Tertiary amine functionalized polyacrylonitrile fiber catalyst for the synthesis of tetrahydrothiophenes

Article abstract of DOI:10.1016/j.tet.2013.02.084

A tertiary amine immobilized fiber was prepared and used to efficiently catalyze tandem Michael-intramolecular Henry reactions between 1,4-dithiane-2,5-diol and trans-β-nitrostyrenes to form the corresponding tetrahydrothiophene derivatives. This newly developed fiber catalyst is applicable to a wide range of trans-β-nitroalkenes and affords good to excellent yields (75-93%) under mild conditions (with 2.5 mol % fiber catalyst at 50 °C in ethanol for 5 h). The fiber catalyst exhibits excellent recyclability and reusability (up to 10 times) after simple workup procedure with only a slight loss in catalytic activity. It is noteworthy that the major diastereomers have r-R, trans-nitro, trans-hydroxy configurations with diastereoselectivities of up to 15:1. This differs from the results obtained when the same reaction is catalyzed by a homogeneous catalyst. This is the first example of a fiber catalyst exhibiting excellent diastereoselectivity.

Full text of DOI:10.1016/j.tet.2013.02.084

Tetrahedron 69 (2013) 4749e4757
Contents lists available at SciVerse ScienceDirect
Tetrahedron
journal homepage: www.elsevier.com/locate/tet
Tertiary amine functionalized polyacrylonitrile fiber catalyst
for the synthesis of tetrahydrothiophenes
*
Changzhu Xu, Jianguo Du, Lichao Ma, Guowei Li, Minli Tao , Wenqin Zhang
Department of Chemistry, School of Sciences, Tianjin University, No. 92 Weijin Road, Tianjin 300072, PR China
a r t i c l e i n f o
a b s t r a c t
Article history:
A
tertiary amine immobilized fiber was prepared and used to efficiently catalyze tandem Mi-
chaeleintramolecular Henry reactions between 1,4-dithiane-2,5-diol and trans- -nitrostyrenes to form
the corresponding tetrahydrothiophene derivatives. This newly developed fiber catalyst is applicable to
a wide range of trans- -nitroalkenes and affords good to excellent yields (75e93%) under mild conditions
Received 3 December 2012
Received in revised form 6 February 2013
Accepted 22 February 2013
Available online 13 March 2013
b
b
(with 2.5 mol % fiber catalyst at 50 ꢀC in ethanol for 5 h). The fiber catalyst exhibits excellent recyclability
and reusability (up to 10 times) after simple workup procedure with only a slight loss in catalytic activity.
It is noteworthy that the major diastereomers have r-R, trans-nitro, trans-hydroxy configurations with
diastereoselectivities of up to 15:1. This differs from the results obtained when the same reaction is
catalyzed by a homogeneous catalyst. This is the first example of a fiber catalyst exhibiting excellent
diastereoselectivity.
Keywords:
Tertiary amine
Fiber catalyst
Polyacrylonitrile fiber
Tetrahydrothiophene
Michaeleintramolecular Henry reaction
Ó 2013 Elsevier Ltd. All rights reserved.
1. Introduction
Polyacrylonitrile fiber (PANF) is called artificial wool due to its
good thermal properties, flexibility, and light fastness.16 Its
Tetrahydrothiophenes (THTs) are important intermediates that
form thiophene derivatives through dehydration and aromatiza-
tion.1 The formed thiophene derivatives have many applications,
such as medical intermediates, electrical conductors, and nonlinear
optical devices.2e5 In general, THTs are synthesized in homoge-
neous systems and catalyzed by organic tertiary amines like trie-
thylamine.1 However, it is generally accepted that traditional
homogeneous catalyst reactions have many disadvantages, such as
complicated post-treatment, difficult separation processes, trou-
blesome recovery of the catalysts, and severe pollution to the
environment.
abundance of cyano groups can be converted to other active
functional groups, which can then be used directly as active
catalyst sites or as starting material to generate new catalytic
centers.17 Therefore, PANF should be a suitable starting material
for preparation of heterogeneous catalysts based on fabric
materials.
In our previous work, functionalized PANFs were used to cata-
lyze the Knoevenagel condensation with excellent results.18,19 In
this paper, a new tertiary aminated fiber catalyst based on PANF
was designed and prepared and then was used to catalyze the re-
actions of 1,4-dithiane-2,5-diol with trans-b-nitrostyrenes to form
An effective way to solve these problems is to use heteroge-
neous catalysts, which can be easily recovered from the reaction
mixture using only filtration or centrifugation and then they can be
reused.6 The ever-increasing use and expanding applications of
polymeric supports to prepare heterogeneous catalyst illustrate the
immense significance of this technique to the chemist.7 Heteroge-
neous catalysts based on solid supports, such as silica gel, poly-
styrene, and polyethylene have been prepared and used to simplify
separation and post-treatment procedures,8e14 and some of these
catalysts are used in industry.15 Heterogeneous catalysts based on
fabric materials have particularly attracted interest in recent years.
THTs.
2. Results and discussions
2.1. Preparation of the fiber catalyst
The preparation of the tertiary amine immobilized fiber catalyst
(PANTF) via a two-step process is shown in Scheme 1.
The extent of modification was determined from the acid ex-
change capacity and the weight gain of the produced fiber where
Weight gain ¼ ½ðw2 ꢁ w1Þ=w1ꢂ ꢃ 100%
For the ethylenediamine amination step, w1 and w2 are the
weights of PANF and the ethylenediamine aminated fiber (PANEF),
* Corresponding author. Tel.: þ86 22 27890922; fax: þ86 22 27403475; e-mail
address: mltao@tju.edu.cn (M. Tao).
0040-4020/$ e see front matter Ó 2013 Elsevier Ltd. All rights reserved.
http://dx.doi.org/10.1016/j.tet.2013.02.084

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C. Xu et al. / Tetrahedron 69 (2013) 4749e4757
dimethylpropane-1,3-diamine), and PANPF-3 (from PANF and N,N-
dimethylpropane-1,3-diamine),18 were also synthesized and used
for comparison.
2.2. Characterization of the PANEF and PANTF
2.2.1. Elemental analyzes. The elemental analysis data for PANF,
PANEF, PANTF, PANTF-1 (recovered after 1 run), and PANTF-10 (re-
covered after 10 runs) are listed in Table 1.
Compared to the original PANF, the carbon content of PANEF
decreased noticeably and the hydrogen content increased as ex-
pected. There are two factors contributing to the decrease of ni-
trogen in PANEF. First, cyano groups and the imino groups (eC(]
NH)NHCH2 CH2 NH2) in aqueous media are partial hydrolyzed to
form amides (eCONH2 and eCONHCH2 CH2 NH2) and release the
ammonia. The other factor is due to the cross-linking reaction in-
duced by ethylenediamine. The decrease in sulfur in the PANEF can
be attributed to the removal of the surfactants, which were added
during the manufacture process. Based on the PANEF, the more
carbon and hydrogen as well as the less nitrogen content of 3-
dimethylaminopropyl moieties (C5H11N) lead to a higher carbon
and hydrogen contents and lower nitrogen content of PANTF. After
the first run, the sulfur content of the recovered fiber PANTF-1 in-
crease slightly and after 10 runs, the sulfur content of the fiber
catalyst PANTF-10 increased substantially to 5.08%. This suggests
that some sulfur containing intermediates or products were grafted
onto the surface of the fiber during the reaction. This was further
confirmed by FTIR analysis (Fig. 2).
Scheme 1. Preparation of tertiary amine immobilized fiber catalyst (PANTF).
respectively. For the tertiary amine immobilization step, w1 and w2
are the weights of PANEF and PANTF, respectively.
