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Q.-H. Fan et al. / Tetrahedron: Asymmetry 12 (2001) 1559–1565
matography on silica gel (hexane:ethyl acetate=4:1) to
give (R)-9 as a colorless oil (0.54 g, 92%). [h]2D0=−128.0
(c 1, CHCl3); IR (KBr): 1619, 1292, 1052 cm−1; 1H
NMR (CDCl3): l 7.92–7.17 (m, 20H, Ar-H), 4.90 (m,
4H, BINOL-CH2), 4.73 (s, 4H, Ph-CH2), 4.58–4.45 (dd,
4H, -OCH2O-), 2.77 (s, 6H, -OCH3); MS(EI): m/z (%):
615 (0.3) [M+1]+, 614 (0.6) [M]+, 462 (13.8), 432 (10.8),
400 (14.7), 340 (100), 311 (23.8), 310 (24.4), 309 (13.9),
283 (16.6), 282 (24.9), 281 (23.7), 254 (12.7), 253 (23.7),
252 (14.9), 91 (99.9), 77 (13.4), 45 (57.7), 32 (31.7).
Anal. calcd for C40H38O6: C, 78.15; H, 6.23. Found: C,
78.31; H, 6.05%.
pressure the residue was further purified by column
chromatography on silica gel (hexane:ethyl acetate=
4:1) to give (R)-10 (0.36 g, yield 83%) as a white crystal.
mp: 128–129°C; [h]D20=+36.0 (c 1,CHCl3); IR (KBr):
1
3426 (-OH), 1619, 1292, 1052 cm−1; H NMR (CDCl3):
l 7.92–7.17 (m, 20H, Ar-H), 6.68 (s, 2H, -OH), 5.02–
4.92 (m, 4H, BINOL-CH2), 4.74 (s, 4H, Ph-CH2);
MALDI-TOF-MS: m/z: 549.09 [M+Na]+, 564.12 [M+
K]+, 526.21 [M]+. Anal. calcd for C36H30O4·0.5 H2O: C,
80.73; H, 5.65. Found: C, 80.93; H, 5.78%.
Compound (R)-2a: Prepared according to the above
general procedure, the resulting residue was purified by
column chromatography on silica gel (hexane:
CH2Cl2=1:2) to give (R)-2a as a white foam. Yield:
79%; mp: 39–40°C; [h]2D0=+18 (c 1,CHCl3); IR (KBr):
Compound (R)-8a: Prepared according to the above
general procedure, the resulting residue was purified by
column chromatography on silica gel (hexane:
CH2Cl2=1:2) to give (R)-8a as a white foam. Yield:
80%; mp: 38–39°C; [h]2D0=−64.0 (c 1, CHCl3); IR
1
3442 (-OH), 1590, 1445, 1148, 1053 cm−1; H NMR
(CDCl3): l 7.87–6.49 (m, 38H, Ar-H, -OH), 4.99 (s, 8H,
Ph-CH2), 4.93–4.83 (m, 4H, BINOL-CH2), 4.61 (s, 4H,
Ph-CH2); MALDI-TOF-MS: m/z: 973.26 [M+Na]+,
989.24 [M+K]+, 950.38 [M]+. Anal. calcd for C64H54O8:
C, 80.82; H, 5.72. Found: C, 80.84; H, 5.37%.
1
(KBr): 1590, 1445, 1148, 1053 cm−1; H NMR (CDCl3):
l 8.18–6.65 (m, 36H, Ar-H), 5.11 (s, 8H, Ph-CH2),
4.99–4.94 (m, 4H, BINOL-CH2), 4.74 (s, 4H, Ph-CH2),
4.66–4.51 (dd, 4H, -OCH2O-), 2.83 (s, 6H, -OCH3);
MALDI-TOF-MS: m/z: 1061.49 [M+Na]+, 1077.46
[M+K]+. Anal. calcd for C68H62O10: C, 78.59; H, 6.01.
Found: C, 78.33; H, 6.00%.
Compound (R)-2b: Prepared according to the above
general procedure, the resulting residue was purified by
column chromatography on silica gel (hexane:
CH2Cl2=1:3) to give (R)-2b as a white foam. Yield:
73%; mp: 63–65°C; [h]D20=+6.0 (c 1, CHCl3); IR (KBr):
3441 (-OH), 1590, 1452, 1155, 1053 cm−1; 1H NMR
(CDCl3): l 7.79–6.46 (m, 70H, Ar-H, -OH), 4.95–4.53
(m, 32H, Ph-CH2, BINOL-CH2); MALDI-TOF-MS:
m/z: 1821.33 [M+Na]+, 1837.30 [M+K]+, 1798.72 [M]+.
