Synthesis and thermal stability of imino-1,3-dithietanes. Influence of structural factors

Article abstract of DOI:10.1007/s11172-010-0028-0

The reaction of 1,2-dithiol-3-thiones with isonitriles at room temperature affords imino-1,3-dithietanes. The reaction is reversible. According to ¹H NMR spectroscopy, the rise of the temperature shifts the equilibrium to the starting compounds

Full text of DOI:10.1007/s11172-010-0028-0

Russian Chemical Bulletin, International Edition, Vol. 58, No. 2, pp. 430—436, February, 2009
430
Synthesis and thermal stability of iminoꢀ1,3ꢀdithietanes.
Influence of structural factors*
V. A. Ogurtsov,a Yu. V. Karpychev,a P. A. Belyakov,a
Yu. V. Nelyubina,b K. A. Lyssenko,b and O. A. Rakitina
aN. D. Zelinsky Institute of Organic Chemistry, Russian Academy of Sciences,
47 Leninsky prosp., 119991 Moscow, Russian Federation.
Fax: +7 (499) 135 5328. Еꢀmail: vao@ioc.ac.ru
bA. N. Nesmeyanov Institute of Organoelement Compounds, Russian Academy of Sciences,
28 ul. Vavilova, 119991 Moscow, Russian Federation.
Fax: +7 (499) 135 5085
The reaction of 1,2ꢀdithiolꢀ3ꢀthiones with isonitriles at room temperature affords iminoꢀ
1
1,3ꢀdithietanes. The reaction is reversible. According to H NMR spectroscopy, the rise of
the temperature shifts the equilibrium to the starting compounds. The structure of one of the
iminoꢀ1,3ꢀdithietanes was established by Xꢀray diffraction.
Key words: 1,3ꢀdithietanes, 1,2ꢀdithiolꢀ3ꢀthiones, isonitriles, equilibrium, 1H NMR
spectroscopy, Xꢀray diffraction study.
this reaction and the data on stability of this class of
1,3ꢀDithietanes have been known for more than
130 years1 and are of interest as biologically active comꢀ
pounds.2 For example, cephamycin and cephalosporin
derivatives containing the 1,3ꢀdithietane fragment are very
active against various bacteria.3,4 Methylene derivatives
of 1,3ꢀdithietanes are antibiotics against gramꢀnegative
bacteria.5 Iminoꢀ1,3ꢀdithietanes are structural units of
polymers that form complexes with tetracyanoquinoꢀ
dimethane having high conductivity.6
compounds were not published. However, this method could
serve as a general route to the formation of the 1,3ꢀdithietane
fragment from readily available 1,2ꢀdithiolꢀ3ꢀthiones.
Ketothione 1 was studied in the reactions with isoꢀ
nitriles having different structures in benzene at room
temperature. Isonitriles 2a—e were found to readily react
with ketothione 1 to form the corresponding iminoꢀ1,3ꢀ
dithietanes 3 in yields from moderate to high (Scheme 1).
1,3ꢀDithietanes are poorly known because these comꢀ
pounds are difficult to synthesize.2 More or less general
methods for the synthesis of these compounds are few in
number: the dimerization of headꢀtoꢀtail thiocarbonyl
compounds promoted by heating,7 photochemical action,8
bases,9 acids,10 or other methods and the dimerization of
thioketones.3 It should be noted that these reactions
afford symmetrically substituted 1,3ꢀdithietanes.
Scheme 1
It is known that 1,2ꢀdithiolꢀ3ꢀthiones can be involved
in 1,3ꢀdipolar cycloaddition reactions.11 Isonitriles are
prone to undergo cycloaddition to 1,3ꢀdipoles and double
bonds, including those containing sulfur.12 Previously, we
have reported that the reaction of bis[1,2]dithiolo[1,4]ꢀ
thiazine ketothione 1 with pꢀtoluenesulfonylmethyl isoꢀ
cyanide 2a gives a product, to which the structure of
iminoꢀ1,3ꢀdithietane 3a was assigned based on NMR
spectroscopic and elemental analysis data.13 The scope of
3
3a
CH2Ts
64
3b
Ph 4ꢀMeOC6H4 4ꢀNO2C6H4 CH2CO2Et
38 74 77 41
3c
3d
3e
* On the occasion of the 75th anniversary of the foundation
of the N. D. Zelinsky Institute of Organic Chemistry of the
Russian Academy of Sciences.
