Efficient synthesis of optically active β-hydroxy p-tolylsulfones with very high enantiomeric excess via CBS-oxazaborolidine-catalyzed borane reduction

Article abstract of DOI:10.1016/S0957-4166(01)00359-7

A simple, efficient synthesis of optically active β-hydroxy p-tolylsulfones with >99% e.e. by employing CBS-oxazaborolidine-catalyzed asymmetric borane reduction of β-keto p-tolylsulfones using N-ethyl-N-iso-propylaniline-borane complex as the borane carrier has been established.

Full text of DOI:10.1016/S0957-4166(01)00359-7

TETRAHEDRON:
ASYMMETRY
Pergamon
Tetrahedron: Asymmetry 12 (2001) 2043–2047
Efficient synthesis of optically active b-hydroxy p-tolylsulfones
with very high enantiomeric excess via
CBS–oxazaborolidine-catalyzed borane reduction
Byung Tae Cho* and Dong Jun Kim
Department of Chemistry, Hallym University, Chunchon 200-702, Republic of Korea
Received 16 July 2001; accepted 9 August 2001
Abstract—A simple, efficient synthesis of optically active b-hydroxy p-tolylsulfones with >99% e.e. by employing CBS–oxazaboro-
lidine-catalyzed asymmetric borane reduction of b-keto p-tolylsulfones using N-ethyl-N-iso-propylaniline–borane complex as the
borane carrier has been established. © 2001 Elsevier Science Ltd. All rights reserved.
1
. Introduction
tion of aromatic keto analogues required high pressure
condition (75 bar) to obtain high optical purity. Kinetic
resolution and oxidation of racemic substrates by bio-
catalysts both suffer from the fact that the theoretical
yields are limited to 50%.
Optically active b-hydroxy phenyl or p-tolylsulfones are
extremely useful chiral building blocks for the synthesis
of a variety of chiral organic compounds, because the
a-carbon atom of arylsulfonyl groups of the com-
pounds can be further functionalized and, moreover,
the sulfonyl groups can be easily removed from the
Recently, we have reported highly efficient oxazaboro-
lidine-catalyzed asymmetric borane reductions of a-
1
,2
skeleton without racemization.
been successfully used as starting materials in the syn-
Indeed, they have
functionalized
ketones,
including
a-sulfonyloxy
10a,b
ketones,
a-triorganosilyloxy- or a-tetrahydropyr-
2
a–c
10c,d 10e,f
thesis of optically active g-butenolides,
g-butyrolac-
anyloxy ketones
and a-keto acetals.
From these
2
b–d
2
2c
tones,
d-valerolactones, 2,5-disubstituted tetrahyd-
studies, we have found that the use of N-ethyl-N-iso-
propylaniline–borane complex 2 instead of borane–tet-
rahydrofuran, borane–dimethyl sulfide and catechol
borane commonly employed as borane carriers for such
a reduction is more useful for large-scale applications.
As part of an ongoing program on the asymmetric
reduction of functionalized ketones, we have recently
studied an efficient synthesis of optically active alcohols
containing a sulfur functionality via asymmetric reduc-
e
2f
rofurans and allylic alcohols. Methods for the syn-
thesis of b-hydroxy phenyl or p-tolylsulfones include
the asymmetric reduction of b-keto sulfones using
3,4
5
mediated by either baker’s yeast or a fungus cell, the
Ru(II)-catalyzed enantioselective hydrogenation of b-
6
keto phenylsulfones, kinetic resolution of racemic b-
7
hydroxy sulfones
and/or kinetically controlled
8
oxidation of racemic b-hydroxy sulfoxides using bio-
catalysts. However, baker’s yeast-mediated reduction of
b-keto sulfones was highly dependent on the size of the
groups adjacent to the carbonyl group. For example,
the reduction of 1-phenylsulfonyl-2-propanone pro-
vided the corresponding b-hydroxy sulfone with 95%
e.e. In contrast, the reduction of 1-phenylsulfonyl-2-
heptanone and 1-phenylsulfonyl-2-phenylethanone4
afforded the product b-hydroxy sulfones with 10% e.e.
