Synthesis of 2-iminothiophen-3(2H)-ones from 3H-1,2-dithiol-3-ones

Article abstract of DOI:10.1016/j.mencom.2010.09.015

3H-1,2-Dithiol-3-ones undergo a new transformation into 2-iminothiophen-3(2H)-ones upon treatment with isonitriles; the structure of iminothiophenone 10 was confirmed by X-ray diffraction analysis.

Full text of DOI:10.1016/j.mencom.2010.09.015

Mendeleev
Communications
Mendeleev Commun., 2010, 20, 282–284
Synthesis of 2-iminothiophen-3(2H)-ones from 3H-1,2-dithiol-3-ones
Vladimir A. Ogurtsov,a Yurii V. Karpychev,a Dar’ya A. Pestravkina,a
Pavel A. Belyakov,a Yulia V. Nelyubinab and Oleg A. Rakitin*a
a N. D. Zelinsky Institute of Organic Chemistry, Russian Academy of Sciences, 119991 Moscow, Russian Federation.
Fax: +7 499 135 5328; e-mail: orakitin@ioc.ac.ru
b A. N. Nesmeyanov Institute of Organoelement Compounds, Russian Academy of Sciences, 119991 Moscow,
Russian Federation. Fax: +7 499 135 5085
DOI: 10.1016/j.mencom.2010.09.015
3H-1,2-Dithiol-3-ones undergo a new transformation into 2-iminothiophen-3(2H)-ones upon treatment with isonitriles; the
structure of iminothiophenone 10 was confirmed by X-ray diffraction analysis.
In recent years, 1,2-dithioles have attracted much attention due
to their anticancer activity and versatile chemical reactivity.1
It is known that 1,2-dithiole-3-thiones can be easily involved
in various chemical transformations, especially, in 1,3-dipolar
cycloaddition reactions. There are substantially less examples
of such reactions for 1,2-dithiol-3-ones. They undergo inser-
tion reactions of nucleophilic nitrogen functions (hydrazines,2
amines3 or azides4) with the formation of nitrogen heterocycles
(pyrazoles or isothiazoles) and elimination of sulfur atoms.
Recently, we have reported that the reaction of 1,2-dithiole-
3-thiones with isonitriles at room temperature afforded imino-
1,3-dithietanes.5 The reaction was found reversible and the rise
of the temperature shifted the equilibrium to the starting com-
pounds. To continue our investigation into the synthetic utility
of 1,2-dithioles, we studied the reaction of 1,2-dithiol-3-ones
with isonitriles.
Aliphatic isonitriles 2a–c were found inert towards dithiol-
one 1 at room temperature in CCl4. Heating under reflux for a
few hours led to the decomposition of starting materials; no
isolable products were detected (TLC data). Aromatic isonitriles
2d–f were more reactive towards 1. The reaction between 1 and
2d was investigated in detail. If the process was carried out in
a protic solvent, such as ethanol, or in strong aprotic dipolar
solvents, such as DMSO, isonitrile 2d was decomposed and
starting dithiolone 1 was isolated in practically quantitative
yield. The reaction between 1 and 2d did not proceed in
acetonitrile at room temperature, and heat under reflux resulted
in the decomposition of starting materials. The reaction in an
inert solvent (carbon tetrachloride) at room temperature occurred
slowly; after heating the reaction mixture under reflux for 1 h,
new product 3d was formed. Compound 3d (75% yield), a black
solid with C221H18N2O6S5 according to mass spectra, elemental
analysis, and H and 13C NMR spectra is formally the product
of addition of isonitrile 2d to compound 1 and elimination of
sulfur from the latter with another molecule of isonitrile. Iso-
thiocyanate 4d was isolated from the reaction mixture in prac-
tically quantitative yield (Scheme 1).† Treatment of dithiolone 1
with 2 equiv. of arylisonitriles 2e,f in CCl4 under reflux for
†
General procedure for the preparation of 2-iminothiophen-3(2H)-ones
3d–g, 7, 8, 10–13. A mixture of 1,2-dithiol-3-one 1, 5, 6 or 9 (0.05 mmol)
and isonitrile 2 (0.1 mmol) in CCl4 (10 ml) was stirred at room tempera-
ture or under reflux up to the disappearance of 1,2-dithiol-3-one or
isonitrile (TLC data). The reaction mixture was separated by column
chromatography (Silica gel Merck 60; light petroleum, light petroleum–
CH2Cl2 and CH2Cl2–acetone mixtures).