R
Yield (%)
Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 2, pp. 422—428, February, 2009.
1066ꢀ5285/09/5802ꢀ0430 © 2009 Springer Science+Business Media, Inc.

Iminoꢀ1,3ꢀdithietanes
Russ.Chem.Bull., Int.Ed., Vol. 58, No. 2, February, 2009
431
Scheme 2
It should be noted that the Taft constant σI for all
substituents R in isonitriles 2a—e varies from 0.12 to
0.23.14 By contrast, isonitrile 2f (R = CH2Ph) containing
the more electronꢀdonating benzyl group (σI = 0.03)14
does not react with dithiolthione 1 at room temperature
for 72 h; the starting compounds were isolated from the
reaction mixture in virtually quantitative yields. After
the reaction mixture was heated to reflux, only isonitrile
2f partially decomposed. The relatively low yields of
dithietanes 3b,e are apparently associated with lower staꢀ
bility of the starting isonitriles.
4, 5: R1 = Cl, SPh
Table 1. Yields of 1,3ꢀdithietanes 13 and 14
The influence of the structure of 1,2ꢀdithiolꢀ3ꢀthione
derivatives on the possibility of the formation of 1,3ꢀdiꢀ
thietane molecules remained unknown. Hence, we perꢀ
formed the reactions of isonitriles 2a—e with a series
of 1,2ꢀdithiolꢀ3ꢀthiones, both monocyclic derivatives
containing two substituents (4, 5) or one substituent (6,
7) in the ring, and fused derivatives containing heteroꢀ
cyclic (8—10), cyclohexane (11), or benzene (12) rings.
Dithietane
R1
R2
Yield (%)
13a
13b
13c
13d
14a
14b
14c
14d
Cl
Cl
Cl
CH2Ts
Ph
4ꢀMeOC6H4
4ꢀNO2C6H4
CH2Ts
92
72
72
85
84
73
68
84
Cl
SPh
SPh
SPh
SPh
Ph
4ꢀMeOC6H4
4ꢀNO2C6H4
the reaction mixture at room temperature for 72 h and
under reflux in benzene for 1 h.
Interesting results were obtained for bis[1,2]dithioloꢀ
[1,4]thiazine dithione 8. Thus, although both 1,2ꢀdithiolꢀ
3ꢀthione rings can be involved in the reaction, the reacꢀ
tion of dithione 8 with isonitriles 2a,b,e at room temperaꢀ
ture for 2—3 h was shown to afford 1,3ꢀdithietanes 15a,b,e
in 39—61% yields as a result of the addition of only one
isonitrile group (Scheme 3).
Scheme 3
It appeared that the structure of 1,2ꢀdithiolꢀ3ꢀthiones
influences the possibility of the formation of 1,3ꢀdiꢀ
thietanes, the presence of electronꢀwithdrawing groups in
the starting molecule and the retention of its aromaticity
being the main factors.
Thus, monocyclic dithiolthiones 4 and 5 containing
electronꢀwithdrawing chlorine atoms (σI = 0.47)14 and
the phenylthio group (σI = 0.31)14 react with isonitriles
2a—d in benzene at room temperature to form 1,3ꢀdiꢀ
thietanes 13 and 14 (Scheme 2, Table 1).
By contrast, monocyclic dithiolthiones 6 and 7 conꢀ
taining the less electronꢀwithdrawing phenyl group (σI =
0.12)14 do not react with isonitriles 2a—d. The starting
1,2ꢀdithiolꢀ3ꢀthiones were isolated from the reaction mixꢀ
ture in virtually quantitative yields both upon storage of
15
15a
CH2Ts
61
15b
Ph
15e
CH2CO2Et
39
R
Yield (%)
42
The reaction with the use of a twofold excess of isoꢀ
nitrile and/or performed with heating gives no new
compounds except for 2, 8, and 15 (TLC data).

432
Russ.Chem.Bull., Int.Ed., Vol. 58, No. 2, February, 2009
Ogurtsov et al.
Bis[1,2]dithiolopyrroles 9 and 10 do not react with
isonitriles 2a—d due apparently to a loss of aromaticity of
the pyrrole ring upon the formation of 1,3ꢀdithietanes 16.
