Simple preparation of enantiomeric Michael adducts of thiophenol to chalcones: Easily available new chiral building blocks

Article abstract of DOI:10.1016/S0957-4166(01)00330-5

A facile and enantioselective method for the multigram preparation of the title compounds is described. The Michael addition of thiophenols to chalcones catalyzed by (+)-cinchonine, followed by crystallization, led to the corresponding adducts 2 in up to >95% e.e. The stereoselective Beckmann rearrangement of the oxime of (+)-1,3-diphenyl-3-phenylsulfanylpropan-1-one 2a gives the anilide of (R)-(+)-3-phenyl-3-phenylsulfanylpropanoic acid (as determined by X-ray analysis) and alcoholysis leads to the corresponding enantiomerically pure ethyl ester.

Full text of DOI:10.1016/S0957-4166(01)00330-5

TETRAHEDRON:
ASYMMETRY
Pergamon
Tetrahedron: Asymmetry 12 (2001) 1923–1928
Simple preparation of enantiomeric Michael adducts of
thiophenol to chalcones: easily available new chiral building
blocks
Jacek Skarz;
ewski,a,* Mariola Zielin´ska-Błajeta and Ilona Turowska-Tyrkb
aInstitute of Organic Chemistry, Biochemistry and Biotechnology, Wrocław University of Technology, 50-370 Wrocław, Poland
bInstitute of Physical and Theoretical Chemistry, Wrocław University of Technology, 50-370 Wrocław, Poland
Received 6 July 2001; accepted 24 July 2001
Abstract—A facile and enantioselective method for the multigram preparation of the title compounds is described. The Michael
addition of thiophenols to chalcones catalyzed by (+)-cinchonine, followed by crystallization, led to the corresponding adducts 2
in up to >95% e.e. The stereoselective Beckmann rearrangement of the oxime of (+)-1,3-diphenyl-3-phenylsulfanylpropan-1-one 2a
gives the anilide of (R)-(+)-3-phenyl-3-phenylsulfanylpropanoic acid (as determined by X-ray analysis) and alcoholysis leads to the
corresponding enantiomerically pure ethyl ester. © 2001 Elsevier Science Ltd. All rights reserved.
1. Introduction
During our recent work on the catalytic application of
metal complexes of salicylidene b-amino alcohols,5 we
tested the asymmetric conjugate addition of thiophenol
to enone. For comparison, we also examined cin-
chonine, quinine and quinidine. Herein, we report the
obtained results that were elaborated into a simple
procedure for the preparation of optically pure adducts.
We also demonstrate their utility for further, stereo-
selective transformation.
Catalytic asymmetric synthesis is a very attractive
method for the preparation of chiral building blocks,
necessary for the construction of more complex molecu-
lar structures. Among catalytic reactions, considerable
attention has been focused on the enantioselective con-
jugate addition of sulfur nucleophiles to a,b-unsatu-
rated carbonyl compounds, thus providing a new
stereogenic carbon center at the b-position.1 However,
only a limited number of successful examples have been
reported. In early studies, Wynberg et al. examined the
Michael reaction catalyzed by chiral b-amino alcohols,
including cinchona alkaloids,2 but the enantioselectivi-
ties attained did not reach a desirable level. The only
exception was the catalyzed cinchonine addition of
thiophenol to di-iso-propyl maleate.3 More recently,
high enantiomeric excesses (e.e.s) have been obtained in
some cases; however, these required the use of complex
catalyst systems.4
2. Results and discussion
Firstly, in the addition of thiophenol to 2-cyclo-
hexenone catalyzed by 1.5 mol% of cinchonine, we
observed 59% e.e.5b (versus 54% e.e. obtained by Hiem-
stra and Wynberg).2 Then, we examined a similar reac-
tion with trans-chalcone; the respective results are
shown in Scheme 1. The addition of thiophenol to
trans-chalcone in the presence of chiral amines has
Scheme 1.
* Corresponding author. E-mail: skarzewski@kchf.ch.pwr.wroc.pl
0957-4166/01/$ - see front matter © 2001 Elsevier Science Ltd. All rights reserved.
PII: S0957-4166(01)00330-5

1924
J. Skarz; ewski et al. / Tetrahedron: Asymmetry 12 (2001) 1923–1928
enriched (+)-enantiomers (Scheme 2). In the case of 2a,
a single crystallization was sufficient to isolate an enan-
tiomerically pure product in 70% total yield (>95% e.e.,
no opposite enantiomer detected by 1H NMR using
Eu(hfc)3). Since we are dealing here with a substance
forming a racemic compound in the solid state (higher
mp), not a conglomerate, the composition at the eutec-
tic point should be very close to a pure enantiomer.
