Facile optical resolution of tert-butanethiosulfinate by molecular complexation with (R)-BINOL and study of chiral discrimination of the diastereomeric complexes

Article abstract of DOI:10.1002/chem.200204653

An important synthon, tert-butanethiosulfinate (2), has been effectively resolved by forming molecular complexes with (R)-2,2′-dihydroxy-1,1′-binaphthyl (BINOL, 3) in high enantioselectivity (> 99% ee). The present procedure represents the first example of the resolution of thiosulfinate. The mechanism of chiral discrimination is discussed in terms of molecular recognition based on IR and X-ray analyses of the diastereomeric complexes during the resolution. In the less-soluble complex, (R)-3 and (R)-2 self-assembled as a linear supramolecule; however, in the more-soluble complex, (R)-3 and (S)-2 formed a simple bimolecular complex by one stronger hydrogen bond. Hydrogen bonding is the major driving force for effective resolution.

Full text of DOI:10.1002/chem.200204653

FULL PAPER
Facile Optical Resolution of tert-Butanethiosulfinate by Molecular
Complexation with (R)-BINOL andStu dy of Chiral Discrimination
of the Diastereomeric Complexes
Jian Liao, Xiaoxia Sun, Xin Cui, Kaibei Yu, Jin Zhu, andJingen Deng* [a]
Abstract: An important synthon, tert-butanethiosulfinate (2), has been effectively
resolved by forming molecular complexes with (R)-2,2'-dihydroxy-1,1'-binaphthyl
(BINOL, 3) in high enantioselectivity (>99% ee). The present procedure represents
the first example of the resolution of thiosulfinate. The mechanism of chiral
discrimination is discussed in terms of molecular recognition based on IR and X-ray
analyses of the diastereomeric complexes during the resolution. In the less-soluble
complex, (R)-3 and (R)-2 self-assembled as a linear supramolecule; however, in the
more-soluble complex, (R)-3 and (S)-2 formed a simple bimolecular complex by one
stronger hydrogen bond. Hydrogen bonding is the major driving force for effective
resolution.
Keywords: (R)-BINOL
butanethiosulfinate
¥
tert-
¥
molecular
complex ¥ molecular recognition Á
self-assembly
Introduction
the chemoselective ring-opening of enantiopure N-sulfonyl-
1
,2,3-oxathiazolidine-2-oxide agents.[ In addition, Ellman×s
5]
Chiral sulfoxides are useful synthons for the asymmetric
group also tried to obtain enantiopure 1 by resolving rac-1,
unfortunately, no satisfactory results were given. But this
concept provides us with an alternative route to get enantio-
[1]
[6]
synthesis of biologically active compounds, while sulfin-
amides are increasingly utilized as versatile chiral nitrogen
intermediates for the preparation of a range of chiral
amines.[ However, practical
pure 1, which might be obtained by resolution of its precursor
2]
[7]
rac-2. Over the past few years, our group has also been
methods for the preparation
of enantiopure sulfinamides
engaged in the resolution of chiral sulfoxide synthons, alkyl
pyridyl sulfoxides, and the chiral drugs, omeprazole and
are very few. During the past
few years, the versatility of tert-
lansoprazole (proton-pump inhibitors), through molecular
complexation with chiral host compounds.[
8, 9]
Herein, we
butanesulfinamide (1) for
the asymmetric synthesis of
would like to report the preparation of both enantiopure
isomers of 2 by inclusion complexation with one enantiomer
of the chiral host compound, (R)-2,2'-dihydroxy-1,1'-bi-
naphthyl (BINOL, 3) for the first time.
amines has been well documented,[3] so it is very important
to develop a highly efficient method to prepare enantiopure 1.