C(12)
Cl(1)
C(14)
C(15)
S(5)
C(11)
S(2)
C(16)
C(17)
C(18)
C(13)
C(10)
O(2A)
O(1A)
N(1A)
S(3A)
S(4A)
S(4)
S(1A)
C(9)
S(3)
C(8)
N(1)
O(1)
O(2)
S(2A)
C(1)
C(2)
C(3)
C(4)
C(7)
C(6)
C(5)
Cl(1A)
S(5A)
X = O (9), S (10)
Fig. 1. General view of compound 14a (with displacement ellipꢀ
soids drawn at the 50% probability level) illustrating the formaꢀ
tion of intramolecular S...S and intermolecular S...O contacts.
The atoms labeled with A are related to the unlabeled atoms by
the symmetry operation –x + 1, –y + 1, –z + 1.
Fused dithiolthiones 11 and 12 also do not react with
isonitriles 2a—e both at room temperature and upon heatꢀ
ing. These results correlate well with those described
above. Thus, dithiolthione 11 contains the electronꢀ
donating methylene fragment (σI = –0.02)14 at the dithiol
ring, whereas benzodithiolthione 12 does not react with
isonitriles due apparently to a loss of aromaticity of the
benzene ring.
Table 2. Selected bond lengths (d) and bond angles (ω) in comꢀ
pound 14a
Bond
d/Å
Angle
ω/deg
The structures of 1,3ꢀdithietanes 3, 13, 14, and 15
were confirmed by elemental analysis. The 1H NMR and
IR spectroscopic and mass spectrometric data do not
N(1)—C(9)
S(2)—C(9)
S(3)—C(9)
S(3)—C(10)
1.244(3)
1.800(3) C(10)—S(3)—C(9)
1.793(3)
1.743(3)
C(10)—S(2)—C(9)
80.02(13)
80.36(13)
129.8(2)
C(11)—C(10)—S(3)
S(3)—C(10)—S(2)
1
contradict these structures. The H NMR spectra show
101.68(14)
signals corresponding to the starting dithiolthiones 1, 5,
and 8 and isonitriles 2a—e, but the signals are shifted by
0.1—0.3 ppm. Thus, the signal of the CH2 group in isoꢀ
nitrile 2a is observed at δ 4.59, whereas the signal of the
analogous CH2 group in the spectra of dithietanes 3a,
13a, 14a, and 15a is observed at δ 4.68—4.70. In the mass
spectra, the molecular ion [M]+ with an intensity of
2—4% was detected only for dithietanes 3a,b,e. However,
all mass spectra have the characteristic fragment
[M – RN=C]+ with high intensity. The IR spectra
are also characteristic. Thus, the absorption band at
2180—2100 cm–1 characteristic of the isonitrile group is
absent in the spectra of all 1,3ꢀdithietanes.
C(10)—C(11) 1.344(4)
C—S bond, as evidenced by the Lp—N(1)—C(9)—S(2)
pseudotorsional angle (179.6(1)°).
In spite of the observed distortion, the heterocycle is
virtually planar. The maximum deviation of the atoms of
the central fragment S2C2 from the mean plane is 0.024 Å.
It should be noted that the S(4) atom also lies in this
plane. This conformation is most likely stabilized by the
strong intramolecular S...S contact (2.901(4) Å) linking
the S(4) atom to the central ring (see Fig. 1). Based on
geometric considerations, this interaction is associated
with the charge transfer from the corresponding lone pair
of the sulfur atom to the σ* orbital of the C(9)—S(3) bond
(S(4)—S(3)—C(9), 158(1)°) and leads to an additional
elongation of the latter bond (S—C, 1.793(3) Å) comꢀ
pared to the S(3)—C(10) bond (S—C, 1.743(3) Å). It should
be noted that this distortion of the heterocycle is not,
apparently, a unique feature of dithietane 14a. Thus, a
statistical survey of the Cambridge Structural Database15
showed that the heterocycle in molecules containing the
—C=S bond adjacent to the coplanar C=C(S(2))C=C
fragment is essentially asymmetric.
The structure of one of the 1,3ꢀdithietanes, viz., comꢀ
pound 14a, was established by Xꢀray diffraction. It should
be noted that this is the first Xꢀray diffraction structure of
iminoꢀ1,3ꢀdithietanes.