New compounds were characterised by elemental analysis, IR, 1H and
13C NMR spectroscopy (CDCl3 solutions, 300 and 75.5 MHz for 1H
and 13C, respectively) and mass spectrometry (EI, 70 eV).
3d: reflux for 1 h, yield 75%, black powder, mp 106–108 °C. 1H NMR,
d: 1.21 (t, 3H, MeCH2, J 7.1 Hz), 3.26 (dq, 1H, CH2Me, J 14.3 Hz,
J 7.1 Hz), 3.61 (dq, 1H, CH2Me, J 14.3 Hz, J 7.1 Hz), 3.85 (s, 3H,
MeO2C
Et
N
S
O
MeO2C
S
+
S
2
C
N
OMe), 3.93 (s, 3H, CO2Me), 3.95 (s, 3H, CO2Me), 6.97 (d, 2H, HAr,
CCl4
J 8.8 Hz), 7.31 (d, 2H, HAr, J 8.8 Hz). 13C NMR, d: 13.4 (MeCH2), 48.1
(MeCH2), 53.9 (CO2Me), 54.1 (CO2Me), 55.7 (OMe), 114.9 (2CH),
124.5 (2CH), 124.6, 131.1, 132.0, 133.1, 134.6, 140.5, 148.0, 153.8,
159.6, 160.1 and 160.3 (11sp2 tertiary C), 177.1 (C=O), 191.4 (C=S).
IR (KBr, n/cm–1): 2952 (CH), 1732 and 1684 (C=O). MS, m/z (%): 566
(M+, 3), 404 (100), 376 (65), 274 (68), 165 (SCNC6H4OMe, 38), 150
(42), 133 (36). Found (%): C, 46.71; H, 3.23; N, 4.87. Calc. for
C22H18N2O6S5 (%): C, 46.63; H, 3.20; N, 4.94.
S
R
S
S
1
2a–g
MeO2C
MeO2C
Et
N
S
O
S
+
N
S
C N
3e: reflux for 6 h, yield 71%, black powder, mp 191–192 °C. 1H NMR,
d: 1.24 (t, 3H, MeCH2, J 7.1 Hz), 3.29 (dq, 1H, CH2Me, J 14.2 Hz,
J 7.1 Hz), 3.63 (dq, 1H, CH2Me, J 14.2 Hz, J 7.1 Hz), 3.95 (s, 3H,
OMe), 3.97 (s, 3H, OMe), 7.20 (d, 2H, HAr, J 7.7 Hz), 7.28–7.35 (m,
1H, HAr), 7.43–7.49 (m, 2H, HAr). 13C NMR, d: 13.3 (MeCH2), 48.1
(MeCH2), 53.9 (CO2Me), 54.0 (CO2Me), 120.9, 128.0 and 129.6 (5CH),
131.1, 131.8, 133.1, 134.5, 148.4, 151.7, 154.7, 159.6 and 160.4 (10sp2
tertiary C), 176.7 (C=O), 191.0 (C=S). IR (KBr, n/cm–1): 2952 (CH),
1744, 1720 and 1676 (C=O). MS, m/z (%): 536 (M+, 9), 404 (33), 376
(26), 274 (33), 135 (SCNPh, 13). Found (%): C, 47.08; H, 2.69; N, 5.09.
Calc. for C21H16N2O5S5 (%): C, 47.00; H, 3.00; N, 5.22.
S
R
S
S
R
3d 75%
3e 71%
3f 73%
3g 79%
4d 96%
4e 97%
4f 98%
4g 98%
a R = CH2Ts
b R = CH2Ph
c R = CH2CO2Et
d R = 4-MeOC6H4
e R = Ph
R = 4-NO2C6H4
g R = C(CO2Et)CHNMe2
f
Scheme 1
– 282 –
© 2010 Mendeleev Communications. All rights reserved.

Mendeleev Commun., 2010, 20, 282–284
6 and 30 h, respectively, afforded new products 3e,f in high
O
yields. The reaction of dithiolone 1 with isonitrile 2g proceeded
at room temperature in CCl4, and product 3g was formed after
1 h in high yield (79%). The structure of iminothiophenones 3
was finally proved by X-ray analysis of closely related analogue
10 (see below).
