Reactions of epoxides and episulfides with electrophilic halogens

Article abstract of DOI:10.1016/S0040-4020(02)00699-3

A novel method is described for the conversion of epoxides into β-bromoformates using Ph₃PBr₂, Ph₃P/N-bromosuccinimdes (NBS) and or Ph₃P/2,4,4,6-tetrabromo-2,5-cyclohexadiene-1-one (TABCO) in DMF. Epoxides in the presence of Ph₃P/I₂ were converted into olefins immediately in excellent yields. The application of NBS, NCS, and TABCO as compounds carrying electrophilic halogens for the highly selective alcoholysis of epoxides and dimerization or alcoholysis dimerization of episulfides are also described.

Full text of DOI:10.1016/S0040-4020(02)00699-3

Tetrahedron 58 (2002) 7037–7042
Reactions of epoxides and episulfides with electrophilic halogens
*
Nasser Iranpoor, Habib Firouzabadi, Maryam Chitsazi and Abbas Ali Jafari
*
Department of Chemistry, College of Sciences, Shiraz University, Shiraz 71454, Iran
Received 19 March 2002; accepted 10 May 2002
Abstract—A novel method is described for the conversion of epoxides into b-bromoformates using Ph3PBr2, Ph3P/N-bromosuccinimdes
(NBS) and or Ph3P/2,4,4,6-tetrabromo-2,5-cyclohexadiene-1-one (TABCO) in DMF. Epoxides in the presence of Ph3P/I2 were converted
into olefins immediately in excellent yields. The application of NBS, NCS, and TABCO as compounds carrying electrophilic halogens for the
highly selective alcoholysis of epoxides and dimerization or alcoholysis dimerization of episulfides are also described. q 2002 Elsevier
Science Ltd. All rights reserved.
Epoxides and episulfides as special types of strained
heterocycles play an increasingly pivotal role in organic
synthesis as versatile synthetic intermediates. The inherent
polarity and strain of their three-membered rings make them
susceptible to reaction with a vast number of reagents,
including nucleophiles, acids, bases, reducing and oxidizing
agents, leading to a wide range of important and useful
oxygenated and sulfurated synthons.1–14 Episulfides are
probably the most interesting class of cyclic sulfides both
from theoretical and synthetic point of views. However, due
to ready polymerization, their reactions are less studied
compared to the epoxides. Although there are many
catalysts or reagents reported in the literature for the
nucleophilic ring opening of epoxides and episulfides, but
reports on the selective ring opening of epoxides are rare14e
and as far as we know, the selective ring opening reaction of
episulfides has not been reported yet.
different halogenated compounds.16,17 The very different
behavior of these mixed reagents in dry DMF, provided a
useful method for the formylation of hydroxyl groups.18,19
Wide applications of POCl3 and SOCl2 in dry DMF
have also been reported for the formylation of hydroxyl
groups as well as some activated aromatic rings. The
reaction of ethylene oxide and some symmetrical cyclic
epoxides with [HC(NMe)2POCl2]Cl at 55–658C with
subsequent hydrolysis was also reported for the preparation
of b-chloroformates.22
20
21
The use of Ph3PBr2 for the conversion of epoxides into
bromohydrins and dibromides are reported.23,24 However,
as far as we know, the reaction of epoxides with the
combination of Ph3P and NBS, TABCO, NCS, trichloro-
isocyanuric acid (TCCA), Br2 and I2 in DMF has not been
investigated. This is the focus of part of this study.
Recently, we have reported on some applications of
molecular halogens and compounds carrying electrophilic
halogens in organic synthesis.15 Now, we report on the use
of NBS, TABCO, Br2 and I2 in combination with Ph3P as
efficient systems for the conversion of epoxides into
b-bromoformates or alkenes in DMF. Due to the importance
of selectivity in organic synthesis, we introduced NBS,
NCS, and TABCO for the selective alcoholysis of epoxides
and dimerization or alcoholysis dimerization of episulfides.