This is regarded as an extreme, but not uncommon
case, where one may expect high enantiomeric enrich-
ment by crystallization leaving the enantioenriched,
lower melting material in the mother liquor.7 In two
other cases (2b and 2g), the (+)-enantiomers melted at
higher temperatures than the corresponding racemates
and could be obtained from the crystallizing material.
In the case of 2d, almost no enrichment on crystalliza-
tion was observed. The absolute configuration of (+)-2
was assigned tentatively (R), as it is correlated to the
(R)-(+)-product obtained by the well-known enantiose-
lective east reduction of b-oxoester and subsequent
inversion at the created stereogenic center.8 However, in
the course of this study, we proved this configuration
more directly (see Table 2).
already been studied; however, to date, no cinchonine
was used and the reported enantioselectivities were
unsatisfactory.6 Thus, our results demonstrated that
(+)-cinchonine is the best catalyst for this reaction. The
highest e.e. of 80% was observed for the addition run
on a 0.1 mol scale in toluene for a 5.6 mM catalyst
concentration at −20°C (Table 1). The observed depen-
dency of the e.e. on catalyst concentration and temper-
ature is similar to that described in earlier reports.2,6b
4-Substituted thiophenols and benzyl mercaptan added
to the ring-substituted chalcones in 54–73% e.e. and
excellent chemical yields. Moreover, we observed that
the recrystallization of crude adducts 2a, 2c, 2e and 2f
gave mostly racemic crystals and the concentration of
mother liquors allowed isolation of the correspondingly
Table 1.
Catalysta
Temperature
Yield (%)
E.e. (%)
(°C)
Cinchonidine
Quinine
Cinchonine
Cinchonine
Cinchonine
−20
−20
−20
0
99
98
96–98
91
80
14
17
Thus, the reasonably high enantioselectivity of the
addition and successful crystallization gave optically
pure adducts 2 and now these compounds can be
regarded as easily available in multigram quantities. In
order to test their possible synthetic applications,
64, 70,b 80c
38
50
−70
a Applied in a 1.5 mol% amount (conc. 4.2 mM), 2 mmol reaction
scale.
ketone (+)-2a was converted to oxime (+)-3. Reduction
b For the reaction with 3.0 mol% (conc. 8.4 mM) catalyst, 2 mmol
15
of this product with NaBH4/TiCl4
gave
a
reaction scale.
diastereomeric mixture of amine 4 (d.r. 65:35). The
oxime was subjected to the reaction induced by thionyl
chloride and the chemo- and stereoselective Beckmann
rearrangement16 gave the anilide of (+)-3-phenyl-3-sulfi-
nylpropanoic acid 5. Its alcoholysis furnished the corre-
sponding ethyl ester 6, a known chiral building block,
useful for the synthesis of biologically active prod-
ucts.8,17 X-Ray analysis of a single crystal of (+)-5
proves the (R) configuration of its stereogenic center
(Fig. 1). Thus, the absolute configuration (R) of (+)-2
adducts is also confirmed by analogy (Scheme 3).
c For the reaction with 1.5 mol% (conc. 5.6 mM) catalyst, 0.1 mol
reaction scale.
Scheme 2.
Table 2.
2
R1
R2
R3
Adduct
Crystallization
(R)-Isomer
Racemate
Yield (%)
E.e. (%)
Yield (%)
E.e. (%)
[h]2D0
mp (°C)
mp, lit. mp
(°C)
a
b
c
Ph
Ph
Ph
99
99
98
80
73
58
70
72
44
\95
93
+136
+148
+109
96–97
118.5–119,
119–120a
p-MeOC6H4 Ph
Ph
87.2–88
91.5–92
82–84.5, 86.8b
Ph
Ph
p-MeOC6H4
94
115.5–117
(EtOH)
d
e
Ph
Ph
Ph
Ph
p-MeC6H4
p-ClC6H4
97
96
65
54
67
77
+98
+119
102–106
97.5–99.5
–, 110–111c
99.5–101.5,
103d
13
20
19
f
Ph
Ph
Ph
CH2Ph
Ph
65
84
64
27
92
+138
+175
57–59
68–70, 71e,
72–73e
g
tert-Bu
\95
103–104
85–89, 86–88f
a lit.9; b lit.10 c lit.11 d lit.12 e lit.13 f lit.14
; ; ; ;

J. Skarz
;
ewski et al. / Tetrahedron: Asymmetry 12 (2001) 1923–1928
1925
Figure 1. ORTEP view of molecule 5. Thermal ellipsoids were drawn on the 25% probability level. Hydrogen atoms were
diminished for clarity.
