, 26.7, 25.2, 19.7, 19.4.
Enantiomerically pure (R)-20a with [a]2D5 +124 (c 0.53,
THF) and (R)-20b with [a]2D5 +44.4 (c 0.49, THF) were pre-
pared from (R)-(+)-BINOL, whereas (S)-20a with [a]D25
ꢀ126 (c 0.76, THF) and (S)-20b with [a]2D5 ꢀ44.9 (c 0.72,
THF) were also prepared from (S)-(ꢀ)-BINOL.
4.1.9. 1,10-Binaphthyl 31a. The same procedure was
repeated as described for 19a and 19b except that 0.121 g
(0.200 mmol) of 29 in 8 mL of anhydrous toluene was
treated with 0.42 mL of a 1.0 M solution of potassium tert-
butoxide (0.42 mmol) in 2-methyl-2-propanol, and the reac-
tion mixture was heated under reflux for 5 h to afford 0.070 g
of a mixture of 31a and 31b (31a:31b¼1.5:1, 0.116 mmol,
58%) as a pale yellow solid. Recrystallization from a mixture
of hexanes and methylene chloride produced a crystal of 31a
suitable for X-ray structure analysis. 31a: 1H d 8.41 (1H, d,
J¼8.7 Hz), 8.29 (1H, d, J¼8.9 Hz), 8.13 (1H, d, J¼8.2 Hz),
8.11 (1H, d, J¼8.9 Hz), 7.70 (1H, d, J¼9.7 Hz), 7.56–7.45
(2H, m), 7.34 (1H, d, J¼8.6 Hz), 7.23–7.10 (5H, m), 6.95
(1H, t, J¼8.4 Hz), 6.90–6.82 (2H, m), 6.75 (1H, d, J¼
9.4 Hz), 6.58 (1H, d, J¼8.2 Hz), 6.48 (1H, d, J¼9.2 Hz),
4.1.7. (R)-20a-Camphorsulfonate. To 0.011 g of (R)-20a
(0.023 mmol) and triethylamine (0.05 mL, 0.09 mmol) in
3 mL of anhydrous methylene chloride at 0 ꢁC under a nitro-
gen atmosphere was added 0.031 g of (1S)-(+)-10-camphor-
sulfonyl chloride (24, 0.12 mmol). The reaction mixture
was stirred at 0 ꢁC for 3 h before 2 mL of a 10% aqueous so-
dium hydroxide solution was added. The reaction mixture
was stirred for an additional 2 h. Water was added, and the
reaction mixture was extracted with methylene chloride.
The combined organic extracts were washed with brine
and water, dried over sodium sulfate, and concentrated.

8140
H. Yang et al. / Tetrahedron 62 (2006) 8133–8141
6.31 (1H, ddd, J¼8.2, 6.7, 1.5 Hz), 5.94 (1H, d, J¼8.7 Hz),
4.40 (2H, s), 2.29 (3H, s), 1.71 (9H, s); MS m/z 604
(M+), 547; HRMS calcd for C46H36O 604.2766, found
604.2766.
6.37 (1H, d, J¼8.4 Hz), 5.19 (1H, d, J¼8.4 Hz), 4.24 (1H,
d, J¼21.6 Hz), 4.20 (1H, d, J¼21.0 Hz), 3.98 (1H, s); 13C
(150 MHz) d 149.9, 145.0, 141.9, 141.4, 139.8, 139.5,
134.5, 134.0, 133.7, 133.1, 132.65, 132.63, 131.6, 131.5,
131.4, 130.9, 129.2, 128.6, 128.5, 128.0, 127.85, 127.80,
127.5, 127.30, 127.26, 127.22, 127.21, 127.0, 126.41,
126.38, 126.17, 126.10, 125.92, 125.84, 125.75, 125.4,
125.1, 124.5, 124.2, 123.3, 122.5, 121.7, 116.05, 116.01,
36.6; MS m/z 584 (M+), 315; HRMS calcd for C45H28O
584.2140, found 584.2150. The sample of 34a contains
The 1H NMR spectrum of the 1.5:1 mixture of 31a and 31b
exhibited a set of AB quartet signals at d 3.83 (J¼20.5 Hz)
and 3.54 (J¼21.3 Hz) and a singlet at d 2.44 attributable to
the methylene hydrogens and methoxyl hydrogens of 31b,
respectively.
1
about 5–10% of residual hexanes as determined by the H
NMR spectrum.
4.1.10. 1,10-Binaphthyl 32a. To a mixture of 31a and 31b
(0.058 g, 0.096 mmol) in 10 mL of methylene chloride
was added dropwise 0.2 mL of boron tribromide at 0 ꢁC.
The reaction mixture was stirred at 0 ꢁC for 6 h before
10 mL of water and 20 mL of methylene chloride were intro-
duced. The organic layer was separated, dried over sodium
sulfate, and concentrated. The residue was purified by flash
column chromatography (silica gel/5% ethyl acetate in
hexanes) to provide 0.015 g (0.028 mmol, 29%) of 32a as
Enantiomerically pure (R)-34a with [a]2D0 ꢀ735 (c 1.2, THF)
and (S)-34a with [a]2D0 +722 (c 0.92, THF) were prepared
from (R)-(+)-BINOL and (S)-(ꢀ)-BINOL, respectively.