As a model compound, we first chose glycidyl-isopropyl-
ether and studied its reactions with NBS, NCS, TABCO, Br2
and I2 in the presence of Ph3P. The results of this study are
shown in Table 1 and Scheme 1. As it is demonstrated, the
reaction of glycidyl-isopropylether with Ph3P/Br2 after
15 min produces the corresponding b-bromoformate in an
excellent yield. When we replaced molecular bromine with
NBS or TABCO as solid sources of electrophilic bromine,
the same reaction occurred but considerably slower. The
reaction of glycidyl-isopropylether with the combination of
Ph3P/NCS or Ph3P/TCCA was not very successful and the
corresponding b-chloroformate was obtained in only 30 and
3% yields, respectively, with some chlorohydrin as side
products (Table 1).
1. Results and discussion
The combination of Ph3P and halogens or N-halosuccini-
mides has found wide applications in the synthesis of
Keywords: alcoholysis dimerization; episulfides; electrophilic halogens;
epoxide.
*
Corresponding authors. Tel.: þ98-711-2284822; fax: þ98-711-2280926;
Scheme 1. Reagent: Br2, NBS, TABCO, NCS, TCCA. X¼Br, Cl.
e-mail: iranpoor@chem.susc.ac.ir, firouzabadi@chem.susc.ac.ir.
0040–4020/02/$ - see front matter q 2002 Elsevier Science Ltd. All rights reserved.
PII: S0040-4020(02)00699-3

7038
N. Iranpoor et al. / Tetrahedron 58 (2002) 7037–7042
Table 1. Reaction of glycidyl-isopropylether with Br2, NBS, TABCO,
NCS, TCCA, and I2 in the presence of Ph3P in DMF
We have proposed a general mechanism (Scheme 2) for
this formylation reaction which is similar to the
mechanism formerly proposed for the formylation of
alcohols.18b,c
Reagent
Sub./Ph3P/
Reagents
Product
Time
(h)a
Yield
(%)b
Br2
1:1.5:1.4
1:3.2:3
1:3.2:3
1:3.2:3
1:3.2:3
1:2:2
iPrOCH2CH(OCHO)CH2Br
iPrOCH2CH(OCHO)CH2Br
iPrOCH2CH(OCHO)CH2Br
iPrOCH2CH(OCHO)CH2Cl
iPrOCH2CH(OCHO)CH2Cl
iPrOCH2CHvCH2
0.25
3
81
80
78
30c
3d,e
100e
As it was shown in Table 1, the use of Ph3P/I2 in DMF
resulted the conversion of glycidyl-isopropylether to its
corresponding alkene in an excellent yield. However, the
reported reaction of epoxides with Ph3PCl2 and Ph3PBr2
afforded the corresponding dihalides, which were dehalo-
genated by zinc powder to give the corresponding
alkenes.16h Since the reaction of Ph3PI2 with glycidyl-
isopropylether (Table 1) showed to be very suitable for
deoxygenation of epoxides to alkenes, we used this reagent
system for the direct and quantitative deoxygenation of
different classes of epoxides. The results for the conversion
of structurally different epoxides into their corresponding
alkenes are shown in Table 3. We believe that this reaction
NBS
TABCO
NCS
TCCA
I2
24
24
24
f
–
a
The epoxide disappeared immediately at 08C, with the formation of
b-bromoformate as the major product together with some halohydrin.
The reaction mixture was then stirred at room temperature until all the
produced halohydrin was also converted into its b-bromoformate.
Yield refers to the isolated product.
The corresponding b-chlorohydrin (70%, GC yield) was also produced.
The corresponding b-chlorohydrin (7%, GC yield) was also obtained.
Yields are based on GC analysis.
b
c
d
e
f
The reaction completed immediately.
Table 2. Conversion of epoxides into b-bromoformates using the combination of Ph3P with NBS or Br2 in DMF
Entry
Epoxide
Ph3P/Br2
Time (min)
Ph3P/NBS
Yield (%)b
Producta
Yield (%)a
85
Time (h)
1
15
3
84
Me2CHOCH2CH(OCHO)CH2Br (I)
2
3
4
5
6
30
35
82
78
80
75
57
2
2
83
75
82
73
54
CH2vCHCH2OCH2CH(OCHO)CH2Br (II)
Me(CH2)3CH(OCHO)CH2Br (III)
PhOCH2CH(OCHO)CH2Br (IV)
ClCH2CH(OCHO)CH2Br (V)
120
60
5
7
30
0.5
PhCH(Br)CH2OCHO (VI)
7
30
50
1
51
a
For entries 1–5, the corresponding alkene was obtained in 8–10% yield. For entry 6, styrene (20%) and 2-bromo-2-phenyl ethanol (15%) were also obtained.
