Catalytic asymmetric oxidation of sulfides mediated by a series of novel oxazolines-titanium complexes

Article abstract of DOI:10.1081/SCC-100104828

A series of chiral oxazoline-titanium complexes were found to be efficient catalysts for the enantioselective oxidation of sulfides. The reactivity and enantioselectivity were strongly influenced by the structure of the oxazolines. When (4S,5S)-4,5-dihydro-4,5-diphenyl-2-(2′-hydroxy-3′-tert- butylphenyl) oxazoline was used as ligand, the sulfoxide was obtained in 96%e.e.

Full text of DOI:10.1081/SCC-100104828

Synthetic Communications
An International Journal for Rapid Communication of Synthetic Organic
Chemistry
ISSN: 0039-7911 (Print) 1532-2432 (Online) Journal homepage: http://www.tandfonline.com/loi/lsyc20
CATALYTIC ASYMMETRIC OXIDATION OF SULFIDES
MEDIATED BY A SERIES OF NOVEL OXAZOLINES-
TITANIUM COMPLEXES
YunGui Peng , XiaoMing Feng , Xin Cui , YaoZhong Jiang & Albert S. C. Chan
To cite this article: YunGui Peng , XiaoMing Feng , Xin Cui , YaoZhong Jiang & Albert S. C. Chan
(2001) CATALYTIC ASYMMETRIC OXIDATION OF SULFIDES MEDIATED BY A SERIES OF NOVEL
OXAZOLINES-TITANIUM COMPLEXES, Synthetic Communications, 31:15, 2287-2296, DOI:
10.1081/SCC-100104828
To link to this article: http://dx.doi.org/10.1081/SCC-100104828
Published online: 09 Nov 2006.
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Date: 10 March 2016, At: 00:41

SYNTHETIC COMMUNICATIONS, 31(15), 2287–2296 (2001)
CATALYTIC ASYMMETRIC OXIDATION OF
SULFIDES MEDIATED BY A SERIES OF
NOVEL OXAZOLINES-TITANIUM
COMPLEXES
YunGui Peng,1 XiaoMing Feng,1,2, Xin Cui,1
*
YaoZhong Jiang,1, and Albert S. C. Chan3
*
1Chengdu Institute of Organic Chemistry, Chinese Academy of
Sciences, Chengdu 610041, P. R. China
2The Faculty of Chemistry, Sichuan University,
Chengdu 610064, P. R. China
3Open Laboratory of Chirotechnology and Department of
Applied Biology and Chemical Technology, The Hong Kong
Polytechnic University, Hong Kong, P. R. China
ABSTRACT
A series of chiral oxazoline-titanium complexes were found to
be efficient catalysts for the enantioselective oxidation of sul-
fides. The reactivity and enantioselectivity were strongly influ-
enced by the structure of the oxazolines. When (4S,5S)-4,5-
dihydro-4,5-diphenyl-2-(20-hydroxy-30-tert-butylphenyl) oxa-
zoline was used as ligand, the sulfoxide was obtained in
96%e.e.
*Corresponding author.
2287
Copyright & 2001 by Marcel Dekker, Inc.
www.dekker.com