The above two-steps are greatly influenced by reaction time and
temperature. The weight gains can be enhanced by increasing the
reaction temperature or by prolonging the reaction time. However,
a higher weight gain noticeably reduces the strength of PANEF and
PANTF. The details of ethylenediamine amination process have been
discussed previously.20 Those results were used in this work to
select the optimal reaction conditions (stirring at reflux for
250 min) for preparing PANEF with a weight gain of 12.8%.
For the tertiary amine immobilization process, in addition to an
appropriate reaction time and temperature, an alkaline condition is
necessary. However, a pH value that is too high will also noticeably
reduce the strength of the PANTF. The optimal conditions were
a PANEF to NaHCO3 to 3-dimethylaminopropylchloride hydrochlo-
ride mol ratio of 1:3:4 with stirring at reflux for 180 min to give
PANTF with a weight gain of 13.0%.
Table 1
Elemental analysis data of PANF, PANEF, PANTF, PANTF-1,a and PANTF-10b
Sample
Weight gain (%)
C (%)
H (%)
N (%)
S (%)
PANF
PANEF
PANTF
PANTF-1
PANTF-10
d
66.06
56.39
59.95
59.58
58.21
5.81
6.42
6.86
6.15
6.04
24.42
21.77
18.38
18.14
16.08
0.25
0.12
0.08
0.97
5.08
12.8
13.0c
13.0
13.0
a
Recovered after the first run as the catalyst in the reaction between b-nitro-
styrene and 1,4-dithiane-2,5-diol.
b
Recovered after the 10th run of the reaction.
The weight gain is 27.5% if it was calculated based on PANF.
c
The acid exchange capacity of PANEF in aqueous 0.100 M HCl was
determined to be 1.5 mmol gꢁ1 by titration, indicating that some
ethylenediamine modifiers were grafted onto the PANF. However,
this value is lower than the value calculated for a 12.8% weight gain,
which is 1.9 mmol gꢁ1. This difference is due to the cross-linking
reaction induced by ethylenediamine (Scheme 1).
2.2.2. SEM (Scanning Electron Microscope). The SEM photographs
of PANF, PANEF, PANTF, PANTF-1, and PANTF-10 are shown in Fig. 1.
The commercially available PANF has a smooth surface (Fig. 1a).
After ethylenediamine amination and tertiary-amination, the sur-
face of the fiber became rougher gradually (Fig. 1bec). Although
some surface flaws due to magnetic stirring can be observed on
PANTF-1 (Fig. 1d) and PANTF-10 (Fig. 1e), the fiber catalyst main-
tained fairly good integrity after each use.
The titrated acid exchange capacity of PANTF in aqueous 0.100 M
HCl was 2.4 mmol gꢁ1. Based on a weight gain of 13.0%, the amount
of 3-dimethylaminopropyl moieties in 1 g PANTF was calculated to
be 1.3 mmol (0.885 g of PANEF gives 1.000 g of PANTF so
1.5 mmol gꢁ1ꢃ0.885 g¼1.3 mmol of 2-(aminoethyl) groups). So
based on the weight gain, the total content of the basic amino
groups should be 2.6 mmol gꢁ1. The difference of 0.2 mmol gꢁ1 may
be due to further cross-linking reactions between the 2-(amino-
ethyl) groups and the remaining cyano groups under the alkaline
conditions. After subtracting the cross-linked 0.2 mmol, only
1.1 mmol of 2-(aminoethyl) groups left to react with the 1.3 mmol
of 3-dimethylaminopropylchloride hydrochloride, i.e.,1.3 mmol gꢁ1
more 3-(dimethylaminopropyl) groups have been immobilized on
1.1 mmol gꢁ1 of 2-(aminoethyl) moieties, which result in
1.5 mmol gꢁ1 of tertiary amine groups as the catalyst sites (for
details, see Supplementary data).
2.2.3. FTIR. The samples of PANF, PANEF, PANTF, PANTF-1, and
PANTF-10 were cut until powdered and then prepared as KBr pel-
lets. The FTIR spectra of all samples are shown in Fig. 2.
The FTIR spectrum of PANF (Fig. 2a) clearly shows a C^N vi-
bration at 2244 cmꢁ1 and a C]O vibration from the methyl acrylate
units at 1731 cmꢁ1. After amination, there are broad bands at
3700e3150 cmꢁ1 in PANEF (Fig. 2b) and PANTF (Fig. 2c), which
correspond to the stretching vibrations of NeH. This indicates that
the amines have been grafted onto the PANF or that the cyano
groups have been hydrolyzed. The large decrease in the C]O peak
and the slight decrease in the C^N peak in PANEF (Fig. 2b) imply
that some of the cyano groups were modified by ethylenediamine
and that the ester groups reacted preferentially with the ethyl-
enediamine. In the modified fibers, the strong bands in the region of
1650 cmꢁ1 are attributed to the amide I band and the new peaks in
Some other fiber catalysts, such as PANTTF (from PANF and
triethylenetetramine),19 PANPF-2 (from PANF and N,N0-

C. Xu et al. / Tetrahedron 69 (2013) 4749e4757
4751
Table 2
Catalytic activitiesa and properties of PANF, PANEF, PANTTF, PANPF-2, PANPF-3, PANTF
Entry
Sample
Weight gain (%)
Acid exchange
Yield (%)b
capacity (mmol gꢁ1
)
1
2
3
4
5
6
7
PANF
PANEF
PANTT
PANpF-2
PANPF-3
PANTF
d
0
9
19
37
16
88
93
9
12.8
26.0
22.1
38.0
13.0
d
1.5
3.1
1.5
2.8
2.4
d
F
Blank
a
Reactions were carried out with b-nitrostyrene (4 mmol) 1,4-dithiane-2,5-diol
(2.2 mmol), and catalyst (2.5 mol %) in ethanol (15 mL) at 50 ꢀC for 5 h.
b
Isolated yield after column chromatography.
activities (yields of 19%, 37% and 16%, respectively, Table 2, entries
2e4). However, PANPF-3 (Table 2, entry 5) exhibited good catalytic
activity with a yield of 88%, indicating that the fiber with tertiary
amine groups had a higher catalytic activity for this reaction. When
PANTF (Table 2, entry 6) with tertiary amine group was employed as
the catalyst, the highest yield of 93% was achieved.
Some literature results have shown that the insertion of a long
chain spacer to separate the polymer backbone from the catalytic
sites can greatly enhance the catalytic activity of the system.21e25
This may explain the highest activity results for PANTF. Longer
and more flexible chains stretching from the surface of PANTF make
it easier for the reactants to access to active sites of the catalyst.
A possible mechanism for the Michaeleintramolecular Henry
reaction is depicted in Scheme 2. The PANTF surface acts as
a Brønsted proton scavenger to decompose 1,4-dithiane-2,5-diol
Fig. 1. SEM photographs of (a) PANF, (b) PANEF, (c) PANTF, (d) PANTF-1, and (e) PANTF-
10.
into thiolate anions, which then react with trans-b-nitrostyrene
through a Michael addition reaction. Then THT forms via an intra-
molecular Henry reaction. After this process, the product is released
from the surface of the fiber catalyst and the fiber catalyst returns
back to its original structure.