2-Bromo-2-phenyl ethanol contains a primary hydroxyl group, which cannot be formylated in the reaction mixture.18b For entry 7, cyclohexene (20%) and
two other unknown products (20%) were also obtained.
b
Yield refers to the isolated product.
The reaction of Ph3P/I2 with glycidyl-isopropylether was
very different from other reagents and gave exclusively the
corresponding alkene in a quantitative yield (Table 1). On
the basis of these findings, we studied the reaction of
different epoxides with Ph3P/Br2 and Ph3P/NBS for the
preparation of b-bromoformates and the reaction of
epoxides with Ph3PI2 for the preparation of alkenes.
The conversion of epoxides carrying electron-donating or
electron-withdrawing groups to their corresponding
b-bromoformates was achieved by the use of Ph3P/Br2 or
Ph3P/NBS in DMF at room temperature. However, the
yields of bromoformates obtained from the reaction of the
epoxides carrying electron-withdrawing groups were
found to be higher than styrene and cyclohexene oxides
(Table 2).
Scheme 2. Proposed mechanism for the conversion of epoxides into
b-bromoformates.

N. Iranpoor et al. / Tetrahedron 58 (2002) 7037–7042
7039
Table 3. Immediate conversion of epoxides to alkenes by Ph3P/I2 in DMF
at room temperature
alcoholysis of epoxides having alkyl or aryl substituents in
the presence of those carrying electron-withdrawing
groups (Table 4). We also used successfully these
compounds as efficient catalysts for the selective ring
opening of styrene and cyclohexene oxides in presence of
epoxides such as epichlorohydrin, glycidyl-isopropylether
and also 1,2-hexene oxide.
Entry
1
Epoxide
Product
% Conversiona
100
CH2vCHCH2OCH2CHvCH2
2
3
4
5
6
PhOCH2CHvCH2
ClCH2CHvCH2
(CH3)2CHOCH2CHvCH2
C4H9CHvCH2
100
100
100
100
91
We also used NBS, NCS and TABCO in alcohols and
aqueous acetonitrile for the efficient conversion of epi-
sulfides into their corresponding b,b0-dialkoxy- or
dihydroxydisulfides, respectively. Excellent selectivity
was again observed between episulfides substituted with
alkyl or phenyl groups and those carrying electron-with-
drawing substituents (Table 5).
PhCHvCH2
In comparison with the reaction of epoxides, the reaction of
episulfides with NBS, NCS, or TABCO in protic solvents
occurs immediately. The faster reaction of episulfides could
be due to the better interaction of electrophilic halogens
with sulfur atom of the episulfide ring rather than oxygen of
the epoxide.
7
85
The molar ratio of epoxide to Ph3P to I2 was 1:2:2.
a
Conversion was based on GC analysis using internal standard.
occurs through the formation of the corresponding unstable
di-iodides followed by the rapid dehalogenation to their
alkenes.
The reaction of episulfides in non-nucleophilic solvents
such as dichloromethane furnished the corresponding
substituted 1,4-dithianes in good yields. Here again, high
selectivity was observed and episulfides carrying electron-
withdrawing substituents were remained unreacted
(Table 5).
In the other part of this work, we employed TABCO, NBS
and NCS as mild and highly selective catalysts for the
Table 4. Alcoholysis of epoxides using NBS, NCS, and TABCO as catalyst at room temperature
NBS
Yield (%)
NCS
Yield (%)
95
TABCO
Entry
Epoxide
Solvent
Producta
Time (h)
0.7
Time (h)
5.4
Time (h)
Yield (%)
95
1
2
3
MeOH
EtOH
iPrOH
90
90
91
2
8
PhCH(OMe)CH2OH
PhCH(OEt)CH2OH
PhCH(OPri)CH2OH
2.8
24
–
–
–
–
93
97
20b
4
5
MeOH
EtOH
1.4
30
95
24
5
4.5
28
93
90
93b
–
–
–
–
6
MeOH
MeOH
MeOH
MeOH
MeOH
3
94
0
20
24
24
24
24
93
0
Mixture of isomersc
No reaction
7
24
24
24
24
8
30
0
28
0
ClCH2CH(OH)CH2OMe
No reaction
9
10
0
0
No reaction
The molar ratio of epoxide to NBS, NCS or TABCO was 1:0.2.
a
Isolated yield.