11
tion. We wish to report herein a convenient synthesis
of optically active b-hydroxy p-tolylsulfones with very
high enantiomeric purity via oxazaborolidine-catalyzed
asymmetric reduction using the amine–borane reagent 2
as borane carrier.
2
. Results and discussion
2
e
and 15% e.e., respectively and 1-phenylsulfonyl-2-
octanone was not reduced by baker’s yeast. In the case
of catalytic enantioselective hydrogenation, the reduc-
9
We selected a commercially available CBS–oxazaboro-
12
lidine 1 as a representative catalyst. The reduction
was carried out by slow addition of b-keto p-tolylsul-
fones 3 over 1 h to a solution of 1.0 equiv. of the
reagent 2 in the presence of 10 mol% of 1 in THF at
*
0
Corresponding author. E-mail: btcho@sun.hallym.ac.kr
957-4166/01/$ - see front matter © 2001 Elsevier Science Ltd. All rights reserved.
PII: S0957-4166(01)00359-7

2
044
B. T. Cho, D. J. Kim / Tetrahedron: Asymmetry 12 (2001) 2043–2047
2
5°C. The reduction afforded the corresponding b-
glassware. Liquid materials were transferred with a
double-ended needle. The reactions were monitored
by TLC using silica gel plates and the products were
purified by flash-column chromatography on silica gel
(Merck; 230–400 mesh). NMR spectra were recorded
hydroxy sulfones 4 in high yields (Scheme 1). The e.e.s
of the products were determined by HPLC analysis
using Chiralcel OD, Chiralcel OD-H and Whelk-O1
columns. As shown in Table 1, the reduction of aro-
matic b-keto sulfones 3a–g bearing phenyl, p-substi-
tuted phenyl (p-XC H ; X=Me, MeO, F, Cl and NO )
1
13
at 400 MHz for H and 100 or 125 MHz for
C
using Me Si as the internal standard in CDCl . Opti-
6
4
2
4
3
and 2-naphthyl groups furnished the corresponding b-
cal rotations were measured with a high-resolution
digital polarimeter. Melting points were uncorrected.
Enantiomeric excesses (% e.e.) of the product b-
hydroxy p-tolylsulfones were determined with an
HPLC apparatus fitted with a 25 cm Chiralcel OD or
OD-H column (Daicel) and a Whelk-O1 column
(Regis).
hydroxy sulfones 4a–g with very high enantioselectivity
(
approaching 100% e.e.). Inductive effects of the sub-
stituent groups of phenyl ring on the enantioselectivity
were not observed (entries 1–6). For a heterocyclic
analogue bearing a furan ring, we also obtained the
product 4h with very high enantiomeric excess.
Although the reduction of aliphatic analogues having
ethyl and n-undecyl groups gave products with some-
what lower e.e.s compared with those obtained from
the aromatic analogues, the case of more hindered
aliphatic analogues containing tert-butyl and cyclo-
hexyl groups again proceeded with very high enantiose-
lectivities (entries 9–12). Interestingly these results
indicate that enantioselection is not significantly
affected by the bulk of the p-tolylsulfonyl group of the
b-keto sulfone. The reason for this is unclear at this
4.2. Materials
Most of the organic compounds utilized in this study
were commercial products of the highest purity. They
were further purified by distillation when necessary.
THF was distilled over sodium benzophenone ketyl
and stored in ampules under a nitrogen atmosphere.
The CBS reagent 1 and N-ethyl-N-iso-propylaniline–
borane complex 2 were purchased from the Aldrich
Chemical Company. b-Keto p-tolylsulfones 3 were
prepared from [(p-toluenesulfonyl)methylene]dilithium
and the corresponding esters or acid chlorides with
sodium p-tolylsulfinate according to the known proce-
1
5
time.
3. Conclusion
13
dure.
In summary, we have established a simple and
efficient synthetic method for obtaining near enan-
tiopure aromatic and hindered aliphatic b-hydroxy p-
tolylsulfones by employing CBS–oxazaborolidine-
catalyzed asymmetric borane reduction of the corre-
sponding b-keto sulfones using N-ethyl-N-iso-propyl-
aniline–borane complex as the borane carrier.