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PENG ET AL.
Optically active sulfoxides have been increasingly used as building
blocks and chiral auxiliaries in asymmetric synthesis.1 The most attractive
method for their preparation is the enantioselective oxidation of the readily
available prochiral sulfides. In the past several years, the asymmetric oxida-
tion of sulfides had constituted a very active research area, and excellent
results had been obtained.2–10 In those asymmetric catalytic reactions, the
ligands were mainly limited in the chiral diols and Schiff bases. Oxazoline as
a class of chiral ligands had been successfully employed in the asymmetric
Baeyer-Villiger reaction,11 Mukaiyama Aldol reaction, cyclopropanation
reaction, and many other catalytic asymmetric reactions.12 Bolm tried to use
bis[(4S)-4-isopropyl-4,5-dihydro-2-(oxazolinyl)phenolato]oxovanadium-(IV) as
catalyst to mediate the oxidation of methyl phenyl sulfide, but he obtained
racemic sulfoxide.13 These results prompted us to explore the feasibility of
catalytic enantioselective oxidation of sulfides using chiral oxazoline-
titanium complexes as catalysts. We thought that if we design some
oxazolines with suitable structure, we could achieve this transformation
with good enantioselectivity. Herein, we wish to report our efforts in
the study of enantioselective oxidation of sulfides catalyzed by chiral
oxazoline-titanium complexes.
The chiral oxazolines (1a–1f) were prepared via the reaction of the
corresponding amino alcohols and nitriles (Scheme 1).14
Scheme 1.
Our studies started with methyl phenyl sulfide as a test substrate
(Table 1). The oxidation reaction of sulfide with tert-butylhydroperoxide
(TBHP) was carried out in CH2Cl2/CCl4 at 0ꢀC for 24 h catalyzed by the
complexes formed in situ from a series of oxazolines, titanium alkoxide and
water (Scheme 2).

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2289
Table 1. The Enantioselective Oxidation of Methyl Phenyl Sulfide by TBHP in the
Presence of Ti(OiPr)4 and Chiral Ligandsa
Yield (%)b
Selectivity
Configuration
of 3d
Total
yield
Chemo
(3:4)
E.e. of
3 (%)c
Entry
Ligand
Sulfoxide (3)
1
2
3
4
5
6
1a
1b
1c
1d
1e
1f
67
66
23
58
72
96
41
31
23
13
40
68
62:38
48:52
100:0
78:22
56:44
70:30
11
72
9
12
9
R
R
R
R
S
0
aConditions: sulfide/oxazoline 1/Ti(OiPr)4/H2O ¼ 1.0/0.1/0.05/1.0; reaction tempera-
ture ¼ 0ꢀC; reaction time ¼ 24 h; 1.1 equiv. of TBHP(tert-butyl hydroperoxide, 70%
in water) was used; CH2Cl2/CCl4 ¼ 3:7 was used as solvent; bIsolated yield;
d
cDetermined by HPLC on a Daicel Chiralcel OB column; The absolute configura-
tion was assigned by comparison with literature values.2a,7a
Scheme 2.
The results listed in Table 1 indicated that the chemoselectivity and
enantioselectivity were strongly influenced by the structure of the oxazolines.
1b was found to be the most efficient ligand and gave 72% e.e. for the sulf-
oxide. If the configuration of C(5) in the oxazoline was inverted from S to R,
the e.e. of the sulfoxide was found to decrease from 72% to 11% (Table 1,
entries 2 and 1). If the phenyl group attached to C(5) was replaced by H,
opposite configuration of sulfoxide was observed (Table 1, entries 2 and 5).
So the configuration of C(5) had a strong influence on the enantioselectivity.
The substituent attached to C(4) had an influence on the enantioselectivity
too. When the phenyl was replaced by a benzyl, the e.e. of the sulfoxide
decreased from 9% to 0 (Table 1, entries 5 and 6). The tert-butyl group
(R3) was also necessary for good enantioselectivity. For example, when the
chiral oxazoline changed from 1b to 1d, only 12% e.e. was obtained in the
sulfoxide (Table 1, entry 4).