Cl
S
+
2 N
C
OMe
S
R
5 R = SPh
6 R =
2d
1,2-Dithiol-3-ones fused with aromatic (benzene and pyri-
dine) rings – 3H-1,2-benzodithiol-3-one and 3H-[1,2]dithiolo-
N
O
3f: reflux for 30 h, yield 73%, black powder, mp 208–210 °C. 1H NMR,
d: 1.24 (t, 3H, MeCH2, J 6.8 Hz), 3.22–3.39 (m, 1H, CH2Me), 3.52–3.70
(m, 1H, CH2Me), 3.94 (s, 3H, OMe), 3.97 (s, 3H, OMe), 7.24 (d, 2H,
HAr, J 8.3 Hz), 8.31 (d, 2H, HAr, J 8.3 Hz). 13C NMR, d: 13.3 (MeCH2),
48.5 (MeCH2), 53.9 (CO2Me), 54.0 (CO2Me), 120.5 (2CH), 125.4 (2CH),
131.2, 131.5, 133.2, 134.5, 146.3, 154.1, 154.2, 154.8, 159.4 and 160.8
(11sp2 tertiary C), 176.0 (C=O), 190.0 (C=S). IR (KBr, n/cm–1): 2960
(CH), 1740 and 1688 (C=O), 1344 (NO2). MS, m/z (%): 582 (M+ + 1, 1),
274 (9), 238 (11), 219 (18), 206 (40), 192 (18), 180 (SCNC6H4NO2,
11). Found (%): C, 43.21; H, 2.47; N, 7.00. Calc. for C21H15N3O7S5 (%):
C, 43.36; H, 2.60; N, 7.22.
O
Cl
N
+
SCN
OMe
S
R
4d, 95–98%
OMe
7 R = SPh, 73%
8 R =
, 54%
O
N
3g: room temperature, 1 h, yield 79%, brown powder, mp 148–150 °C.
1H NMR, d: 1.16 (t, 3H, MeCH2N, J 7.0 Hz), 1.31 (t, 3H, MeCH2O,
J 7.1 Hz), 3.19 (dq, 1H, MeCH2N, J 14.1 Hz, J 7.0 Hz), 3.30 (br. s, 3H,
MeN), 3.56 (dq, 1H, MeCH2N, J 14.1 Hz, J 7.0 Hz), 3.73 (br. s, 3H, MeN),
3.90 (s, 3H, CO2Me), 3.91 (s, 3H, CO2Me), 4.23 (q, 2H, MeCH2O,
J 7.1 Hz), 7.65 (s, 1H, CH). 13C NMR, d: 13.3 (MeCH2N), 14.7 (MeCH2O),
41.2 (MeN), 48.0 (MeCH2N), 49.2 (MeN), 53.8 (Me), 53.8 (CO2Me),
60.5 (MeCH2O), 105.9, 130.4, 131.3, 132.9, 132.9, 134.5, 152.5, 159.0,
159.8, 159.9 and 163.9 (11sp2 tertiary C), 151.5 (CH), 178.2 (C=O),
194.6 (C=S). IR (KBr, n/cm–1): 2952 and 2920 (CH), 1716, 1652 and
1620 (C=O). MS, m/z (%): 599 (M+ – 2, 1), 404 (1), 376 (2), 274 (6), 200
[SCNC(CO2Et)=CH(NMe2), 5]. Found (%): C, 44.01; H, 3.97; N, 6.83.
Calc. for C22H23N3O7S5 (%): C, 43.91; H, 3.85; N, 6.98.
Scheme 2
[3,4-b]pyridin-3-one – were found inert towards isonitriles 2,
and they were recovered in practically quantitative yields from
the reaction mixtures after heating under reflux for 20 h. On the
other hand, monocyclic 1,2-dithiol-3-ones 5, 6 reacted with
2 equiv. of isonitrile 2d in CCl4 to afford thiophenones 7, 8 in
high to moderate yields (Scheme 2).