5. Supplementary information
Experimental procedures and spectroscopic data for (R)-
20b-camphorsulfonate, (S)-20b-camphorsulfonate, 27–30,
(R)-34a-camphorsulfonate, and (S)-34a-camphorsulfonate;
1H and/or 13C NMR spectra of compounds 13–15, 17, 18,
20a, 20b, (R)-20a-camphorsulfonate, (R)-20b-camphorsul-
fonate, (S)-20a-camphorsulfonate, (S)-20b-camphorsulfo-
nate, 27–30, 31a, 32a, 34a, (R)-34a-camphorsulfonate, and
(S)-34a-camphorsulfonate; the ORTEP drawings of the crys-
tal structures of 20a, 20b, and 31a; Crystallographic data for
the structures in this paper have been deposited with the
Cambridge Crystallographic Data Centre. The CCDC nos.
292506, 292507, and 292508 have been assigned for the
compounds 20a, 20b, and 31a, respectively. Copies of the
data can be obtained, free of charge, on application to
CCDC, 12 Union Road, Cambridge CB2 1EZ, UK [fax:
+44 1223 336033 or e-mail: deposit@ccdc.cam.ac.uk].
1
a yellow solid: H (600 MHz) d 8.48 (2H, s), 8.25 (1H, d,
J¼8.4 Hz), 8.22 (1H, d, J¼7.8 Hz), 7.74 (1H, s), 7.63 (1H,
ddd, J¼8.4, 7.2, 1.2 Hz), 7.60 (1H, d, J¼7.2 Hz), 7.41
(1H, d, J¼7.8 Hz), 7.31–7.24 (6H, m), 7.23 (1H, d, J¼
9.0 Hz), 7.173 (1H, d, J¼8.4 Hz), 7.169 (1H, d, J¼
9.0 Hz), 7.06 (1H, ddd, J¼8.4, 7.2, 1.2 Hz), 7.04 (1H, t,
J¼7.2 Hz), 6.78 (1H, ddd, J¼7.8, 6.0, 1.8 Hz), 6.67 (1H,
d, J¼8.4 Hz), 6.52 (1H, d, J¼9.0 Hz), 6.26–6.21 (2H, m),
4.32 (1H, s), 4.14 (1H, d, J¼21.6 Hz), 4.06 (1H, d,
J¼21.0 Hz); MS m/z 534 (M+), 265; HRMS calcd for
C41H26O 534.1984, found 534.1970.
4.1.11. 1,10-Binaphthyl 34a. The same procedure was re-
peated as described for 19a and 19b except that 0.087 g
(0.133 mmol) of 30 in 5 mL of anhydrous toluene was
treated with 0.30 mL of a 1.0 M solution of potassium tert-
butoxide (0.30 mmol) in 2-methyl-2-propanol, and the reac-
tion mixture was heated under reflux for 5 h to afford 0.082 g
of a mixture of 33a, 33b, 33c, and 33d (33a:33b:33c:
33d¼6:1:1:1, 0.125 mmol, 94%) as a yellow solid. A domi-
nant set of AB quartet 1H NMR signals at d 4.51
(J¼21.5 Hz) and 4.42 (J¼21.0 Hz) attributable to 33a along
with three minor sets of AB quartet signals between d 4.60
and 3.91 attributable to 33b–d were also observed.
Acknowledgements
The financial support of the Petroleum Research Fund
(38169-AC1), administered by the American Chemical
Society, and the National Science Foundation (CHE-
0414063) is gratefully acknowledged. K.K.W. thanks the
National Science Council of Taiwan, the Republic of China,
for a grant to support sabbatical leave in the Department of
Chemistry at the National Taiwan University. J.L.P. ac-
knowledges the support (CHE-9120098) provided by the
National Science Foundation for the acquisition of a Siemens
P4 X-ray diffractometer. The financial support of the NSF-
EPSCoR (1002165R) for the purchase of a 600 MHz NMR
spectrometer is also gratefully acknowledged.
To a mixture of 33a, 33b, 33c, and 33d (0.039 g,
0.060 mmol) in 5 mL of methylene chloride was added drop-
wise 0.1 mL of boron tribromide at 0 ꢁC. The reaction mix-
ture was stirred at 0 ꢁC for 2 h before 10 mL of water and
20 mL of methylene chloride were introduced. The organic
layer was separated, dried over sodium sulfate, and concen-
trated. The residue was purified by flash column chromato-
graphy (silica gel/5% ethyl acetate in hexanes) to provide
0.019 g (0.032 mmol, 53%) of 34a as a yellow solid: IR
Supplementary data
3541, 1517, 1141 cmꢀ1 1H (600 MHz) d 8.84 (1H, d,
;
Supplementary data associated with this article can be found
in the online version, at doi:10.1016/j.tet.2006.06.004.
J¼9.0 Hz), 8.60 (1H, d, J¼8.4 Hz), 8.15 (1H, d, J¼
8.4 Hz), 7.93 (1H, d, J¼8.4 Hz), 7.87 (1H, s), 7.61 (2H, t,
J¼6.9 Hz), 7.47 (1H, d, J¼8.4 Hz), 7.43 (1H, d,
J¼7.8 Hz), 7.40 (1H, t, J¼7.8 Hz), 7.39 (1H, d, J¼
7.8 Hz), 7.31 (1H, d, J¼7.8 Hz), 7.29–7.27 (2H, m), 7.21
(1H, d, J¼9.0 Hz), 7.04–6.99 (3H, m), 6.97 (1H, d,
J¼8.4 Hz), 6.96 (1H, d, J¼8.4 Hz), 6.79 (1H, d, J¼
7.8 Hz), 6.73 (1H, d, J¼8.4 Hz), 6.61 (1H, t, J¼7.8 Hz),
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