Enantioenriched (S)-6,6′-diphenylBinol-Ca: A novel and efficient chirally modified metal complex for asymmetric epoxidation of α,β-unsaturated enones

Article abstract of DOI:10.1016/j.tetasy.2003.08.022

A novel enantioenriched-Ca complex was generated using low cost commercially available CaCl₂ and the potassium salt of (S)-6,6′-diphenylBINOL and its application to α,β-unsaturated enone epoxidation is described. Furthermore the absolute stereo

Full text of DOI:10.1016/j.tetasy.2003.08.022

TETRAHEDRON:
ASYMMETRY
Pergamon
Tetrahedron: Asymmetry 14 (2003) 3797–3803
Enantioenriched (S)-6,6%-diphenylBinol-Ca: a novel and efficient
chirally modified metal complex for asymmetric epoxidation of
a,b-unsaturated enones
G. Kumaraswamy,a,* M. N. V. Sastry,a Nivedita Jena,a K. Ravi Kumarb and M. Vairamanic
aSpeciality Gas based Chemicals and Processes, Indian Institute of Chemical Technology, Hyderabad 500 007, India
bLaboratory of X-ray Crystallography, Indian Institute of Chemical Technology, Hyderabad 500 007, India
cNational Center for Mass Spectrometry, Indian Institute of Chemical Technology, Hyderabad 500 007, India
Received 6 August 2003; accepted 21 August 2003
Abstract—A novel enantioenriched-Ca complex was generated using low cost commercially available CaCl2 and the potassium salt
of (S)-6,6%-diphenylBINOL and its application to a,b-unsaturated enone epoxidation is described. Furthermore the absolute
stereochemistry of (S)-6,6%-diphenylBINOL has been corrected and unequivocally established by single crystal X-ray analysis, 500
MHz NMR spectroscopy and mass spectra. The enantiomeric excess (ee) was determined by 1H NMR spectroscopy of its
corresponding MTPA ester and was found to be >98%.
© 2003 Elsevier Ltd. All rights reserved.
1. Introduction
Michael reaction.9 Further, we envisioned examining
the BINOL-Ca complex for the asymmetric epoxida-
tion of a,b-unsaturated ketones. Herein, we report our
results on the asymmetric epoxidation of substituted
chalcones using the 6,6%-diphenylBINOL–Ca complex
and alkylhydroperoxides. Initially we chose chalcone 5a
as the substrate and BINOL-Ca (S)-2a (10 mol%)
complex. The complexes (S)-2a–g were generated from
potassium salt of the corresponding alcohols (S)-1a–g
and CaCl2 in absolute ethanol as shown in Scheme 1.
Asymmetric epoxidation of a,b-unsaturated enones is a
powerful strategy for the synthesis of enantiomerically
enriched organic compounds.1 Early studies by Wyn-
berg revealed that catalytic amount of cinchona alka-
loids of quaternary ammonium salts could effect the
epoxidation of a,b-unsaturated ketones with moderate
enantioselectivity.2 Following this report, a variety of
methods have been developed3 for this reaction includ-
ing the use of biphasic system using hydrogen peroxide
in the presence of polyaminoacids.4 Impressive practical
methods developed recently for this transformation
include (a) stoichiometric diethylzinc-N-methylpseudo-
ephedrine using molecular oxygen;5 (b) chirally
modified magnesium–diethyltartrate with tert-butylhy-
droperoxide;6 (c) lanthanoid-BINOL derivatives using
tert-butylhydroperoxide or cumene hydroperoxide7 and
triphenylphosphine oxide as synergistic additive.8
The epoxidation reaction was carried out in toluene at
−10°C using tert-butylhydroperoxide in the presence of
,
activated MS 4 A. The product 6a was obtained in 88%
yield with moderate enantioselectivity (55%) after 48 h
(Scheme 2).