According to the Xꢀray diffraction data, the geometric
parameters of the heterocycle in dithietane 14a are typical
of compounds containing the C=C(S(2))C=C fragment.15
However, the heterocycle is somewhat asymmetric. Thus,
the C—S bond lengths in 14a vary in the range of
1.743(3)—1.800(3) Å, the C(9)—S bond being the longest
(Fig. 1, Table 2). This feature is apparently attributed to a
difference in the conjugation of the sulfur atoms with the
C=N and C=C double bonds. The elongation of the
C(9)—S(2) bond in 14a can be additionally associated
with the anomeric effect, i.e., the charge transfer from the
lone pair (Lp) of the N(1) atom to the σ* orbital of the
In turn, the S(2) atom of the dithietane fragment
in 14a is involved in the shortened S...O interaction with
the O(2) atom of the tosyl fragment (3.168(4) Å). This
interaction links molecules 14a into headꢀtoꢀtail centroꢀ
symmetric dimers. These supramolecular associates are

Iminoꢀ1,3ꢀdithietanes
Russ.Chem.Bull., Int.Ed., Vol. 58, No. 2, February, 2009
433
Table 3. Amount of 1,3ꢀdithietane in the equilibrium 1,2ꢀdithiolꢀ
3ꢀthione (1, 4, 5)—isonitrile (2)—1,3ꢀdithietane (3, 13, 14)
mixture
linked by numerous weak interactions, for example, such
as H...S, H...O, and H...π, as well as by S(5)...S(5), to
form a threeꢀdimensional framework.
We observed the appearance of signals of the CH2
group (δ 4.59), the CH3 group (δ 2.49), and the protons of
the benzene ring (δ 7.43 and 7.90) of the starting isonitrile
2a, as well as signals of the benzene ring (δ 7.53, 7.61, and
7.73) of the starting dithiolthione 5, in the 1H NMR specꢀ
trum (CDCl3) recorded 2 h after the preparation of an
analytically pure sample of 1,3ꢀdithietane 14a. We meaꢀ
sured the IR spectrum of a solution of 1,3ꢀdithietane 14a
in chloroform. This spectrum showed an absorption band
of the isonitrile group (2156 cm–1) of compound 2a, which
was absent in the IR spectrum of 14a measured in KBr
pellets. We suggested that there is an equilibrium between
1,3ꢀdithietane and the starting compounds in solution.
Starting compounds
Product
Yield
(%)
Isonitrile
Dithiolꢀ
thione
(σ )14
I
2a (0.23)
2b (0.12)
2c (0.12)
2d (0.20)
1
4
5
1
4
5
1
4
5
1
4
5
3a
13a
14a
3b
13b
14b
3c
13c
14c
3d
13d
14d
98
88
72
75
40
40
56
34
20
95
75
60
1
We studied this equilibrium by H NMR spectroscopy in
deuterochloroform by comparing the integrated intensiꢀ
ties of the signals of the starting and final compounds. It
appeared that the storage of a 1 M solution of 14a at room
temperature for 24 h afforded thione 5 and isonitrile 2a in
14% yield each; 72% of dithietane 14a remained unconꢀ
sumed (Scheme 4).
protons of the final and starting compounds. It appeared
that the equilibrium depends on the structures of both
1,2ꢀdithiolꢀ3ꢀthione and isonitrile. The amount of 1,3ꢀdiꢀ
thietane that remained unconsumed after the storage for
24 h is given in Table 3.
It should be noted that the ratio of the compounds in
the equilibrium mixture remains unchanged after the storꢀ
age for a longer time of each compound at room temperaꢀ
ture; most likely, the equilibrium is established earlier. An
analysis of the above results showed that the higher the
Taft constant σI of the substituent in isonitrile the more
stable 1,3ꢀdithietane.
Scheme 4
Scheme 5
R1R2 =
(1, 3); R1 = R2 = Cl (4, 13);
R1 = Cl, R2 = SPh (5, 14)
R3 = CH2Ts (a), Ph (b), 4ꢀMeOC6H4 (c), 4ꢀO2NC6H4 (d)
After cooling of this solution to –20 °C and the storꢀ
age at this temperature for one week, the equilibrium is
completely shifted toward 1,3ꢀdithietane 14a, and the
signals of compounds 5 and 2a disappeared. According to
TLC data, the spot of dithietane 14a disappeared after
refluxing in chloroform for 10 min, and compounds 5 and
2a were formed. It should be noted that compound 2a
decomposed under reflux for a longer time.