The reaction was performed under reflux.
Mixture of 2-methoxy-1-hexanol and 1-methoxy-2-hexanol was obtained in the ratio of 70:30.
b
c

7040
N. Iranpoor et al. / Tetrahedron 58 (2002) 7037–7042
Table 5. Reaction of episulfides with NBS, NCS or TABCO in alcohols, aqueous acetonitrile and dichloromethane at room temperature
NBS
Time (min)
NCS
Time (min)
TABCO
Time (min)
Entry
Episulfide
Solvent
Product
Yield (%)
85
Yield (%)
85
Yield (%)
85
1
2
3
4
MeOH
3
3
3
5
3
3
3
4
4
4
4
6
PhCH(OMe)CH2S–)2
PhCH(OEt)CH2S–)2
PhCH(OH)CH2S–)2
PhCH(OPri)CH2S–)2
EtOH
70
75
53
75
75
50
78
85
60
CH3CN/H2O
iPrOH
5
6
7
8
MeOH
3
3
3
5
92
85
90
64
3
3
3
5
80
79
85
60
4
4
4
5
92
86
92
72
EtOH
CH3CN/H2O
iPrOH
9
MeOH
MeOH
60
60
0
0
60
60
0
0
60
60
0
0
No reaction
No reaction
10
11
CH2Cl2
20
77
15
70
20
75
12
13
CH2Cl2
CH2Cl2
5
80
0
5
80
0
5
82
0
60
60
60
No reaction
The molar ratio of episulfide to NBS, NCS or TABCO in protic solvents was 1:0.55. For the reactions of entries 11 and 12, the ratio of episulfide to the reagents
were 1:0.2 and 1:0.5, respectively.
2. Conclusion
purchased from Fluka and Merck chemical companies. The
purity determination of the products was accomplished by
GC on a Shimadzu model GC-14A instrument or by TLC on
silica gel polygram SIL G/UV 254 plates. Mass spectra were
run on a Shimadzu GC-Mass-QP 1000 EX at 20 eV. The IR
spectra were recorded on a Perkin–Elmer 781 spectro-
photometer. The NMR spectra were recorded on a Bruker
advance DPX 250 MHz spectrometer.
In this study, we have introduced the uses of Ph3P in the
presence of Br2, NBS and TABCO in DMF for the
conversion of epoxides into their b-bromoformates in
good to high yields. We have also presented the application
of Ph3P/I2 system for the direct conversion of epoxides into
their corresponding alkenes with excellent yields. The use
of NBS, NCS, and TABCO as efficient catalysts provides
highly selective methods for alcoholysis of epoxides
carrying alkyl or phenyl substituents. Immediate dimeriza-
tion or alcoholysis dimerization of episulfides were also
observed using NBS, NCS, and TABCO.
3.1. General procedure for the conversion of epoxides to
b-bromoformates by Ph3PBr2 in DMF
To a solution of Ph3P (1.5 mmol, 393 mg) in dry DMF
(2 ml) at 08C under nitrogen was added bromine (1.4 mmol,
0.07 ml) in DMF (2 ml) dropwise. After 10 min, the epoxide
(1 mmol) was added. GC and TLC analysis using
n-hexane/EtOAc (3:1) as eluent monitored the progress of
the reaction. Epoxide was disappeared immediately with
3. Experimental
Chemicals were either prepared in our laboratories or were

N. Iranpoor et al. / Tetrahedron 58 (2002) 7037–7042
7041
formation of the corresponding b-bromoformate as the
major product together with some halohydrin. The reaction
mixture was then stirred at room temperature for 15–
180 min (Table 2), until the complete conversion of
halohydrin into its b-bromoformate was observed (except
styrene oxide, which its halohydrin has a primary hydroxyl
group and cannot be formylated18b). The reaction mixture
was then poured into saturated brine and the product was
extracted by ether (2£30 ml) and washed by water
(2£15 ml). The combined organic layers were dried over
anhydrous Na2SO4. Filtration and evaporation of the solvent
followed by column chromatography on silica gel using
n-hexane/EtOAc (20:1) gave the corresponding b-bromo-
formate (Table 2). All the obtained b-bromoformates gave
satisfactory elemental analysis. Their spectral data are
shown below.