Introduction of substituents on the BINOL (i.e. 3-posi-
tion and 6,6%-position) has been shown to have pro-
found effects not only on the activity but also on the
enantioselectivities of the product 6a.10 En route to the
synthesis of substituted BINOL ligands, we have ini-
tiated the synthesis of (S)-6,6%-diphenylBINOL (S)-1d
following the Qian et al., procedure.11 We were able to
produce the ligand in good yield, the absolute configu-
ration of 4 {[h]D25=+100 (c 1, CHCl3); lit.11 −89.6 (c
0.67, CHCl3)} and the specific rotation of (S)-1d
2. Results and discussion
Recently, we described the first Lewis acid-Bronsted
base BINOL-Ca complex for the promotion of the
* Corresponding author. Tel.: +91-40-27193275; fax: +91-40-
27160921; e-mail: gkswamy@iict.ap.nic.in
0957-4166/$ - see front matter © 2003 Elsevier Ltd. All rights reserved.
doi:10.1016/j.tetasy.2003.08.022

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G. Kumaraswamy et al. / Tetrahedron: Asymmetry 14 (2003) 3797–3803
Scheme 1.
resolve the crystal structure of this compound. The dihe-
dral angle between the naphthalene rings (C8–C12 and
C15–C23) is 84.4°, which is larger than that of BINOL
(82°). The enantiomeric purity of (S)-1d was deter-
1
mined by H NMR spectroscopy of its corresponding
MTPA monoester and was found to be >98%.
Scheme 2.
In an effort to increase the enantioselectivity of the
product 6a, a range of substituted BINOL catalyst
(S)-2b–e and C2-symmetric ligands (R,R)-2f–g were
screened. As expected, a remarkable improvement in
enantioselectivity was observed with (S)-2d (70% ee,
85% yield) over (S)-2a (55% ee, 88% yield).10 The
increase in enantioselectivity by (S)-2d catalyst is not
only due to the electronic effect of 6,6%-arylsubstitution
as predicted by de Vries et al.,10 but also due to the
increase in bond angle between two naphthyl rings,
which may provide favorable coordination environment
at metal-ligand site. The catalysts (S)-2b and (S)-2e
possessing strong coordinating groups at the reaction
site showed substantial decreases in enantioselectivity
{(S)-2b; 10% ee, 70% yield and (S)-2e; 5% ee, 89%
yield}. This is in sharp contrast to the lanthanoid based
catalyst wherein hydroxymethyl group substituted at
3-position of BINOL strongly influenced the enantiose-
lectivity of the product 6a.7a 6,6%-Bromosubstituted cat-
alyst (S)-2c also gave the product with low
stereoselectivity (40% ee, 60% yield). C2-Symmetric cat-
{[h]2D5=+215 (c 1, CHCl3); lit.11 −19.5 (c 1.3, CHCl3)}
did not match with those reported in the literature.
Surprisingly,
[1,2-bis(diphenylphosphino)ethane]di-
chloronickel(II) (dppe)NiCl2 as a catalyst exhibits
remarkable activity for the transformation of 3 to
4
over
bis[triphenylphosphino]dichloronickel(II)
Ni[P(C6H5)3]2Cl2. The above transformation using 5
mol% of Ni[P(C6H5)3]2Cl2 as catalyst needs the reaction
to be refluxed for 22 h in ether whereas, with 5 mol% of
(dppe)NiCl2 as catalyst the reaction proceeded at ambi-
ent temperature in only 2 h (Scheme 3). Our experi-
ments on arylation with (dppe)NiCl2 or Ni[P-
(C6H5)3]2Cl2 as catalyst resulted in the product 4 with
identical absolute configuration which was contrary to
the original report.11,12 Furthermore, single crystal X-
ray analysis, 500 MHz NMR and mass spectral data
have unequivocally established the structure of the
product as (S)-1d (Fig. 1). This is the first attempt to
Scheme 3.