stage apparatus and are uncorrected. IR spectra were
reordered on a Zeiss–Jena Specord 75 spectrophoto-
1
meter. H and 13C NMR spectra were measured on a
Bruker CPX (300 MHz) spectrometer using TMS as
an internal standard. GC/MS spectra were determined
on a Hewlett–Packard 5890 II gas chromatograph (25
m capillary column) with a Hewlett–Packard mass
spectrometer 5971A operating on the electron-impact
mode (70 eV). Optical rotations at 578 nm were mea-
sured using an Optical Activity Ltd. model AA-5
automatic polarimeter. Separations of products by
chromatography were performed on silica gel 60 (230–
400 mesh) purchased from Merck. TLC analyses were
performed using silica gel 60 precoated plates
(Merck).
Scheme 3.
3.2. X-Ray crystallographic data
In conclusion, the method described in this paper
offers a convenient route to some enantioenriched
Michael adducts obtained in the catalytic presence of
(+)-cinchonine in good yield and often excellent e.e.
from the readily available chalcones and thiophenols.
Work on further synthetic applications of the pre-
pared chiral ketones is underway.
Colorless crystals of 5 suitable for X-ray diffraction
studies were grown by dissolving the compound in an
n-hexane/methylene chloride mixture, and then by the
slow evaporation at rt. Monoclinic, P21, a=8.0552(9),
,
b=5.1806(5), c=20.8294(18) A, i=96.732(9)°, V=
3
−1
,
863.23(15) A , Z=2, v=0.194 mm , F(000)=352,
CCD camera, 5088 reflections collected, 2567 unique
reflections, 2362 observed unique reflections, Rint=
0.0347, SHELXL-97,18 R1=0.050 and wR2=0.129 for
3. Experimental
3.1. General
I>2|(I), R1=0.054 and wR2=0.132 for all data, S=
−3
,
1.17, zmax=0.46, zmin=−0.34 e A , Flack absolute
structure parameter x=0.05(12).
Melting points were determined using a Boetius hot-

1926
J. Skarz; ewski et al. / Tetrahedron: Asymmetry 12 (2001) 1923–1928
Crystallographic data (excluding structure factors) for
the structure in this paper has been deposited with the
Cambridge Crystallographic Data Centre as supple-
mentary publication number CCDC 165607. Copies of
the data can be obtained, free of charge, on application
to CCDC, 12 Union Road, Cambridge, CB2 1EZ, UK
[fax: +44(0)-1223-336033 or e-mail: deposit@ccdc.
cam.ac.uk].
J1=7.1 Hz, J2=3.0 Hz, 2H, CH2), 3.76 (s, 3H, OMe),
4.78 (t, J=7.1 Hz, 1H, *CH), 6.75 (d, J=8.8 Hz, 2H,
ArH), 7.17–7.25 (m, 7H, ArH), 7.42 (t, J=7.5 Hz, 2H,
ArH), 7.54 (t, J=7.3 Hz, 1H, ArH), 7.87 (d, J=7.8 Hz,
1
2H, ArH); H NMR (CCl4, Eu(hfc)3): *CH, Dl 0.048
ppm, [h]2D0=+109 (1.02, CH2Cl2), 94% e.e.
3.3.4. (R)-(+)-3-(4-Methyl-phenylsulfanyl)-1,3-diphenyl-
propan-1-one 2d. Yield 97%, recrystallized twice, mp
1
3.3. Preparation of the chiral Michael adducts 2
102–106°C; H NMR (300 MHz, CDCl3): 2.29 (s, 3H,
CH3), 3.59 (m†, J1=17.1 Hz, J2=9.9 Hz, J3=7.1 Hz,
2H, CH2), 4.87 (t, J=7.1 Hz, 1H, *CH), 7.02 (d, J=7.9
Hz, 2H, ArH), 7.17–7.32 (m, 7H, ArH), 7.42 (t, J=7.5
Hz, 2H, ArH), 7.53 (t, J=7.4 Hz, 1H, ArH), 7.86 (d,
A solution of the appropriate chalcone (2.0 mmol) in
dry toluene (4 mL) was added to a stirred solution of
cinchonine (8.8 mg, 1.5% mol) in dry toluene (2 mL).