2H, J¼5.31 Hz); 13C NMR (63 MHz, CDCl3):
d
(ppm)¼159.8, 71.4, 43.4, 30.2; MS (20 eV), m/e (%): 158
(10.8), 154 (35.7), 156 (46.3), 123 (57.8), 121 (25.6), 77
(24), 75 (70.8), 43 (100), 41 (20.8). Anal. Calcd for
C4H6BrClO2: C, 23.85; H, 3.00. Found: C, 23.92; H, 2.90.
3.1.6. Formic acid 2-bromo-2-phenyl-ethyl ester (VI). IR
(neat): 3421, 3059, 3027, 2927, 2873, 1714, 1452, 1138,
756, 703 cm21
;
1H NMR (250 MHz, CDCl3):
d
(ppm)¼8.06 (s, 1H), 7.17–7.35 (m, 5H), 5.05 (t, 1H,
J¼7.3 Hz), 4.49–4.66 (m, 2H); 13C NMR (63 MHz,
CDCl3): d (ppm)¼160.4, 138.1, 129.4, 129.2, 127.0, 67.1,
49.6; MS (20 eV), m/e (%): 184 (9.0), 182 (9.6), 171 (9.2),
169 (9.2), 149 (49.2), 121 (100), 103 (81.7), 91 (17), 77
(14.2). Anal. Calcd for C9H9BrO2: C, 47.19; H, 3.96. Found:
C, 47.24; H, 3.90.
3.1.1. Formic acid 1-bromomethyl-2-isopropyl-ethyl
ester (I). IR (neat): 4433, 2933, 2892, 2808, 1668, 1350,
1266, 1250, 1000, 800 cm21; 1H NMR (250 MHz, CDCl3):
d (ppm)¼8.04 (s, 1H), 5.09–5.17 (m, 1H), 3.44–3.57 (m,
5H), 1.08–1.12 (d, 6H, J¼9 Hz); 13C NMR (63 MHz,
CDCl3): d (ppm)¼160.4, 72.9, 71.8, 67.1, 30.8, 22.3. Anal.
Calcd for C7H13BrO3: C, 37.35; H, 5.82. Found: C, 37.24;
H, 5.90.
3.1.7. trans-Formic acid 2-bromo-cyclohexyl ester (VII).
IR (neat): 3419, 2928, 2857, 1711, 1447, 1369, 1245, 1154,
1109, 1002, 860, 762 cm21; 1H NMR (250 MHz, CDCl3): d
(ppm)¼8.03 (s, 1H), 4.89–4.98 (m, 1H), 3.87–3.97 (m,
1H), 2.28 (m, 1H), 2.1 (m, 1H), 1.63–1.84 (m, 3H), 1.29–
1.41 (m, 3H); 13C NMR (63 MHz, CDCl3): d (ppm)¼160.3,
76.1, 52.5, 35.9, 31.4, 25.8, 23.6; MS (20 eV), m/e (%): 193
(10.1), 191 (10.4), 127 (13.4), 99 (20.4), 97 (20.9), 81 (100),
57 (66.7). Anal. Calcd for C7H11BrO2: C, 40.60; H, 5.35.
Found: C, 40.72; H, 5.40.
