Notes
J . Org. Chem., Vol. 61, No. 24, 1996 8713
2 H), 7.86 (d, J ) 8.5 Hz, 2 H), 8.37 (s, 2 H); MS (L-SIMS, m/ z)
871 (M + H+, 2, C40H4179Br2O8S2 requires 871). Anal. Calcd
for C40H40Br2O8S2: C, 55.05; H, 4.62. Found: 54.93; H, 4.60.
3b (R ) 3-Br ): white solid; mp 227-229 °C; 1H-NMR (CDCl3)
δ 0.41 (s, 6 H), 0.78 (s, 6 H), 1.25-1.48 (m, 4 H), 1.81 (d, J )
18.5 Hz, 2 H), 1.86-1.97 (m, 4 H), 2.02 (d, J ) 15.5 Hz, 2 H),
2.20-2.27 (m, 4 H), 3.37 (d, J ) 15 Hz, 2 H), 7.21 (d, J ) 8.5
Hz, 2 H), 7.34 (t, J ) 8.5 Hz, 2 H), 7.50 (t, J ) 7.5 Hz, 2 H), 7.84
(d, J ) 8 Hz, 2 H), 8.38 (s, 2 H); MS (L-SIMS, m/ z) 871 (M +
H+, 3, C40H4179Br2O8S2 requires 871). Anal. Calcd for
of the faster running isomers 3a -e had an (S)-configu-
ration while those of the slower running isomers 2a -e
had an (R)-configuration. The observed Cotton effect
pattern is closely parallel to the previous findings by
Mason9 and Harada,10 in which case the (S)-enantiomer
of C2-symmetrically substituted binaphthyls was shown
to consistently exhibit positive first and negative second
Cotton effects.
With the rapid development in asymmetric synthesis
and the design of chiral catalysts, our method therefore
offers a rapid and reliable procedure to resolve a variety
of racemic binaphthols using the inexpensive compound
camphorsulfonyl chloride. Although this resolution
method relies on the chromatographic separation and
scaling up could be a problem, we believe this is the only
method available for the resolution of substituted bi-
naphthols without the trouble of finding the appropriate
resolving agent or recrystallization solvent associated
with the other methods. More importantly, this method
allows us to assign the absolute configuration of the
binaphthol chiral axis from the relative chromatographic
mobility data.
C
40H40Br2O8S2: C, 55.05; H, 4.62. Found: 54.79; H, 4.58.
2d (R ) 6-OMe): white solid; mp 85-87 °C; 1H-NMR (CDCl3)
δ 0.54 (s, 6 H), 0.79 (s, 6 H), 1.25-1.44 (m, 4 H), 1.80 (d, J )
18.5 Hz, 2 H), 1.80-1.90 (m, 2 H), 1.94-1.98 (m, 2 H), 2.02-
2.10 (m, 2 H), 2.18-2.26 (m, 2 H), 2.44 (d, J ) 14.5 Hz, 2 H),
2.89 (d, J ) 14.5 Hz, 2 H), 3.91 (s, 6 H), 7.02 (dd, J ) 8.5, 2 Hz,
2 H), 7.19 (d, J ) 9 Hz, 2 H), 7.22 (d, J ) 2.5 Hz, 2 H), 7.71 (d,
J ) 9 Hz, 2 H), 7.91 (d, J ) 9 Hz, 2 H); MS (L-SIMS, m/ z) 775
(M + H+, 30, C42H47O10S2 requires 775).
3d (R ) 6-OMe): white solid; mp 94-95 °C; 1H-NMR (CDCl3)
δ 0.47 (s, 6 H), 0.64 (s, 6 H), 1.25-1.44 (m, 4 H), 1.75-1.82 (m,
2 H), 1.78 (d, J ) 18.5 Hz, 2 H), 1.85-1.94 (m, 4 H), 2.18-2.26
(m, 2 H), 2.23 (d, J ) 15 Hz, 2 H), 3.25 (d, J ) 15 Hz, 2 H), 3.91
(s, 6 H), 7.00 (dd, J ) 9, 2 Hz, 2 H), 7.14 (d, J ) 9 Hz, 2 H), 7.21
(d, J ) 2 Hz, 2 H), 7.72 (d, J ) 9 Hz, 2 H), 7.91 (d, J ) 9 Hz, 2
H); MS (L-SIMS, m/ z) 775 (M + H+, 100, C42H47O10S2 requires
775). Anal. Calcd for C42H46O10S2: C, 65.10; H, 5.98. Found:
C, 65.15; H, 5.92.
