Iodine-Promoted Synthesis of Thioamides from 1,2-Dibenzylsulfane and Difurfuryl Disulfide

Article abstract of DOI:10.1055/s-0035-1562509

Thioamides can be generated at 100 °C in high yield through the reaction of 1,2-dibenzyldisulfane with difurfuryldisulfide using iodine as oxidant and DMSO as solvent. The protocol is metal- and additive-free, providing a convenient and economical way for the synthesis of various kinds of thioamides under mild conditions.

Full text of DOI:10.1055/s-0035-1562509

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© Georg Thieme Verlag Stuttgart · New York
2016, 27, A–F
letter
A
S. Chen et al.
Letter
Synlett
Iodine-Promoted Synthesis of Thioamides from 1,2-Dibenzyl-
sulfane and Difurfuryl Disulfide
Sihai Chen1
You Li1
S
R1
N
I2 (0.5 equiv)
R1
N
R2
R
S
R
+
R2
DMSO, 100 °C
H
S
R
Jinyang Chen
Xinhua Xu*
Lebin Su
R = phenyl, furyl
R1 = benzyl
2 = (hetero)aryl
ligand- and metal-free
functional group tolerance
26 examples
yields: up to 95%
R
Zhi Tang
Chak-Tong Au
Renhua Qiu*
State Key Laboratory of Chemo/Biosensing and Chemometrics,
College of Chemistry and Chemical Engineering, Hunan Univer-
sity, Changsha, 410082, P. R. of China
xhx1581@hnu.edu.cn
renhuaqiu@hnu.edu.cn
Received: 15.05.2016
Previous works
Accepted after revision: 31.05.2016
Published online: 05.07.2016
DOI: 10.1055/s-0035-1562509; Art ID: st-2016-w0343-l
R1
N
S
R
R
NH2
O
sulfur
(a)
R1
+
R2
H
R
N
R2
Willgerodt–Kindler
R1
N
Abstract Thioamides can be generated at 100 °C in high yield through
the reaction of 1,2-dibenzyldisulfane with difurfuryldisulfide using io-
dine as oxidant and DMSO as solvent. The protocol is metal- and addi-
tive-free, providing a convenient and economical way for the synthesis
of various kinds of thioamides under mild conditions.
S
S
Cu(II)
R1
R1
+
+
(b)
(c)
R
SH
R2
H
H
R
N
R2
TBD, O2 (1 atm)
R1
N
sulfur
R
H
R
R2
N
pyridine
R2
Key words thioamide, metal-free, iodine, disulfide, synthesis
S
OH
OH
R1
N
R1
Ar
Ar
sulfur
Ar
N
R2
+
(d)
O
The disulfide moiety can be found in many biologically
important structures and is considered as a useful synthon
for many organic synthetic transformations.2 It has wide
applications in material science and participates in chemi-
cal substitution or addition reactions.3 In view of the pres-
ence of sulfur in numerous chemically and biologically ac-
tive compounds, there is much interest to develop ways for
the generation of carbon–sulfur bonds.4 Thioamides are
structural motifs widely used as key intermediates5 and
versatile building blocks for the construction of heterocy-
cles6 and other compounds containing both nitrogen and
sulfur in their backbones.7 Furthermore, replacement of an
oxygen atom by a sulfur atom in carboxamide moieties was
used to modify the stability and catalytic activity of a vari-
ety of target molecules.8
R2
H
H
S
Ar
R
R1
O
N
R2
This work
R1
N
S
I2 (0.5 equiv)
R1
R
S
+
(e)
R
S
R2
N
R2
H
DMSO, 100 °C
Ligand- and metal-free
Functional group tolerance
Scheme 1 Preparation of thioamides
thioamides by subjecting copper(II) complexes and 1,5,7
triazabicyclo[4.4.0]dec-5-ene(TBD) to aerobic conditions in
toluene for 18 hours (Scheme 1, b). In the present work,
twelve kinds of aromatic thioamides were synthesized in
poor to excellent yield. It is noted that the presence of the
copper complexes is critical because without them the
product yields are poor. Also, Nguyen and co-workers13 uti-
lized a three-component process to afford thioamides from
alkynes, elemental sulfur, and aliphatic amines (Scheme 1,
c). In addition, Guntreddi et al.14 reported a three-compo-
nent reaction that involves arylacetic or cinnamic acids,
amines and sulfur to prepare thioamides without the need
of a transition metal or an external oxidant (Scheme 1, d).