G. Kumaraswamy et al. / Tetrahedron: Asymmetry 14 (2003) 3797–3803
3799
DME showed deleterious effects on the enantioselec-
tivity of the product. The best choice of solvent
appeared to be toluene:cyclohexane (1:9) mixture. The
optimum temperature range was found to be −5 to
−10°C. In line with previous reports,7a activated MS 4
,
A (260–280°C/10 mmHg, 3 h) is essential for the ini-
tiation of the reaction. Although satisfactory yields
were obtained with as less as 5 mol% of catalyst (5
mol% of (S)-2d; 60% ee), good levels of enantiomeric
excess was achieved with 10 mol% catalyst.13 The cat-
alyst prepared from (S)-1d and various CaX2 (X=
OTf, F, Br) were also evaluated for 5a to 6a and
found to be inferior to CaCl2.14 No significant change
in enantioselectivity of the product 6a was observed
on varying the CaCl2 ratio to ligand (S)-1d (1:1 mol
equivalent CaCl2: (S)-1d=68% ee, 80% yield; 2:1 mol
equivalent CaCl2: (S)-1d=66% ee, 78% yield). On the
other hand, variation in ligand to CaCl2 showed
detrimental effect on enantioselectivity of product 6a
(2:1 mol equivalent of (S)-1d: CaCl2=10% ee, 70%
yield). We then sought to explore the generality of
the process using 10 mol% of complex (S)-2d to a
range of enone substrates (Table 1).
The results obtained show that, the catalyst tolerates
a variety of substituents on the phenyl group. Simple
enone substrates like chalcone (entry 1), phenyl group
bearing substituents like chloro and methyl lead to
moderate to good ees with good product yield
(entries 2 and 3). Strong coordinating groups substi-
tuted at 2-position of phenacyl gave very high yield
of the product but drastically decreased the enantiose-
lectivity (entries 7 and 8). 2-Naphthylketo enone also
epoxidized under standard condition with moderate
enantioselectivity (entry 4).
Figure 1. X-Ray crystal structure of S-6,6%-diphenyl-1,1%-bi-
2-naphthol. A suitable crystal of X-ray crystallography was
grown on slow evaporation of a mixture of hexane and
dichloromethane solvent. The crystal structure showed a
molecule of dichloromethane. Crystal data: C36H30O4.
CH2Cl2, M=523.00, orthorhombic, a=8.841(1), b=
10.051(1), c=29.202(2) A°, U=2594.7(4), T=173 K, space
group P212121 (no. 19), Z=4, v(Mo-Ka)=0.28 mm−1
,
16453 reflections measured, 6022 unique (Rint=0.0181), WR
(F2)=0.1659, S=1.043, R1=0.0558 for 5425, Fo>4|(Fo),
0.0612 for all 6.022 data. Crystal and atomic data may be
obtained free of charge from The Director CCDC, 12
Union Road, Cambridge CB2 1EZ, UK, on quoting the
deposition number CCDC 209446, the names of the authors
and the journal citation (fax: +44-1223-336-033; e-mail:
deposit@ccdc.cam.ac.uk; web site: http://www.ccdc.cam.
ac.uk). Method used for absolute configuration: Flack HD,
Acta cryst. 1983, 39, 876–881.
The precise nature of the catalyst structure of (S)-2d
is presently not known, however, we believe that the
oligomeric structure of (S)-2d appears to be responsi-
ble for the observed enantioselectivity as predicted by
Shibasaki et al.7a The catalyst prepared from 1 equiv.
of each (S)-1d and CaCl2 gave MALDI-TOF spec-
trum that exhibits a major peak at m/z 1429 and
minor peak at m/z 1906, indicating the possible exis-
tence of trimeric (A) and tetrameric oligomers. Acti-
vation by hydroperoxide can generate monomeric-Ca
hydroperoxide (B) from oligomers. These chirally
modified Ca-hydroperoxide in turn controls the orien-
tation of the enone which when followed by oxygen
transfer (C) leads to the observed enantioselectivity of
the product as shown in Scheme 4.
alysts (R,R)-2f and (R,R)-2g gave excellent yields of
product 6a but almost negligible ees (6% ee, 88%
yield, and 2% ee, 95% yield, respectively). Addition of
additives such as triphenylphosphine oxide lowered
the enantioselectivity of product 6a (20% ee). In
marked contrast to our previous report,9 ethanol as
additive has a detrimental effect on the epoxidation
of 6a (45% ee, 40% yield). Water as additive gave
racemic product with 95% yield.