Exp er im en ta l Section
2e (R ) 7-OMe): white solid; mp 75-76 °C; 1H-NMR (CDCl3)
δ 0.50 (s, 6 H), 0.75 (s, 6 H), 1.22-1.45 (m, 4 H), 1.79 (d, J )
18.5 Hz, 2 H), 1.80-1.90 (m, 2 H), 1.92-1.98 (m, 2 H), 2.00-
2.10 (m, 2 H), 2.17-2.26 (m, 2 H), 2.35 (d, J ) 15 Hz, 2 H), 2.86
(d, J ) 15 Hz, 2 H), 3.56 (s, 6 H), 6.60 (d, J ) 1.5 Hz, 2 H), 7.16
(dd, J ) 9, 2.5 Hz, 2 H), 7.60 (d, J ) 9.5 Hz, 2 H), 7.83 (d, J )
9 Hz, 2 H), 7.95 (d, J ) 9 Hz, 2 H); MS (Electrospray, m/ z) 797
(M + Na+, 100). Anal. Calcd for C42H46O10S2: C, 65.10; H, 5.98.
Found: C, 65.48; H, 6.02.
3e (R ) 7-OMe): white solid; mp 81-82 °C; 1H-NMR (CDCl3)
δ 0.50 (s, 6 H), 0.68 (s, 6 H), 1.25-1.44 (m, 4 H), 1.73-1.82 (m,
2 H), 1.78 (d, J ) 18.5 Hz, 2 H), 1.84-1.97 (m, 4 H), 2.18-2.26
(m, 2 H), 2.26 (d, J ) 15 Hz, 2 H), 3.24 (d, J ) 15 Hz, 2 H), 3.52
(s, 6 H), 6.55 (d, J ) 1.5 Hz, 2 H), 7.14 (dd, J ) 9, 1.5 Hz, 2 H),
7.64 (d, J ) 9 Hz, 2 H), 7.83 (d, J ) 9 Hz, 2 H), 7.96 (d, J ) 9
Hz, 2 H); MS (Electrospray, m/ z) 797 (M + Na+, 100). Anal.
Calcd for C42H46O10S2: C, 65.10; H, 5.98. Found: C, 65.54; H,
6.38.
Hyd r olysis of Bis((1S)-ca m p h or -10-su lfon a tes). To a
suspension of the sulfonate 2 or 3 (1 mmol) in methanol (20 mL)
was added an aqueous solution of sodium hydroxide (1.1 M, 15
mL). The resulting mixture was warmed to 60 °C until tlc
indicated completion of hydrolysis (≈20 h). After the solution
was cooled to room temperature, it was acidifed with a diluted
HCl solution, and excess methanol evaporated in vacuo. The
residue was taken up in dichloromethane and washed with a
saturated NaCl solution, dried (Na2SO4), filtered, and evaporated
Gen er a l. All reactions were conducted under a nitrogen
atmosphere. Melting points were taken on a hot-plate micro-
scope apparatus and were uncorrected. 1H-NMR spectra were
acquired on a 500 MHz NMR spectrometer. (1S)-Camphor-10-
sulfonyl chloride was purchased from Aldrich Chemical Co. and
used without further purification. Mass spectra were obtained
by liquid secondary ion mass spectrometry (L-SIMS) technique
using 3-nitrobenzyl alcohol as matrix.
P r ep a r a tion of Bis((1S)-ca m p h or -10-su lfon a tes) 2 a n d
3. To a solution of the 1,1′-bi-2-naphthol (2 mmol) in dry
dichloromethane (15 mL) was added dry triethylamine (5 mmol)
at 0 °C followed by (1S)-camphor-10-sulfonyl chloride (4.5 mmol).
The mixture was stirred at 0 °C until thin layer chromatography
indicated completion of the reaction (≈3 h). Water was added,
and the reaction mixture was extracted with dichloromethane.
The combined extracts were washed with saturated NaCl
solution, dried (Na2SO4), filtered, evaporated in vacuo, and
chromatographed on silica gel with an ethyl acetate-toluene
mixture as the eluent to give the diastereomeric bis(sulfonates
2 and 3.
2a (R ) H): white solid; mp 148-149 °C; 1H-NMR (CDCl3) δ
0.53 (s, 6 H), 0.77 (s, 6 H), 1.25-1.37 (m, 4 H), 1.78 (d, J ) 18.5
Hz, 2 H), 1.81-1.87 (m, 2 H), 1.93-2.05 (m, 4 H), 2.17-2.24
(m, 2 H), 2.43 (d, J ) 14.5 Hz, 2 H), 2.87 (d, J ) 14.5 Hz, 2 H),
7.29 (d, J ) 8.5 Hz, 2 H), 7.37 (t, J ) 8 Hz, 2 H), 7.51 (t, J ) 7.5
Hz, 2 H), 7.77 (d, J ) 9 Hz), 7.95 (d, J ) 8.5 Hz, 2 H), 8.05 (d,
J ) 9 Hz, 2 H); MS (L-SIMS, m/ z) 715 (M + H+, 35, C40H43O8S2
requires 715). Anal. Calcd for C40H42O8S2: C, 67.21; H, 5.92.