Fig. 2. FTIR spectra of (a) PANF, (b) PANEF, (c) PANTF, (d) PANTF-1, and (e) PANTF-10.
the region of 1560 cmꢁ1 are the overlap of the amide II band. The IR
spectra of PANTF-1 and PANTF-10 (Fig. 2d and e) are almost the same
as that for PANTF (Fig. 2c), which indicates that the functional groups
on the fiber catalyst still exist after being reused 10 times. The new
peaks at 700 cmꢁ1 and 750 cmꢁ1 in the recovered fiber PANTF-10
(Fig. 2e) are characteristic for mono-substituted benzene bending
vibrations, which further indicates that some intermediates or
products have been grafted onto the surface of the fibers.
Scheme 2. Possible mechanism of the tandem Michaeleintramolecular Henry reaction
catalyzed by PANTF.
2.3. Catalytic activity
2.4. Optimization of reaction conditions
The catalytic activity of different functionalized fibers was then
studied for the reaction between trans-
b-nitrostyrene and 1,4-
2.4.1. Effect of solvents. Several commonly used solvents were
dithiane-2,5-diol and the results are listed in Table 2. PANF did not
show any catalytic activity (Table 2, entry 1). PANEF with primary
amine groups, PANTTF with multiple secondary amine groups and
PANPF-2 with secondary amine groups all showed poor catalytic
tested for the reaction of trans-b-nitrostyrene with 1,4-dithiane-
2,5-diol catalyzed by PANTF and the results are listed in Table 3.
Polar solvents, such as methanol, ethanol, 1,3-propanediol, H2O,
and acetonitrile afforded relatively good yields (Table 3, entries

4752
C. Xu et al. / Tetrahedron 69 (2013) 4749e4757
Table 3
screened. The yield of the reaction increased sharply to the maxi-
Reaction yields in different solvent
mum of 93% as the reaction temperature increased from 25 to 50 ꢀC.
However, at temperatures higher than 50 ꢀC, the yield steadily
decreased as the temperature approached reflux, which is due to
the instability of the products at higher temperatures. In addition,
the yield of the reaction at lower temperature could not be im-
proved by prolonging the reaction time and increasing the dose of
catalyst (Table 4, entry 2) because of the poor solubility of 1,4-
dithiane-2,5-diol in ethanol below 45 ꢀC. Consequently, 50 ꢀC was
selected as the best reaction temperature for this reaction.
The effect of the amount of catalyst was also explored and the
results are given in Table 4 (entries 5, 9e12). When the amount of
catalyst was increased from 1.25 to 2.5 mol %, the yield increased
from 86% to 93%. However, there was no further yield enhancement
when the amount of catalyst was further increased to 12.5 mol %.
Therefore 2.5 mol % of PANTF was selected for all subsequent
reactions.
Entry
Solvents
Polarity
SPa
Yield (%)b,c
1
2
3
4
5
6
7
8
9
Ethanol
Methanol
1,3-Propanediol
H2O
Acetonitrile
Ethyl acetate
Isopropyl ether
Cyclohexane
Dioxane
4.3
6.6
d
12.7
14.8
d
93
94
82
78
65
8
12
7
21
7
10.2
6.2
4.3
d
23.41
11.9
9.1
d
0.1
4.8
2.4
8.18
10.1
8.9
10
Toluene
a
Polymer solubility parameter.
Reactions were carried out with
b
b
-nitrostyrene (4 mmol), 1,4-dithiane-2,5-diol
(3 mmol), and PANTF (12.5 mol %) in different solvents (15 mL) at 50 ꢀC for 5 h.
c
Isolated yield after column chromatography.
1e5), which is due to the good solubility of 1,4-dithiane-2,5-diol in
these solvents. The best proton donating solvents gave the highest
yields (Table 3, entries 1e4). Whereas the solvents with weaker
polarities gave much lower yields (Table 3, entries 6e10). Typical
nonpolar solvents like cyclohexane and toluene gave the worst
yields (Table 3, entries 8, 10).
Next the influence of the reactant ratio on the yield was in-
vestigated and the results are listed in Table 4 (entries 5,13, and 18).
A slight excessive of 1,4-dithiane-2,5-diol is favorable to improve
the yield. The highest yield was obtained when the ratio of trans-b-
nitrostyrene to 1,4-dithiane-2,5-diol was 2:1.1. A further increase in
amount of 1,4-dithiane-2,5-diol did not further improve the yield.
For the solvents with similar polarities, the polymer solubility
parameter (SP), which represents the compatibility of the fiber
catalyst with the solvent plays an important role. For example,
methanol and ethanol have polymer solubility parameters
(SP¼14.8 and 12.7, respectively) that are similar to that of the fiber
catalyst (SP¼14.5). This means that the reactants in these solvents
have easy access to catalyst. These results suggest that the solubility
of the reactants and the compatibility of the fiber catalyst with the
solvent are two essential factors for this reaction. Considering the
tenets of green chemistry and product yield, ethanol was chosen as
the best solvent.
So a ratio of 2:1.1 of trans-b-nitrostyrene to 1,4-dithiane-2,5-diol
was selected as the best reactant ratio.
Finally, the effect of reaction time on the yield was investigated
and the results are shown in Table 4 (entries 14e21). There is
a sharp increase in the yield from 1 to 2 h, then the yield increases
gradually from 2 to 5 h and reached its maximum at 5 h. However,
a small decrease was observed if a longer reaction time was applied,
which can be attributed to the instability of the products under the
reaction condition. Consequently, 5 h at 50 ꢀC was chosen as the
optimal reaction time.
2.5. Scope of substrates catalyzed by PANTF
2.4.2. Optimization of reaction conditions. Next the effect of the
reaction temperature on the reaction was studied and the results
are presented in Table 4 (entries 1e8). Reaction temperatures
ranging from 25 to 78 ꢀC (the boiling point of ethanol) were
With the optimized reaction conditions established, the pro-
cedure was extended to other trans-
are presented in Table 5. Most of the trans-
b
-nitroalkenes and the results
-nitroalkenes worked
b
well and high yields were obtained. The reaction proceeded
smoothly and the desired THTs containing the two main di-
astereomers were obtained in yields of 75%e93%. These results
indicate that both steric and electronic withdrawing effects affect
the formation of the THTs. For instance, for the electron donating
methoxy group, the ortho-substituted trans-b-nitroalkene had
a lower yield (78% for 5 h and 82% for 8 h) than the para-substituted
one with a yield of 92% (Table 5, entries 2 and 4). For the electron
withdrawing NO2 group, the yield of the para-substituted trans-b-
nitroalkene was 7% lower than that of the meta-substituted sub-
strate under the same condition (Table 5, entries 5 and 6). In the
case of entry 14, the o-trifluoromethyl group has both of the steric
and electron withdrawing effects, and therefore, had the lowest
yield of 75% even the reaction time was prolonged to 8 h. It is very
interesting that both furanyl and thiophenyl trans-b-nitroalkenes
(Table 5, entries 15 and 16) gave pretty good yields, which suggest
that this fiber catalyst is also efficient for heteroaryl substrates.
Table 4
Optimization of reaction conditionsa
Entry Temp (ꢀC) Cat. loading (%mmol)b Time (h) Substrate ratioc Yield (%)d
1
2
3
4
5
6
7
8
25
25
40
45
50
55
60
78
50
50
50
50
50
50
50
50
50
50
50
50
50
2.5
12.5
2.5
2.5
2.5
2.5
2.5
2.5
1.25
5
10
5
5
5
5
5
5
5
5
5
5
5
1
2
3
4
2:1.5
2:1.5
2:1.5
2:1.5
2:1.5
2:1.5
2:1.5
2:1.5
2:1.5
2:1.5
2:1.5
2:1.5
2:1
2:1.1
2:1.1
2:1.1
2:1.1
2:1.1
2:1.1
2:1.1
2:1.1
28
32
61
88
93
86
83
75
86
93
93
93
89
45
74
80
88
93
91
90
89
9
10
11
12
13
14
15
16
17
18
19
20
21
3.75
6.25
12.5
2.5
2.5
2.5
2.5
2.5
2.5
2.5
2.5
2.5
5
6
8
10
2.6. Stability of stereoisomers
The optimization of the geometries and the energy of
the products were calculated using DFT method with the B3LYP/6-
31G** level of theory. The calculations were performed
using the GAUSSIAN 03 computational program package.26 The
possible structures and their relative internal energies are shown in
Scheme 3.
a
Reactions were carried out with
b-nitrostyrene, 1,4-dithiane-2,5-diol, and
PANTF in ethanol (15 mL).
b
Calculated base on the catalyst site (the acid exchange capacity).