In 1997, Ellman and co-workers developed an elegant method
for the preparation of enantiopure (R)-1 by means of catalytic
asymmetric oxidation of di-tert-butyldisulfide followed by
amidation of (R)-tert-butanethiosulfinate (2).[ (R)-1 has
recently been synthesized by Senanayake and co-workers by
4]
[
a] Prof. Dr. J. Deng, Dr. J. Liao, X. Sun, X. Cui, Prof. K. Yu, Prof. J. Zhu
Union Laboratory of Asymmetric Synthesis
Chengdu Institute of Organic Chemistry
Chinese Academy of Sciences, Chengdu 610041 (China)
Fax : (‡86)28-8522-3978
As is well known, the molecular recognition between host
and guest molecules is directed by specific intermolecular
forces (e.g., hydrogen bonding and second-order interac-
tions), as well as by steric complementarity. It is important to
elucidate the resolution mechanism in terms of molecular
recognition between host and two enantiomers of guest in the
solid state, especially by X-ray crystallographic analyses.
E-mail: jgdeng@cioc.ac.cn
Supporting information for this article is available on the WWW under
http://www.chemeurj.org or from the author: NMR and IR spectra of
all compounds plus DSC analyses of the complexes.
Chem. Eur. J. 2003, 9, 2611 ± 2615
DOI: 10.1002/chem.200204653
¹ 2003 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
2611

J.-G. Deng et al.
FULL PAPER
To the best of our knowledge, relatively few reports have
probed both crystal structures of the less- and more-soluble
diastereomers of host ± guest complexes to gain insight into
the mechanism of chiral discrimination,[ and furthermore,
no example concerns the less- and more-soluble diastereo-
meric complexes of sulfoxides.[ Herein, we will study the
molecular recognition during resolution by X-ray crystallo-
graphic analysis, as well as IR spectroscopic analysis of the
less-soluble molecular complex, which consists of (R)-3 and
10]
9]
Scheme 1. The resolution of rac-2 by inclusion crystallization. The yields
are calculated on the basis of half of the starting rac-2.
(
R)-2, and the more-soluble molecular complex, which
consists of (R)-3 and (S)-2.
(R)-3 left after separation of 2 by distillation can be used
again.
In our previous works,[7] we found that IR spectroscopic
analysis is an effective approach to elucidate the interactions
between host and guest molecules, because of the character-
istic peaks between the hydrogen-bonded and free sulfoxides.
In this work, we systematically studied the interactions
between (R)-3 and two enantiomers of 2 by IR spectroscopic
analysis (Table 2).
Results andDiscussion
Inclusion crystallization has been used since the early 1980s to
selectively and reversibly include chiral guest molecules into
[8]
host lattices of chiral molecules. To the best of our knowl-
edge, successful resolution has been limited to the preparation
of enantiopure aryl- or alkylsulfoxides to date.[
8, 9]
The only
two other examples for chiral sulfur-containing compounds
Table 2. IR spectroscopic data of host and guest compounds and inclusion
complexes.[
a]
[8]
are the resolution of sulfoximines and alkyl phenylsulfina-
[
9e]
tes. Thus, we initially utilized chiral host (S,S)-(‡)-trans-4,5-
Compound
nÄ OH
nÄ OH
nÄ SˆO
[cm ]
À1
À1
À1
[
cm
]
[cm
]
bis(hydroxydiphenylmethyl)-2,2-dimethyl-1,3-dioxolane
11]
(
TADDOL),[ to resolve rac-2, which gave low resolving
1
2
3
4
5
6
(R)-3
rac-2
(R)-2
(S)-2
(R,R)-2 ¥ 3
(S,R)-2 ¥ 3
3509(s)
3435(s)
efficiency (<28% ee). Fortunately, while the readily available
1075
1075
1075
995
R)-3[ was used as chiral host, successful resolution of rac-
12]
[13]
(
2
was achieved. In order to improve the efficiency of the
3324 (brs)
3254 (brs)
resolution, several kinds of solvents and their mixtures were
examined, and ethanol was found to be an excellent solvent
3534 (s)
1039
[
a] Samples in nujol for entries 1, 5, and 6, and neat for entries 2, 3, and 4.
(
Table 1, entry 7).