Interesting results were obtained for bis[1,2]dithiolo[1,4]-
thiazine dione 9, in which two 1,2-dithiol-3-one rings can be
involved in the reaction with isonitriles 2. Treatment of dione 9
with 2 equiv. of isonitrile 2d or 2g at room temperature in CCl4
led to a mixture of monothiophenones 10 or 11, bis(thio-
phenones) 12 or 13 together with starting bis(1,2-dithiole) 9.
Further reaction of monothiophenones 10 or 11 with another
2 equiv. of 2d or 2g at room temperature for 20 h gave 12 or 13
in moderate yields (45 and 57%, respectively) (Scheme 3). It
means that the reactivity of 1,2-dithiole rings in 9 and in mono-
thiophenones is comparable.
The structure of imine 10 was confirmed by X-ray analysis‡
(Figure 1). According to its results, this monothiophenone crys-
tallizes with four independent molecules in a unit cell, which
are related by pseudo-symmetry elements – inversion centre and
translation. The latter manifests itself in the similarity of the
geometrical parameters for the independent species; all of them
fall in the ranges typical of this type of heterocyclic compounds.
As thiophenone 10 lacks any convenient proton donor, the
strongest intermolecular interactions are C=O···S ones [O···S
1
7: reflux for 12 h, yellow powder, mp 153–154 °C. H NMR, d: 3.79
(s, 3H, Me), 6.88 (d, 2H, HAr, J 8.8 Hz), 7.15 (d, 2H, HAr, J 8.8 Hz),
7.45–7.50 (m, 2H, Ph), 7.54–7.63 (m, 3H, Ph). 13C NMR, d: 55.6 (Me),
114.8 (2CH, Ar), 124.4 (2CH, Ar), 130.0, 131.8 and 136.1 (5CH, Ph),
117.2, 125.4, 140.4, 147.9, 160.0 and 167.3 (6sp2 tertiary C), 177.4 (C=O).
IR (KBr, n/cm–1): 2992 and 2836 (CH), 1688 (C=O). MS, m/z (%): 363
(M+ + 2, 25), 361 (M+, 60), 230 (12), 228 (30), 202 (5), 200 (15). Found
(%): C, 56.26; H, 3.17; N, 4.04. Calc. for C17H12ClNO2S2 (%): C, 56.42;
H, 3.34; N, 3.87.
8: room temperature, 30 h, yield 54%, yellow powder, mp 185–187 °C.
1H NMR, d: 3.82–3.84 (m, 7H, 2CH2 + MeO), 3.97–4.00 (m, 4H, 2CH2),
6.95 (d, 2H, HAr, J 8.8 Hz), 7.19 (d, 2H, HAr, J 8.8 Hz). 13C NMR, d:
51.4 (2CH2), 55.6 (Me), 66.7 (2CH2), 98.6, 141.7, 148.7, 159.2 and
163.1 (5sp2 tertiary C), 114.7 (2CH), 123.1 (2CH), 178.9 (C=O). IR (KBr,
n/cm–1): 2924 and 2852 (CH), 1652 (C=O). MS, m/z (%): 340 (M+ + 2, 8),
338 (M+, 24), 210 (36), 208 (100), 179 (6), 177 (24), 165 (17). Found (%):
C, 53.24; H, 4.57; N, 8.23. Calc. for C15H15ClN2O3S (%): C, 53.17;
H, 4.46; N, 8.27.
10: room temperature, 20 h, yield 41%, black crystals, mp 149–150 °C.
1H NMR, d: 1.26 (t, 3H, MeCH2N, J 7.1 Hz), 3.84 (s, 3H, MeO), 3.87
(q, 2H, MeCH2N, J 7.1 Hz), 6.97 (d, 2H, HAr, J 9.0 Hz), 7.31 (d, 2H,
HAr, J 9.0 Hz). 13C NMR, d: 14.1 (MeCH2N), 42.6 (MeCH2N), 55.7 (MeO),
114.9 (2CH), 124.6 (2CH), 133.8, 133.9, 140.0, 142.8, 147.1, 147.7 and
160.4 (7sp2 tertiary C), 175.67 (C=O), 182.97 (C=O). IR (CDCl3, n/cm–1):
2936 (C-H), 1684 and 1656 (C=O). MS, m/z (%): 408 (M+, 19), 376 (24),
348 (5), 275 (87), 247 (45), 243 (100), 232 (37), 219 (78). Found (%):
C, 47.05; H, 2.79; N, 6.82. Calc. for C16H12N2O3S4 (%): C, 47.04; H, 2.96;
N, 6.86.