3. Conclusion
In conclusion, we have developed a simple and practi-
cal method for the enantioselective epoxidation of
a,b-unsaturated ketones using low cost commercially
available eco-friendly CaCl2 as the metal source. To
the best of our knowledge, it is for the first time that
chirally modified Ca has been used for epoxidation.15
Next, we investigated the effect of solvents and found
that the coordinating solvents such as THF, DMF,

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G. Kumaraswamy et al. / Tetrahedron: Asymmetry 14 (2003) 3797–3803
Table 1. Enantioenriched (S)-6,6%-diphenylBINOL-Ca catalyzed epoxidation of a,b-unsaturated enonesa
Entry
Ar1
Ar2
Productb
Temp. (°C)
Time (h)
%eec
Config.d
% Yielde
1
2
3
4
5
6
7
8
Ph
Ph
Ph
Ph
6a
6b
6c
6d
6e
6f
6g
6h
6i
−10
−15
−10
0
5
0
0
0
0
−15
48
48
48
58
48
48
48
48
52
48
70
74
80
73
62
74
26
22
25
32
(2R,3S)
(2R,3S)
(2R,3S)
(2R,3S)
(2R,3S)
85
91
78
72
68
82
60
70
76
82
p-ClPh
p-MePh
Ph
Ph
m-PhO-Ph
Ph
2-Naphthyl
p-MePh
Ph
o-NH2Ph
o-MeO-Ph
Ph
Ph
(2R,3S)
(2R,3S)
9
10
1-Naphthyl
Ph
p-BrPh
6j
a
,
Unless otherwise stated, all reactions were conducted using 2.5 mmol substrate, 3.75 mmol of TBHP (3.2 M in toluene), MS 4 A powder (750
mg, activated at 260–280°C/10 mmHg, 3 h).
b Characterized by NMR, mass.
c The ee was determined by HPLC using Chiralpak AD-H column.
d The sign of optical rotation of products10 determined the absolute configurations.
e Isolated yields.
1
reagents. H and 13C NMR spectra were recorded on a
Varian 200, 500 spectrometer. Chemical shifts (a) are
given in ppm and are referenced to residual solvent
peaks. Mass spectra and accurate mass measurement
were carried out with a VG MICROMASS instrument.
Elemental analyses were performed on an Elementar
Vario EL spectrometer. Optical rotations were recorded
on a Perkin–Elmer 341 polarimeter in a 10 cm cell.
Melting points were measured on a BUCHI Melting
Point machine. HPLC analyses were performed using a
SHIMADZU LC-10AT VP Model SPD-10AVP 486
UV detector. THF and Ether were freshly distilled from
sodium/benzophenone ketyl, while toluene, heptane
were distilled from CaH2. All other chemicals were used
as received.
4.1. A typical procedure for the asymmetric epoxida-
tion of enone, 6a
A mixture of (S)-6,6-diphenylBINOL (98.5 mg, 0.224
mmol), pot.t-butoxide (50.4 mg, 0.449 mmol) in abso-
lute ethanol (6 ml) was stirred under argon for 0.5 h.
The ethanol was evaporated under reduced pressure
and to the residue, solid CaCl2 (99%) (24.9 mg, 0.224
mmol) was added. Then the combined components
were dried under vacuum (10 mmHg, 15 min) followed
by the addition of absolute ethanol (6 ml) to give a
white suspension. After being stirred for 3 h at ambient
temperature, ethanol was evaporated under reduced
pressure to give a white solid powder. To this solid
complex, cyclohexane (10 ml) and toluene (1 ml) were
added sequentially and allowed to stir for 3 h. Then MS
Scheme 4.
4. Experimental
,
4 A powder (750 mg, activated at 260–280°C/10
All reactions were carried out under an inert atmo-
sphere of dry nitrogen and were followed by TLC.