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PENG ET AL.
We screened a series of solvents including C6H6, C7H8, Et2O, THF,
CH2Cl2, CCl4, DCE (1,2-dichloroethane) and investigated their function on
the reaction. A mixture of CH2Cl2 and CCl4 (CH2Cl2/CCl4 ¼ 3:7) was found
to give the best results in both chemoselectivity and enantioselectivity.
The oxidation of methyl phenyl sulfide with Ti(IV)-1b as catalyst and 1.4
equiv. of oxidant, the enantioselectivity was found to be 63% e.e. in CH2Cl2
and 70% e.e. in CCl4, respectively. However, when a mixed solvent
(CH2Cl2/CCl4 ¼ 3:7) was used under identical conditions, the enantioselec-
tivity increased to 80% e.e. Further studies showed that the influence of the
ligand-to-metal ratio was not obvious for both the reactivity and selectivity.
The best results were obtained when 2.0 equivalents of oxazoline were used
per Ti (Table 1, entry 2). We also investigated the effect of the amount of
catalyst on the chemoselectivity and enantioselectivity of the reaction. The
chemoselectivity and enantioselectivity were not obviously influenced by the
catalyst level too. The best catalyst level used was 5 mol%. The effect of
temperature was also tested. The experiments showed that the reactivity and
enantioselectivity varied with the temperature from À25ꢀC to 20ꢀC. An
optimum reaction temperature was found to be 0ꢀC. We optimized the
amount of water and the kind of oxidant in this reaction system. The influ-
ence of the amount of water was not obviously in the range of literature
reported,6b the best amount of water relative to the sulfide was 1.0 equiv. We
also found that TBHP (70% in water) was superior to TBHP (5–6 M in
decane), H2O2 (30%) and MCPBA.
A phenomenon of kinetic resolution was observed in the enantio-
selective oxidation of sulfides. When other reaction conditions were kept
constant in the oxidation of methyl phenyl sulfide, the amount of oxidant
increased from 1.1 equiv. to 1.4 equiv., the yield of sulfoxide increased from
31% (72%e.e.) to 33% (80%e.e.). The isolated yield of sulfone increased
from 35% to 54%. In order to confirm this phenomenon, racemic methyl
phenyl sulfoxide was treated with 5 mol% Ti(OiPr)4/1b complex and 0.55
equiv. TBHP in CH2Cl2/CCl4, the e.e. value of the recovered sulfoxide was
found to be 45% (R) (isolated yield, 50%).
krel ¼ kf/ks ¼ ln[(1 À C)(1 À e.e.)/ln(1 À C)(1 þ e.e.) ¼ 4
15
The krel was lower than the literature reported (krel15).6c So this
