Chemistry of sulfines, part V: Chemo- and stereoselective synthesis and hetero-diels-alder reactions of stable sulfines

Article abstract of DOI:10.1080/10426507.2013.800984

The stereoselective synthesis of a variety of Z-sulfines by the oxidation of organic trithiocarbonates with m-chloroperbenzoic acid (m-CPBA) is described. Transient E-sulfines that are formed upon heating of Z-sulfines during cycloaddition reactions were trapped with 2,3-dimethyl-1,3-butadiene to yield only one of the possible diastereomers of the functionalized cyclic allylic sulfoxides. An X-ray analysis and ab initio calculations were performed to provide insight into the steric course of the oxidation and cycloaddition reactions. [Supplementary materials are available for this article. Go to the publisher's online edition of Phosphorus, Sulfur, and Silicon and the Related Elements for the following free supplemental files: Additional tables and figures.]

Full text of DOI:10.1080/10426507.2013.800984

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Chemistry of Sulfines, Part V: Chemo-
and Stereoselective Synthesis and
Hetero-Diels–Alder Reactions of Stable
Sulfines
Ahmed A. El Gokha a , Omar M. Ali a , Ibrahim F. Zeid a , Takayuki
Kudoh b & Ibrahim El-Sayed a
a Chemistry Department, Faculty of Science , El-Menoufeia
University , Shebin El-Kom , Egypt
b Department of Medical and Bioengineering Science, The Graduate
School of Natural Science and Technology , Okayama University ,
Tsushima-Naka , Okayama , Japan
Accepted author version posted online: 12 Aug 2013.Published
online: 03 Dec 2013.
To cite this article: Ahmed A. El Gokha , Omar M. Ali , Ibrahim F. Zeid , Takayuki Kudoh & Ibrahim
El-Sayed (2014) Chemistry of Sulfines, Part V: Chemo- and Stereoselective Synthesis and Hetero-
Diels–Alder Reactions of Stable Sulfines, Phosphorus, Sulfur, and Silicon and the Related Elements,
189:2, 185-197, DOI: 10.1080/10426507.2013.800984
To link to this article: http://dx.doi.org/10.1080/10426507.2013.800984
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Phosphorus, Sulfur, and Silicon, 189:185–197, 2014
Copyright ꢀC Taylor & Francis Group, LLC
ISSN: 1042-6507 print / 1563-5325 online
DOI: 10.1080/10426507.2013.800984
CHEMISTRY OF SULFINES, PART V: CHEMO-
AND STEREOSELECTIVE SYNTHESIS
AND HETERO-DIELS–ALDER REACTIONS
OF STABLE SULFINES
Ahmed A. El Gokha,1 Omar M. Ali,1 Ibrahim F. Zeid,1
Takayuki Kudoh,2 and Ibrahim El-Sayed1
1Chemistry Department, Faculty of Science, El-Menoufeia University,
Shebin El-Kom, Egypt
2Department of Medical and Bioengineering Science, The Graduate School of
Natural Science and Technology, Okayama University, Tsushima-Naka, Okayama,
Japan
GRAPHICAL ABSTRACT
O
O
S
C
S
C
SR1
SR2
R1S
SR2
R1S
SR2
S
E-sulfine
Z-sulfine
O
Trans-cycloadduct
Abstract The stereoselective synthesis of a variety of Z-sulfines by the oxidation of organic
trithiocarbonates with m-chloroperbenzoic acid (m-CPBA) is described. Transient E-sulfines
that are formed upon heating of Z-sulfines during cycloaddition reactions were trapped with
2,3-dimethyl-1,3-butadiene to yield only one of the possible diastereomers of the functionalized
cyclic allylic sulfoxides. An X-ray analysis and ab initio calculations were performed to provide
insight into the steric course of the oxidation and cycloaddition reactions.
[Supplementary materials are available for this article. Go to the publisher’s online edition of
Phosphorus, Sulfur, and Silicon and the Related Elements for the following free supplemental
files: Additional tables and figures.]
Keywords Chlorodithioformates; trithiocarbonates; oxidation; sulfines; Diels–Alder; 1,3-
dienes; thiopyran S-oxides; X-ray; Ab initio calculations
INTRODUCTION
Sulfines (thiocarbonyl S-oxides) 1 constitute an interesting class of tetracoordi-
nate sulfur compounds containing cumulative double bonds.1 One of the methods to
Received 21 January 2013; accepted 26 April 2013.