Glassware was flame dried before use. Standard syringe
techniques were applied to transfer dry solvents and
mmHg, 3 h) was added, the reaction mixture was
cooled to −10°C followed by the addition of TBHP
(1.12 ml, 3.75 mmol, 3.3 M solution in toluene). After
15 min, a toluene solution of chalcone 5a (520 mg, 2.5

G. Kumaraswamy et al. / Tetrahedron: Asymmetry 14 (2003) 3797–3803
3801
mmol) 1 ml was added and the reaction mixture was
maintained at −10°C for 48 h. The reaction mixture was
quenched with saturated NH4Cl solution (15 ml) and
extracted with ethylacetate (3×20 ml). The combined
organic layers were dried over anhydrous Na2SO4 and
evaporated under reduced pressure. The residue was
purified by column chromatography (SiO2, hexane/acet-
one, 25/2) to give epoxy ketone 6a (476 mg), as a solid
(85%).
excess was determined by HPLC analysis, using
DAICEL Chiralpak AD-H column, (hexane/2-
propanol, 95:5); tr=18.40 min (2R,3S minor), tr=19.23
min (2S,3R major); [h]2D5=−141 (c 1, CH2Cl2); 1H
NMR (CDCl3, 200 MHz): l 2.41 (s, 3H), 4.05 (d, 1H,
J=1.8 Hz), 4.20 (d, 1H, J=1.8 Hz), 7.2–7.24 (d, 2H,
J=8.2 Hz), 7.30–7.38 (m, 5H), 7.82–7.92 (m, 2H);
EIMS 238 (M+).
4.7. trans-2,3-Epoxy-3-(3-phenoxyphenyl)-1-phenyl-
propan-1-one, 6f
4.2. trans-(2R,3S)-Epoxy-1,3-diphenylpropan-1-one, 6a
Mp=89–91°C; Enantiomeric excess was determined by
HPLC analysis, using DAICEL Chiralpak AD-H
column, (hexane/2-propanol, 97:3); tr=17.98 min,
(2R,3S minor), tr=18.73 min, (2S,3R major); [h]2D5=
−188 (c 1, CHCl3); 1H NMR (CDCl3, 200 MHz): l 4.09
(d, 1H, J=1.96 Hz), 4.18 (d, 1H, J=1.96 Hz), 7.22–
7.52 (m, 7H), 7.58–7.65 (m,1H), 8.01–8.03 (m, 2H);
EIMS 224 (M+).
Yield: 82% (647.8 mg); enantiomeric excess was deter-
mined by HPLC analysis, using DAICEL Chiralpak
AD-H column, (hexane/2-propanol, 95:5); tr=17.95
min (2R,3S major), tr=21.15 min (2S,3R minor); mp=
1
74–76°C; [h]D25=−133 (c 1, CH2Cl2); H NMR (CDCl3,
200 MHz): l 4.02 (d, 1H, J=1.92 Hz), 4.16 (d, 1H,
J=1.92 Hz), 6.92–7.18 (m, 6H), 7.27–7.62 (m, 6H),
7.95–8.05 (d, 2H, J=8.00 Hz); EIMS 298 (M+).
4.3. trans-(2R,3S)-Epoxy-3-(4-chlorophenyl)-1-phenyl-
propan-1-one, 6b
4.8. trans-2,3-Epoxy-3-phenyl-1-(2-aminophenyl)-
propan-1-one, 6g
Yield: 91% (588 mg); mp=68–70°C; enantiomeric
excess was determined by HPLC analysis, using
DAICEL Chiralpak AD-H column, (hexane/2-
propanol, 97:3); tr=18.67 min, (2R,3S minor), tr=
Yield: 60% (358.5 mg); mp=124–126°C; enantiomeric
excess was determined by HPLC analysis, using
DAICEL Chiralpak AD-H column, (hexane/2-
propanol, 95:5); tr=17.45 min (minor), tr=18.45 min
1
1
20.48 min (2S,3R major); [h]2D5=−172 (c 1, CHCl3); H
(major); [h]2D5=−162 (c 1, CHCl3); H NMR (CDCl3,
NMR (CDCl3, 200 MHz): l 4.06 (d, 1H, J=1.8 Hz),
4.19 (d, 1H, J=1.8 Hz), 7.25–7.68 (m, 7H), 7.97–8.08
(m, 2H); EIMS 258 (M+).