3.1.2. Formic acid 1-bromomethyl-2-vinyloxy-ethyl ester
(II). IR (neat): 3421, 3072, 2994, 2904, 2857, 1714, 1642,
1421, 1345, 1149, 927 cm21; 1H NMR (250 MHz, CDCl3):
d (ppm)¼8.03 (s, 1H), 5.76–5.87 (m, 1H), 5.12–5.25 (m,
3H), 3.95 (d, 2H, J¼1.2 Hz), 3.48–3.62 (m, 4H); 13C NMR
(63 MHz, CDCl3): d (ppm)¼160.3, 134.3, 118.1, 72.8, 71.0,
69.0, 30.5; MS (20 eV), m/e (%): 167 (23.6), 165 (23), 123
(3.0), 121 (3.0), 97 (26.5), 71 (42.9), 57 (28.3), 41 (100).
Anal. Calcd for C7H11BrO3: C, 37.69; H, 4.97. Found: C,
37.80; H, 4.72.
3.2. General procedure for the alcoholysis of epoxides
Either of the catalysts, TABCO, NBS or NCS (0.2 mmol,)
was added to a solution of epoxide (1 mmol) in alcohol
(2 ml). The mixture was stirred for 15 min–48 h at room
temperature or under reflux condition (Table 4). GC and
TLC monitored the progress of reaction. After the
completion of the reaction, 10% aqueous solution of
NaOH (20 ml) was added to the mixture. The product was
then extracted with diethyl ether (2£20 ml) and washed with
water (2£10 ml). The organic layer was separated and dried
with anhydrous Na2SO4. Filtration and evaporation of the
solvent followed by purification on a short column of silica
gel produced the desired product (0–97%). All the products
are known compounds and were identified by comparison of
their spectral data with known samples reported in the
literature.12,14a–c,e,f
3.1.3. Formic acid 1-bromomethyl-penthyl ester (III). IR
(neat): 3442, 2958, 2917, 2875, 1733, 1183 cm21; 1H NMR
(250 MHz, CDCl3): d (ppm)¼8.13 (s, 1H), 5.11–5.2 (m,
1H), 3.44–3.58 (m, 2H), 1.64–1.78 (m, 2H), 1.34 (m, 4H),
0.92 (t, 3H); 13C NMR (63 MHz, CDCl3): d (ppm)¼160.6,
72.7, 34.0, 32.5, 27.4, 22.7, 14.2; MS (20 eV), m/e (%): 163
(1.5), 165 (1.5), 129 (14.1), 83 (21.2), 55 (42.3), 57 (33.9),
43 (100), 41 (92.1). Anal. Calcd for C7H13BrO2: C, 40.21;
H, 6.27. Found: C, 40.34; H, 6.20.
3.3. General procedure for the conversion of episulfides
into bis(2-alkoxy ethane)disulfides with NBS
3.1.4. Formic acid 1-bromomethyl -2-phenoxy-ethyl
ester (IV). IR (neat): 3431, 3078, 3065, 3036, 2931, 2869,
1714, 1598, 1490, 1239, 1145, 753 cm21
;
1H NMR
To a solution of episulfide (1 mmol), in alcohol (3 ml), NBS
(0.55 mmol, 0.098 g) was added and the mixture was stirred
at room temperature for the appropriate time (Table 5).
After completion of reaction, the solvent was evaporated
and then 10% aqueous solution of NaOH (20 ml) was added
to the mixture. The product was extracted by ether
(2£30 ml) and the combined organic layers were dried on
anhydrous Na2SO4. The solution was filtered and evapor-
ated. The product was purified by column chromatography
on silica-gel using petroleum ether/ethyl acetate (80:20) as
eluent. The pure product was obtained in 20–93% yield
(Table 5). All the products are known compounds and were
identified by comparison of their spectral data with those of
known samples reported in the literature.14d
(250 MHz, CDCl3): d (ppm)¼8.05 (s, 1H), 7.17–7.25 (m,
2H), 6.82–6.94 (m, 3H), 5.37 (m, 1H), 4.09–4.15 (m, 2H),
3.54–3.64 (m, 2H); 13C NMR (63 MHz, CDCl3): d
(ppm)¼160.2, 158.4, 130.0, 122.0, 115.0, 70.9, 66.9,
30.2; MS (20 eV), m/e (%): 260 (4), 258 (4), 167
(96.2), 165 (100), 133 (23.5), 94 (32.3), 57 (31.4). Anal.
Calcd for C10H11BrO3: C, 46.36; H, 4.28. Found: C, 46.50;
H, 4.14.