Partial financial support from Danish International Development Agency (DANIDA) is highly appreciated.
Address correspondence to Ibrahim El-Sayed, Chemistry Department, Faculty of Science, El-Menoufeia
University, Shebin El-Kom, Egypt. E-mail: ibrahimtantawy@yahoo.co.uk
185

186
A. A. EL GOKHA ET AL.
synthesize sulfines is the oxidation of thioketones with peracid,1 ozone,2 or singlet oxy-
gen,3 and they have many interesting and synthetically useful properties such as cycloaddi-
tions,1,4,5 chemokine receptor ligands,6 metal complexation,7,8 control agents for synthesiz-
ing polymers via free radical polymerization,9 thiating reagent,10 and nucleophilic additions
at carbon or sulfur atoms.4,11
Moreover, the functionalized six-membered cyclic allylic sulfoxides (dihydrothiopy-
ran S-oxides) which are obtained through hetero-Diels–Alder cycloaddition reactions of
sulfines with 1,3-dienes, are versatile synthons of potential interest in many organic trans-
formation such as substrates in Pummerer-type reactions,12 and intermediates for other
synthetic applications targeting biomolecules (see, e.g., thioglycosides,13 thionucleosides,14
cephalosporins,15 and antibacterial agents16).
In this context, organic trithiocarbonates 3 have received much attention due to their
numerous industrial, synthetic, and medicinal applications.17 However, information on the
chemistry and the stabilities of the corresponding sulfines 4 are scant and deserve further
investigation.18 With the aim of further developing sulfines as a useful synthons for organic
synthesis, we became interested in the regioselective oxidation of trithiocarbonates 3,
compounds contain three oxidizable sulfur atoms. Another intriguing point to be addressed
is the diastereoselectivity and the dienophilicity of the >C = S double bonds of sulfines 4
toward the hetero-Diels–Alder reactions.
RESULTS AND DISCUSSION
In the present study, new examples of trithiocarbonates 3 were prepared by the
reaction of chlorodithioformates 2 with thiolates according to Scheme 1 in isolated yields
ranging from 81%--93%. This synthesis included an optimization of the previous method.14
Employing sodium hydride as a base instead of NaOH greatly facilitates the reaction by
drastically reducing the time for completion from 1 week to a few hours and at the same
time improves the yield greatly.
R2SH/NaH
S
S
CH2Cl2
rt., 2h
C
C
R1S
Cl
R1S
SR2
R2
2
3
R1
R2
R1
3
3
4-ClC6H4
4-ClC6H4
2,4,5-Cl3C6H2
4-CH3C6H4
2,4,5-Cl3C6H2
4-CH3C6H4
C6Cl5
C6Cl5
C6Cl5
4-CH3C6H4
2-Naphthyl
2,4,5-Cl3C6H2
A
B
C
d
e
f
Scheme 1 Synthesis of diaryl trithiocarbonates.

CHEMO- AND STEREOSELECTIVE SYNTHESIS
187
The 13C NMR signal of the >C = S group of 3a–f resonates at 212–226 ppm a
downfield shift of 22 to 36 ppm from the starting chlorodithioformates 1 (190–192 ppm).19
The oxidation of trithiocarbonates 3 with m-chloroperbenzoic acid (m-CPBA) at 0◦C in
chloroform for 25 min affords the corresponding sulfines 4 in good to excellent yields
(76%–92%) with a high chemoselectivity according to Scheme 2.
O
S
C
S
C
m-ClC6H4COOOH (m-CPBA)
R1S
SR2
R1S
SR2
CHCl3/0 oC, 15-30 mins.