11: room temperature, 1.5 h, yield 51%, dark brown powder, mp 155–
156 °C. 1H NMR, d: 1.17 (t, 3H, MeCH2N, J 7.3 Hz), 1.26 (t, 3H,
MeCH2O, J 6.9 Hz), 3.27 (s, 3H, MeN), 3.63 (s, 3H, MeN), 3.78 (q, 2H,
MeCH2N, J 7.3 Hz), 4.18 (q, 2H, MeCH2O, J 6.9 Hz), 7.61 (s, 1H,
CH). 13C NMR, d: 13.7 (MeCH2N), 14.6 (MeCH2O), 41.1 (MeN), 42.4
(MeCH2N), 49.2 (MeN), 60.3 (MeCH2O), 104.9, 130.8, 132.4, 133.8,
144.0, 145.8 and 163.7 (7sp2 tertiary C), 151.5 (CH), 176.3 (C=O),
183.4 (C=O). IR (KBr, n/cm–1): 2920 (CH), 1660 and 1620 (C=O). MS,
m/z (%): 443 (M+, 26), 411 (17), 300 (17), 275 (36), 228 (26), 219 (58).
Found (%): C, 43.22; H, 3.94; N, 9.53. Calc. for C16H17N3O4S4 (%):
C, 43.32; H, 3.86; N, 9.47.
12: room temperature, 20 h, yield 11%, dark brown powder, mp 177–
178 °C. H NMR, d: 1.24 (t, 3H, Me, J 7.1 Hz), 3.85 (s, 6H, 2OMe),
1
4.03 (q, 2H, CH2, J 7.1 Hz), 6.97 (d, 4H, HAr, J 8.9 Hz), 7.31 (d, 4H, HAr
,
J 8.9 Hz). 13C NMR, d: 14.1 (Me), 42.3 (CH2), 55.7 (2MeO), 115.0 (4CH),
124.7 (4CH), 132.1, 140.3, 143.0, 146.1 and 160.5 (10sp2 tertiary C),
175.8 (2C=O). IR (KBr, n/cm–1): 2928 (CH), 1676 and 1664 (C=O).
MS, m/z (%): 509 (M+, 1), 199 (12), 165 (100). Found (%): C, 47.05;
H, 2.79; N, 6.82. Calc. for C16H12N2O3S4 (%): C, 47.04; H, 2.96; N, 6.86.
13: room temperature, 1.5 h, yield 9%, dark brown powder, mp 185–
186 °C. 1H NMR, d: 1.12 (t, 3H, MeCH2N, J 7.0 Hz), 1.29 (t, 6H,
2MeCH2O, J 7.1 Hz), 3.28 (br. s, 6H, 2MeN), 3.67 (br. s, 6H, 2MeN),
3.93 (q, 2H, MeCH2N, J 7.0 Hz), 4.21 (q, 4H, 2MeCH2O, J 7.1 Hz),
7.61 (s, 1H, CH). 13C NMR, d: 13.4 (MeCH2N), 14.7 (2MeCH2O), 41.1
and 49.0 (2br. s, 4Me), 42.1 (MeCH2N), 60.4 (2MeCH2O), 105.4, 125.0,
131.2, 143.3 and 163.9 (10sp2 tertiary C), 151.1 (2CH), 176.9 (2C=O).
IR (KBr, n/cm–1): 2980 and 2896 (CH), 1640 and 1624 (C=O). MS, m/z
(%): 579 (M+, 1), 453 (1), 240 (8), 228 (20), 211 (12), 200 (SCNR, 16),
171 (16), 154 (30), 139 (13), 126 (10), 109 (21), 89 (49), 83 (100).
Found (%): C, 49.85; H, 5.14; N, 11.99. Calc. for C24H29N5O6S3 (%):
C, 49.72; H, 5.04; N, 12.08.
– 283 –

Mendeleev Commun., 2010, 20, 282–284
C(9)
Et
N
O(1)
C(1)
O
O
C(8)
O(2)
C(5)
C(4)
N(1)
S
S
C(6)
S(1)
S
S
C(7)
S
N(2)
C(10)
C(2)
9
C(3)
C(11)
C(12)
2d or 2g
(2 equiv.)