system was inferior to the Ti-binaphthol complex in the catalytic kinetic
resolution of sulfoxides.
Encouraged by the result obtained for the enactioselective oxidation
of methyl phenyl sulfide, we investigated other sulfides by using the
[(1b)2-Ti(OiPr)4] catalyst system. As shown in Table 2, moderate isolated
yield and good to high e.e.’s were obtained for most of substrates. In the

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OXAZOLINE-TITANIUM COMPLEXES
2291
Table 2. The Enantioselective Oxidation of Sulfides (ArSR)a
Yield (%)b
Enantioselectivity
Total
yield
Chemo
(3:4)
E.e of
3 (%)c
Entry
Ar
R
Sulfoxide (3)
1
Ph
Ph
Ph
p-BrC6H4
p-MeC6H4
Ph
Me
Me
Et
Me
Me
PhCH2
Me
87
95
79
78
90
86
88
33
16
32
27
38
37
50
38:62
17:83
41:59
34:66
42:58
43:57
57:43
80 (R)
96 (R)
72 (R)
75 (R)
81 (R)
70 (R)e
21 (R)
2d
3
4
5
6
7
Pyridyl
aConditions: sulfide/ligand-1b/Ti(OiPr)4/H2O ¼ 1.0/0.1/0.05/1.0; reaction tempera-
ture ¼ 0ꢀC; reaction time ¼ 24 h; 1.4 equiv. of TBHP (70% in water) was used;
c
CH2Cl2/CCl4 ¼ 3:7 was used as solvent; bIsolated yield; Determined by HPLC on
a Daicel Chiralcel OB column; dCCl4 as solvent, 2.0 equiv. of TBHP (70% in water)
e
was used; Determined by HPLC on a Daicel Chiralcel OD column.
oxidation of methyl pyridyl sulfide, only 21%e.e. was obtained (Table 2,
entry 7). When 2.0 equiv. of TBHP was used in the oxidation of methyl
phenyl sulfide, up to 96%e.e. was obtained, even though the chemoselec-
tivity was lower (ratio of 3 and 4 was 17:83) (Table 2, entry 2). The high e.e.
might be due to concomitant kinetic resolution of the sulfoxide.
In conclusion, we have first probed and set up a novel oxazoline-
titanium catalytic system for the enantioselective oxidation of sulfide.
Good to high enantiomeric excess was obtained (up to 96%e.e.). Further
efforts will be devoted to the optimization of the oxazoline structure to
enhance both chemoselectivity and enantioselectivity for the enantioselec-
tive oxidation of sulfides.
EXPERIMENTAL
Melting points were determined on a Southend SS25PH apparatus
and were uncorrected. Elemental analyses were recorded on a Carlo Erba-
1106 instrument. HPLC analyses were performed on a Beckman-110A
chromatography with a Beckman 165 variable wavelengh detector.
1H-NMR and 13C-NMR spectra were performed on a Bruker 300 MHz
NMR spectrometer. Optical rotations were measured on a Perkin-Elmer
341 polarimeter. OB and OD Column was purchased from Daicel
Chemical Industries, LTD.