This mixture was stirred for 15 min at rt and cooled to
−20°C. Then a solution of thiophenol (0.226 mL, 2.2
mmol) in dry toluene (1 mL) was added dropwise. The
resulting mixture was kept for 4–24 h (monitored by
TLC) at −20°C under argon, then quenched with 1N
HCl (4 mL) and extracted with Et2O (2×2 mL). The
combined extracts were washed with 10% NaOH, brine,
dried over Na2SO4 and the solvent was evaporated. The
1
J=7.4 Hz, 2H, ArH); H NMR (CCl4, Eu(hfc)3): *CH,
Dl 0.107 ppm, [h]D20=+95 (1.10, CH2Cl2), 65% e.e.
3.3.5. (R)-(+)-3-(4-Chlorophenylsulfanyl)-1,3-diphenyl-
propan-1-one 2e. Yield 13%, recrystallized twice, mp
1
97.5–99.5°C; H NMR (300 MHz, CDCl3): 3.59 (dd,
J1=6.9 Hz, J2=5.0 Hz, 2H, CH2), 4.91 (t, J=7.0 Hz,
1H, *CH), 7.16–7.32 (m, 9H, ArH), 7.44 (t, J=7.5 Hz,
2H, ArH), 7.55 (t, J=7.3 Hz, 1H, ArH), 7.88 (d, J=7.3
Hz, 2H, ArH); 1H NMR (CCl4, Eu(hfc)3): *CH, Dl
0.083 ppm, [h]2D0=+119 (1.78, CH2Cl2), 77% e.e.
1
crude product obtained was chemically pure 2 (by H
1
NMR) The e.e. of the adduct was determined by H
NMR with ca. equimolar amount of Eu(hfc)3 as a
chiral shift reagent.
3.3.6. (R)-(+)-3-Benzylsulfanyl-1,3-diphenylpropan-1-one
2f. Yield 20%, recrystallized three times, mp 57–59°C;
1H NMR (300 MHz, CCl4): 3.01 (d, J=7.0 Hz, 2H,
(S)CH2), 3.10 (m†, J1=13.5 Hz, J2=13.3 Hz, 2H, CH2),
3.99 (t, J=6.9 Hz, 1H, *CH), 6.76–7.09 (m, 13H, ArH),
7.44 (d, J=7.8 Hz, 2H, ArH); 1H NMR (CCl4,
Eu(hfc)3): *CH, Dl 0.095 ppm, [h]2D0=+138 (1.04,
CH2Cl2), 92% e.e.
The products were enantioenriched by recrystallization
from hexane/methylene chloride. For 2a and 2c–f the
enantiomeric forms were isolated from the mother
liquors and had lower mp’s than the corresponding
racemic crystals. For 2b and 2g, the enantioenriched
crystals were separated and had higher mp’s than the
respective racemates (see Scheme 2).
3.3.1. (R)-(+)-1,3-Diphenyl-3-phenylsulfanylpropan-1-one
3.3.7. (R)-(+)-4,4-Dimethyl-1-phenyl-1-phenylsulfanyl-
pentan-3-one 2g. Yield 19%, recrystallized four times,
1
2a. Yield 70%, after recrystallization, mp 96–97°C; H
NMR (300 MHz, CDCl3): 3.62 (m†, J1=17.2 Hz, J2=
11.1 Hz, J3=7.4 Hz, 2H, CH2), 4.95 (t, J=7.1 Hz, 1H,
*CH), 7.18–7.56 (m, 13H, ArH), 7.88 (d, J=7.5 Hz,
mp 103–104°C; H NMR (300 MHz, CDCl3): 0.99 (s,
1
9H, tert-Bu), 3.08 (m†, J1=21.8 Hz, J2=17.3 Hz, J3=
7.1 Hz, 2H, CH2), 4.78 (dd, J1=8.0 Hz, J2=6.2 Hz,
1
1
2H, ArH); H NMR (CCl4, Eu(hfc)3): *CH, Dl 0.077;
1H, *CH), 7.15–7.28 (m, 10H, ArH); H NMR (CCl4,
IR (KBr): 3058, 1679, 1581, 1450, 1231, 738, 698 cm−1;
[h]2D0=+136 (1.02, CH2Cl2), >95% e.e. The reported
value of [h]2D0=+127.2 7.6 (CH2Cl2), extrapolated for
100% e.e.6b
Eu(hfc)3): *CH, Dl 0.045, [h]2D0=+175 (1.04, CH2Cl2),
>95% e.e.