- m-ClC6H4COOH (m-CBA)
3a-f
4a-f
Scheme 2
The crude material of the yellow sulfines 4 was carefully analyzed by NMR spec-
troscopy, which showed that the oxidation of the thiocarbonyl group was stereoselective and
mainly a single isomer was formed. No evidence for the oxidation of the other sulfur atoms
of 3 was detected. The quaternary (>C S O) carbon of the sulfines 4 exhibited an upfield
shift ranging from 180--188 ppm in 13C NMR, upfield from the corresponding (>C S)
group of the starting thiocarbonyl compounds 3 (212-226). This shift was found to be within
the range reported for other sulfines (176--196 ppm).4 The highfield resonance position for
the thiocarbonyl carbon atom in 4 relative to that in 3 is rationalized by the anisotropic
effect of >C S O group. Moreover, the strong IR absorption at 1089--1126 cm−1 can
be attributed to the (>C S O) group of 4. It should be noted that these sulfines can be
purified by crystallization (cf. Experimental part) and kept without alteration for months at
ambient temperature in contrast to other reported sulfines, which are very sensitive toward
reductive hydrolysis.5 The (Z)-configuration of 4d,e was confirmed by an X-ray structure
determination, which proves delivery of the oxygen to >C S proceeds from the side of
the more bulky aryl group (cf., Figures 1 and 2 as well as Table 1).
Furthermore, the X-ray structure established the nonlinearity of the >C S O system
of 4d and 4e. The >C S and the S O bonds were found to be 1.654, 1.638 and 1.477,
1.481 Å for sulfines 4d and 4e, respectively, whereas the >C S O angles were found to
be 110.81o and 110.70o for sulfines 4d and 4e, respectively. These results fall within the
usual range for analogues sulfine.4 The sulfine exhibits a nonplanar arrangement with the
oxygen atom located cis to the pentachlorophenylthio group. The dihedral angles between
the planes of the sulfine group and the p-tolyl and 2-naphthyl groups are 103.57o and
102.30o respectively, demonstrating a nonplanar arrangement around the C(11)-S(2) and
,
C(19)-S(2) bonds for sulfines 4d and 4e, respectively. Moreover, the sulfine moiety π-
plane and the pentachlorophenyl group are arranged perpendicularly to each other, where
the p-tolyl and 2-naphthyl groups hinder the sulfine moiety to adopt a position in the same
plane. The sulfines 4 were further structurally elucidated by their cycloaddition reactions
with 2,3-dimethyl-1,3-butadiene in chloroform at 65◦C according to Scheme 3. After
working up and cooling overnight in ether/hexane (1:3), the cycloadducts 5 were obtained
as crystalline products in good yields. According to the NMR spectra and extensive TLC
analysis, only one of the two possible diastereomers of the functionalized six-membered
cyclic allylsulfoxide 5 was obtained. It should be noted that despite the presence of chlorine
atoms at the phenyl rings of sulfines 4c,d, the sulfines 4 failed to undergo the cycloaddition

188
A. A. EL GOKHA ET AL.
Table 1 Crystal structure and data refinement parameters
Compound
4d
4e
5c
5d
Empirical formula
Formula weight
C14H7Cl5OS3
464.666
C17H7Cl5OS3
500.699
C20H17Cl5OS3
546.812
C20H19Cl3OS3
477.922
Crystal system/space Group
a/Å
b/Å
Monoclinic/P21/c
10.7748 (3)
11.9506 (4)
13.9069 (4)
90.00
90.847 (2)
90.00
1790.53 (9)
4
1.724 Mg m−3
1.16
Triclinic/P-1
7.3565 (2)
8.5279 (3)
16.3902 (8)
101.4729 (13)
97.7507 (13)
105.294 (3)
952.74 (6)
2
Monoclinic/P21/c
15.9230 (6)
17.4011 (5)
8.3534 (2)
90.00
92.6173 (11)
90.00
2312.13 (12)
4
1.571 Mg m−3
0.91
Monoclinic/P21/c
12.1756 (3)
14.1166 (4)
12.8155 (5)
90.00
106.2426 (11)
90.00
2114.78 (11)
4
1.501 Mg m−3
0.74
c/Å
α/◦
β/◦
γ /◦
V/Å3
Z
Dcalc (g/cm3)
1.745 Mg m−3
1.10
μ (mm−1
)
Crystal size (mm)
Color/shape
Temp (K)
Yellow/prismatic
298
Brown/needle
298
Colorless/needle
298
Colorless/needle
298
Theta range for collection
Reflections collected
Independent reflections
Data/restraints/parameters
R indices (all data)
6684
4326
6029
4769
9119
5943
9093
5877
−/0/208
−/0/241
−/0/262
−/0/244
0.057
0.098n
0.100
0.185
reactions with 2,3-dimethyl-1,3-butadiene at ambient temperature in chloroform for 1 week.