3.1.5. Formic acid 1-bromomethyl-2-chloro-ethyl ester
(V). IR (neat): 3446, 2975, 2909, 2888, 1645, 1300, 1194,
978, 807 cm21
;
1H NMR (250 MHz, CDCl3):
d
(ppm)¼8.08 (m, 1H), 3.72 (dd, 2H, J¼5.17 Hz), 3.56 (dd,

7042
N. Iranpoor et al. / Tetrahedron 58 (2002) 7037–7042
1991, 47, 149–154. (e) Safavi, A.; Iranpoor, N.; Fotuhi, L.
Bull. Chem. Soc. Jpn 1995, 68, 2591–2594. (f) Iranpoor, N.;
Tarrian, T.; Movahedi, Z. Synthesis 1996, 1473–1476.
(g) Iranpoor, N.; Kazemi, F. Tetrahedron 1997, 53,
11377–11382. (h) Iranpoor, N.; Tamami, B.; Niknam, K.
Can. J. Chem. 1997, 75, 1913–1919. (i) Iranpoor, N.;
Shakarriz, M.; Shiriny, F. Synth. Commun. 1998, 28,
347–366. (j) Iranpoor, N.; Adibi, H. Bull. Chem. Soc. Jpn
2000, 73, 675–680. (k) Salomon, C. J. Synlett 2001, 65–68.
15. (a) Firouzabadi, H.; Iranpoor, N.; Karimi, B.; Hazarkhani, H.
Synlett 2000, 263–265. (b) Firouzabadi, H.; Iranpoor, N.;
Hazarkhani, H. Synlett 2001, 1641–1643. (c) Firouzabadi, H.;
Iranpoor, N.; Hazarkhani, H. J. Org. Chem. 2001, 66,
7527–7529. (d) Iranpoor, N.; Firouzabadi, H.; Shaterian,
H. R. J. Org. Chem. 2002, 67, 2826–2830. (e) Iranpoor, N.;
Firouzabadi, H.; Shaterian, H. R. Phosphorous, Sulfur Silicon
2002, 177, 1047–1071. (f) Firouzabadi, H.; Iranpoor, N.;
Hazarkhani, H.; Karimi, B. J. Org. Chem. 2002, 67,
2572–2576.
3.4. General procedure for dimerization of episulfides
into 1,4-dithianes with NBS
To a solution of episulfides (1 mmol), in dichloromethane
(2 ml), NBS (0.2 mmol, 0.04 g) was added and the mixture
was stirred at room temperature for the appropriate time
(Table 5). After completion of the reaction, 10% aqueous
solution of NaOH (20 ml) was added to the reaction
mixture. The product was extracted by ether (2£30 ml)
and the combined organic layers were dried on anhydrous
Na2SO4. After filtration and evaporation of the solvent, the
product was purified by column chromatography on silica-
gel using petroleum ether/ethyl acetate (80:20) as eluent.
The pure product was obtained in 75–80% yield (Table 5).
The spectral data of the products were compared with those
of known samples.14d
Acknowledgments
16. (a) Horner, L.; Oediger, H.; Hofmann, H. Liebigs Ann. Chem.
1959, 626, 26–34. (b) Wiley, G. A.; Hershkowiz, R. L.; Rein,
B. M.; Chung, B. C. J. Am. Chem. Soc. 1964, 86, 964–965.
(c) Wiley, G. A.; Rein, B. M.; Hershkowitz, R. L. Tetrahedron
Lett. 1964, 2509–2513. (d) Kaplan, L. J. Org. Chem. 1966, 31,
3454. (e) Schaefer, J. P.; Weinberg, D. S. J. Org. Chem. 1965,
30, 2635–2639. (f) Brett, D.; Downie, I. M.; Lee, J. B. M.;
Matough, F. S. Chem. Lett. 1969, 1017–1018. (g) Arain, R. A.;
Hargreaves, M. K. J. Chem. Soc. C 1970, 67–70. (h) Sonnet,
P. E.; Oliver, J. E. J. Org. Chem. 1976, 41, 3279–3284.
(i) Hrubiec, R. T.; Smith, M. B. J. Org. Chem. 1984, 49,
431–435.