The equilibrium between 1,3ꢀdithietane, 1,2ꢀdithiolꢀ
3ꢀthione, and isonitrile at room temperature and after the
storage for 24 h was studied also for a series of the prodꢀ
1
ucts, which were prepared in the present study, by H
Reagents and conditions: i. DMAD, reflux, 10 min, C6H6.
ii. 2a. iii. DMAD.
NMR spectroscopy under conditions analogous to 14a by
measuring the integrated intensities of the signals for the

434
Russ.Chem.Bull., Int.Ed., Vol. 58, No. 2, February, 2009
Ogurtsov et al.
chromatographed on a column with Silica gel Merck 60 using
a CH2Cl2—petroleum ether mixture as the eluent (successively,
1 : 2, 1 : 1, 2 : 1, 1 : 0).
To confirm the formation of 1,2ꢀdithiolꢀ3ꢀthiones
from 1,3ꢀdithietanes, we studied the reaction of dithietane
3a with dimethyl acetylenedicarboxylate (DMAD). It was
reported16 that tricyclic dithiolthione 1 reacts with DMAD
to give 1,3ꢀdithiol 17 in 81% yield under reflux in benꢀ
zene for 10 min. We showed that 1,3ꢀdithietane 3a reacts
analogously to 1,2ꢀdithiolꢀ3ꢀthione 1 to give the same
product 17 in almost the same yield (80%) (Scheme 5);
compound 2a was detected in the reaction mixture by TLC.
Apparently, the transformation under consideration
proceeds as the concerted addition of the carbon atom
of the isonitrile group at the endoꢀ and exocyclic sulfur
atoms through the fourꢀcenter transition state (Scheme 6).
4ꢀEthylꢀ5ꢀ[4({(4ꢀmethylphenyl)sulfonyl}methylimino)ꢀ1,3ꢀ
dithietanꢀ2ꢀylidene]ꢀ6ꢀthioxoꢀ5,6ꢀdihydroꢀ3H,4Hꢀ[1,2]dithioloꢀ
[3,4ꢀb][1,4]thiazinꢀ3ꢀone (3a). The yield was 64%, yellow
crystals, m.p. 94—96 °C, Rf 0.10 (CH2Cl2). The reaction time
was 4 h. Found (%): C, 39.66; H, 2.71; N, 5.19. C17H14N2O3S7.
Calculated (%): C, 39.36; H, 2.72; N, 5.40. 1H NMR (CDCl3),
δ: 1.18 (t, 3 H, CH3CH2, J = 6.9 Hz); 2.45 (s, 3 H, CH3); 3.48
(br.s, 2 H, CH2CH3); 4.68 (br.s, 2 H, CH2); 7.38 and 7.80 (both
d, 2 H each, Ph, J = 8.1 Hz). 13C NMR (CDCl3), δ: 206.4
(C=S), 184.6 (C=O), 156.3, 155.4, 147.3, 145.8, 138.6, 134.1,
2
131.8 (7 Csp ), 130.1 and 129.2 (2 C—HAr), 73.9 (CH2), 49.3
(CH2CH3), 21.8 (CH3), 13.6 (CH2CH3). MS (EI, 70 eV), m/z
(Irel (%)): 518 [M]+ (2), 323 [M – ArCH2N=C]+ (10), 155 (20),
72 (100). IR (KBr), ν/cm–1: 2963 (C—H), 1651 (C=O), 1521,
1324, 1279 (C=S), 1144.