A typical resolution process is described as follows. (R)-3
17.34 g, 60.6 mmol) and rac-2 (11.76 g, 60.6 mmol) were
The IR spectrum of host (R)-3 exhibits two sharp and strong
(
À1
À1
hydroxyl absorption bands at 3509 cm
and 3435 cm
dissolved in ethanol (60 mL), and the mixture was kept at
room temperature for 12 h. An inclusion complex, (R,R)-2 ¥ 3
in a 1:1 ratio was obtained as colorless crystals by filtration.
After recrystallization from ethanol, the complex, (R,R)-2 ¥ 3
was heated in vacuo to give (R)-2 by distillation (728C/40 Pa)
with >99% ee. The filtrate was concentrated, and the 1:1
complex of (S,R)-2 ¥ 3 was obtained as colorless crystals. After
twice being recrystallized from ethanol, the inclusion complex
of (S,R)-2 ¥ 3 was also heated in vacuo to give (S)-2 by
distillation (648C/30 Pa) with >99% ee (Scheme 1). The host
(
Table 2, entry 1), and guest compound 2, racemate and
enantiomers, exhibits a strong sulfinyl absorption band at
À1
1
075 cm (Table 2, entries 2, 3 and 4). Meanwhile, in the less-
soluble complex (R,R)-2 ¥ 3, the two original hydroxyl absorp-
tion bands of (R)-3 disappear and a new absorption band
À1
appears at 3324 cm . The sulfinyl absorption band of 2
À1
À1
appears at 995 cm , a shift to lower wavenumber of 80 cm .
In the more-soluble complex, (S,R)-2 ¥ 3, both original hy-
droxyl absorption bands of (R)-3 also disappear and two new
À1
À1
bands appear at 3534 cm and 3254 cm . The sulfinyl
absorption band of 2 appears at 1039 cm ; a smaller shift to
lower wavenumber, of 36 cm , than for (R,R)-2 ¥ 3. Moreover,
À1
Table 1. Resolution of rac-2 with (R)-3 in different solvents.[a]
À1
Solvent (v/v)
ee [%][b,c]
Yield [%][c,d]
in the more-soluble complex, (S,R)-2 ¥ 3, one hydroxyl group
À1
1
2
3
4
5
6
7
8
9
0
toluene
acetone
86.1(73.9)
91.7(41.3)
95.0(63.3)
76.3(70.5)
92.1(55.7)
92.0(77.1)
91.7(85.3)
88.2(76.8)
78.0(88.4)
82.3(76.9)
98.3(72.3)
43.7(134.4)
58.3(132.6)
80.0(105.0)
54.6(137.8)
77.3(109.2)
91.7(105.0)
93.6(100.0)
120.0(67.2)
113.1(63.9)
of (R)-3 shifts further towards lower wavenumbers (181 cm )
À1
than that in (R,R)-2 ¥ 3 (111 cm ). These results showed that
acetone/hexane (1:2)
acetone/hexane (1:3)
butanone
butanone/hexane (1:3)
ethanol
ethanol/hexane (1:1)
iPrOH
iPrOH/hexane (2.5:1)
in the less-soluble complex, (R,R)-2 ¥ 3, two (R)-3 hydroxyl
groups formed hydrogen bonds and the sulfinyl group formed
two hydrogen bonds; but in the more-soluble complex, (S,R)-
¥ 3, only one stronger hydrogen bond exists between (S)-2
and (R)-3 (Scheme 2). Thus, two possible hydrogen-bonding
models between (R)-2 and (R)-3 were proposed for (R,R)-2 ¥ 3
2
1
(
Scheme 2A and A'). Interestingly (S,R)-2 ¥ 3 consists of
[
a] Resolution with a 1:1 molar ratio of host (R)-3 and guest rac-2 on a scale
locally hydrogen-bonded 1:1 host ± guest entities (Sche-
me 2B), which are usually observed in the less-soluble
complexes of TADDOLs.[
of 2.5 mmol. [b] Enantiomeric excess of 2 was determined by chiral HPLC
analysis (Chiral Pak AS column). [c] The value of the (S,R)-2 ¥ 3 complex is
in parenthesis. [d] Yield based on half of the starting rac-2.