Mole ratio of 1,4-dithiane-2,5-diol to
Isolated yield after column chromatography.
c
b
-nitrostyrene.
d

C. Xu et al. / Tetrahedron 69 (2013) 4749e4757
4753
Table 5
Reaction of trans-
b
-nitroalkenes with 1,4-dithiane-2,5-diola
OH
OH
O2N
O2N
NO2
S
S
OH
Fiber cat. 2.5 mol%
C2H5OH
R
+
+
S
S
R
R
HO
Major (I)
Time (h)
Minor (II)
Entry
trans-
b
-Nitroalkenes (a)
Products (b)
Yield % of b (I:II)b
Yield % of b (I:II) in Ref. 1
I
II
1
5
93 (6:1)
99(1:1.5)
77 (1:2)
2
3
5
8
78
82 (2:1)
5
5
81 (6:1)
d
4
5
92 (15:1)
99 (1.2:1)
74 (1:1)
5
8
80 (11:1)
80
6
8
87 (3:1)
80 (1:1.25)
7
8
7
7
85 (3:1)
85 (4:1)
d
d
9
8
89 (4:1)
d
10
11
8
5
82 (2.5:1)
88 (3.5:1)
84 (1:1.3)
d
(continued on next page)

4754
C. Xu et al. / Tetrahedron 69 (2013) 4749e4757
Table 5 (continued )
Entry
trans-
b
-Nitroalkenes (a)
Products (b)
Time (h)
Yield % of b (I:II)b
Yield % of b (I:II) in Ref. 1
I
II
12
8
5
75 (5.5:1)
77
13
14
90 (6:1)
d
5
8
75(8:1)
75
71
15
16
5
5
85 (10:1)
92 (3:1)
92 (1.4:1)
99 (1:1.2)
a
Reactions were carried out with trans-b
-nitroalkenes (4 mmol), 1,4-dithiane-2,5-diol (2.2 mmol), with 2.5 mol % PANTF in ethanol (15 mL) at 50 ꢀC.
Isolated yield after column chromatography.
b
Scheme 3. Possible structures and their relative energies.
Owing to the trans nature of the b-nitroalkene, the products
contained the two main diastereomers (Scheme 3I and II). Connor
and his co-workers1 reported that there is an anti-relationship
between the nitro and the phenyl groups in both diastereomers,
and this conclusion is confirmed by the computational results
(Scheme 3), which show that the internal energies of III and IV are
4.9 and 7.1 kJ/mol higher than that of I, i.e., III and IV are thermo-
dynamically unstable. The internal energies of I and II are almost
the same within the calculation error. By comparing Connor’s 1H
NMR spectrum (Fig. 3a) with ours (Fig. 3b), it is found that the
major diastereomer in this article has a r-R, trans-nitro, trans-hy-
droxy configuration (Scheme 3I). It is worth mentioning that the
diastereoselectivity was much better (15:1, Table 5, entry 4) than
that for the reaction catalyzed by a homogeneous system (1.2:1).
The reverse selectivity and high diastereoselectivity may be due to
the surface micro-environmental effects of the fiber catalyst.
Fig. 3. The 1H NMR comparison of products (b4) catalyzed by (a) triethylamine and by
(b) our fiber catalyst PANTF.
2.7. Reusability of the PANTF
PANTF was reused for the reaction of trans-
1,4-dithiane-2,5-diol in ethanol to test the reusability of the fiber
catalyst. After each run, the fiber catalyst was filtered out and
b
-nitrostyrene and
washed with ethyl acetate (3ꢃ10 mL) to remove any residue that
had adhered onto the fiber catalyst. The fiber was then directly used
in the next cycle without any additional treatment. The yield of

C. Xu et al. / Tetrahedron 69 (2013) 4749e4757
4755
each cycle is listed in Table 6. After 10 runs, the yield of
Michaeleintramolecular Henry reaction only decreased by 3%e
89%. Compared to the homogeneous catalysts, this new fiber cat-
alyst has advantages of a simple workup procedure and excellent
reusability.
4.1.2. Acid exchange capacities of the aminated fiber catalyst (PANEF
and PANTF). The dried fiber catalyst PANEF or PANTF (0.200 g) was
immersed into 20mL ofaqueous 0.100 M HClfor 6 h. The treated fiber
was then filtered out and repeatedly washed with boiled deionized
water. The filtrates were combined and the concentration was de-
termined by titration with aqueous 0.100 M NaOH. The exchange
capacity was calculated based on the amount of acid consumed.
Table 6
Reusability of the PANTFa
4.1.3. General procedure for Michaeleintramolecular Henry re-
action. A mixture of trans-b-nitroalkene (4 mmol), 1,4-dithiane-
Entry
No. of recycling runs
Yield (%)b
2,5-diol (2.2 mmol) and the fiber catalyst PANTF (0.066 g, with
0.10 mmol tertiary amine functionalities) in ethanol (15 mL) was
stirred at 50 ꢀC for the desired time. Progress of the reaction was
monitored by thin layer chromatography (TLC). After completion of
the reaction, the fiber catalyst was filtered out and washed with
ethyl acetate (3ꢃ10 mL). The filtrates were combined and washed
with saturated ammonium carbonate solution and the aqueous
phase was extracted by ethyl acetate (3ꢃ10 mL). The organic layer
was combined, dried over Na2SO4, filtered, concentrated, and pu-
rified by column chromatography on silica gel [ethyl acetate/pe-
troleum ether] to afford the products.
a
b
c
d
e
f
g
h
i
1
2
3
4
5
6
7
8
9
92
93
92
92
92
92
91
90
89
89
j
10
a
Reactions were carried out with trans-b-nitrostyrene (4 mmol) and 1,4-
dithiane-2,5-diol (2.2 mmol) with 2.5 mol % PANTF in ethanol (15 mL) at 50 ꢀC for
5 h.
b
Isolated yield after column chromatography.
4.1.3.1. 4-Nitro-5-phenyltetrahydrothiophen-3-ol
(b1-I): 1H NMR (400 MHz, CDCl3)
(b1). Major
7.47 (d, J¼7.0 Hz, 2H), 7.39e7.27
d
3. Conclusions
(m, 3H), 5.24 (d, J¼9.7 Hz, 1H), 5.06 (s, 1H), 5.04e4.98 (m, 1H), 3.51
(dd, J¼12.0, 4.3 Hz, 1H), 3.07 (dd, J¼12.0, 2.0 Hz,1H), 2.91 (s,1H). 13C
In summary, an innovative tertiary aminated fiber catalyst was
prepared by a two-step modification procedure of polyacrylonitrile
fiber and was then used to catalyze the synthesis of 4-hydroxy-3-
nitro-2-substituted tetrahydrothiophenes. The Michaeleintramolec-
ular Henry reaction proceeded smoothly at 50 ꢀC in the presence of
the fiber catalyst (2.5 mol %) in various solvents, such as ethanol,
methanol and water. Ethanol was selected to be the most suitable
solvent owing to the advantages of the highest yield, low cost and
environmentally benign. At the end of each reaction, the fiber catalyst
can be easily separated from the reaction system by filtration and can
be reused conveniently in another cycle. This fiber catalyst is suitable
NMR (101 MHz, CDCl3)
48.39, 36.13.
d 136.64, 128.96, 128.60, 128.18, 95.51, 75.44,
Minor (b1-II): 1H NMR (400 MHz, CDCl3) 7.44e7.39 (m),
7.39e7.27 (m), 4.93 (dt, J¼24.0, 11.5 Hz), 3.33e3.26 (m), 3.17 (dt,
J¼10.9), 2.91 (s). 13C NMR (101 MHz, CDCl3)
d 136.72, 129.08, 128.86,
127.74, 97.94, 49.65, 34.09.