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2292
PENG ET AL.
General Procedure for the Syntheses of Oxazolines
In a 50 mL three-necked flask, 27.2 mg (0.2 mmol) of zinc chloride was
melted under high vacuum and cooled under argon. After cooling to
room temp., 10 mL of chlorobenzene was added followed by 5 mmol of
the corresponding benzonitrile and 5 mmol of the amino alcohol. The mix-
ture was refluxed for 20 h. The solvent was removed under reduced pressure
to give an oily residue, which was dissolved in 20 mL dichloromethane. The
solution was extracted for three times with 20 mL of water and the aqueous
phase with 10 mL of dichloromethane. The combined organic phases were
dried over anhydrous sodium sulfate and the solvent was removed in
vacuum. The residue was purified by flash chromatography (petroleum
ether/ethyl acetate 40:1).
(4S,5R)-4,5-Dihydro-4,5-diphenyl-2-(20-hydroxy-30-tert-butylphenyl)-
25
oxazoline 1a: (1.19 g, 65%); Yellow solid; M.p. ¼ 145ꢁ146ꢀC; [aŠ ¼ À 9.8ꢀ
D
(c 0.24, EtOH); IR (mull) ꢀ (cmÀ1) 1633 (C ¼ N), 1251 (C-O-C), 1213 (C-OH).
1H-NMR (CDCl3, 300 MHz); d 1.47 (s, 9H, C(CH3)3), 5.81 (d, 1H,
J ¼ 10.09 Hz, NCH), 5.98 (d, 1H, J ¼ 10.1 Hz, OCH), 6.88 (t, 1H,
J ¼ 7.72 Hz, ArH), 7.04 (m, 10H, ArH), 7.47 (dd, 1H, J ¼ 7.75 Hz, 1.45 Hz,
ArH), 7.76 (dd, 1H, J ¼ 7.77 Hz, 1.43 Hz, ArH), 12.76 (s, 1H, OH);
13C-NMR (CDCl3, 300 MHz): d 167.9, 160.3, 138.1, 137.8, 136.54, 131.64,
128.45, 128.42, 128.39, 128.36, 127.91, 127.12, 116.72, 110.96, 84.94, 73.99,
35.74, 30.11. EIMS (M/Z): 371 (Mþ), 204, 161, 91 (100), 77, 41. Anal. Calcd
for C25H25NO2: C, 80.83; H, 6.78; N, 3.77. Found: C, 80.96; H, 6.90; N, 3.87.
(4S,5S)-4,5-Dihydro-4,5-diphenyl-2-(20-hydroxy-30-tert-butylphenyl)-
25
D
oxazoline 1b: (1.54 g, 84%); Yellow solid; M.p. ¼ 94 ꢁ 95.5ꢀC; [aŠ ¼ þ94.4ꢀ
(c 0.77, EtOH); IR (mull) v (cmÀ1): 1632 (C ¼ N), 1251 (C-O-C), 1208 (C-
1
OH); H-NMR (CDCl3, 300 MHz): d 1.46 (s, 9H, C (CH3)3), 5.28 (d, 1H,
J ¼ 7.8 Hz, NCH), 5.36 (d, 1H, J ¼ 7.8 Hz. OCH), 6.84 (t, 1H, J ¼ 7.86 Mz,
ArH), 7.35 (m, 10H, ArH), 7.44 (dd, 1H, J ¼ 7.71 Hz, 1.41 Hz, ArH), 7.71
(dd, 1H, J ¼ 7.92 Hz, 1.38 Hz, ArH), 12.67 (s, 1H, OH); 13C-NMR (CDCl3,
300 MHz): d 167.0, 160.2, 141.9, 140.2, 138.0, 131.5, 129.6, 129.3, 128.6,
127.2, 127.1, 126.5, 118.6, 111.0, 88.6, 78.3, 35.7, 30.0; EIMS (M/Z): 371
(Mþ), 204 (100), 161, 91, 77, 41. Anal. Calcd for C25H25NO2: C, 80.83;
H, 6.78; N, 3.77; Found: C, 80.92; H, 6.78; N, 3.76.
(4S,5R)-4,5-Dihydro-4,5-diphenyl-2-(20–hydroxyphenyl)oxazoline
1c:
20
(1.09 g, 69%); M.p. ¼ 51–52ꢀC; [aŠ ¼ À42.4ꢀ(c 1.53, EtOH); IR (mull) v
D
(cmÀ1) 3030 (O-H), 1641 (C ¼ N), 1490, 1258, 1069; 1H-NMR (CDCl3,
300 MHz): d 4.8 (s, 1H, OH), 5.77 (d, 1H, J ¼ 10.02 Hz, NCH), 5.96 (d,
1H, J ¼ 10.02 Hz, OCH), 6.9 (m, 5H, ArH), 7.0 (m, 5H, ArH), 7.4 (m,
3H, ArH), 7.84 (d, 1H, J ¼ 7.74 Hz, ArH): 13C-NMR (CDCl3, 300 MHz): d
167.2, 161.0, 137.7, 136.3, 134.5, 131.4, 129.2, 129.1, 129.0, 128.9, 128.6,