7a, 14]
2612
¹ 2003 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
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Chem. Eur. J. 2003, 9, 2611 ± 2615

Optical Resolution of tert-Butanethiosulfinate
2611±2615
cases, the guest molecules were
included in the void construct-
ed by the supramolecules,
which formed by the self-as-
sembly of the host molecules
only.[
9b, 18]
It is noticeable that a
large dihedral angle (107.38)
between the two naphthyl units
of (R)-3[ is due to the steric
complementarity of the bulky
tert-butyl groups of (R)-2.[
9i]
12a,b]
Gratifyingly, we also ob-
tained a single crystal of the
more-soluble complex, (S,R)-
Scheme 2. Proposed hydrogen bond relationship for inclusion complexes, (R,R)-2 ¥ 3 (A and A') and
(
S,R)-2 ¥ 3 (B).
2
¥ 3, and studied the crystal
structure (Figure 1B)[ in order to reveal the chiral discrim-
15]
In order to clarify the interactions between (R)-3 and (R)-2,
we prepared a single crystal of the less-soluble complex,
ination of the diastereomeric complexes.[
13b,c]
(R)-3 and (S)-2
(
R,R)-2 ¥ 3 and studied the structure by X-ray crystallographic
formed a molecular complex through a hydrogen bond with a
shorter distance of 2.658 ä than that proposed above by IR
analysis (Scheme 2B).[ Again, the large dihedral angle
(107.48) between the two naphthyl units of (R)-3 is due to
the steric complementarity of the bulky tert-butyl groups of
(S)-2,[ and it is noteworthy that this steric complementarity
is also related to the different conformations of (R)- and (S)-2
in the diastereomeric complexes. The C1-S1-S2-C5 torsion
angles of 2 in both complexes are obviously different,
À135.278 for (R,R)-2 ¥ 3 and 175.678 for (S,R)-2 ¥ 3, in which
two bulky tert-butyl groups from (S)-2 exhibit a strained anti
arrangement. No second-order interactions, such as a C-H ¥¥¥
p interaction between the methyl groups of 2 and the
naphthalene rings of (R)-3 were found in the crystal structures
of the less- and more-soluble complexes. Crystal packing is
stabilized by weaker van der -
[15]
analysis (Figure 1).
19]
Figure 1A illustrates the intermolecular hydrogen-bonding
scheme found in the crystal structure of (R,R)-2 ¥ 3. It consists
of continuous hydrogen-bonded chains that are aligned along
the a axis of the crystal. This confirmed that the correct
hydrogen interaction proposed by IR is model A (Scheme 2).
The sulfoxide moiety acts as a proton acceptor from, and thus
bridges between, two different binaphthol molecules, which
are related to each other by the two-fold screw symmetry
13c]
(
2
Figure 1A); the hydrogen bonding distances are 2.747 ä and
.907 ä. This result showed that the molecular recognition is
on the basis of an enantiodifferentiating self-assembly of host
[16, 17]
[9b,d,f]
(
R)-3 and guest (R)-2
that is different from Ogura×s
[9c]
and Fantin×s results in the inclusion phenomena. In the later
Waals forces among the linear
supramolecules in (R,R)-2 ¥ 3, as
well as the bimolecular com-
plexes in (S,R)-2 ¥ 3 (Figure 1).
The preferential crystallization
of (R,R)-2 ¥ 3 is due to the dual
hydrogen bonds of (R)-2, which
contribute to the thermody-
namic stability of the complex.
Differential scanning calori-
[20]
metric (DSC) analysis dem-
onstrated that the heats of
fusion are large differences
between the more- and
less-soluble
complexes
and
À1
(
38.9 kJmol
À1
5
8.9 kJmol , respectively) and
a higher melting point was ob-
served in the less-soluble com-
plex (see the Experimental Sec-
tion). The different hydrogen-
bonding relationships in the
diastereomeric complexes are
the key factor for the successful
resolution of rac-2 with host
compound (R)-3.