This is probably due to the retarding effect exerted by the bulky arylthio groups. To compare
the reactivity of sulfines as heterodienophiles with the starting trithiocarbonates 3, we also
treated 3c,d with 2,3-dimethyl-1,3-butadiene under the same conditions and noted that the
starting material was recovered. This experiment confirms the higher dienophilic reactivity
of sulfines 4c,d in [4+2] cycloaddition reactions as compared with the starting compounds
3c,d.
O
O
S
S
CHCl3, 65 oC
SR1
SR2
C
C
R1S
R1S
SR2
SR2
CHCl3, 65 oC
S
O
Z-4c,d
4c; R1 = C6Cl5
E-4c,d
R2 = 4-CH3C6H4
trans-5c,d
4d; R1 = 2,4,5-C6H2Cl3 R2 = 4-CH3C6H4
Scheme 3 Sulfine isomerizaton and Diels–Alder cycloaddition.
To gain an insight into the steric course of the cycloaddition reactions, the structure
of the crystalline cycloadducts 5c,d was determined by X-ray crystallographic analysis (cf.
Figures 3 and 4 as well as Table 1).
To our surprise, the trans- [4 + 2] adducts 5c,d, instead of the anticipated cis, were
identified as the sole products as verified by the X-ray crystallography analysis. It showed

CHEMO- AND STEREOSELECTIVE SYNTHESIS
189
Figure 1 The molecular structure of sulfine 4d with 50% probability ellipsoids.
that the more bulky arylthio group and sulfoxide oxygen are in a trans position to each
other (i.e., the electrostatic interaction of the arylthio group and the sulfoxide oxygen will
be minimized when these functions are placed in an anti position). This implies that Z to E
isomerization of the parent sulfines occurs during the cycloaddition. However, we cannot
exclude the initial formation of the cis- cycloadducts followed by diastereomerization into
more stable trans-isomers via retro-Diels–Alder mechanism. To rationalize the observed
(Z) selectivity for sulfines 4 and the trans selectivity for cycloadducts 5, we performed ab
initio calculations with the suite of programs.19,20 The geometries were optimized at the
RHF/3-21G(d) level of theory, and the energies were calculated at the B3LYP/6-31+G(d,p).

190
A. A. EL GOKHA ET AL.
Figure 2 The molecular structure of sulfine 4e with 50% probability ellipsoids.
Indeed, the results obtained indicated that the (Z)-sulfine 4c is thermodynamically more
stable than its (E)-isomer by 3.9 kcal/mol. Moreover, the calculations on cycloadduct 5c
reveal that the energy difference between the cis- and trans-isomers is 1.8 kcal/mol at the
B3LYP/6-31+G(d,p)//RHF/3-21Gld level favoring the trans-isomer.
CONCLUSION
In summary, the thiocarbonyl group in trithiocarbonates is oxidized selectively to af-
ford a variety of stable sulfines with Z-stereochemistry. The study also revealed the different
reactivity of 3 and 4 as dienophiles in [4+2] cycloaddition reactions. The cycloaddition of
sulfines with dienes proceeds diastereospecifically to yield a single cycloadduct with the

CHEMO- AND STEREOSELECTIVE SYNTHESIS
191
Figure 3 The molecular structure of the cycloadduct 5c with 50% probability ellipsoids.
opposed stereochemistry compared with the expected one. Therefore, these sulfines are in-
teresting substrates in cycloaddition, and the results presented here clearly stimulate further
research of asymmetric reactions with sulfines. Study the extent of asymmetric induction
of the Diels–Alder reaction with sulfines bearing a chiral substituent is currently underway
in our laboratory.
EXPERIMENTAL SECTION
General
1
All H and 13C NMR experiments (CDCl3) were carried out with a Varian Unity
400 MHz spectrometer (400 MHz for 1H, 100 MHz for 13C). Chemical shifts are reported
in ppm relative to TMS using appropriate solvent signals as internal standard. The elemental
analysis results agreed with the calculated values within experimental error; melting points
were recorded on a Bu¨chi melting point apparatus. TLC was done on Merck Kieselgel F254
precoated plates (Merck, Darmstadt, Germany). Solvents were dried/purified according to
literature procedures. Single crystals suitable for X-ray studies from sulfines 4d,e and the
cycloadducts 5c,d were grown in a mixture of CH2Cl2 and n-hexane (1/3), intensity data
were measured at room temperature on a Siemens SMART CCD (Siemens AG Germany)

192
A. A. EL GOKHA ET AL.
Figure 4 The molecular structure of the cycloadduct 5d with 50% probability ellipsoids.