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OXAZOLINE-TITANIUM COMPLEXES
2293
128.46, 128.3, 127.9, 127.6, 127, 119.5, 117.6, 110.9, 85.2, 73.8; EMIS (M/Z):
315 (Mþ), 209, 195, 148, 121, 104, 91 (100), 77, 65, 51, 39, 27; Anal. Calcd
for C21H17NO2: C, 79.98; H, 5.43; N, 4.44; Found: C, 79.95; H, 5.56; N, 4.40.
(4S,5S)-4,5-Dihydro-4,5-diphenyl-2-(20-hydroxyphenyl)oxazoline
1d:
20
D
(1.34 g, 85%); M.p. ¼ 70 ꢁ 71ꢀC; [aŠ ¼ þ42.9ꢀ(c 0.99, EtOH); 1H-NMR
(CDCl3, 300 MHz): d 5.28 (d, 1H, J ¼ 7.83 Hz, NCH), 5.36 (d, 1H,
J ¼ 7.71 Hz, OCH), 6.91 (t, 1H, J ¼ 7.60 Hz, ArH), 7.07 (d, 1H,
J ¼ 8.43 Hz, ArH), 7.4 (m, 11H, ArH), 7.8 (d, 1H, J ¼ 7.89 Hz, ArH), 12.1
(s, 1H, OH); 13C-NMR (CDCl3, 300 MHz): d 165.9, 160.4, 140.6, 138.9,
134.2, 129.0, 128.97, 128.91, 128.5, 128.1, 126.4, 125.9, 118.8, 117.1, 109.6,
88.5, 76.7. IR (mull) v (cmÀ1) 3028 (O-H), 1642 (C ¼ N), 1617, 1584, 1455,
1258, 1065; EIMS (M/Z): 315 (Mþ), 209 (100), 195, 165, 148, 121, 105, 89,
77, 65, 51, 28; Anal. Calcd for C21H17NO2:C, 79.98; H, 5.43; N, 4.44;
Found: C, 79.96; H, 5.55; N, 4.35.
(4S )-4,5-Dihydro-4-phenyl-2-(20-hydroxy-30-tert-butylphenyl)oxazoline
20
1e: (0.99 g, 67%); M.p. ¼ 139ꢁ140ꢀC; [aŠ ¼ þ 69.7ꢀ (c 0.90, EtOH);
D
1H-NMR (CDCl3, 300 MHz): d 1.35 (s, 9H, C(CH3)3), 4.12 (t, 1H,
J ¼ 8.35 Hz, NCH), 4.66 (t, 1H, J ¼ 9.24 Hz, OCH), 5.35 (t, 1H,
J ¼ 9.18 Hz, OCH), 6.74 (t, 1H, J ¼ 7.74 Hz, ArH), 7.27 (m, 6H, ArH), 7.53
(d, 1H, J ¼ 7.71 Hz, ArH), 12.6 (s, 1H, OH); 13C-NMR (CDCl3, 300 MHz): d
166.9, 159.2, 141.5, 137.2, 130.6, 128.8, 127.8, 126.5, 126.2, 117.8, 110.4, 73.7,
68.8, 34.9, 29.3; IR (mull) v (cmÀ1) 3031 (O-H), 1628 (C ¼ N); EIMS (M/Z):
295 (Mþ), 280, 252, 161 (100), 120, 91, 77, 65, 41, 27; Anal. Calcd for
C19H21NO2, C, 77.26, H, 7.17, N, 4.74; Found: C, 76.99, H, 7.23, N, 4.57.
(4S )-4,5-Dihydro-4-benzyl-2-(20-hydroxy-30-tert-butylphenyl)oxazoline
20
D
1
1f: (1.24 g, 80%); M.p. ¼ 39ꢁ40ꢀC; [aŠ ¼ þ13.4ꢀ(c 0.74, EtOH); H-NMR
(CDCl3, 300 MHz): d 1.44 (s, 9H, C(CH3)3), 2.78 (dd, 1H, J ¼ 13.71 Hz,
8.07 Hz; PhCH), 3.17 (dd, 1H, J ¼ 13.71 Hz, 5.94 Hz; PhCH), 4.1 (t, 1H,
J ¼ 7.92 Hz, OCH2); 4.35 (t, 1H, J ¼ 8.76 Hz, OCH2), 4.62 (m, 1H, NCH),
6.8 (t, 1H, J ¼ 7.74 Hz, ArH), 7.3 (m, 6H, ArH), 7.5 (d, 1H, J ¼ 6.87 Hz,
ArH), 12.7 (s, 1H); 13C-NMR (CDCl3, 300 MHz): d 166.1, 159.1, 137.6,
137.1, 130.4, 129.1, 128.6, 126.6, 126.0, 117.7, 110.5, 70.9, 66.7, 41.8, 34.9,
29.3; IR (mull) v (cmÀ1) 3050 (O-H), 1633 (C ¼ N), 1497, 1455, 1433, 1367,
1252, 1211; EIMS (M/Z): 309 (Mþ), 294, 266, 218, 176, 161, 132, 105, 91
(100), 77, 65, 51, 41, 27; Anal. Calcd for C20H23NO2: C, 77.64; H, 7.49;
N, 4.53; Found: C, 77.56; H, 7.52; N, 4.44.
General Procedure for the Asymmetric Oxidation of Sulfides
To a solution of oxazoline (0.05 mmol) in a suitable solvent was
introduced Ti(OiPr)4 (0.025 mmol) by means of a syringe under an argon