Found: C, 67.41; H, 6.27.
3a (R ) H): white solid; mp 195-196 °C; 1H-NMR (CDCl3) δ
0.46 (s, 6 H), 0.60 (s, 6 H), 1.20-1.35 (m, 4 H), 1.69-1.84 (m, 4
H), 1.76 (d, J ) 18.5 Hz, 2 H), 1.86-1.92 (m, 2 H), 2.17-2.24
(m, 2 H), 2.29 (d, J ) 15 Hz, 2 H), 3.25 (d, J ) 15 Hz, 2 H), 7.24
(d, J ) 8 Hz, 2 H), 7.34 (t, J ) 8 Hz, 2 H), 7.49 (t, J ) 8 Hz, 2
H), 7.80 (d, J ) 9.5 Hz), 7.95 (d, J ) 8.5 Hz, 2 H), 8.05 (d, J )
9 Hz, 2 H); MS (L-SIMS, m/ z) 715 (M + H+, 70, C40H43O8S2
requires 715). Anal. Calcd for C40H42O8S2: C, 67.21; H, 5.92.
Found: C, 67.43; H, 6.16.
in vacuo to give the optically pure binaphthol 1 as a solid.
25
(S)-1,1′-Bi-2-n a p h th ol [(S)-1a ]: 50% yield from 2a ; RD
)
-29.6 (c ) 0.24, THF) [lit.11 RD ) -35.2 (c ) 1.0, THF)]; mp
25
205-207 °C (lit.11 206-207 °C). (R)-1,1′-Bi-2-n a p h th ol [(R)-
25
1a ]: 57% yield from 3a ; RD ) +30.2 (c ) 0.12, THF); mp 205-
208 °C (lit.11 206-207 °C).
(S)-3,3′-Dibr om o-1,1′-bi-2-n a p h th ol [(S)-1b]: 63% yield
25
1
from 2b; RD ) -40.0 (c ) 0.15, CHCl3); mp 242-244 °C; H-
NMR (CDCl3) δ 5.56 (br s, 2 H), 7.10 (d, J ) 8.4 Hz, 2 H), 7.31
(t, J ) 8 Hz, 2 H), 7.39 (t, J ) 8 Hz, 2 H), 7.82 (d, J ) 7.7 Hz,
2 H), 8.26 (s, 2 H); HRMS calcd for C20H1279Br81BrO2 443.9185,
found 443.9187. (R)-3,3′-Dibr om o-1,1′-bi-2-n a p h th ol [(R)-
2b (R ) 3-Br ): white solid; mp 177-178 °C; 1H-NMR (CDCl3)
δ 0.71 (s, 6 H), 0.92 (s, 6 H), 1.20-1.30 (m, 4 H), 1.80 (d, J ) 18
Hz, 2 H), 1.86-1.92 (m, 2 H), 1.95-2.07 (m, 4 H), 2.20-2.29
(m, 2 H), 2.68 (d, J ) 15 Hz, 2 H), 2.92 (d, J ) 15 Hz, 2 H), 7.23
(d, J ) 8.5 Hz, 2 H), 7.38 (t, J ) 8 Hz, 2 H), 7.54 (t, J ) 7.5 Hz,
25
1b]: 67% from 3b; RD ) +43.0 (c ) 0.22, CHCl3); mp 243-244
°C; MS (L-SIMS, m/ z) 443.9 (M+, 10, C20H1279Br81BrO2 requires
444).
(S)-6,6′-Dim eth oxy-1,1′-bi-2-n a p h th ol [(S)-1d ]: 42% yield
from 2d ; RD ) +25.8 (c ) 0.10); mp 177-179 °C; 1H-NMR
25
(CDCl3) δ 3.91 (s, 6 Η), 5.30 (br s, 2 H), 6.98 (dd, J ) 9.2, 2.4
Hz, 2 H), 7.06 (d, J ) 9.2 Hz, 2 H), 7.22 (d, J ) 2.4 Hz, 2 H),
7.35 (d, J ) 8.9 Hz, 2 H), 7.86 (dd, J ) 8.9 Hz, 2 H); HRMS
(9) Mason, S. F.; Seal, R. H.; Roberts, D. R. Tetrahedron 1974, 30,
1671.
(10) Harada, N.; Nakanishi, K. Circular Dichroic Spectroscopy,
Exciton Coupling in Organic Stereochemistry; University Science
Books: Mill Valley, CA, 1983: pp 193-201.
(11) Gong, B.-q.; Chen, W.-y.; Hu, B.-f. J . Org. Chem. 1991, 56, 423.