4.1.3.2. 5-(2-Methoxyphenyl)-4-nitrotetrahydrothiophen-3-ol
(b2). Major (b2-I): 1H NMR (400 MHz, CDCl3)
7.51e7.41 (m, 1H),
d
7.32 (t, J¼7.9 Hz, 1H), 7.03e6.83 (m, 2H), 5.49 (d, J¼7.7 Hz, 1H), 5.31
(dd, J¼7.7, 4.5 Hz, 1H), 5.00 (d, J¼6.1 Hz, 1H, H5), 3.88 (s, 3H), 3.44
(dd, J¼11.7, 4.1 Hz, 1H), 3.11 (dd, J¼11.7, 3.7 Hz, 1H), 2.98 (ddd,
for a wide range of trans-b-nitroalkenes and shows excellent recy-
clability and reusability (up to 10 times) without any additional
treatment. The fiber catalyst produced a different major product (a r-
R, trans-nitro, trans-hydroxy configuration) compared with the same
reaction catalyzed by homogeneous triethylamine, and the diaster-
eoselectivity of the major to minor product increased to 15:1. As far
as is known, there are no other reports of a heterogeneous catalyst
being used in the synthesis of THTs with excellent diaster-
eoselectivity. These attractive features make the tertiary aminated
fiber catalyst a useful tool for the synthesis of THT through the
Michaeleintramolecular Henry reaction.
J¼31.0, 17.8, 5.5 Hz, 1H). 13C NMR (101 MHz, CDCl3)
d 157.38, 129.63,
128.90, 125.40, 120.88, 111.26, 93.47, 75.59, 55.62, 44.57, 36.43.
Minor (b2-II): 1H NMR (400 MHz, CDCl3)
d 7.51e7.41 (m), 7.32 (t,
J¼7.9 Hz), 7.03e6.83 (m), 5.31 (dd, J¼7.7, 4.5 Hz), 5.00 (d, J¼6.1 Hz),
5.18e5.11 (m), 3.86 (s), 3.29 (dd, J¼11.2, 6.1 Hz), 3.17 (dd, J¼11.1,
7.6 Hz), 2.98 (ddd, J¼31.0, 17.8, 5.5 Hz). 13C NMR (101 MHz, CDCl3)
d
157.25, 129.78, 128.44, 125.47, 120.99, 111.15, 96.30, 77.97, 55.55,
45.22, 35.26.
4.1.3.3. 5-(3-Methoxyphenyl)-4-nitrotetrahydrothiophen-3-ol
(b3). Major (b3-I): 1H NMR (400 MHz, CDCl3)
d
7.28 (t, J¼7.9 Hz,
4. Experimental
4.1. General
1H), 7.05 (dd, J¼9.5, 4.8 Hz, 2H), 6.91e6.81 (m, 1H), 5.24 (d,
J¼9.5 Hz, 1H), 5.07 (s, 1H), 5.03 (dd, J¼9.6, 3.8 Hz, 1H), 3.83 (s, 3H),
3.51 (dd, J¼12.0, 4.3 Hz, 1H), 3.09 (d, J¼2.0 Hz, 1H), 3.06 (d, J¼2.1 Hz,
1H). 13C NMR (101 MHz, CDCl3)
d 148.64, 139.30, 134.90, 129.93,
4.1.1. Preparation of the fiber catalysts. The fiber catalyst was pre-
pared by the following two-step process:
123.59, 123.29, 95.22, 75.36, 47.36, 36.06.
Minor (b3-II): 1H NMR (400 MHz, CDCl3)
d
7.28 (t, J¼7.9 Hz),
Dried PANF (5.0 g), ethylenediamine (50 mL), and deionized water
(100 mL) were added to a three-necked flask. Afterstirringatrefluxing
temperature for 250 min, the fiber was filtered out and washed re-
peatedly with water (70 ꢀC) until the filtrate was neutral. Then the
fiber was dried overnight under vacuum at 70 ꢀC to give PANEF.
A mixture of 3-dimethylaminopropylchloride hydrochloride
(3.6 g), sodium bicarbonate (2.6 g), deionized water (200 mL), and
dried PANEF (4.0 g) was stirred at refluxing for 180 min, and then
the fiber was filtered out and washed repeatedly with deionized
water (70 ꢀC) until the filtrate was neutral. Finally, the fiber was
dried overnight under vacuum at 70 ꢀC to give PANTF.
7.02e6.96 (m), 6.91e6.81 (m), 5.00e4.88 (m), 3.86 (d, J¼5.9 Hz),
3.34e3.27 (m), 3.23e3.17 (m), 3.06 (d, J¼2.1 Hz). 13C NMR
(101 MHz, CDCl3)
48.58, 34.04.
d 139.54, 134.14, 130.13, 123.85, 122.97, 97.39,
HRMS: (m/z-ESI) calcd for C11H12NO4S (MꢁH)ꢁ 254.0487, found
254.0489.
IR nmax: 3446, 2942, 2838, 1602, 1552, 1491, 1454, 1373, 1266,
1157, 1084, 1045, 782, 754, 695 cmꢁ1
.
4.1.3.4. 5-(4-Methoxyphenyl)-4-nitrotetrahydrothiophen-3-ol
(b4). Major (b4-I): 1H NMR (400 MHz, CDCl3)
7.38 (d, J¼8.7 Hz,
d

4756
C. Xu et al. / Tetrahedron 69 (2013) 4749e4757
2H), 6.87 (d, J¼8.7 Hz, 2H), 5.21 (d, J¼9.9 Hz, 1H), 5.04 (s, 1H), 4.95
(dd, J¼9.9, 3.8 Hz, 1H), 3.79 (s, 3H), 3.49 (dd, J¼12.0, 4.2 Hz, 1H),
3.04 (dd, J¼12.0, 1.8 Hz, 1H), 2.94 (s, 1H). 13C NMR (101 MHz, CDCl3)
8.5 Hz, 2H), 7.30 (dd, J¼11.7, 5.7 Hz, 2H), 5.21 (d, J¼9.9 Hz, 1H), 5.07
(d, J¼1.3 Hz, 1H), 4.93 (dd, J¼9.9, 3.7 Hz, 1H), 3.51 (dd, J¼12.0,
4.3 Hz, 1H), 3.08e3.01 (m, 1H), 2.82e2.73 (m, 1H). 13C NMR
d
136.65, 128.96, 128.60, 128.19, 95.51, 75.45, 48.38, 36.13.