diffractometer with graphite monochromated. Table 1 shows the X-ray data collection
parameters. Complete X-ray data for compounds 4d, 4e, 5c, and 5d were deposited at
the Cambridge Crystallographic Data Center under the reference numbers CCDC 259328,
259329, 259330, and 259331, respectively. Copies of the data can be obtained free of charge,
on application to CCDC, 12 Union Road, Cambridge CB2 IEZ, UK [Fax: int. code + 44-
1223-336033 or E-mail: deposit@ccdc.cam.ac.uk]. The starting aryl chlorodithioformates 2
were prepared according to the literature procedures.21 The Supplemental Material contains
sample 1H and 13C NMR spectra for 4a, 5c, and 7d (Figures S 1–S 3).
p-Chlorophenyl p-Tolyl Trithiocarbonate (3a)
The p-methylthiophenol (224 mg, 1.8 mmol) was dissolved in a small portion of dry
dichloromethane (3 mL), sodium hydride (72 mg, 1.8 mmol, 60%) was added portionwise
at 0◦C. After 10 min, p-chlorophenylchlorodithioformate 1a (312 mg, 1.4 mmol) dissolved
in dichloromethane (5 mL) was added dropwise to the above-mentioned mixture at room
temperature over a period of 10 min. The resulting solution was stirred for 2 h at room
temperature. The dichloromethane solution was washed with water (three times). The
organic layer was dried over anhydrous CaCl2, filtered, and then concentrated under reduced
pressure to leave an oily residue, which was precipitated with n-hexane. This was then
recrystallized from n-hexane. Yield (396 mg, 91%) as yellow crystals, mp 103–105◦C, IR
(KBr): 3064 (νC-H, Ar), 2970, 2880 (νC-H, Aliph), 1600 (νC C, Ar), 1474, 1375 (νC-H, Aliph),
1082 (νC S), 750 (νC-Cl). 1H NMR (CDCl3): δ 2.44 (s, 3H, CH3); 7.31 (d, 2H, J = 8 Hz,
Ar); 7.46 (m, 6H, Ar). 13C NMR (CDCl3): δ 21.6 (CH3), 127.1, 129.2, 129.9, 130.5, 135.5,

CHEMO- AND STEREOSELECTIVE SYNTHESIS
193
136.9, 137.3, 141.5 (8C, Ar), 224.7 (C S). Calcd. for C14H11ClS3 (310.89): C, 54.09; H,
3.57; S, 29.89. Found: C, 54.09; H, 3.32; S, 29.95.
p-Chlorophenyl 2,4,5-Trichlorophenyl Trithiocarbonate (3b)
The procedure as given for 2a was followed; yield (454 mg, 81%) as yellow crystals,
1
mp 100–101◦C. IR(KBr): 3070 (νC-H,Ar); 1600 (νC C,Ar), 1080 (νC S); 760 (νC-Cl). H
NMR (CDCl3): δ 7.03 (d, 2H, J = 12 Hz, Ar); 7.21(s, 1H,Ar); 7.26 (d, J = 12 Hz, 2H,
Ar), 7.53 (s, 1H, Ar). 13C NMR (CDCl3): δ 128.9, 129.9, 130.0, 131.1, 131.1, 131.8, 136.9,
136.9, 137.6, 138.4 (10C,Ar), 223.1 (>C S). Calcd. for C13H6Cl4S3 (400.20): C, 39.02;
H, 1.51; S, 24.04. Found: C, 39.36; H, 2.1; S, 22.26.
p-Tolyl 2,4,5-Trichlorophenyl Trithiocarbonate (3c)
The procedure as given for 3a was followed; yield (494 mg, 93%) as a light brown
crystals, mp 65–68◦C. IR (KBr): 3060, 3048 (νC-H,Aliph); 1592 (νC C,Ar); 1488, 1433
1
(νC-H,Aliph); 1055 (νC S); 804 (νC-Cl). H NMR (CDCl3): δ 2.43 (s, 3H, CH3); 7.30 (d,
2H, J = 8Hz, Ar); 7.43 (d, 2H, J = 8Hz, Ar); 7.49 (s, 1H, Ar); 7.66 (s, 1H, Ar). 13C NMR
(CDCl3): δ 21.6 (CH3), 127.4, 130.0, 130.4, 130.6, 131.7, 135.4, 135.5, 138.4, 138.6, 141.2
(10C, Ar); 226.3 (>C S). Calcd. for C14H9Cl3S3(379.78): C, 44.28; H, 2.39; S, 25.33.