Further applications of this methodology are under
investigation and will be reported in due course.
4.3. General procedure for CBS–oxazaborolidine-cata-
lyzed borane reduction of b-keto p-tolylsulfones 3
To a solution of 1 (0.2 M, 1.0 mL, 0.2 mmol) in
THF was added a solution of N-ethyl-N-iso-propyl-
aniline–borane complex 2 (2.0 M, 1.0 mL, 2.0 mmol)
in THF. To this was added slowly a THF solution of
3 (1 M, 2 mL, 2 mmol) over a period of 1 h using a
syringe pump at 25°C. After the addition, the reac-
tion mixture was stirred for 10 min, quenched cau-
tiously with methanol (0.5 mL), and stirred for an
additional 30 min. The solvent was evaporated under
reduced pressure. The crude products 4 obtained were
further purified by flash-column chromatography on
silica gel (230–400 mesh) using hexane/ethyl acetate
(1/1) as the eluent, unless otherwise indicated.
4. Experimental
4.1. General
All operations with air-sensitive materials were carried
out under a nitrogen atmosphere with oven-dried
1
2
(0.1 eq)
(1.0 eq)
O
OH
SO C H CH -p
2
6
4
3
SO C H CH -p
2
6
4
3
o
R
THF, 25 C
R
3
4
Ph
R = aryl or alkyl
Et
N
Ph
N
O
Ph
Pr-i
B
BH3
1
2
Me
Scheme 1.

B. T. Cho, D. J. Kim / Tetrahedron: Asymmetry 12 (2001) 2043–2047
2045
a
Table 1. CBS–oxazaborolidine-catalyzed asymmetric borane reduction of b-keto p-tolylsulfones 3
a
[
3]:[2]:[1]=1:1:0.1. [3]=0.5 M.
b
c
Isolated and purified yields.
The absolute configuration is unknown, but is probably S based on comparison of the order of elution of HPLC analysis using a chiral column
and the sign of the optical rotation with that of the phenylsulfonyl analogue: Ref. 6.
Determined by HPLC analysis using a Whelk-O1 column; eluent: hexane–iso-PrOH 9:1.
Determined by HPLC analysis using a Chiralcel OD-H column; eluent: hexane–iso-PrOH 4:1.
Determined by HPLC analysis of its benzoate using a Whelk-O1 column; eluent: hexane–iso-PrOH 9:1.
Determined by HPLC analysis using a Chiralcel OD column; eluent: hexane–iso-PrOH 9:1.
d
e
f
g
h
i
In acetone.
25
Based on [h]D +16.4 (c 2.1, CHCl ), S: Ref. 14.
3
4
.3.1. (S)-1-Phenyl-2-(p-toluenesulfonyl)ethanol 4a.
and 14.51 Hz), 3.40 (dd, 1 H, J=10.01 and 14.17 Hz),
3.69 (brs, 1 H), 5.18 (dd, 1 H, J=1.6 and 10.11 Hz),
2
0
White solid; mp 94–96°C (EtOH); [h] +20.6 (c 1.02,
D
1
3
CHCl ); HPLC analysis using a Whelk-O1 column
showed it to be >99% e.e. [iso-PrOH/hexane=1/9, flow
rate=1.0 mL/min, t (S) 21.84 min and t (R) 26.12
min]; IR (KBr, cm ) 3491, 1285, 1135; H NMR (400
MHz, CDCl ): l 2.40 (s, 3 H), 3.25 (dd, 1 H, J=1.84
7.19–7.33 (m, 7 H), 7.77 (d, 2 H, J=7.83 Hz);
NMR (100, MHz, CDCl ): l 21.67, 63.99, 68.44,
125.63, 128.00, 128.30, 128.74, 130.10, 136.11, 140.64,
145.27. Anal. calcd for C15 S: C, 65.19; H, 5.84; S,
11.60. Found: C, 65.14; H, 5.90; S, 11.63%.
C
3
3
R
R
−
1
1
H O
16 3
3

2
046
B. T. Cho, D. J. Kim / Tetrahedron: Asymmetry 12 (2001) 2043–2047
4
.3.2. (S)-1-p-Tolyl-2-(p-toluenesulfonyl)ethanol 4b.