Indeed, considerable efforts were directed towards the syn-
There are different methods to prepare thioamides.9 The
Willgerodt–Kindler reaction,10 in which unsaturated hydro-
carbons and aldehydes react with sulfur and secondary
amines to give thioamides as a result of consecutive oxida-
tion and rearrangement actions (Scheme 1, a), is well
known, but suffers from the limitations that only one oxy-
gen atom is replaced by a sulfur atom and there is no for-
mation of any new bond. Lawesson’s reagent,11 used in this
scheme, is also common. More recently, Wang et al.12 dis-
covered a method for the direct conversion of thiols into
© Georg Thieme Verlag Stuttgart · New York — Synlett 2016, 27, A–F

B
S. Chen et al.
Letter
Synlett
thesis of thioamides, but the methods have drawbacks such
as harsh reaction conditions, long reaction time, and low
yield. Therefore, it is necessary to develop fresh strategies
for the synthesis of thioamides, desirably employing new,
readily available and inexpensive raw materials. Herein, we
present an efficient way to prepare thioamides using iodine
as oxidant.
Table 1 Reaction Optimizationa
S
N
S
I2 (equiv)
S
N
solvent, temp.
N
H
N
1
2a
3a
Initial efforts were focused on the optimization of con-
ditions through the variation of reaction parameters using
1,2-dibenzyldisulfane and 1-methylpiperazine as model re-
actants (Table 1). The desired thioamide 3a was obtained in
83% yield at 90 °C. After studying the effect of reaction tem-
perature within the 90–110 °C range, it is concluded that
the temperature for best yield is 100 °C (entry 2, 90%). As
for the use of solvents (entries 4–7), we found that the use
of toluene and THF results in poor yields (entries 4 and 5)
whereas the use of MeCN and DMF results in moderate
yield (entries 6 and 7, 45% and 38%, respectively). As one
can see from Table 1, iodine is necessary to accelerate the
reaction. The minimum amount of iodine required to pro-
mote the oxidation process is 0.5 equivalents and the suit-
able reaction time is eight hours.
With the optimized conditions in hand, we examined
the scope and versatility of the method for the interaction
of amides with 1,2-dibenzyldisulfane, and the outcomes are
depicted in Scheme 2. One can see that the use of secondary
amines as substrates affords the desired products (3a–e)
with excellent yields. The substrates 1-methylpiperazine
and 1-ethylpiperazineare are converted into the corre-
sponding thioamides (3a and 3b) in 91% and 95% yield, re-
spectively. With morpholine (3c), pyrrolidine (3d) and
piperidine (3e), the corresponding product is obtained in
85%, 81%, and 87% isolated yield, respectively. For primary
amines, cyclohexanamine affords the product 3f in 84%
Entry
Temp (°C) Solvent
Additive
(equiv)
Time (h)
Yield (%)b
1
90
DMSO
DMSO
DMSO
I2 (3)
12
12
12
12
12
12
12
12
12
12
12
12
12
12
8
83
2
100
110
100
100
100
100
100
100
100
100
100
100
100
100
100
I2 (3)
90
3
I2 (3)
85
4
toluene
THF
I2 (3)
trace
trace
45
5
I2 (3)
6
MeCN
DMF
I2 (3)
7
I2 (3)
38
8
DMSO
DMSO
DMSO
DMSO
DMSO
DMSO
DMSO
DMSO
DMSO
–
44
9
THBP (3)
DTBP (3)
BPO (3)
CuBr (3)
I2 (0.5)
I2 (0.4)
I2 (0.5)
I2 (0.5)
50
10
11
12
13
14
15
16
45
75
28
91
84
91
7
84
a Reaction conditions: 1 (0.5 mmol), 2a (1.2 mmol), solvent (1.0 mL).