Found: C,43.99; H, 2.55; S, 25.60.
Pentachlorophenyl (p-Tolyl) Trithiocarbonate (3d)
The procedure as given for 3a was followed; yield 578 mg; 92% (yellow crystals),
mp 140–143◦C. IR(KBr): 3019(νC-H,Ar); 2918, 2875(νC-H,Aliph); 1591(νC C,Ar); 1335,1298
(νC-H,Aliph); 1053(νC S); 800(νC-Cl) cm−1. 1H NMR (CDCl3): δ = 2.43 (s, 3H, Me); 7.32
(d, 2H, J = 8 Hz, Ar); 7.50 (d, 2H, J = 8 Hz, Ar).13C NMR (CDCl3): δ 21.6 (CH3), 126.8,
127.4, 129.8, 130.4, 131.4, 135.4, 139.0, 142.0 (8C, Ar), 226.3 (>C S).
2-Naphthyl (Pentachlorophenyl) Trithiocarbonate (3e)
The procedure as given for 3a was followed with reaction time of 8 h. Yield (604 mg,
89%), light brown crystals, mp 130–132◦C. IR (KBr): 3050 (νC-H,Ar), 1580 (νC C,Ar), 1094
1
(νC S), 740 (νC-Cl). H NMR (CDCl3): δ 7.32–8.03 (m, 7H, Ar). 13C NMR (CDCl3): δ
125.9, 126.4, 126.7, 126.9, 127.0, 127.6, 127.9, 128.1, 128.7, 129.1, 129.7, 131.2, 136.1,
139.1 (14C, Ar), 217.2 (>C S). Calcd. for C17H7Cl5S3 (484.703): C, 42.13; H, 1.46; S,
19.85. Found: C, 41.92; H, 1.68; S, 19.87.
Pentachlorophenyl (2,4,5-Trichlorophenyl) Trithiocarbonate (3f)
The procedure as given for 3a was followed; yield (640 mg, 85%), yellow crystals,
mp 72–75◦C. IR (KBr): 3075 (νC-H,Ar), 1560 (νC C,Ar), 1093 (νC S); 781(νC-Cl). 1H NMR
(CDCl3): δ 7.50 (s, 1H, Ar), 7.68 (s, 1H, Ar). 13C NMR (CDCl3): δ 128.9, 131.1, 131.9,
132.7, 133.0, 133.1, 137.1, 138.3, 138.7, 139.1 (10C, Ar), 212.2 (>C S). Calcd. for
C13H2Cl8S3 (537.98): C, 29.02; H, 0.38; S, 17.88. Found: C, 29.32; H, 0.63; S, 17.60.

194
A. A. EL GOKHA ET AL.
p-Chlorophenylthio(p-tolylthio)sulfine (4a)
To the stirred solution of 3a (345 mg, 1.11 mmol) in chloroform (10 mL) and cooled
at 0◦C, was added m-chloroperoxy-benzoic acid 306 mg (1.33 mmol, 75%) dissolved in
chloroform (5 mL) over a period of 10 min. After 15 min the orange color changed to light
yellow. The chloroform solution was washed successively with saturated aqueous NaHCO3
(30 mL) and brine (30 mL). The organic layer was dried over anhydrous CaCl2, filtered,
and then concentrated under reduced pressure to leave the sulfine 4a as a single isomer.
This was then recrystallized from CH2Cl2/n-hexane (1:3) to give pale yellow crystals.