C H ClO S: C, 57.97; H, 4.86; S, 10.32. Found: C,
15 15 3
57.93; H, 4.98; S, 10.39%.
2
0
White solid; mp 57–59°C (EtOH); [h] +11.8 (c 1.04,
D
CHCl ); HPLC analysis using a Whelk-O1 column
showed it to be 98% e.e. [iso-PrOH/hexane=1/9, flow
rate=1.0 mL/min, t (S) 23.86 min and t (R) 31.02
min]; IR (KBr, cm ) 3502, 1284, 1134; H NMR (400
MHz, CDCl ): l 2.24 (s, 3 H), 2.39 (s, 3 H), 3.23 (dd,
3
4
4
.3.6. (S)-1-p-Nitrophenyl-2-(p-toluenesulfonyl)ethanol
20
f. Light yellow solid; mp 143–145°C (EtOH); [h]
D
R
R
−
1
1
+33.7 (c 1.07, acetone); HPLC analysis using a Chiral-
cel OD-H column showed it to be 98% e.e. [iso-PrOH/
3
hexane=1/4, flow rate=0.5 mL/min, t (R) 28.04 min
R
1
1
7
2
2
1
H, J=2.0 and 14.39 Hz), 3.40 (dd, 1 H, J=10.51 and
4.39 Hz), 3.59 (brs, 1 H), 5.13 (d, 1 H, J=10.03 Hz),
.04–7.11 (m, 4 H), 7.31 (d, 2 H, J=6.83 Hz), 7.76 (d,
−
1
and t (S) 30.48 min];IR (KBr, cm ) 3446, 1343, 1138;
R
1
H NMR (400 MHz, CDCl ): l 2.48 (s, 3 H), 3.32 (dd,
3
1
3
1 H, J=1.84 and 14.32 Hz), 3.43 (dd, 1 H, J=9.89 and
H, J=7.79 Hz); C NMR (100, MHz, CDCl ): l
3
1
4.29 Hz), 4.03 (s, 1 H), 5.40 (d, 1 H, J=9.77 Hz), 7.41
1.08, 21.66, 63.96, 68.30, 125.57, 127.99 129.37,
30.05, 136.16, 137.71, 138.10, 145.19. Anal. calcd for
(
d, 2 H, J=8.19 Hz), 7.50 (d, 2 H, J=8.77 Hz), 7.84 (d,
13
2
H, J=8.26 Hz), 8.18 (d, 2 H, J=8.72 Hz); C NMR
C H O S: C, 66.18; H, 6.25; S, 11.04. Found: C,
1
6
18
3
(
1
100, MHz, CDCl ): l 21.68, 63.55, 67.65, 123.92,
26.58, 127.98, 130.25, 135.75, 145.71, 147.62, 147.69.
3
6
6.18; H, 6.18; S, 11.14%.
Anal. calcd for C H NO S: C, 56.06; H, 4.70; N, 4.36;
S, 9.98. Found: C, 56.07; H, 4.67; N, 4.41; S, 9.93%.
15
15
5
4
.3.3. (S)-1-p-Methoxyphenyl-2-(p-toluenesulfonyl)ethan-
20
ol 4c. White solid; mp 84–86°C (EtOH); [h] +10.8 (c
D
1.12, CHCl ); HPLC analysis using a Whelk-O1
3
4
4
1
.3.7.