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2294
PENG ET AL.
atmosphere. This solution was stirred for 2 h at rt. and the solvent was
removed under reduced pressure, and then an appropriate solvent
(2.5 mL) and water (9 mL) were added. After the mixture was stirred at rt.
for 1 h, the sulfide (0.50 mmol) was introduced by means of a syringe and the
mixture was cooled to the appropriate temperature. After 0.5 h, TBHP (70%
in water) was introduced by means of a syringe, and the mixture was stirred
for 24 h. The reaction mixture was directly purified by flash chromatograph.
(petroleum ether/ethyl acetate 2:1).
1
Methyl phenyl sulfoxide: H-NMR (CDCl3, 300 MHz): d 2.72 (s, 3H),
7.58 (m, 5H, ArH); IR (KBr) v (cmÀ1) 1477, 1443, 1415, 1089, 1036 (S ¼ 0).
(R) 81% e.e.; [aŠ ¼ þ34.4ꢀ(c 0.36, CH3COCH3).
27
D
p-Methylphenyl methylsulfoxide: 1H-NMR(CDCl3, 300 MHz):
d
2.42 (s, 3H, PhCH3), 2.71 (s, 3H, SOCH3), 7.33 (d, 2H, J ¼ 7.98 Hz, ArH),
7.54 (d, J ¼ 7.89 Hz, 2H, ArH); IR(KBr) v (cmÀ1) 1493, 1421, 1088, 1048 (S,
27
D
S ¼ O). (R) 80.7% e.e.; [aŠ ¼ þ53.5ꢀ (c 1.0, CH3COCH3).
1
p-Bromophenyl methylsulfoxide: H-NMR (CDCl3, 300 MHz): d 2.72
(s, 3H, CH3), 7.60 (m, 4H, ArH); IR (KBr) ꢀ (cmÀ1) 1469, 1417, 1387, 1084,
1043 (S ¼ O), 1008, 516 (C-Br). (R) 75% e.e.; [a2D7] ¼ þ37.6ꢀ (c 0.60,
CH3COCH3).
1
Ethyl phenyl sulfoxide: H-NMR (CDCl3, 300 MHz): d 1.20 (t, 3H,
J ¼ 7.36 Hz, CH3), 2.80 (m, 2H, CH2), 7.60 (m, 5H, ArH); IR (KBr)
27
D
v (cmÀ1) 1443, 1086, 1044 (S ¼ O), 1021. (R) 71.8% e.e.; [aŠ ¼ þ65.2ꢀ
(c 1.0, CH3COCH3).
1
Benzylphenyl sulfoxide: H-NMR (CDCl3, 300 MHz): d 4.0 (d, 1H,
J ¼ 12.57 Hz, CH2), 4.06 (d, 1H, J ¼ 12.57 Hz, CH2), 6.96–7.45 (m, 10H,
ArH); IR (KBr) ꢀ (cmÀ1) 1494, 1455, 1034 (S ¼ O). (R) 70% e.e.;
[aŠ ¼ þ75.5ꢀ(c 1.56, CH3COCH3).
27
D
ACKNOWLEDGMENTS
We thank the National Natural Science Foundation of China
(No. 29832020) and The Hong Kong Polytechnic University ASD Fund
for financial support of the study.
REFERENCES
1. (a) Mata, E.G. Phosphorus Sulfur Silicon 1996, 117, 231; (b) Kagan,
H.B.; Rebiere, F.; Samuel, O. Phosphorus Sulfur Silicon 1991, 58, 89;
(c) Carreno, M.C. Chem. Rev. 1995, 95, 1717; (d) Waker, A.J.
Tetrahedron: Asymmetry 1992, 3, 961.

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2295
2. (a) Pitchen, P.; Dunach, E.; Deshmukh, M.N.; Kagan, H.B. J. Am.
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ORDER
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Received in Japan July 31, 2000

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