Yield (308 mg, 85%), mp 91–93◦C. IR (KBr): 3076 (νC-H,Ar); 2977, 2918 (νC-H, Aliph), 1570
(νC C,Ar); 1475, 1419 (νC-H,Ar), 1089 (νC
O), 747 (νC-Cl). 1H NMR (CDCl3): δ 2.36 (s,
S
3H, CH3); 6.92–7.26 (m, 8H, Ar). 13CNMR (CDCl3-): δ 21.9 (CH3), 129.2, 129.2, 129.8,
130.0, 130.4, 131.2, 135.6, 136.7 (12C,Ar); 188.0 (>C S O). Calcd. for C14H8ClOS3
(326.89): C, 51.44; H, 3.34,; S, 29.43. Found: C, 51.66; H, 3.36; S, 11.47.
2,4,5-Trichlorophenylthio(p-chlorophenylthio)sulfine (4b)
The procedure as given for 4a was followed; yield (393 mg, 85%) as light yellow
crystals, mp 105–107◦C. IR(KBr): 3080, 3057 (νC-H,Ar); 1566 (νC C,Ar); 1112(νC
O);
S
814 (νC-Cl). 1H NMR (CDCl3): 6.95–7.60 (m, 6H). 13C NMR (CDCl3): δ = 124.9, 129.3,
129.4, 130.0, 131.1, 135.1, 136.5, 136.7, 137.0, 138.0 (12C,Ar); 186.0 (>C S O). Calcd.
for C13H6Cl4OS3 (416.20): C, 37.52; H, 1.45; S, 23.11. Found: C, 37.60; H, 1.50; S, 23.14.
2,4,5-Trichlorophenylthio(p-tolythio)sulfine (4c)
The procedure as given for 4a was followed; yield (386.6 mg, 88%) as light yellow
crystals, mp 110–113◦C, IR (KBr): 3080 (νC-H,Ar); 2922, 2850 (νC-H, Aliph); 1565
(νC C,Ar); 1471, 1431 (νC-H, Aliph); 1126 (νC
O); 814 (νC-Cl). 1H NMR (CDCl3):
S
δ 2.35 (s, 3H), 6.97 (d, J = 8 Hz, 2H), 6.97 (d, J = 8 Hz, 2H), 7.08 (d, J = 8 Hz, 2H), 7.15
(s, 1H), 7.53 (s, 1H). 13C NMR (CDCl3): δ 21.2(CH3), 126.0, 127.3, 130.1, 130.3, 131.1,
131.1, 135.8, 138.0, 138.4, 139.7 (10C, Ar); 184.6 (>C S O). Calcd. for C14H9Cl3OS3
(395.78): C, 42.49; H, 2.29; S, 24.31. Found: C, 42.50; H, 2.30; S, 24.18.
Pentachlorophenylthio(p-tolylthio)sulfine (4d)
The procedure as given for 4a was followed; yield (475 mg, 92%), pale yellow
crystals, mp 104–106◦C, IR (KBr): 3060 (νC-H,Ar); 2924, 2853(νC-H,Aliph); 1615 (νC C,Ar);
1
1329,1297(νC-H,Aliph); 1115(νC
O); 760(νC-Cl). H NMR(CDCl3): δ 2.34 (s, 3H,CH3),
S
6.94 (d, 2H, J = 7.2 Hz, Ar), 7.04 (d, 2H, J = 8 Hz, Ar). 13CNMR (CDCl3): δ 21.3 (CH3),
126.5, 127.6, 130.1, 130.8, 132.3, 136.5, 138.9, 140.1 (8C, Ar); 182.4 (>C S O). Calcd.
for C14H7Cl5OS3 (464.67): C, 36.19; H, 1.52; S, 20.70. Found: C, 36.36; H, 1.87; S, 20.48.
2-Naphthylthio(pentachlorophenylthio)sulfine (4e)
The procedure as given for 4a was followed; yield (427 mg, 76%) as light brown
crystals, mp 128–130◦C, IR (KBr): 3037 (νC-H,Ar), 1584 (νC C,Ar); 1106 (νC
O); 809
S
(νC-Cl) 1H NMR (CDCl3): δ 7.09–7.77 (7H, Ar). 13C NMR (CDCl3): δ 126.9, 127.4, 127.6,
127.8, 127.9, 128.1, 128.1, 129.5, 129.6, 130.8, 132.6, 133.4, 135.2, 139.1 (32C, Ar);

CHEMO- AND STEREOSELECTIVE SYNTHESIS
195
182.1 (>C S O). Calcd. for C17H7Cl5OS3 (500.70): C, 40.78; H, 1.41; S, 19.21. Found:
C, 40.87; H, 1.39; S, 19.68.