(S)-1-(2-Naphthyl)-2-(p-toluenesulfonyl)ethanol
20
column showed it to be 98% e.e. [iso-PrOH/hexane=1/
g. White solid; mp 122–124°C (EtOH); [h]D +6.0 (c
9
5
, flow rate=1.0 mL/min, t (S) 38.45 min and t (R)
R R
−1 1
.02, CHCl ); HPLC analysis using a Whelk-O1
3
7.33 min]; IR (KBr, cm ) 3442, 1302, 1144; H NMR
column showed it to be >99% e.e. [iso-PrOH/hexane=
(400 MHz, CDCl ): l 2.38 (s, 3 H), 3.22 (dd, 1 H,
3
1
4
/9, flow rate=1.0 mL/min, t (S) 23.80 min and t (R)
R R
−1 1
J=1.70 and 14.39 Hz), 3.40 (dd, 1 H, J=10.11 and
4.27 Hz), 3.60 (brs, 1 H), 3.70 (s, 3 H), 5.12 (d, 1 H,
1.64 min]; IR (KBr, cm ) 3503, 1283, 1135; H NMR
1
(
400 MHz, CDCl ): l 2.44 (s, 3 H), 3.40 (dd, 1 H,
3
J=9.28 Hz), 6.77 (d, 2 H, J=8.55 Hz), 7.14 (d, 2 H,
J=8.75 Hz), 7.31 (d, 2 H, J=8.51 Hz), 7.76 (d, 2 H,
J=8.79 Hz); C NMR (100, MHz, CDCl ): l 21.66,
J=1.86 and 14.34 Hz), 3.55 (dd, 1 H, J=9.91 and
1
4.36 Hz), 3.84 (brs, 1 H), 5.41 (d, 1 H, J=9.83 Hz),
1
3
3
7
.33–7.36 (m, 3 H), 7.44–7.49 (m, 2 H), 7.77–7.84 (m, 6
5
1
5.28, 63.94, 68.07, 114.95, 126.95, 127.94, 130.06,
32.81, 136.17, 145.19, 159.52. Anal. calcd for
13
H); C NMR (100, MHz, CDCl ): l 21.66, 63.90,
3
6
1
1
9
8.63, 123.29, 124.77, 126.28, 126.42, 127.67, 127.99,
28.02, 128.66, 130.08, 133.13, 133.18, 135.17, 137.97,
45.25. Anal. calcd for C H O S: C, 69.91; H, 5.56; S,
C H O S: C, 62.72; H, 5.92; S, 10.47. Found: C,
1
6
18
4
62.80; H, 6.01; S, 10.44%.
19
18
3
.82. Found: C, 69.89; H, 5.60; S, 9.85%.
4
4
1
.3.4. (S)-1-p-Fluorophenyl-2-(p-toluenesulfonyl)ethanol
2
0
d. White solid; mp 74–76°C (EtOH); [h] +20.0 (c
4.3.8. (S)-1-(2-Furyl)-2-(p-toluenesulfonyl)ethanol 4h.
20
D
.24, CHCl ); HPLC analysis using a Whelk-O1
White solid; mp 75–77°C (EtOH); [h]D +5.8 (c 1.02,
3
column showed it to be 98% e.e. [iso-PrOH/hexane=1/
CHCl ); HPLC analysis of its benzoate using a Whelk-
3
9
, flow rate=1.0 mL/min, t (S) 20.09 min and t (R)
3.50 min]; IR (KBr, cm ) 3583, 1298, 1133; H NMR
O1 column showed it to be 97% e.e. [iso-PrOH/hex-
R
R
−
1
1
2
ane=1/9, flow rate=1.0 mL/min, t (S) 41.77 min and
R
−
1
1
(
400 MHz, CDCl ): l 2.40 (s, 3 H), 3.21 (dd, 1 H,
t (R) 47.71 min]; IR (KBr, cm ) 3469, 1298, 1146; H
3
R
J=1.96 and 14.15 Hz), 3.37 (dd, 1 H, J=10.23 and
4.39 Hz), 3.75 (d, 1 H, J=1.96 Hz), 5.17 (d, 1 H,
NMR (400 MHz, CDCl ): l 2.46 (s, 3 H), 3.51 (dd, 1
3
1
H, J=2.44 and 14.46 Hz), 3.56 (brs, 1 H), 3.64 (dd, 1
H, J=9.56 and 14.38 Hz), 5.25 (d, 1 H, J=9.27 Hz),
6.28–6.31 (m, 2 H), 7.30 (d, 1 H, J=0.73 Hz), 7.39 (d,
J=9.75 Hz), 6.93 (t, 2 H, J=8.77 Hz), 7.18–7.22 (m, 2
H), 7.32 (d, 2 H, J=7.55 Hz), 7.76 (d, 2 H, J=8.55
1
3
13
Hz); C NMR (100, MHz, CDCl ): l 21.66, 63.94,
2 H, J=8.16 Hz), 7.81 (d, 2 H, J=8.23 Hz); C NMR
3
6
1
7.83, 115.50, 115.72, 127.38, 127.46, 127.98, 130.12,
35.99, 136.44, 136.47, 145.38, 161.24, 163.69. Anal.