(101 MHz, CDCl3)
35.95.
d 135.15,134.46,129.62,129.14, 95.41, 75.33, 47.67,
Minor (b4-II): 1H NMR (400 MHz, CDCl3)
d
7.33 (d, J¼8.7 Hz),
6.87 (d, J¼8.7 Hz), 5.04 (s), 4.88 (dd, J¼16.4, 8.6 Hz), 3.79 (s), 3.28
Minor (b9-II): 1H NMR (400 MHz, CDCl3)
d
7.38 (dd, J¼25.4,
(dd, J¼11.0, 6.6 Hz), 3.13 (dd, J¼10.9, 7.9 Hz), 2.94 (s). 13C NMR
8.5 Hz), 7.30 (dd, J¼11.7, 5.7 Hz), 4.81e4.69 (m), 3.23 (dd, J¼15.3,
2.4 Hz), 3.11e3.08 (m), 2.85 (d, J¼6.0 Hz).
(101 MHz, CDCl3)
34.07.
d 136.72, 129.08, 128.87, 127.75, 97.93, 49.64,
HRMS: (m/z-ESI) calcd for C10H9ClNO3S (MꢁH)ꢁ 257.9992,
found 257.9995.
4.1.3.5. 5-(4-Nitrophenyl)-4-nitrotetrahydrothiophen-3-ol
(b5). Major (b5-I): 1H NMR (400 MHz, CDCl3)
IR nmax: 3482, 2942, 1551, 1491, 1409, 1171, 1091, 1043, 1014, 832,
d
8.16 (dd, J¼15.4,
748 cmꢁ1
.
11.7 Hz, 2H), 7.67 (dd, J¼12.6, 9.0 Hz, 2H), 5.38e5.30 (m,1H), 5.06 (s,
1H), 4.97 (dd, J¼10.1, 3.4 Hz, 1H), 3.49 (dt, J¼7.7, 3.8 Hz, 1H), 3.03 (d,
4.1.3.10. 5-(4-Bromophenyl)-4-nitrotetrahydrothiophen-3-ol
(b10). Major (b10-I): 1H NMR (400 MHz, CDCl3)
7.56e7.45 (m,
J¼11.7 Hz, 1H). 13C NMR (101 MHz, DMSO)
d
147.58, 146.31, 130.39,
d
124.10, 94.32, 76.81, 46.80, 36.77.
2H), 7.38 (d, J¼8.4 Hz), 5.22 (d, J¼9.9 Hz), 5.10 (s, 1H), 4.95 (dd,
Minor (b5-II): 1H NMR (400 MHz, CDCl3)
d
8.16 (dd, J¼15.4,
J¼9.9, 3.6 Hz, 1H), 3.53 (dd, J¼12.0, 4.3 Hz, 1H), 3.12e3.04 (m, 1H),
11.7 Hz), 7.60e7.46 (m), 5.17 (s), 4.91 (d, J¼5.3 Hz), 3.22 (d,
2.89e2.80 (m, 1H). 13C NMR (101 MHz, CDCl3)
129.93, 122.57, 95.35, 75.33, 47.74, 36.05.
Minor (b10-II): 1H NMR (400 MHz, CDCl3)
d
135.69, 132.11,
J¼5.5 Hz), 3.14 (s). 13C NMR (101 MHz, DMSO)
d 147.92, 146.06,
129.97, 124.36, 97.08, 76.84, 47.49, 33.46.
d
7.56e7.45 (m),
7.33e7.21 (m), 4.83e4.71 (m), 3.26 (dd, J¼15.3, 2.2 Hz), 3.22e3.15
4.1.3.6. 5-(3-Nitrophenyl)-4-nitrotetrahydrothiophen-3-ol
(b6). Major (b6-I): 1H NMR (400 MHz, CDCl3)
8.44e8.20 (m, 1H),
(m), 2.89e2.80 (m). 13C NMR (101 MHz, CDCl3)
d 132.47, 129.53,
d
99.98, 77.22, 48.53, 37.29.
8.11 (d, J¼7.0 Hz, 1H), 7.80 (d, J¼6.6 Hz, 1H), 7.49 (tt, J¼8.0, 4.1 Hz,
1H), 5.41e5.28 (m, 1H), 5.07 (s, 1H), 5.00e4.74 (m, 1H), 3.60e3.44
4.1.3.11. 5-(2,4-Dimethylphenyl)-4-nitrotetrahydrothiophen-3-ol
(b11). Major (b11-I): 1H NMR (400 MHz, CDCl3)
(m, 1H), 3.08e2.91 (m, 1H). 13C NMR (101 MHz, CDCl3)
d
148.66,
139.33, 134.92, 129.93, 123.57, 123.31, 95.23, 75.37, 47.34, 36.08.
Minor (b6-II): 1H NMR (400 MHz, CDCl3)
8.44e8.20 (m), 8.11
d
7.18 (dd, J¼18.7,
10.8 Hz, 2H), 7.14e7.01 (m, 1H), 5.19 (d, J¼9.5 Hz, 1H), 5.05 (d,
J¼1.7 Hz, 1H), 5.01 (dd, J¼9.6, 3.8 Hz), 3.49 (dd, J¼12.0, 4.3 Hz,
1H), 3.05 (dd, J¼12.0, 1.8 Hz, 1H), 2.99 (d, J¼18.8 Hz, 1H), 2.28
d
(d, J¼7.0 Hz), 7.68 (d, J¼7.5 Hz), 7.49 (tt, J¼8.0, 4.1 Hz), 5.00e4.74
(m), 3.33e3.21 (m), 3.21e3.09 (m). 13C NMR (101 MHz, CDCl3)
(dd, J¼25.8, 6.2 Hz, 6H). 13C NMR (101 MHz, CDCl3)
d 137.12,
d
139.58, 134.09, 130.13, 123.83, 122.97, 97.43, 48.65, 33.94.
133.87, 130.16,129.24, 125.46, 95.44, 75.43, 48.24, 36.13, 19.75,
19.40.
4.1.3.7. 5-(4-Fluorophenyl)-4-nitrotetrahydrothiophen-3-ol
Minor (b11-II): 1H NMR (400 MHz, CDCl3)
d 7.14e7.01 (m),
(b7). Major (b7-I): 1H NMR (400 MHz, CDCl3)
d
7.45 (dd, J¼8.6,
4.98e4.92 (m), 4.75 (d, J¼7.8 Hz), 3.33e3.21 (m), 3.21e3.11 (m),
5.3 Hz, 1H), 7.08e6.99 (m, 1H), 5.21 (t, J¼13.7 Hz, 1H), 5.07 (s, 1H),
4.94 (dd, J¼10.0, 3.7 Hz, 1H), 3.51 (dd, J¼12.0, 4.3 Hz, 1H), 3.06 (dd,
J¼12.0, 1.8 Hz, 1H), 2.90 (s, 1H, eOH). 13C NMR (101 MHz, CDCl3)
2.99 (d, J¼18.8 Hz), 2.28 (dd, J¼25.8, 6.2 Hz). 13C NMR (101 MHz,
CDCl3)
d 137.24, 133.90, 130.26, 128.87, 125.06, 98.00, 77.26, 46.05,
34.05, 19.75, 19.40.
d
161.47, 129.97, 116.02, 115.81, 95.55, 75.29, 47.67, 36.00.
HRMS: (m/z-ESI) calcd for C12H14NO3S (MꢁH)ꢁ 252.0693, found
Minor (b7-II): 1H NMR (400 MHz, CDCl3)
d
7.42e7.34 (m),
252.0698.
7.08e6.99 (m), 4.94 (dd, J¼10.0, 3.7 Hz), 4.89 (d, J¼3.7 Hz), 3.30 (dd,
IR nmax: 3445, 2941, 1552, 1509, 1373, 1324, 1045, 750, 670 cmꢁ1
.