Figure 1. Stereoview of the hydrogen bond relationship of molecular complexes (R,R)-2 ¥ 3 (A) and
(
S,R)-2 ¥ 3 (B).
Chem. Eur. J. 2003, 9, 2611 ± 2615
www.chemeurj.org
¹ 2003 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
2613

J.-G. Deng et al.
FULL PAPER
determined by HPLC on a Chiral Pak AS column with propan-2-ol/
Conclusion
À1
hexanes (5:95 v/v) as eluent, 1.0 mLmin , t
S
ˆ 5.6 min, t ˆ 7.2 min.
R
The mother liquid was condensed to about 30 mL and kept at room
temperature for 12 h. The colorless crystalline solid was collected by
filtration and after recrystallization from ethanol (2 Â ), the enantiopure
In summary, we have demonstrated a highly efficient and
practical optical resolution of the important synthon, tert-
butanethiosulfinate (2), by inclusion crystallization with (R)-
[22]
complex (S,R)-2 ¥ 3 was obtained. Yield: 5.20 g (35.7%);
m.p. 136.0 ±
2
0
ˆ À43 (c ˆ 0.4 in acetone); 1H NMR (300 MHz, CDCl
2,2'-dihydroxy-1,1'-binaphthyl (BINOL, 3), which is the first
138.08C, [a]
D
3
):
d ˆ 1.40 (s, 9H; tert-butyl CH
3 3
), 1.58 (s, 9H; tert-butyl CH ), 7.16 ± 8.01 (m,
example of the optical resolution of the thiosulfinate. Both
enantiomers of 2 were prepared in high enantiomeric purity
1
3
1
1
3
2H; ArH); C NMR (75 MHz, CDCl
3
): d ˆ 24.1, 32.2, 48.7, 59.4, 111.4,
17.8, 123.7, 124.3, 127.1, 128.2, 129.2, 131.0, 133.5, 152.7; IR (Nujol): nÄ ˆ
(
>99% ee) with one enantiomer of the chiral host, (R)-3. IR
À1
324, 2925, 995 cm ; elemental analysis calcd (%) for C28
32 2 3
H S O : C 69.96,
spectroscopic analysis was found to be an effective tool for
studying the molecular recognition of sulfoxides. The struc-
tures of the diastereomeric complexes, (R,R)-2 ¥ 3 and (S,R)-
H 6.71, S 13.34; found: C 70.02, H 6.71, S 13.38.
(S)-2 was obtained (1.69 g, 80.5%,[22] 99.2% ee) by distillation (648C/
2
4
1
30 Pa). [a]
D
ˆ À159 (c ˆ 0.57 in CH
2
Cl
2
); H NMR (300 MHz, CDCl
); IR (Neat): nÄ ˆ
O: C 49.44, H
3
): d ˆ
1.39 (s, 9H; tert-butyl CH
3
), 1.57 (s, 9H; tert-butyl CH
3
2
¥ 3, was studied by IR spectroscopic and X-ray crystallo-
À1
2
9
962, 1075 cm ; elemental analysis calcd (%) for C
.33, S 33.00; found: C 49.32, H 9.23, S 33.08.
8 18 2
H S
graphic analyses for the chiral discrimination. In the less-
soluble complex, host (R)-3 and guest (R)-2 self-assembled as
a linear supramolecule along the a axis of the crystal by dual
hydrogen bonds; however, the more-soluble (R)-3 and (S)-2
formed a bimolecular complex that consists of locally hydro-
gen-bonded 1:1 host ± guest entities. Different hydrogen
bonding contributes to the chiral discrimination of the
diastereomeric complexes and the successful resolution of
racemic 2 with host (R)-3. It is noteworthy that the large
dihedral angle (107.38and 107.48for (R,R)-2 ¥ 3 and (S,R)-2 ¥ 3,
respectively) between two naphthalene units of (R)-3 is due to
the flexibility of the BINOL molecule, which might contribute
Crystal data for (R,R)-2 ¥ 3: M
orthorhombic, space group P2
w
ˆ 480.66, crystal size 0.52  0.50  0.50 mm,
1
2
1
2
1
,
a ˆ 12.979(2), b ˆ 13.133(2), c ˆ
3
14.953(2) ä, a ˆ 90, b ˆ 90, g ˆ 908, Vˆ 2548.8(6) ä , Z ˆ 4,
D
calcd
ˆ
À3
1
.253 Mgm , F(000) ˆ 1024, Tˆ 296(2) K. Final R indices [I > 2s(I)]:
R1 ˆ 0.0357, wR2 ˆ 0.0739. All non-hydrogen atoms were anisotropically
generated, whereas the hydrogen atoms were generated geometrically. The
[23]
Flack parameter, x ˆ 0.02(6), confirms the absolute configuration.