(100, MHz, CDCl ): l 22.07, 61.07, 63.19, 107.70,
3
110.84, 128.46, 130.47, 136.49, 142.99, 145.66, 152.99.
Anal. calcd for C H O S: C, 58.63; H, 5.30; S, 12.04.
calcd for C H FO S: C, 61.21; H, 5.14; S, 10.89.
1
5
15
3
13 14
4
Found: C, 61.26; H, 5.07; S, 10.73%.
Found: C, 58.70; H, 5.42; S, 12.00%.
4
4
1
.3.5. (S)-1-p-Chlorophenyl-2-(p-toluenesulfonyl)ethanol
4.3.9. (S)-1-(p-Toluenesulfonyl)butan-2-ol 4i. Colorless
20
20
e. White solid; mp 83–85°C (EtOH); [h] +10.1 (c
viscous oil; [h]D +17.6 (c 1.07, CHCl ); HPLC analysis
D
3
.04, CHCl ); HPLC analysis using a Whelk-O1
using a Chiralcel OD column showed it to be 73% e.e.
3
column showed it to be 99% e.e. [iso-PrOH/hexane=1/
[iso-PrOH/hexane=1/9, flow rate=0.5 mL/min, t (S)
R
−
1
9
2
, flow rate=1.0 mL/min, t (S) 20.97 min and t (R)
5.83 min]; IR (KBr, cm ) 3469, 1283, 1151; H NMR
33.02 min and t (R) 37.00 min]; IR (neat, cm ) 3505,
R
R
R
−
1
1
1
2932, 1288, 1141; H NMR (400 MHz, CDCl ): l 0.92
3
(
400 MHz, CDCl ): l 2.40 (s, 3 H), 3.21 (dd, 1 H,
(t, 3 H, J=7.45 Hz), 1.53–1.63 (m, 2 H), 2.47 (s, 3 H),
3.17–3.20 (m, 2 H), 3.37 (d, 1 H, J=2.23 Hz), 4.06 (m,
1 H), 7.38 (d, 2 H, J=8.20 Hz), 7.81 (d, 2 H, J=8.32
3
J=1.84 and 14.27 Hz), 3.35 (dd, 1 H, J=10.23 and
1
1
4.39 Hz), 3.77 (brs, 1 H), 5.16 (dd, 1 H, J=1.58 and
0.13 Hz), 7.14–7.22 (m, 4 H), 7.31 (d, 2 H, J=8.03
13
Hz); C NMR (100, MHz, CDCl ): l 9.34, 21.69,
3
1
3
Hz), 7.75 (d, 2 H, J=8.55 Hz); C NMR (100, MHz,
29.46, 62.03, 67.18, 127.98, 130.12, 136.35, 145.18.
Anal. calcd for C H O S: C, 57.87; H, 7.06; S, 14.05.
CDCl ): l 21.66, 63.78, 67.80, 127.04, 127.95, 128.84,
3
11 16
3
130.11, 134.00, 135.93, 139.12, 145.39. Anal. calcd for
Found: C, 57.89; H, 7.07; S, 13.96%.

B. T. Cho, D. J. Kim / Tetrahedron: Asymmetry 12 (2001) 2043–2047
Synthesis; Academic Press: New York, 1994.
2047
4
.3.10. (S)-1-(p-Toluenesulfonyl)tridecan-2-ol 4j. White
20
solid; mp 51–53°C (80% EtOH); [h] +11.0 (c 1.03,
2. (a) Solladi e´ , G.; Frechou, C.; Demailly, G.; Greck, C.