Scheme 6
4ꢀEthylꢀ5ꢀ[4ꢀ(phenylimino)ꢀ1,3ꢀdithietanꢀ2ꢀylidene]ꢀ
6ꢀthioxoꢀ5,6ꢀdihydroꢀ3H,4Hꢀ[1,2]dithiolo[3,4ꢀb][1,4]thiazinꢀ
3ꢀone (3b). The yield was 38%, brown crystals, m.p. 99—101 °C,
Rf 0.60 (CH2Cl2). The reaction time was 2 h. Found (%): C,
42.25; H, 2.39; N, 6.33. C15H10N2OS6. Calculated (%): C, 42.23;
1
H, 2.36; N, 6.57. H NMR (CDCl3), δ: 1.23 (t, 3 H, CH3CH2,
J = 7.2 Hz); 3.53 (d, 2 H, CH2CH3, J = 6.6 Hz); 7.04 (d, 2 H,
Ph, J = 7.2 Hz); 7.25 (t, 1 H, Ph, J = 7.5 Hz); 7.40 (d, 2 H, Ph,
J = 7.5 Hz). MS (EI, 70 eV), m/z (Irel (%)): 426 [M]+ (2), 323
[M – PhN=C]+ (55), 135 (100), 77 (80). IR (KBr), ν/cm–1
:
2952 и 2922 (C—H), 1640 (C=O), 1508, 1280 (C=S), 1004, 756.
4ꢀEthylꢀ5ꢀ{4ꢀ[(4ꢀmethoxyphenyl)imino]ꢀ1,3ꢀdithietanꢀ
2ꢀylidene}ꢀ6ꢀthioxoꢀ5,6ꢀdihydroꢀ3H,4Hꢀ[1,2]dithiolo[3,4ꢀb]ꢀ
[1,4]thiazinꢀ3ꢀone (3c). The yield was 74%, black crystals,
m.p. 52—54 °C, Rf 0.45 (CH2Cl2). The reaction time was
15 min. Found (%): C, 42.12; H, 2.56; N, 6.01. C16H12N2O2S6.
Calculated (%): C, 42.08; H, 2.65; N, 6.13. 1H NMR (CDCl3),
δ: 1.21 (t, 3 H, CH3CH2, J = 7.2 Hz); 3.52 (m, 2 H, CH2CH3);
3.82 (s, 3 H, OCH3); 6.91 and 7.03 (both d, 2 H each, Ph,
J = 8.8 Hz). MS (EI, 70 eV), m/z (Irel (%)): 323 [M – ArN=C]+
(5), 100 (75), 64 (100). IR (KBr), ν/cm–1: 2962 and 2928 (CH),
1632 (C=O), 1496, 1280 (C=S), 1248, 1000, 828, 708.
4ꢀEthylꢀ5ꢀ{4ꢀ[(4ꢀnitrophenyl)imino]ꢀ1,3ꢀdithietanꢀ
2ꢀylidene}ꢀ6ꢀthioxoꢀ5,6ꢀdihydroꢀ3H,4Hꢀ[1,2]dithioloꢀ
[3,4ꢀb][1,4]thiazinꢀ3ꢀone (3d). The yield was 77%, black crysꢀ
tals, m.p. 82—84 °C, Rf 0.50 (CH2Cl2). The reaction time was
1 h. Found (%): C, 38.27; H, 1.72; N, 8.68. C15H9N3O3S6.
Calculated (%): C, 38.20; H, 1.92; N, 8.91. 1H NMR (CDCl3),
δ: 1.22 (t, 3 H, CH2CH3, J = 7.3 Hz); 3.55 (q, 2 H, CH2CH3,
J = 7.2 Hz); 7.17 (d, 2 H, Ph, J = 9.2 Hz); 8.28 (d, 2 H, Ph,
J = 9.3 Hz). 13C NMR (CDCl3), δ: 206.3 (C=S), 184.6 (C=O),
To sum up, the reaction of 1,2ꢀdithiolꢀ3ꢀthiones with
isonitriles can be considered as a simple route to diffiꢀ
cultly available 1,3ꢀdithietanes, which are rather stable in
the solid state but are prone to dissociation into the startꢀ
ing compounds in solution upon heating.
Experimental
The 1H and 13C NMR spectra (in CDCl3) were recorded on
Bruker WMꢀ250 and Bruker AMꢀ300 instruments operating at
250 and 300 MHz, respectively, using the signals of the residual
protons of the solvent as the internal standard. The melting
points were measured on a Kofler hotꢀstage apparatus and are
uncorrected. The mass spectra were obtained on a Finnigan
MAT INCOS 50 instrument (EI). The IR spectra were meaꢀ
sured on a Specord M80ꢀ2 spectrometer in KBr pellets. The
reaction mixtures were monitored by TLC on Sorbfil plates;
spots were visualized under UV light and with I2 vapor.