– RNCS
S(2)
S(4)
S(3)
C(15)
C(14)
Et
O
O
C(13)
N
O(3)
S
N
S
S
C(16)
S
R
10 R = 4-MeOC6H4, 41%
11 R = C(CO2Et)CHNMe2, 51%
Figure 1 General view of an independent molecule in the crystal of 10 in
representation of atoms via thermal ellipsoids at a 50% probability level.
+
2d or 2g (2 equiv.)
– RNCS
Et
O
O
N
O
R3
O
N
R1
R2
R1
R2
S
N
N
+
S
C N
S
S
R
S
R
R3
S
S
12 R = 4-MeOC6H4, 7% (45% from 10)
13 R = C(CO2Et)CHNMe2, 9% (57% from 11)
2
14
O
O
+
R1
R2
R1
R2
C
9, 9–10%
+
C
N
N
– SCNR3
R3
R3
Scheme 3
S
S
4
15
2
16
3.296(2)–3.309(2) Å] assembling three of the independent mole-
cules into trimers. A slightly weaker C=O···S contact [O···S
3.410(3) Å] links these associates with the fourth monothio-
phenone molecule to give corrugated tapes along the crys-
tallographic plane ac. A number of weaker interactions, such
as C–H···S, C–H···O, H···H, complete the formation of a 3D
framework.
Scheme 4
and the elimination of sulfur with another molecule of iso-
nitrile (isothiocyanate formation). The most plausible pathway
(Scheme 4) includes the cycloaddition of dithiolone and iso-
nitrile 2 to give 1,3-oxathietane 14, which can release the mole-
cule of isothiocyanate 4 and form the key intermediate – ketene
15. Isonitrile 2 is likely to react with ketene 15 to produce
thiophenone 16.
The above reactions are the novel conversions of 1,2-dithiol-
3-one into thiophenone ring through the insertion of isonitrile
‡
Crystallographic data. Crystals of 10 (C16H12N2O3S4, M = 408.52)
are monoclinic, space group P21/n, at 100 K: a = 28.9379(13), b =
= 7.4455(3) and c = 31.7694(14) Å, b = 102.5740(10)°, V = 6680.8(5) Å3,
Z = 16 (Z' = 4), dcalc = 1.625 g cm–3, m(MoKα) = 5.88 cm–1, F(000) = 3360.
Intensities of 72870 reflections were measured with a Bruker SMART
APEX2 CCD diffractometer [l(MoKα) = 0.71072 Å, w-scans, 2q < 56°]
and 16112 independent reflections (Rint = 0.0677) were used in a further
refinement. The structure was solved by a direct method and refined by the
full-matrix least-squares technique against F2 in the anisotropic-isotropic
approximation. The positions of hydrogen atoms were calculated, and
they were refined in isotropic approximation in riding model. For 10, the
refinement converged to wR2 = 0.1006 and GOF = 1.003 for all inde-
pendent reflections [R1 = 0.0430 was calculated against F for 10900
observed reflections with I > 2s(I)]. All calculations were performed
using SHELXTL PLUS 5.0.6
References
1 (a) C. Th. Pedersen, Adv. Heterocycl. Chem., 1982, 31, 63; (b) C. Th.
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prehensive Heterocyclic Chemistry II, ed. I. Shinkai, Pergamon, Oxford,
1996, vol. 3, chapter 3.11, p. 593; (d) R. Markovic´ and A. Rašovic´, in
Comprehensive Heterocyclic Chemistry III, ed. J. A. Joule, Elsevier,
Oxford, 2008, vol. 4, chapter 4.11, p. 893.
2 B. Böttcher and F. Bauer, Liebigs Ann. Chem., 1950, 568, 227.
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(Russ. Chem. Bull., Int. Ed., 2009, 58, 430).
CCDC 786198 contains the supplementary crystallographic data for this
paper. These data can be obtained free of charge from The Cambridge
Crystallographic Data Centre via www.ccdc.cam.ac.uk/data_request/cif.
For details, see ‘Notice to Authors’, Mendeleev Commun., Issue 1, 2010.
6 G. M. Sheldrick, Acta Crystallogr., Sect. A, 2008, 64, 112.
Received: 31st March 2010; Com. 10/3499
– 284 –