3.4. Preparation of the oxime 3
3.3.2. (R)-(+)-3-(4-Methoxyphenyl)-1-phenyl-3-phenyl-
sulfanylpropan-1-one 2b. Yield 72%, recrystallized twice,
mp 87.2–88.0°C; 1H NMR (300 MHz, CDCl3): 3.58
(m†, J1=17.1 Hz, J2=15.0 Hz, J3=7.1 Hz, 2H, CH2),
3.75 (s, 3H, OMe), 4.92 (dd, J1=8.2 Hz, J2=6.0 Hz,
1H, *CH), 6.78 (d, J=8.6 Hz, 2H, ArH), 7.21–7.56 (m,
A solution of 2a (3.184 g, 10.0 mmol) in abs. ethanol
(90 mL) was treated with NH2OH·HCl (3.972 g, 57.2
mmol) and dry pyridine (13.2 mL, 163.6 mmol). The
reaction mixture was stirred under reflux for 3.5 h, then
the solvent and pyridine were removed under reduced
pressure. The residue was dissolved in ether (15 mL)
and washed with water, dried over Na2SO4, and evapo-
rated. The product was purified by column chromatog-
raphy on silica gel, Rf=0.63 (tert-BuOMe/CHCl3,
1.0:1.0).
1
10H, ArH), 7.86 (d, J=7.4 Hz, 2H, ArH); H NMR
(CCl4, Eu(hfc)3): *CH, Dl 0.128 ppm, [h]2D0=+148
(0.98, CH2Cl2), 93% e.e.
3.3.3. (R)-(+)-3-(4-Methoxyphenylsulfanyl)-1,3-diphenyl-
propan-1-one 2c. Yield 44%, recrystallized twice, mp
3.4.1. (R)-(+)-1,3-Diphenyl-3-phenylsulfanylpropan-1-one
1
1
91.5–92.0°C; H NMR (300 MHz, CDCl3): 3.58 (dd,
oxime 3. Yield 99%; oil; H NMR (300 MHz, CDCl3):
3.43 (dd, J1=7.8 Hz, J2=4.5 Hz, 2H, CH2), 4.60 (t,
J=7.9 Hz, 1H, *CH), 7.15–7.37 (m, 15H, ArH), 8.18
(br s, 1H, OH); 13C NMR (75 MHz, CDCl3): 33.6
(C-2), 49.8 (C-3), 126.6, 127.2, 127.4, 127.5, 127.6,
† The reported J values are those observed from the splitting patterns
in the spectrum and may not reflect the true coupling constant
values.

J. Skarz
;
ewski et al. / Tetrahedron: Asymmetry 12 (2001) 1923–1928
1927
127.8, 127.9, 128.2, 128.4, 128.5, 128.7, 129.1, 129.2,
132.4, 133.0, 134.6, 135.4, 140.7 (phenyl moiety), 157.3
(C-1); IR (film): 3231, 3059, 1583, 1481, 1439, 1324,
1078, 1026, 916, 749, 696 cm−1; [h]D20=+105 (1.48,
CH2Cl2).
reaction ampoule. The sealed ampoule was heated at
90°C for 5 days. Thereafter, the solvent was evaporated
and the residue was dissolved in ether (5 mL). The
resultant solution was washed with water, satd aq.
NaHCO3, brine and dried (Na2SO4). After evaporation
the product was purified by column chromatography
on silica gel, Rf=0.65 (tert-BuOMe/CHCl3/hexane,
2.5:2.0:10.0).
3.5. Reduction of the oxime 3 to amine 4
A solution of 3 (1.110 g, 3.33 mmol) in anhydrous
DME (3.5 mL) was added dropwise to an ice-cooled,
stirred mixture of TiCl4 (7.0 mmol) and NaBH4 (0.53 g,
14 mmol) in anhydrous DME (15 mL). Stirring was
continued for 20 h at rt and then the reaction was
quenched by the addition of water (30 mL) with ice
cooling. The mixture was basified with 25% aq. NH3
and then extracted with Et2O (2×30 mL). The extract
was washed with brine and dried over Na2SO4. The
solvent was evaporated and the product was purified by
column chromatography on silica gel, Rf=0.18 (tert-
BuOMe/CHCl3/hexane, 1.0:1.0:1.0).