Pentachlorophenylthio(2,4,5-trichlorophenylthio)sulfine (4f)
The procedure as given for 4a was followed; yield (486 mg, 79%) as light yellow
crystals, mp 154–156◦C. IR (KBr): 3077, 3049 (νC-H,Ar), 1563(νC C,Ar), 1118(νC
O),
S
748(νC-Cl). 1H NMR (CDCl3): δ 7.26–7.51 (m, 2H, Ar). 13C NMR (CDCl3): δ 127.0, 130.1,
131.0, 132.4, 133.0, 133.1, 133.2, 134.4, 137.4, 138.1 (12 C,Ar); 179.6 (>C S O).
3,6-Dihydro-4,5-dimethyl-2-(2,4,5-trichlorophenylthio)-2-(p-tolythio)-
2H-thiopyran S-oxide (5c)
A large excess of 2,3-dimethyl-1,3-butadiene was added to a solution of 4c (200 mg,
0.50 mmol) in dry chloroform (5 mL), and the mixture was refluxed for 20 h at 65
◦C until the yellow color disappeared. After removal of the solvent under reduced
pressure, the crude product was crystallized from dichloromethane/diethyl ether (1:3),
cooled overnight, to afford 5c as colorless crystals, yield (183 mg, 76%) mp 131–133◦C.
IR (KBr): 3072(νC-H,Ar); 2974,2855(νC-H,Aliph), 1640 (νC C,Alkene), 1594(νC C,Ar),
1
1434,1395,(νC-H,Aliph), 1060(νS O), 809(νC-Cl). H NMR (CDCl3):δ 1.40 (s, 3H, CH3),
1.71(s, 3H, CH3), 2.30 (d, J = 18.4Hz, 1H); 2.41(s, 3H, CH3), 2.65 (d, J = 18.4 Hz,
1H), 3.57(d, J = 17.2 Hz, 1H), 3.91 (d, J = 17.6 Hz, 1H), 7.21(d, J = 8 Hz, 2H, Ar),
7.54 (d, J = 8.4 Hz, 2H), 7.58 (s, 1H, Ar), 8.12 (s, 1H, Ar). 13C NMR (CDCl3): δ 19.4
(CH3), 19.7 (CH3), 21.4 (CH3), 36.3 (CH2), 53.0 (CH2), 77.9 (Cchiral), 118.0, 124.4, 125.0,
129.1, 129.8, 130.8, 135.0, 137.4, 139.3, 140.8, 140.9 (14C, Ar&Alkene). Calcd. for
C20H19Cl3OS3 (477.92): C, 50.26; H, 4.01; S, 20.13. Found: C, 50.06; H, 3.93; S, 19.88.
3,6-Dihydro-4,5-dimethyl-2-(pentachlorophenylthio)-2-(p-tolythio)-2H-
thiopyran S-oxide (5d)
The procedure as given for 5c was followed; yield (296 mg, 83%) as colorless crystals,
mp 143–145◦C. IR (KBr): 3050 (νC-H,Ar), 2984, 2917 (νC-H,Aliph), 1650(νC C,Alkene), 1512
1
(νC C,Ar), 1487, 1402 (νC-H,Aliph), 1056 (νS O), 688 (νC-Cl). H NMR(CDCl3): δ 1.43 (s,
3H, CH3), 1.71(s, 3H, CH3), 2.20 (d, J = 18 Hz, 1H), 2.38 (s, 3H, CH3), 2.71(d, J = 18 Hz,
1H), 3.61 (d, J = 17.2Hz, 1H), 3.88 (d, J = 16.8Hz, 1H), 7.15 (d, J = 8Hz, 2H, Ar), 7.51 (d,
J = 8Hz, 2H, Ar). 13C NMR (CDCl3): δ 19.5 (CH3), 19.9 (CH3), 21.5 (CH3), 36.41(CH2),
80.47 (Cchiral), 118.9, 123.8, 125.0, 129.6, 131.0, 132.4, 136.4, 137.9, 140.8, 141.5 (10C,
Ar & Alkene). Calcd. for C20H17Cl5OS3 (546.81): C, 43.93; H, 3.13; S, 17.59. Found: C,
43.91; H, 3.48; S, 17.30.
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