J¼11.0, 7.0 Hz), 3.15 (dd, J¼10.9, 8.2 Hz), 2.90 (s, eOH). 13C NMR
(101 MHz, CDCl3)
33.90.
d
163.93,129.55,116.17,115.95, 97.99, 76.83, 48.90,
4.1.3.12. 3-Nitro-2-[4-nitro-5-phenyltetrahydrothiophen-3-ol-yl]
tetrahydrothiophen-3-ol (b12). Major (b12-I): 1H NMR (400 MHz,
HRMS: (m/z-ESI) calcd for C10H10FNO3S (MꢁH)ꢁ 242.0287,
DMSO)
d
7.49e7.40 (m, 4H), 6.17 (d, J¼4.7 Hz, 2H), 5.55 (d,
found 242.0291.
J¼10.2 Hz, 2H), 5.08 (d, J¼10.2 Hz, 2H), 4.88 (t, J¼7.4 Hz, 2H), 3.48
IR nmax: 3433, 2944, 1604, 1552, 1510, 1372, 1160, 1084, 1044, 841,
(dd, J¼11.3, 4.1 Hz, 2H), 2.79 (d, J¼11.4 Hz, 2H). 13C NMR (101 MHz,
807, 751 cmꢁ1
.
DMSO) d 137.79, 129.10, 94.44, 76.81, 47.30, 33.18.
Minor (b12-II): 1H NMR (400 MHz, DMSO)
d 7.38e7.29 (m), 6.25
4.1.3.8. 5-(2-Chlorophenyl)-4-nitrotetrahydrothiophen-3-ol
(b8). Major (b8-I): 1H NMR (400 MHz, CDCl3)
(d, J¼6.1 Hz), 5.55 (d, J¼10.2 Hz), 5.14 (t, J¼8.0 Hz), 4.84 (d,
d
7.60 (dd, J¼7.6,
J¼10.2 Hz), 3.18e3.10 (m), 3.05 (t, J¼9.7 Hz). 13C NMR (101 MHz,
1.6 Hz, 1H), 7.47e7.40 (m, 1H), 7.36e7.26 (m, 2H), 5.70 (d, J¼8.5 Hz,
1H), 5.23 (dd, J¼8.5, 4.1 Hz, 1H), 5.08 (dd, J¼8.0, 4.6 Hz, 1H), 3.52
(dd, J¼11.8, 4.5 Hz, 1H), 2.88 (d, J¼5.3 Hz, 1H), 2.75 (s, 1H). 13C NMR
DMSO) d 137.79, 129.10, 94.34, 75.28, 47.30, 36.55.
4.1.3.13. 5-Methyl-4-nitro-5-phenyltetrahydrothiophen-3-ol
(b13). Major (b13-I): 1H NMR (400 MHz, CDCl3)
7.60e7.32 (m,
(101 MHz, CDCl3)
d
134.48, 130.38, 129.58, 129.14, 128.69, 127.45,
d
93.41, 75.07, 45.32, 35.89.
5H), 5.23 (s, 1H), 5.21e5.13 (m, 1H), 3.26 (dd, J¼10.4, 7.6 Hz, 1H),
Minor (b8-II): 1H NMR (400 MHz, CDCl3)
d 7.70e7.66 (m),
2.89 (t, J¼10.2 Hz, 1H), 2.59 (d, J¼5.2 Hz, 1H), 1.45 (s). 13C NMR
7.47e7.40 (m), 7.36e7.26 (m), 5.51 (d, J¼8.4 Hz), 5.12 (d, J¼7.4 Hz),
(101 MHz, CDCl3)
31.22, 11.31.
d 134.01,129.18,128.90,128.47, 98.17, 78.60, 52.94,
5.08 (dd, J¼8.0, 4.6 Hz), 3.34 (dd, J¼11.2, 6.2 Hz), 3.22 (dd, J¼11.1,
7.6 Hz), 2.75 (s, 1H). 13C NMR (101 MHz, CDCl3)
130.14, 130.03, 128.87, 127.65, 96.16, 45.82, 34.49.
d
134.55, 130.53,
Minor (b13-II): 1H NMR (400 MHz, CDCl3)
d 7.60e7.32 (m), 5.46
(s), 3.13 (d, J¼7.5 Hz), 3.02 (dd, J¼11.6, 4.2 Hz), 2.59 (d, J¼5.2 Hz),
HRMS: (m/z-ESI) calcd for C10H9ClNO3S (MꢁH)ꢁ 257.9992,
1.49 (s). 13C NMR (101 MHz, CDCl3)
99.07, 80.35, 51.84, 33.78, 19.78.
d 135.01, 130.02, 128.56, 128.38,
found 257.9995.
IR nmax: 3430, 2941, 1551, 1473, 1437, 1071, 1082, 1039, 745 cmꢁ1
.
HRMS: (m/z-ESI) calcd for C12H14NO5S (MþHCOO)ꢁ 284.0592,
found 284.0593.
4.1.3.9. 5-(4-Chlorophenyl)-4-nitrotetrahydrothiophen-3-ol
(b9). Major (b9-I): 1H NMR (400 MHz, CDCl3)
7.38 (dd, J¼25.4,
IR nmax: 3313, 2949, 1543, 1494, 1451, 1346, 1187, 1136, 1080,
d
1029, 752, 703 cmꢁ1
.

C. Xu et al. / Tetrahedron 69 (2013) 4749e4757
4757
4.1.3.14. 4-Nitro-5-(2-(trifluoromethyl)phenyl)tetrahy-
drothiophen-3-ol (b14). Major (b14-I): 1H NMR (400 MHz, CDCl3)
Supplementary data
d
7.82e7.72 (m, 1H), 7.64 (d, J¼7.4 Hz, 1H), 7.57 (dd, J¼16.8,
Supplementary data associated with this article can be found in
the online version, at http://dx.doi.org/10.1016/j.tet.2013.02.084.
These data include MOL files and InChiKeys of the most important
compounds described in this article.
9.2 Hz, 1H), 7.52e7.34 (m, 1H), 5.64e5.52 (m, 1H), 5.14 (dd,
J¼8.2, 4.2 Hz), 5.12e5.01 (m, 1H), 3.47 (dd, J¼11.6, 4.8 Hz, 1H),
3.12 (dd, J¼11.7, 3.7 Hz, 1H). 13C NMR (101 MHz, CDCl3)
d 136.10,
132.54, 129.61, 129.32, 128.38, 126.35, 122.54, 94.30, 74.76, 43.75,
35.80.
References and notes
Minor (b14-II): 1H NMR (400 MHz, CDCl3)
d 7.94e7.86 (m), 7.64
1. O’Connor, C. J.; Roydhouse, M. D.; Przybyƚ, A. M.; Wall, M. D.; Southern, J. M. J.
Org. Chem. 2010, 75, 2534.
(d, J¼7.4 Hz), 7.57 (dd, J¼16.8, 9.2 Hz), 7.52e7.34 (m), 5.32e5.23
(m), 5.12e5.01 (m), 4.88e4.62 (m), 3.34e3.20 (m). 13C NMR
€
2. Gutschow, M.; Neumann, U. J. Med. Chem. 1998, 41, 1729.
3. For a book, see:Australian Medicines Handbook; Rossi, S., Ed.; Australian Medi-
cines Handbook Pty Ltd: Adelaide, 2006.
4. For a book, see: Malamed, S. F. Handbook of Local Anaesthesia, 5th ed.; St. Louis:
Mosby, 2004.