Crystal data for (S,R)-2 ¥ 3: M
w
ˆ 480.66, crystal size 0.52  0.46  0.46 mm,
triclinic, space group P1, a ˆ 8.661(2), b ˆ 8.827(2), c ˆ 9.346(2) ä, a ˆ
3
67.22(2), b ˆ 86.86(1), g ˆ 79.52(2)8, Vˆ 647.7(3) ä , Z ˆ 1,
D
calcd
ˆ
À3
1.232 Mgm
,
F(000) ˆ 256, Tˆ 289(2) K. Final
R indices [I > 2s(I)]:
R1 ˆ 0.0409, wR2 ˆ 0.1084. All non-hydrogen atoms were anisotropically
generated, whereas the hydrogen atoms were generated geometrically. The
to the effective resolution of a variety of chiral compounds
[23]
Flack parameter, x ˆ 0.01(8), confirms the absolute configuration.
with BINOLs by steric complementarity.[
8, 12, 13]
This will
Crystal structure determinations: Both single crystals of (R,R)-2 ¥ 3 and
(S,R)-2 ¥ 3 were grown from an ethanol/hexane mixture. All X-ray
diffraction data were collected on a Siemens P4 automatic four-circle
diffractometer by using graphite monochromatic MoKa radiation (l ˆ
provide a guiding concept for us to design novel hosts and
improve the resolving efficiency of tert-butanethiosulfinate in
the future.[7, 17]
0
.71073 ä) at room temperature. The structure was solved by direct
[
24]
method by using SHELXS-97 and refined by full-matrix least-square
calculation on F with SHELXL-97.[25] Calculations were performed on a
PII-350 computer with the Siemens SHELXTL program package.[
Further data have been deposited with the Cambridge Crystallographic
Data Centre.[
2
26]
Experimental Section
15]
General: H NMR and 13C NMR spectra were measured in CDCl
Bruker 300 (300 MHz) spectrometer and are reported in ppm (d) relative
to CDCl as internal references, unless otherwise noted. Infrared spectra
1
3
on a
3
Acknowledgement
were recorded on a NICOLET 200SXV FTIR spectrometer. Melting
points were determined on a digital melting-point apparatus and uncor-
rected. Optical rotations were measured on a Perkin ± Elmer 341 polar-
imeter. Liquid-chromatographic analyses were conducted on a Beck-
man 110 instrument equipped with a model 168 detector as ultraviolet light
source (254 nm). Differential scanning calorimetry (DSC) was performed
with a Perkin ± Elmer DSC7 system. Racemic tert-butanethiosulfinate (2)
was prepared according to the reported procedure.[ (R)-BINOL (3) is a
commercially available product.
This work was supported by the National Natural Science Foundation of
China (Grants No. 29790125, 29972039, 20025205).
[
1] For a comprehensive review, see: M. C. Carreno, Chem. Rev. 1995, 95,
717 ± 1760.
21]
1
[
2] For comprehensive reviews, see: a) P. Zhou, B.-C. Chen, F. A. Davis in
Advances in Sulfur Chemistry, Vol. 2 (Eds.: C. M. Raynor), JAI Press,
Stamford, CT, 2000, pp. 249 ± 282; b) F. A. Davis, P. Zhou, B.-C. Chen,
Chem. Soc. Rev. 1998, 27, 13 ± 18; c) F. A. Davis, R. E. Reddy,
Phosphorus, Sulfur, Silicon Relat. Elem. 1997, 120/121, 291 ± 303.