200 MHz): l 4.02 (d, 1H, J=2.00 Hz), 4.21 (d, 1H,
J=2.00 Hz), 6.30 (bs, 2H), 6.57–6.72 (m, 2H), 7.22–
7.40 (m, 6H), 7.69–7.75 (d, 1H, J=8.00 Hz); EIMS 239
(M+).
4.4. trans-(2R,3S)-Epoxy-3-(4-methylphenyl)-1-phenyl-
propan-1-one, 6c
4.9. trans-(2R,3S)-Epoxy-3-phenyl-1-(2-methoxyphenyl)-
propan-1-one, 6h
Yield: 78% (464.1 mg); mp=89–91°C; enantiomeric
excess was determined by HPLC analysis, using
DAICEL Chiralpak AD-H column, (hexane/2-
propanol, 95:5); tr=17.48 min (2R,3S minor), tr=18.11
Yield: 70% (444.5 mg); mp=122–124°C; enantiomeric
excess was determined by HPLC analysis, using
DAICEL Chiralpak AD-H column, (hexane/2-
propanol, 95:5); tr=17.89 min (2R,3S minor), tr=18.52
1
min (2S,3R major); [h]2D5=−190 (c 1, CHCl3); H NMR
1
(CDCl3, 200 MHz): l 2.39 (s, 3H), 4.01 (d, 1H, J=1.85
Hz), 4.19 (d, 1H, J=1.85 Hz), 7.16–7.29 (m, 4H),
7.42–7.51 (m, 2H), 7.56–7.62 (m, 1H), 8.01–8.03 (m,
2H); EIMS 238 (M+).
min (2S,3R major); [h]2D5=−30 (c 1, CH2Cl2); H NMR
(CDCl3, 200 MHz): l 3.6 (s, 3H), 3.98 (d, 1H, J=1.82
Hz), 4.22 (d, 1H, J=1.82 Hz), 6.89–7.90 (m, 9H);
EIMS 254 (M+).
4.5. trans-(2R,3S)-Epoxy-3-phenyl-1-(2-naphthyl)-
propan-1-one, 6d
4.10. trans-(2R,3S)-Epoxy-3-(1-naphthyl)-1-phenyl-
propan-1-one, 6i
Yield: 72% (493.2 mg); mp=110–112°C; enantiomeric
excess was determined by HPLC analysis, using
DAICEL Chiralpak AD-H column, (hexane/2-
propanol, 97:3); tr=22.69 min (2R,3S major), tr=24.12
min (2S,3R minor); [h]2D5=−100 (c 1, CH2Cl2); 1H
NMR (CDCl3, 200 MHz): l 4.15 (d, 1H, J=2.0 Hz),
4.36 (d, 1H, J=2.0 Hz), 7.32–7.65 (m, 6H), 7.81–7.96
(m, 4H), 8.01–8.12 (d, 1H, J=8.10 Hz), 8.58 (s, 1H);
EIMS 274 (M+).
Yield: 76% (520.6 mg); mp=106–107°C; enantiomeric
excess was determined by HPLC analysis, using
DAICEL Chiralpak AD-H column, (hexane/2-
propanol, 94:6); tr=17.55 min (2R,3S minor), tr=18.32
1
min (2S,3R major); [h]2D5=+25 (c 1, CHCl3); H NMR
(CDCl3, 200 MHz): l 4.22 (d, 1H, J=2.00 Hz), 4.7 (d,
1H, J=2.00 Hz), 7.45–7.62 (m, 7H), 7.70–7.98 (m, 3H),
8.05–8.12 (d, 2H, J=7.80 Hz); EIMS 274 (M+).