Anal. calcd for C120H102O16: C, 80.07; H, 5.71. Found:
C, 79.76; H, 5.89%.
Compound (R)-8b: Prepared according to the above
general procedure, the resulting residue was purified by
column chromatography on silica gel (hexane:
CH2Cl2=1:3) to give (R)-8b as a white foam. Yield:
74%; mp: 52–54°C; [h]D20=−36.0 (c 1,CHCl3); IR (KBr):
1590, 1452, 1155, 1053 cm−1; 1H NMR (CDCl3): l
8.13–6.57 (m, 68H, Ar-H), 5.04 (s, 16H, Ph-CH2), 5.00
(s, 8H, Ph-CH2), 4.9–4.90 (m, 4H, BINOL-CH2), 4.68
(s, 4H, Ph-CH2), 4.60–4.45 (dd, 4H, -OCH2O-), 2.79 (s,
6H, -OCH3); MALDI-TOF-MS: m/z: 1909.79 [M+Na]+,
1925.74 [M+K]+. Anal. calcd for C124H110O18: C, 78.88;
H, 5.87. Found: C, 79.04; H, 6.00%.
Compound (R)-2c: Prepared according to the above
general procedure, the resulting residue was purified by
column chromatography on silica gel (hexane:
CH2Cl2=1:4) to give (R)-2c as a white foam. Yield:
72%; mp: 58–60°C; [h]2D0=+3.3 (c 4.8,CHCl3); IR
Compound (R)-8c: Prepared according to the above
general procedure, the resulting residue was purified by
column chromatography on silica gel (hexane:
CH2Cl2=1:4) to give (R)-8c as a white foam. Yield:
72%; mp: 54–56°C; [h]2D0=−16.0 (c 1, CHCl3); IR
1
(KBr): 3434 (-OH), 1598, 1452, 1148, 1046 cm−1; H
NMR (CDCl3): l 7.85–6.54 (m, 134H, Ar-H, -OH),
5.08–4.17 (m, 64H, BINOL-CH2, Ph-CH2); MALDI-
TOF-MS: m/z: 3517.77 [M+Na]+, 3533.73 [M+K]+,
3495.39 [M]+. Anal. calcd for C232H198O32: C, 79.66; H,
5.71. Found: C, 79.79; H, 6.04%.
1
(KBr): 1598, 1452, 1148, 1046 cm−−; H NMR (CDCl3):
l 8.17–6.51 (m, 132H, Ar-H), 5.03–4.79 (m, 64H,
BINOL-CH2, Ph-CH2), 4.50–4.48 (dd, 4H, -OCH2O-),
2.79 (s, 6H, -OCH3); LALDI-TOF-MS: m/z: 3517.77
[(M−2MOM)+Na]+. Anal. calcd for C236H206O34: C,
79.04; H, 5.79. Found: C, 78.96; H, 5.83%.
3.5. General procedure for asymmetric addition of
diethylzinc to benzaldehyde
Under nitrogen, Ti(O-iso-Pr)4 (34 mL, 0.10 mmol) was
added to a solution of (R)-10 (13.2 mg, 0.025 mmol) in
toluene (1 mL) at room temperature and the mixture
was stirred at ambient temperature for 10 min followed
by the addition of diethylzinc (1.0 M, 0.375 mL) in
hexane with continued stirring for 10 min. Benzalde-
hyde (13 mL, 0.125 mmol) was added via syringe at 0°C
and the mixture was allowed to stir at 0°C for a given
time. The reaction was quenched with aqueous hydro-
chloric acid solution (1.0N, 2.0 mL), the mixture was
then filtered through a short pad of Celite to remove
the insoluble material and the filtrate was extracted
with ethyl acetate (2×1.0 mL). The combined organic
3.4. General procedure for the synthesis of dendritic
BINOL ligands (R)-10 and (R)-2a-(R)-2c
Typical procedure: To a stirred solution of (R)-9 (0.5 g,
0.81 mmol) in 1:1 ethanol/CH2Cl2 (10 mL/10 mL) was
added a catalytic amount of TsOH (monohydrate) at
40°C. The solution was stirred overnight. After evapo-
ration of most of the solvent, the residue was diluted
with ethyl acetate, washed with water and the aqueous
layer was extracted with ethyl acetate. The combined
organic layer was washed with brine and dried over
Na2SO4. After removing the solvent under reduced