(101 MHz, CDCl3)
97.78, 77.23.
d 132.78, 129.92, 128.93, 128.57, 126.41, 123.14,
5. (a) For a book, see: Skotheim, T.; Rey-nolds, J.; Elsenbamer, R. Handbook of
Conducting Polymers, 2nd ed.; Marcel Dekker: New York, NY, 1998; (b) For
a book, see: Skotheim, T. Handbook of Conducting Polymers; Marcel Dekker:
New York, NY, 1986.
6. For reviews, see: Song, C. E.; Lee, S.-g. Chem. Rev. 2002, 102, 3495.
7. For reviews, see: McNamara, C. A.; Dixon, M. J.; Bradley, M. Chem. Rev. 2002, 102,
3275.
4.1.3.15. 4-Nitro-5-(furan-2-yl)tetrahydrothiophen-3-ol
(b15). Major (b15-I): 1H NMR (400 MHz, CDCl3)
7.46e7.36 (m,
d
1H), 6.39e6.30 (m, 2H), 5.34 (d, J¼8.8 Hz, 1H), 5.25 (dd, J¼8.7,
3.8 Hz, 1H), 5.09 (s, 1H), 3.49 (dd, J¼11.9, 4.2 Hz), 3.06 (dd, J¼11.9,
2.6 Hz, 1H), 2.97 (s, 1H). 13C NMR (101 MHz, CDCl3)
110.80, 109.03, 92.18, 75.15, 41.35, 35.90.
d
149.33, 143.19,
8. Regen, S. L. J. Am. Chem. Soc. 1975, 97, 5956.
Minor (b15-II): 1H NMR (400 MHz, CDCl3)
d 7.46e7.36 (m),
9. Bergbreiter, D. E.; Blanton, J. R. J. Org. Chem. 1985, 50, 5828.
10. Grinberg, S.; Kas’yanov, V.; Srinivas, B. React. Funct. Polym. 1997, 34, 53.
11. Neimann, K.; Neumann, R. Chem. Commun. 2001, 487.
12. Tsubokawa, N.; Kimoto, T.; Endo, T. J. Mol. Catal. A: Chem. 1995, 101, 45.
13. Geller, T.; Roberts, S. M. J. Chem. Soc., Perkin Trans. 1 1999, 1397.
14. For reviews, see: Bergbreiter, D. E. Chem. Rev. 2002, 102, 3345.
15. For reviews, see: Mizuno, N.; Misono, M. Chem. Rev. 1998, 98, 199.
16. Shao, L.; Liu, J.; Ye, Y.; Zhang, X.-M.; Qi, C. Appl. Organomet. Chem. 2011, 25, 699.
17. Vatutsina, O. M.; Soldatov, V. S.; Sokolova, V. I.; Johann, J.; Bissen, M.; Weis-
senbacher, A. React. Funct. Polym. 2007, 67, 184.
18. Li, G.; Xiao, J.; Zhang, W. Green Chem. 2011, 13, 1828.
19. Li, G.; Xiao, J.; Zhang, W. Green Chem. 2012, 14, 2234.
20. Zhang, L.; Li, Z.; Chang, R.; Chen, Y.; Zhang, W. React. Funct. Polym. 2009,
69, 234.
21. Molinari, H.; Montanari, F.; Quici, S.; Tundo, P. J. Am. Chem. Soc. 1979, 101, 3920.
22. Montanari, F.; Tundo, P. J. Org. Chem. 1981, 46, 2125.
23. Montanari, F.; Quici, S.; Tundo, P. J. Org. Chem. 1983, 48, 199.
24. Anelli, P. L.; Montanari, F.; Quici, S. J. Chem. Soc., Perkin Trans. 2 1983, 1827.
25. Anelli, P. L.; Czech, B.; Montanari, F.; Quici, S. J. Am. Chem. Soc. 1984, 106, 861.
26. Frisch, M. J.; Trucks, G. W.; Schlegel, H. B.; Scuseria, G. E.; Robb, M. A.; Cheeseman,
J. R.; Montgomery, J. A., Jr.; Vreven, T.; Kudin, K. N.; Burant, J. C.; Millam, J. M.;
Iyengar, S. S.; Tomasi, J.; Barone, V.; Mennucci, B.; Cossi, M.; Scalmani, G.; Rega,
N.; Petersson, G. A.; Nakatsuji, H.; Hada, M.; Ehara, M.; Toyota, K.; Fukuda, R.;
Hasegawa, J.; Ishida, M.; Nakajima, T.; Honda, Y.; Kitao, O.; Nakai, H.; Klene, M.;
Li, X.; Knox, J. E.; Hratchian, H. P.; Cross, J. B.; Bakken, V.; Adamo, C. J., J.; Gom-
perts, R.; Stratmann, R. E.; Yazyev, O.; Austin, A. J.; Cammi, R.; Pomelli, C.; Och-
terski, J. W.; Ayala, P. Y.; Morokuma, K.; Voth, G. A.; Salvador, P.; Dannenberg, J. J.;
Zakrzewski, V. G.; Dapprich, S.; Daniels, A. D.; Strain, M. C.; Farkas, O.; Malick, D.
K.; Rabuck, A. D.; Raghavachari., K.; Foresman, J. B.; Ortiz, J. V.; Cui, Q.; Baboul, A.
G.; Clifford, S.; Cioslowski, J.; Stefanov, B. B.; Liu, G.; Liashenko, A.; Piskorz, P.;
Komaromi, I.; Martin, R. L.; Fox, D. J.; Keith, T.; Al-Laham, M. A. P., C. Y.; Na-
nayakkara, A.; Challacombe, M.; Gill, P. M. W.; Johnson, B.; Chen, W.; Wong, M.
W.; Gonzalez, C.; Pople, J. A. Gaussian 03; Gaussian: Pittsburgh.
6.39e6.30 (m), 5.16 (t, J¼7.7 Hz), 4.98 (d, J¼6.2 Hz), 4.92 (d,
J¼7.8 Hz), 3.27 (dd, J¼11.1, 6.4 Hz), 3.18 (dd, J¼11.1, 7.9 Hz), 2.97
(s, 1H).
4.1.3.16. 4-Nitro-5-(thiophen-2-yl)tetrahydrothiophen-3-ol
(b16). Major (b16-I): 1H NMR (400 MHz, CDCl3)
d
7.29 (dt, J¼7.5,
4.3 Hz, 1H), 7.11 (d, J¼3.4 Hz, 1H), 6.97e6.91 (m, 1H), 5.56 (d,
J¼9.3 Hz, 1H), 5.05 (dd, J¼6.1, 3.9 Hz, 1H), 4.97 (dd, J¼9.3, 3.8 Hz,
1H), 3.51 (dd, J¼11.9, 4.4 Hz, 1H), 3.08e3.02 (m, 1H), 2.93e2.85 (m,
1H).13C NMR (101 MHz, CDCl3)
96.14, 75.38, 43.96, 36.04.
d 140.90, 127.25, 126.75, 126.03,
Minor (b16-II): 1H NMR (400 MHz, CDCl3)
d
7.29 (dt, J¼7.5,
4.3 Hz), 7.16e7.13 (m), 6.97e6.91 (m), 5.49 (dd, J¼9.3, 4.5 Hz), 4.87
(dd, J¼13.1, 6.1 Hz), 3.24 (dd, J¼16.5, 2.8 Hz), 3.18 (dt, J¼11.5, 5.2 Hz),
2.93e2.85 (m, 1H). 13C NMR (101 MHz, CDCl3)
d 141.10, 127.17,
127.04, 99.99, 77.24, 37.29.
Acknowledgements
The authors are grateful for the financial support from the Key
Program of the National Natural Science Foundation of China (No:
20834002), and would like to thank Dr. Jeanne L. Wynn for English
revision and correction.