3] For a review, see: a) J. A. Ellman, T. D. Owens, T. P. Tang, Acc. Chem.
Res. 2002, 35, 984 ± 995; for more recent papers, see: b) T. D. Owens,
A. J. Souers, J. A. Ellman, J. Org. Chem. 2003, 68, 3 ± 10; c) T. P. Tang,
J. A. Ellman, J. Org. Chem. 2002, 67, 7819 ± 7832; d) D. D. Staas, K. L.
Savage, C. F. Homnick, N. N. Tsou, R. G. Ball,J. Org. Chem. 2002, 67,
Optical resolution of tert-butanethiosulfinate (2): A mixture of (R)-BINOL
(
3) (17.34 g, 60.6 mmol) and racemic tert-butanethiosulfinate (2) (11.76 g,
0.6 mmol) in anhydrous ethanol (60 mL) was heated under reflux until the
solid was dissolved, then allowed to cool to room temperature, and kept for
2 h. The colorless crystals were collected by filtration and after recrystal-
6
1
[
lization from ethanol (1 Â ), the enantiopure complex, (R,R)-2 ¥ 3 was
[
22]
20
D
obtained. Yield: 10.81 g (74.3%); m.p. 151.0 ± 153.08C; [a]
ˆ ‡80 (c ˆ
0
.4 in acetone); 1H NMR (400 MHz, CDCl
CH ), 1.55 (s, 9H; tert-butyl CH
3
): d ˆ 1.40 (s, 9H; tert-butyl
), 7.14 ± 7.19 (m, 12H; ArH); 1 C N MR
3
3
3
(
1
75 MHz, CDCl
3
): d ˆ 24.1, 32.2, 48.6, 59.4, 111.2, 117.8, 123.8, 124.2, 127.2,
8
1
276 ± 8279; e) G. K. S. Prakash, M. Mandal, J. Am. Chem. Soc. 2002,
24, 6538 ± 6539.
À1
28.2, 129.3, 131.1, 133.4, 152.6; IR (Nujol): nÄ ˆ 3324, 2925, 995 cm
;
elemental analysis calcd (%) for C28
32 2 3
H S O : C 69.96, H 6.71, S 13.34;
[
4] a) G. Liu, D. A. Cogan, J. A. Ellman, J. Am. Chem. Soc. 1997, 119,
913 ± 9914; b) S. A. Blum, R. G. Bergman, J. A. Ellman, J. Org.
Chem. 2003, 68, 150 ± 155.
found: C 70.15, H 6.66, S 13.46.
9
[
22]
(
4
1
2
9
R)-2 was obtained (3.50 g, 80.1%,
99.5% ee) by distillation (728C/
0 Pa). [a]2
4
ˆ ‡159 (c ˆ 0.58 in CH
Cl
); H NMR (300 MHz, CDCl
1
): d ˆ
); IR (Neat): nÄ ˆ
O: C 49.44, H
.33, S 33.00; found: C 49.24, H 9.23, S 33.14. Enantiomeric purity was
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D
2
2
3
.39 (s, 9H; tert-butyl CH
3
), 1.57 (s, 9H; tert-butyl CH
3
À1
962, 1075 cm ; elemental analysis calcd (%) for C H S
8 18 2
2614
¹ 2003 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.chemeurj.org
Chem. Eur. J. 2003, 9, 2611 ± 2615

Optical Resolution of tert-Butanethiosulfinate
2611±2615
[
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[20] The details of the DSC analyses are shown in the Supporting
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9
2 ± 138.
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[
11]
TADDOLs, see: a) T. Olszewska, M. J. Milewska, M. Gdaniec, T.
Received: December 9, 2002 [F4653]
Chem. Eur. J. 2003, 9, 2611 ± 2615
www.chemeurj.org
¹ 2003 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
2615