b Isolated yields.
yield whereas tert-butylamine and 2,2,2-trifluoroethana-
mine give 3g and 3h in 41% and 18% yield, respectively. Fur-
thermore, n-butylamine and n-hexylamine give 3i and 3j in
S
R1
R2
R1
S
I2 (0.25 equiv)
N
N
R1
S
+
DMSO, 100 °C, 8 h
H
1
2
3
S
N
S
S
S
S
S
N
N
N
N
N
H
N
O
N
3a, 91%
3b, 95%
3c, 85%
3d, 81%
3e, 87%
3f, 84%
S
S
S
S
S
N
S
F
F
(n-Hexane)
(n-Bu)
F
N
H
N
H
N
H
N
H
N
H
N
H
3g, 41%
3h, 18%
3i, 72%
3j, 43%
3k, 80%
3l, 77%
S
S
S
S
N
N
H
N
H
H
N
H
CF3
Cl
3m, 58%
3n, 50%
3o, 82%
3p, 17%
Scheme 2 Reaction scope using 1,2-dibenzyldisulfane as substrate. a Reagents and conditions: 1,2-dibenzyldisulfane (1, 0.5 mmol), amides 2 (1.2
mmol), iodine (0.25 mmol) for 8 h. Isolated yields.
© Georg Thieme Verlag Stuttgart · New York — Synlett 2016, 27, A–F

C
S. Chen et al.
Letter
Synlett
72% and 43% yield, respectively. In addition to aliphatic
amines, a variety of benzyl amines were tested. The sub-
strates benzylamine, phenylethylamine, and 1-pheny-
lethanamine afford product 3k–m in 80%, 77%, and 58%
yield, respectively. The substrates 4-chlorobenzylamine and
4-trifluoromethylbenzylamine give the desired product in
moderate (3n, 50%) to excellent (3o, 82%) yield. When pyri-
din-4-amine reacts with 1,2-dibenzyldisulfane, 3p is ob-
tained in 17% yield. Finally, the reaction was successfully
scaled-up to 1 g with benzylamine (Scheme 3, yield 77%).
To shed light on the mechanism of the oxidation pro-
cess, the reaction of 1,2-dibenzyldisulfane and 1-ethylpip-
erazine was treated with 2,2,6,6-tetramethyl-1-piperidiny-
loxy (TEMPO) or 2,6-di-tert-butyl-4-methylphenol (BHT,
Scheme 5) under the optimized conditions. It was observed
that the addition of the two radical-trapping agents does
not inhibit the reaction, and 3b is obtained in 87% and 91%
isolated yield, respectively. The results suggest that there is
no involvement of single-electron transfer in the synthesis
of thioamide process.15
S
S
S
S
S
1
N
S
I2 (0.64 g)
H
1: 1.24 g
DMSO (5 mL)
100 °C, 10 h
standard conditions
N
+
3k: 1.76 g (77%)
N
3 equiv TEMPO 87%
NH2
3 equiv BHT
91%
N
NH
3b
2k: 1.34 g
2b
Scheme 3 Gram-scale reaction for the synthesis of 3k
Scheme 5 Preliminary mechanistic study
In subsequent studies, we examined the reaction of var-
ious substrates with difurfuryl disulfide under the optimal
conditions. One can see from Scheme 4 that benzyl amines
afford better yield than aliphatic amines. As for 1-meth-
ylpiperazine (6a) the corresponding product yield is 56%.