We are thankful to Shiraz University Research Council for
the partial support of this work.
References
1. Rosewsky, A. Heterocyclic Compounds with Three and Four
Membered Rings, Part I; Interscience: New York, 1964;
Chapter I.
2. Izydore, R. A.; Ghirardelli, G. R. J. Org. Chem. 1973, 38,
1790–1793.
3. Sexton, A. R.; Britton, E. C. J. Am. Chem. Soc. 1948, 70,
3606–3607.
17. (a) Hanack, M.; Auchter, G. J. Am. Chem. Soc. 1985, 107,
5238–5245. (b) Sandr, J.; Viala, J. Synth. Commun. 1992, 22,
2945–2948. (c) Machinek, R.; Luttke, W. Synthesis 1975,
255–256. (d) Wiely, G. A.; Hershkowitz, R. L.; Rein, B. M.;
Chung, B. C. J. Am. Chem. Soc. 1964, 86, 964–965. (e) Hodge,
P.; Khoshdel, E. J. Chem. Soc., Perkin Trans. 1 1984,
195–198.
4. Bridger, R. F.; Russel, R. R. J. Org. Chem. 1960, 25, 863–866.
5. Gilman, H.; Fullhart, L. J. Am. Chem. Soc. 1949, 71,
1478–1481.
6. Goodman, L.; Benitez, A.; Baker, B. R. J. Am. Chem. Soc.
1958, 80, 1680–1687.
7. Bordwell, F. G.; Anderson, H. M. J. Am. Chem. Soc. 1953, 75,
495–496.
18. (a) Heer, M. E.; Johnson, R. A. J. Org. Chem. 1972, 37,
310–312. (b) Boeckman, R. K., Jr.; Ganem, B. Tetrahedron
Lett. 1974, 11, 913–916. (c) Barluenga, J.; Campos, P. J.;
Gonzalez-Nunez, E.; Asensio, G. Synthesis 1985, 426–428.
19. Caputo, R.; Ferreri, C.; Palumbo, G. Synth. Commun. 1987,
17, 1629–1636.
8. Christensen, B. G.; Strachan, R. G.; Trenner, N. R.; Arison,
B. H.; Hir Schmann, R.; Chemerds, J. M. J. Am. Chem. Soc.
1960, 82, 3995–4000.
9. Norton, J. R.; Shenton, K. E.; Schwartz, J. Tetrahedron Lett.
1975, 51–54.
20. Morimura, S.; Horiuchi, H.; Murayama, K. Bull. Chem. Soc.
Jpn 1977, 50, 2189–2190.
10. Brown, H. C.; Krishnamurthy, S. Tetrahedron 1979, 35,
567–607.
21. Fernandez, I.; Garsia, B.; Munoz, S.; Pedro, J. R.; Salud, R.
Synlett 1993, 489–490.
11. Brown, H. C.; Yoon, N. M. J. Am. Chem. Soc. 1966, 88,
1464–1472.
22. Ziegenble, W.; Franke, W. Chem. Ber. 1960, 93, 1681–1683.
23. (a) Thakore, A. N.; Pope, A. N. P.; Oehlschlager, A. C.
Tetrahedron 1971, 27, 2617–2625. (b) Sonnet, P. E.; Oliver,
J. E. J. Org. Chem. 1976, 41, 3279–3283.
12. Smith, J. C. Synthesis 1984, 629–656.
13. Sander, M. Chem. Rev. 1966, 66, 297–339.
14. (a) Iranpoor, N.; Mohammadpour Baltork, I. Synth. Commun.
1990, 20, 2789–2797. (b) Iranpoor, N.; Mohammadpour
Baltork, I.; Shiriny, F. Tetrahedron 1991, 47, 9861–9866.
(c) Iranpoor, N.; Mohammadpour Baltork, I. Tetrahedron Lett.
1990, 31, 735–738. (d) Iranpoor, N.; Owji, J. Tetrahedron
24. (a) Palumbo, G.; Ferreri, C.; Caputo, R. Tetrahedron Lett.
1983, 24, 1307–1310. (b) Caputo, R.; Ferreri, C.; Noviello, S.;
Paluma, G. Synthesis 1986, 499–501.