3.7.1. (R)-(+)-Ethyl-3-phenylsulfanyl-3-phenylpropionate
1
6. Yield 71%; oil; H NMR (300 MHz, CDCl3): 1.15 (t,
J=7.1 Hz, 3H, CH3), 2.94 (dd, J1=7.8 Hz, J2=3.1 Hz,
2H, CH2), 4.01–4.09 (dq, J1=7.1 Hz, J2=2.1 Hz, 2H,
CH2 (CH3)), 4.65 (t, J=7.8 Hz, 1H, *CH), 7.23–7.33
(m, 10H, ArH), IR (film): 3061, 2981, 1735, 1583, 1439,
1371, 1250, 1149, 1025, 749, 696 cm−1; MS (EI, 70 eV):
m/z (%)=286 (11) [M+], 177 (28), 135 (100), 109 (30),
105 (59), 91 (21), 77 (30), 65 (20), 51 (15); [h]2D0=+132
(1.0, CHCl3), >95% e.e., lit.8 [h]D20=+129.5 (CHCl3) and
lit.17 [h]2D0=+138.3 (CHCl3).
3.5.1. (3R)-1,3-Diphenyl-3-phenylsulfanylpropylamine 4
(diastereomeric ratio 65:35). Yield 40%; crystallized on
1
Acknowledgements
standing; H NMR (300 MHz, CCl4): 1.04 (br s, 2H,
NH2), 1.81 (dd, J1=14.7 Hz, J2=7.6 Hz, 2H, CH2),
3.41 and 3.57 (dd, J1=8.3 Hz, J2=5.9 Hz, t, J=6.8 Hz,
1H, (N)CH), 3.71 and 3.87 (t, J=7.6 Hz; dd, J1=8.5
Hz, J2=6.7 Hz, 1H, (S)CH), 6.73–6.89 (m, 15H, ArH);
IR (film): 3370, 3060, 2927, 1583, 1492, 1453, 1025, 747,
699 cm−1; MS (EI, 70 eV): m/z (%)=319 (1) [M+],
302(25), 209(27), 208(19), 109(14), 106(100), 79 (100),
77(22), 51(7); [h]2D0=+168 (0.96, MeOH).
The support of the Foundation for Polish Science for
the purchase of the CCD camera (grant MOLTEK’96)
is gratefully acknowledged.
References
3.6. Beckmann rearrangement of 3
1. For recent reviews, see: (a) Krause, N.; Hoffmann-Roder,
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In a dry test tube was placed oxime 3 (0.333 g, 1 mmol)
and anhydrous ether (5 mL). The solution was cooled
to −20°C and SOCl2 (0.22 mL, 3.0 mol) was added
dropwise. The resulting mixture was stirred at 0°C for
5–10 min and then the solvent was evaporated under
reduced pressure. The ice-water mixture was added to
the residue and shaken. The reaction mixture was neu-
tralized with satd aq. NaHCO3 and extracted with Et2O
(2×5 mL). The ether solution was washed with water
and dried (MgSO4). After removal of the solvent the
crude product was purified by chromatography.
2. Hiemstra, H.; Wynberg, H. J. Am. Chem. Soc. 1981, 103,
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3.6.1. (R)-(+)-3-Phenyl-3-phenylsulfanylpropionic acid
anilide 5. Yield 78%; mp 109.2–110°C (hexane,
4. (a) Nishimura, K.; Ono, M.; Nagaoka, Y.; Tomioka, K.
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1
CH2Cl2); H NMR (300 MHz, CDCl3): 2.87 (m†, J1=
14.9 Hz, J2=14.7 Hz, J3=7.5 Hz, 2H, CH2), 4.69 (t,
J=7.4 Hz, 1H, *CH), 6.97–7.34 (m, 16H, ArH and
NH); IR (KBr): 3338, 1660, 1600, 1532, 1441, 743, 692
cm−1; [h]D20=+122 (1.0, CH2Cl2). Anal. calcd for
C21H19NOS (333.45): C, 75.65; H, 5.75; N, 4.20; S, 9.60.
Found: C, 75.40; H, 6.00; N, 4.40; S, 9.88%. For X-ray
analysis, see Section 3.2.
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