For the other heterocyclic compounds, viz. morpholine,
pyrrolidine, and piperidine, 6b–d are produced in 54%, 37%
and 57% yield, respectively. For primary amines, that is, cy-
clohexanamine, n-butylamine and n-hexylamine, the de-
sired products 6e–g are formed in 51%, 44%, and 50% yield,
respectively. To our delight, benzyl amines are also prone to
the oxidation reaction, giving moderate to good yield: From
4-methylbenzylamine, phenylethylamine, and 1-phenyl-
ethanamine, 6h–j are formed in 69%, 78% and 54% yield, re-
spectively. However, plausibly due to the unstable interme-
diates, the use of dipropyl sulfide or diallyl disulfide ether as
substrate does not produce the target aliphatic thioamides.
To investigate the mechanism, the interaction between
1,2-dibenzylsulfane and iodine was examined by NMR
spectroscopy using DMSO-d6 as solvent. From Figure 1, one
can see that when 1,2-dibenzylsulfane was mixed with io-
dine, the peaks of benzene and methylene shift only slight-
ly. However, the characteristic peak (–CH2–S) of 1,2-diben-
zyldisulfane(II) significantly shifts from δ = 4.56 ppm to δ =
9.76 ppm, and such shift could be considered as evidence of
the conversion of –CH2–S– to –CH=S.
S
R1
R2
R1
I2 (0.5 equiv)
S
N
N
R1
S
+
O
DMSO, 100 °C, 8 h
O
H
O
4
5
6
S
S
S
S
O
O
N
O
O
N
N
N
O
N
6b, 54%
6c, 37%
6a, 56%
6d, 57%
Figure 1 1H NMR spectra of 1,2-dibenzylsulfane with iodine in DMSO-d6:
(1) original, (2) 1 h, (3) 2 h, and (4) 3 h.
S
S
S
O
O
O
N
N
N
H
H
H
6f, 44%
6g, 50%
6e, 51%
To further understand the mechanism, 1,2-dibenzyldi-
sulfane and morpholine was examined in hourly intervals
by NMR spectroscopy in DMSO-d6 using iodine as oxidant
(Figure 2). When 1,2-dibenzyldisulfane was mixed with
morpholine and iodine, the characteristic –CH2–S peak of
1,2-dibenzyldisulfane disappears (Figure 2, e), and the peak
S
S
S
O
O
O
N
H
N
H
N
H
6h, 69%
6i, 78%
6j, 54%
Scheme 4 Reaction scope using difurfuryl as aubstrate. a Reagents
and conditions: difurfuryl 4 (0.5 mmol), amides 5 (1.2 mmol), iodine
(0.5 mmol) for 8 h. b Isolated yields.
© Georg Thieme Verlag Stuttgart · New York — Synlett 2016, 27, A–F

D
S. Chen et al.
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DMS + H2O
I2
S
S
N
S
DMSO
O
1
3c
HI
S
H
Bn
S
S
H
S–
8
N
O
7
O
10
HI
N
H
2c
S–
DMSO
N
I2
O
9
Figure 2 1H NMR spectra of (a) product 3c in DMSO-d6 solvent; (b)
1,2-dibenzyldisulfane and morpholine mixed with iodine in DMSO-d6
solvent; (c) to (g) are taken at different time intervals: (c) 1 h, (d) 2 h,
(e) 3 h, (f) 4 h, and (g) 5 h.
DMS + H2O
Scheme 6 A plausible mechanism
of morpholine shifts to positions ‘i’ and ‘j’. The results con-
firm that 1,2-dibenzyldisulfane is first oxidized by iodine,
and then converted into the corresponding thioamide when
mixed with morpholine.
Figure 3 X-ray crystal structure of 3c
Based on the information available in the literature12,16
1
Acknowledgment
as well as on the H NMR results of the present work, a
plausible mechanism is proposed and briefly outlined in
Scheme 6. Initially, the reaction of 1,2-dibenzylsulfane (1)
with molecular iodine results in the formation of interme-
diate 7, which is subsequently converted into benzothialde-
hyde 8 in the presence of iodine. However, due to the excess
of iodine, there is the generation of HI as byproduct. The re-
duction reaction of dimethyl sulfoxide (DMSO) with HI re-
sults in HI conversion into iodine and the formation of di-
methyl sulfide (DMS).16 The reaction of benzothialdehyde 8
and morpholine affords intermediate 9, which is converted
into intermediate 10 in reaction with 2. Finally, 10 is subse-
quently converted into morpholino(phenyl)methanethione
3c. The structure of representative product 3c has been
conclusively proved by single-crystal XRD analysis (Figure
3, CCDC: 1430907).