4.11. trans-2,3-Epoxy-3-phenyl-1-(4-bromophenyl)-
propan-1-one, 6j
4.6. trans-(2R,3S)-Epoxy-3-phenyl-1-(4-methylphenyl)-
propan-1-one, 6e
Yield: 82% (620.9 mg); mp=90–91°C; enantiomeric
Yield: 68% (404.6 mg); mp=60–62°C; enantiomeric
excess was determined by HPLC analysis, using

3802
G. Kumaraswamy et al. / Tetrahedron: Asymmetry 14 (2003) 3797–3803
DAICEL Chiralpak AD-H column, (hexane/2-
propanol, 95:5); tr=18.78 min (minor), tr=20.58 min
(major); [h]2D5=−71 (c 1, CHCl3); 1H NMR (CDCl3, 200
MHz): l 4.01 (d, 1H, J=2.00 Hz), 4.15 (d, 1H, J=2.00
Hz), 7.28–7.35 (m, 5H), 7.58–7.62 (m, 2H), 7.85–7.89
(m, 2H); EIMS 302 (M+).
(t, J=8.5 Hz), 7.59 (dd, J=8.5, 2.0 Hz), 7.67 (dd,
J=8.5, 1.2 Hz), 8.05 (d, J=8.8 Hz), 8.10 (d, J=2 Hz);
13C NMR (CDCl3) l 152.96, 140.91, 137.07, 132.70,
131.86, 129.86, 129.00, 127.36, 126.49, 124.92, 118.38,
110.89; m/z (EI) 438 (M+); EI HRMS calcd for
C32H22O2 438.16198, obsd 438.16060.
4.12. (S)-2,2-Bis(methoxymethoxy)-6,6%-dibromo-1,1%-
4.15. (S)-MTPA-monoester
binaphthalene, 3
1H NMR (CDCl3, 200 MHz) l 2.89 (s, 3H, 1×OCH3),
5.21 (s, 1H, 1×OH), 7.09–8.2 (m, 25H, Ar).
To NaH (60%) (6.4 g, 16 mmol) in dry DMF (15 ml),
(S)-6,6%-dibromo-1,1%-binaphthol (10 g, 22.5 mmol) dis-
solved in DMF (150 ml) was added slowly at 0°C. The
reaction mixture stirred for 30 min and then
chloromethyl methylether (6.34 g, 78.9 mmol) was
added dropwise. After 3h stirring at same temperature,
100 ml water added and the precipitate formed was
filtered off. The crude product was purified by column
chromatography over silica gel (hexane:EtOAc) to give
10.5 g (87%yield). Mp=130–131°C; [h]2D5=−17.3 (c 1,
CHCl3) [lit.12 [h]D20=−16.3 (c 1, CHCl3)]; 1H NMR
(CDCl3, 200 MHz) l 3.15 (s, 6H), 4.98 (d, 2H, J=6.8
Hz), 5.07 (d, 2H, J=6.8 Hz), 6.98 (d, 2H, J=9.0 Hz),
7.29 (dd, 2H, J=9.0, 2.1 Hz), 7.60 (d, 2H, J=9.0 Hz),
7.88 (d, 2H, J=9.0 Hz), 8.03 (d, 2H, J=9.01 Hz). Anal
calcd for C24H20Br2O2 requires C, 54.16; H, 3.79, found
C, 55.38; H, 3.62.
Acknowledgements
We are grateful to Dr. K. V. Raghavan, Director, IICT
for his constant encouragement, and for the award of
Prolog discovery programme of IICT to G.K. Thanks
are also due to Dr. M. Hari Babu for his support.
M.N.V.S. and N.J. are thankful to UGC & CSIR (New
Delhi) for award of fellowships. We also gratefully
acknowledge Gerchem labs (India) Pvt Ltd, Hyderabad
for supplying (R)-(+)- and (S)-(−)-BINOL.
References
4.13. (S)-2,2-Bis(methoxymethoxy)-6,6%-bis(2-phenyl)-
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1
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4.14. (S)-6,6%-Diphenyl-1,1%-bi-2-naphthol, (S)-1d
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1
2.85 g. Mp=127–129°C; [h]2D5=+215.0 (c 1, CHCl3), H
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