J. Org. Chem. 1986, 51, 1912–1914; (b) Robin, S.;
Huet, F.; Fauve, A.; Veschambre, H. Tetrahedron:
Asymmetry 1993, 4, 239–246; (c) Kozikowski, A. P.;
Mugrage, B. B.; Li, C. S.; Felder, L. Tetrahedron Lett.
1986, 27, 4817–4820; (d) Sato, T.; Okumura, Y.; Itai,
J.; Fujisawa, T. Chem. Lett. 1988, 1537–1540; (e)
Tanikaga, R.; Hosoya, K.; Kaji, A. J. Chem. Soc.,
Perkin Trans. 1 1987, 1799–1803; (f) Tanikaga, R.;
Hosoya, K.; Kaji, A. Chem. Lett. 1987, 829–832.
D
CHCl ); HPLC analysis using a Chiralcel OD column
3
showed it to be 87% e.e. [iso-PrOH/hexane=1/9, flow
rate=0.6 mL/min, t (S) 19.28 min and t (R) 24.71 min];
R
R
1
IR (neat) 3530, 2921, 1284, 1138; H NMR (400 MHz,
CDCl ): l 0.80 (t, 3 H, J=6.94 Hz), 1.16–1.56 (m, 20 H),
3
2
.40 (s, 3 H), 3.06–3.16 (m, 2 H), 3.31 (d, 1 H, J=2.44
Hz), 4.05 (m, 1 H), 7.31 (d, 2 H, J=8.80 Hz), 7.74 (d,
1
3
2
2
3
H, J=8.55 Hz); C NMR (100, MHz, CDCl ): l 14.10,
3
1.65, 22.66, 24.94, 29.28, 29.31, 29.44, 29.49, 29.58,
1.88, 36.39, 62.28, 65.95, 127.92, 130.06, 136.27, 145.11.
Anal. calcd for C H O S: C, 67.75; H, 9.67; S, 9.04.
3. For reviews, see (a) Servi, S. Synthesis 1990, 1–25; (b)
2
0
34
3
Csuk, R.; Gl a¨ nzer, B. I. Chem. Rev. 1991, 91, 49–97;
Found: C, 67.52; H, 9.87; S, 9.29%.
(
1
c) Robert, S. M. J. Chem. Soc., Perkin Trans. 1 1999,
–21.
4
4
0
.3.11. (S)-1-(p-Toluenesulfonyl)-3,3-dimethylbutan-2-ol
2
0
4. Crumbie, R. L.; Deol, B. S.; Nemorin, J. E.; Ridley, D.
k. White solid; mp 66–67°C (80% EtOH); [h] +42.5 (c
D
D. Aust. J. Chem. 1978, 31, 1965–1980.
.97, CHCl ); HPLC analysis using a Chiralcel OD
3
5. Goto, V.; Rebolledo, F.; Liz, R. Tetrahedron: Asymme-
column showed it to be 99% e.e. [iso-PrOH/hexane=1/9,
flow rate=0.6 mL/min, t (S) 15.62 min and t (R) 18.63
try 2001, 12, 513–515.
R
R
−
1
1
6. Bertus, P.; Phansavath, P.; Ratovelomanana-Vidal, V.;
Gen eˆ t, J.-P.; Touati, A. R.; Homri, T.; Ben Hassine, B.
Tetrahedron Lett. 1999, 40, 3175–3178 and Tetrahedron:
Asymmetry 1999, 10, 1369–1380.
7. Chinchilla, R.; N a´ jera, C.; Pardo, J.; Yus, M. Tetra-
hedron: Asymmetry 1990, 1, 575–578.
min]; IR (KBr, cm ) 3530, 1280, 1135; H NMR (400
MHz, CDCl ): l 0.90 (s, 9 H), 2.40 (s, 3 H), 3.03 (dd,
H, J=9.87 and 14.27 Hz), 3.16 (s, 1 H), 3.19 (brs, 1
H), 3.68(d, 1 H, J=10.99 Hz), 7.32 (d, 2 H, J=7.31 Hz),
3
1
13
7
.75 (d, 2 H, J=9.03 Hz); C NMR (100, MHz, CDCl ):
3
l 21.66, 25.35, 34.85, 58.80, 73.21, 127.93, 130.04, 136.20,
1
1
45.05. Anal. calcd for C H O S: C, 60.91; H, 7.86; S,
8. Ohta, H.; Kato, Y.; Tsuchihashi, G. J. Org. Chem.
1987, 52, 2735–2739.