The authors thank the National Natural Science Foundation of China
(No. 21273068, 21373003, J1210040), the Natural Science Foundation
of Hunan Province(14JJ7027), and the Fundamental Research Funds
for the Central Universities, Hunan University, for financial support.
CTA thanks HNU for an adjunct professorship. R. Qiu thanks Prof.
Kambe (Osaka University) and Prof. Li-Biao Han (AIST, Tsukuba, Ja-
pan) for helpful discussions.
Supporting Information
Supporting information for this article is available online at
http://dx.doi.org/10.1055/s-0035-1562509.
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References and Notes
(1) The two authors contributed equally.
In conclusion, the present report describes a practical
and easy approach to synthesize thioamides through a nov-
el way of oxidation using iodine. It is complementary to the
existing protocols for the synthesis of thioamides.17,18
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Lindeberg, G.; Gogoll, A.; Lai, Z.; Thörnwall, M.; Synnergren, B.;
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(c) Firouzabadi, H.; Iranpoor, N.; Samadi, A. Tetrahedron Lett.
2014, 55, 1212.
© Georg Thieme Verlag Stuttgart · New York — Synlett 2016, 27, A–F

E
S. Chen et al.
Letter
Synlett
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(17) General Procedure for the Preparation of 3
Iodine (0.25 mmol, 63.4 mg) and 1,2-dibenzyldisulfane (0.5
mmol, 123.4 mg) was added to a solution of 1-methylpiperazine
(1.2 mmol, 119.1 mg) in DMSO (0.5 mL), and the reaction
mixture was stirred for 8 h at 100 °C. The solvent was removed
under vacuum, and the residue was purified by flash silica gel
column chromatography with PE–EtOAc (1:1) as eluent to afford
the product 3a.
(4-Methylpiperazin-1-yl)(phenyl)methanethione(3a)
Yield 200.4 mg, 91%. Purified by column chromatography with
PE–EtOAc (1:1) as eluent and obtained as a yellow oil. H NMR
(400 MHz, CDCl3): δ = 7.34 (m, 3 H), 7.28 (t, J = 5.9 Hz, 2 H),
4.51–4.37 (m, 2 H), 3.67–3.51 (m, 2 H), 2.69–2.56 (m, 2 H),
2.41–2.35 (m, 2 H), 2.33 (s, 3 H). 13C NMR (100 MHz, CDCl3): δ =
200.6, 142.9, 128.6, 128.4, 125.8, 55.2, 54.3, 51.8, 49.1, 45.6. MS
(EI): m/z = 220.1 [M+]. HRMS (EI): m/z calcd for C12H16N2S [M]+:
220.1034; found: 220.1030.
1
Morpholino(phenyl)methanethione (3c)
Yield 175.3 mg, 85%. Purified by column chromatography with
PE–EtOAc (4:1) as eluent and obtained as a yellow solid. 1H NMR
(400 MHz, CDCl3): δ = 7.35–7.32 (m, 3 H), 7.31–7.21 (m, 2 H),
4.49–4.35 (m, 2 H), 3.96–3.79 (m, 2 H), 3.59 (m, 4 H). 13C NMR
(100 MHz, CDCl3): δ = 200.9, 142.5, 128.9, 128.5, 125.9, 66.7,
66.5, 52.5, 49.6. MS (EI): m/z = 207.1 [M+]. HRMS (EI): m/z calcd
for C11H13NOS [M]+: 207.0718; found: 207.0714.
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N-Butylbenzothioamide (3i)
Yield 141.0 mg, 72%. Purified by column chromatography with
PE–EtOAc (10:1) as eluent and obtained as a yellow oil. 1H NMR
(400 MHz, CDCl3): δ = 7.98 (s, 1 H), 7.63 (d, J = 7.4 Hz, 2 H), 7.38
(t, J = 7.3 Hz, 1 H), 7.28 (dd, J = 9.3, 4.7 Hz, 2 H), 3.70 (dd, J = 9.3,
4.4 Hz, 2 H), 1.65 (dd, J = 13.7, 6.8 Hz, 2 H), 1.43–1.32 (m, 2 H),
0.93 (t, J = 7.3 Hz, 3 H). 13C NMR (100 MHz, CDCl3): δ = 198.8,
141.7, 130.9, 128.3, 126.7, 46.6, 30.0, 20.3, 13.8. MS (EI): m/z =
193.1 [M+]. HRMS (EI): m/z calcd for C11H15NS [M]+: 193.0925;
found: 193.0920.
N-(1-Phenylethyl)benzothioamide (3m)
Yield 140.0 mg, 58%. Purified by column chromatography with
PE–EtOAc (10:1) as eluent and obtained as a yellow oil. 1H NMR
(400 MHz, CDCl3): δ = 7.87 (s, 1 H), 7.66 (d, J = 7.4 Hz, 2 H), 7.43–
7.26 (m, 8 H), 5.93–5.77 (m, 1 H), 1.64 (d, J = 6.9 Hz, 3 H). 13C
NMR (100 MHz, CDCl3): δ = 198.1, 142.0, 141.5, 131.1, 128.9,
128.5, 127.9, 126.8, 126.6, 55.2, 20.3. MS (EI): m/z = 241.1 [M+].
HRMS (EI): m/z calcd for C15H15NS [M]+: 241.0925; found:
241.0920.
(18) General Procedure for the Preparation of 6
(10) (a) Hurd, R. N.; DeLaMater, G. Chem. Rev. 1961, 61, 45.
(b) Wegler, R.; Kuhle, E.; Schafer, W. Angew. Chem., Int. Ed. Engl.
1958, 70, 351. (c) Darabi, H. R.; Aghapoor, K.; Tajbakhsh, M. Tet-
rahedron Lett. 2004, 45, 4167.
(11) (a) Moghaddam, F. M.; Ghaffarzadeh, M. Synth. Commun. 2001,
31, 317. (b) Kaleta, Z.; Tárkányi, G.; Gömöry, Á.; Kálmán, F.;
Nagy, T.; Soós, T. Org. Lett. 2006, 8, 1093. (c) Kaleta, Z.;
Makowski, B. T.; Soós, T.; Dembinski, R. Org. Lett. 2006, 8, 1625.
(12) Wang, X.; Ji, M.; Lim, S.; Jiang, H.-Y. J. Org. Chem. 2014, 79, 7256.
(13) Nguyen, T. B.; Tran, M. Q.; Ermolenko, L.; Al-Mourabit, A. Org.
Lett. 2014, 16, 310.
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(15) (a) Aihara, Y.; Chatani, N. J. Am. Chem. Soc. 2013, 135, 5308.
(b) Wang, X.; Qiu, R.; Yan, C.; Reddy, V. P.; Zhu, L.; Xu, X.; Yin, S.-
F. Org. Lett. 2015, 17, 1970.
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2016, 18, 524.
Iodine (0.25 mmol, 63.4 mg) and difurfuryl disulfide (0.5 mmol,
113.9 mg) was added to a solution of 1-methylpiperazine (1.5
mmol, 153.8 mg) in DMSO (0.5 mL), and the reaction mixture
was stirred for 10 h at 100 °C. The solvent was removed under
vacuum, and the residue was purified by flash silica gel column
chromatography with PE–CH2Cl2 (1:1) as eluent to afford
product 6a.