1
3
20
3
2.51. Found: C, 60.92; H, 7.95; S, 12.48%.
9. Nakmura, K.; Ushio, K.; Oka, S.; Ohno, A.; Yasui, S.
4
.3.12. (S)-1-Cyclohexyl-2-(p-toluenesulfonyl)ethanol 4l.
Tetrahedron Lett. 1984, 25, 3979–3982.
20
White solid, mp 72–73°C (80% EtOH); [h] +21.8 (c 1.05,
10. (a) Cho, B. T.; Yang, W. K.; Choi, O. K. J. Chem.
Soc., Perkin Trans. 1 2001, 1204–1211; (b) Choi, O. K.;
Cho, B. T. Org. Proc. Prep. Int. 2000, 32, 493–497; (c)
Cho, B. T.; Chun, Y. S. J. Org. Chem. 1998, 63, 5280–
D
CHCl ); HPLC analysis using a Chiralcel OD column
showed it to be >99% e.e. [iso-PrOH/hexane=1/9, flow
rate=0.6 mL/min, t (S) 22.34 min and t (R) 26.74 min];
IR (KBr, cm ) 3514, 2927, 1288, 1140; H NMR (400
MHz, CDCl ): l 0.87–1.17 (m, 5 H), 1.29–1.46 (m, 1 H),
3
R
R
−
1
1
5282; (d) Cho, B. T.; Chun, Y. S. Tetrahedron: Asym-
3
metry 1999, 10, 1843–1846; (e) Cho, B. T.; Chun, Y. S.
Bull. Korean Chem. Soc. 1999, 20, 397; (f) Cho, B. T.;
Chun, Y. S. J. Chem. Soc., Perkin Trans. 1 1999, 2095–
1
1
.54–1.67 (m, 5 H), 2.39 (s, 3 H), 3.11 (s, 1 H), 3.13 (d,
H, J=1.20 Hz), 3.21 (d, 1 H, J=2.92 Hz), 3.83–3.87
(
m, 1 H), 7.31 (d, 2 H, J=7.55 Hz), 7.74 (d, 2 H, J=8.27
2100.
13
Hz); C NMR (100, MHz, CDCl ): l 21.65, 25.86, 25.95,
3
1
1. For a recent review, see: Cho, B. T.; Chun, Y. S. In
2
1
7
6.21, 27.51, 28.44, 43.10, 60.29, 69.78, 127.91, 130.03,
Organoboranes for Syntheses (ACS Symposium Series
36.25, 145.06. Anal. calcd for C H O S: C, 63.80; H,
1
5
22
3
7
83); Ramachandran, P. V.; Brown, H. C., Eds.; Amer-
ican Chemical Society: Washington, DC, 2001; Chapter
, pp. 122–135.
.85; S, 11.35. Found: C, 63.78; H, 7.97; S, 11.48%.
8
1
1
1
1
2. Corey, E. J.; Bakshi, R. K.; Shibata, S.; Chen, C.-P.;
Singh, V. K. J. Am. Chem. Soc. 1987, 109, 7925–7926.
3. Thomsen, M. W.; Handwerker, B. M.; Katz, S. A.;
Belser, R. B. J. Org. Chem. 1988, 53, 906–907.
4. Chinchilla, R.; N a´ jera, C.; Pardo, J.; Yus, M. Tetra-
hedron: Asymmetry 1990, 1, 575–578.
Acknowledgements
This work was supported from Grant No. 2000-1-12300-
02-1 from the Basic Research Program of the Korea
Science and Engineering Foundation.
0
5. In the same reduction of a-oxygenated prochiral
1
0a,b
ketones, such as a-sulfonyloxy ketones,
a-siloxy
10c,d
10e,f
References
ketones
and a-keto acetals,
we also observed
that the effects of the size of the oxygen-containing
1. Metzner, P.; Thuillier, A. Sulfur Reagents in Organic
groups on enantioselection was insignificant.