Furan-2-yl(4-methylpiperazin-1-yl)methanethione (6a)
Yield 117.8 mg, 56%. Purified by column chromatography with
PE–CH2Cl2 (1:1) as eluent and obtained as a yellow oil. 1H NMR
(400 MHz, CDCl3): δ = 7.37 (s, 1 H), 6.97 (d, J = 3.4 Hz, 1 H), 6.38
(dd, J = 3.2, 1.7 Hz, 1 H), 4.26 (s, 2 H), 3.85 (s, 2 H), 2.49 (s, 4 H),
2.28 (s, 3 H). 13C NMR (100 MHz, CDCl3): δ = 185.8, 152.4, 142.8,
118.2, 112.0, 45.3, 38.8. MS (EI): m/z = 210.1 [M+]. HRMS (EI):
m/z calcd for C10H14N2OS [M]+: 210.0827; found: 210.0822.
Furan-2-yl(pyrrolidin-1-yl)methanethione (6c)
Yield 67.3 mg, 37%. Purified by column chromatography with
PE–CH2Cl2 (10:1) as eluent and obtained as a yellow oil. 1H NMR
© Georg Thieme Verlag Stuttgart · New York — Synlett 2016, 27, A–F

F
S. Chen et al.
Letter
Synlett
(400 MHz, CDCl3): δ = 7.42 (s, 1 H), 7.25–7.18 (m, 1 H), 6.39 (dd,
J = 3.1, 1.5 Hz, 1 H), 3.93 (dd, J = 15.4, 7.3 Hz, 4 H), 2.04–1.90 (m,
4 H). 13C NMR (100 MHz, CDCl3): δ = 180.5, 153.0, 143.7, 118.8,
112.1, 54.9, 53.5, 26.9, 23.8. MS (EI): m/z = 181.1 [M+]. HRMS
(EI): m/z calcd for C9H11NOS [M]+: 181.0561; found: 181.0556.
N-Butylfuran-2-carbothioamide (6f)
Yield 80.6 mg, 44%. Purified by column chromatography with
PE–CH2Cl2 (10:1) as eluent and obtained as a yellow oil. 1H NMR
(400 MHz, CDCl3): δ = 7.92 (s, 1 H), 7.44 (s, 1 H), 7.36 (d, J = 3.5
Hz, 1 H), 6.48 (dd, J = 3.0, 1.4 Hz, 1 H), 3.81 (dd, J = 13.1, 7.0 Hz, 2
H), 1.72 (dt, J = 14.9, 7.4 Hz, 2 H), 1.44 (dt, J = 14.7, 7.4 Hz, 2 H),
0.98 (t, J = 7.3 Hz, 3 H). 13C NMR (100 MHz, CDCl3): δ = 182.3,
152.3, 143.6, 117.6, 113.1, 44.8, 30.4, 20.2, 13.8. MS (EI): m/z =
183.1 [M+]. HRMS (EI): m/z calcd for C9H13NOS [M]+: 183.0718;
found: 183.0713.
N-(1-Phenylethyl)furan-2-carbothioamide (6j)
Yield 124.1 mg, 54%. Purified by column chromatography with
PE–CH2Cl2 (10:1) as eluent and obtained as a yellow oil. 1H NMR
(400 MHz, CDCl3): δ = 8.08 (s, 1 H), 7.44–7.33 (m, 6 H), 7.29 (t, J
= 7.0 Hz, 1 H), 6.46 (dd, J = 3.3, 1.6 Hz, 1 H), 5.91 (p, J = 7.0 Hz, 1
H), 1.68 (d, J = 6.9 Hz, 3 H). 13C NMR (100 MHz, CDCl3): δ =
181.2, 152.2, 143.7, 141.5, 128.9, 127.9, 126.6, 118.1, 113.24,
53.4, 20.5. MS (EI): m/z = 231.1 [M+]. HRMS (EI): m/z calcd for
C
13H13NOS [M]+: 231.0718; found: 231.0713.
© Georg Thieme Verlag Stuttgart · New York — Synlett 2016, 27, A–F