2
151.6, 151.0, 147.3, 145.8, 139.2, 134.7, 131.7 (7 Csp ), 125.5
Compound 2a is a commercially available product (Acros).
Isonitriles 2b—d17 and 2e18 and 1,2ꢀdithioloꢀ3ꢀthiones 1, 6, 11,
12 (see Ref. 19), 4, 5 (see Ref. 20), and 7—10 (see Ref. 21) were
synthesized according to known procedures.
Synthesis of iminoꢀ1,3ꢀdithietanes (general procedure). Isoꢀ
nitrile 2 (1 mmol) was added with stirring to a solution of
1,2ꢀdithiolꢀ3ꢀthione 1, 4, or 5 (1 mmol) in benzene (5 mL) at
room temperature. The reaction mixture was kept for a certain
time (TLC monitoring). When the precipitate of the final
products (13a, 13d, and 14d) formed, it was filtered off and
washed with benzene. In other cases, the reaction mixture was
and 121.6 (2 C—HAr), 49.4 (CH2CH3), 13.6 (CH2CH3). MS
(EI, 70 EV), m/z (Irel (%)): 323 [M – ArN=C]+ (12), 180 (100),
150 (55), 122 (65), 90 (68), 50 (96). IR (KBr), ν/cm–1: 2956 and
2920 (C—H), 1644 (C=O), 1512, 1276 (C=S), 1000, 716.
Ethyl Nꢀ[4ꢀ(4ꢀethylꢀ3ꢀoxoꢀ6ꢀthioxoꢀ3H,4Hꢀ[1,2]dithioloꢀ
[3,4ꢀd][1,4]thiazinꢀ5(6H)ꢀylidene)ꢀ1,3ꢀdithietanꢀ2ꢀylidene]ꢀ
glycinate (3e). The yield was 41%, black crystals, m.p. 49—50 °C,
Rf 0.13 (CH2Cl2). The reaction time was 1 h. Found (%):
C, 35.57; H, 2.62; N, 6.68. C, 35.76; H, C13H12N2O3S6. Calcuꢀ
1
lated (%): 2.77; N, 6.42. H NMR (CDCl3), δ: 1.19 (t, 3 H,
CH2CH3, J = 7.2 Hz); 1.31 (t, 3 H, CH2CH3, J = 6.9 Hz); 3.98

Iminoꢀ1,3ꢀdithietanes
Russ.Chem.Bull., Int.Ed., Vol. 58, No. 2, February, 2009
435
(q, 2 H, CH2CH3, J = 7.3 Hz); 4.20 (s, 2 H, CH2); 4.29 (q, 2 H,
CH2CH3, J = 6.9 Hz). MS (EI, 70 eV), m/z (Irel (%)): 436 [M]+
(4), 323 [M – EtOCOCH2N=C]+ (32), 145 (55), 72 (80). IR
(KBr), ν/cm–1: 2968 (C—H), 1689 (C=O), 1648 (C=O), 1521,
1318, 1278 (C=S), 1057, 718.
MS (EI, 70 eV), m/z (Irel (%)): 276 [M – PhN=C]+ (20), 135
(100), 103 [PhN=C]+ (60), 76 (73). IR (KBr), ν/cm–1: 3052
(C—H), 1644, 1536, 1208 (C=S), 1032, 856, 740, 684.
Phenyl 2ꢀ(chloro)ethaneꢀ2ꢀ{4ꢀ[(4ꢀmethoxyphenyl)imino]ꢀ
1,3ꢀdithietanꢀ2ꢀylidene}dithioate (14c). The yield was 68%, paleꢀ
brown crystals, m.p. 85—87 °C, Rf 0.68 (CH2Cl2). The reaction
time was 15 min. Found (%): C, 49.33; H, 2.98; N, 3.26.
C17H12ClNOS4. Calculated (%): C, 49.80; H, 2.95; N, 3.42.
1H NMR (CDCl3), δ: 3.82 (s, 3 H); 6.92 (dd, 2 H, Ar, J = 12.11 Hz,
J = 2.94 Hz); 7.04 (d, 2 H, Ar, J = 8.1 Hz); 7.39 (d, 2 H, Ph,
J = 6.9 Hz); 7.54 (m, 3 H, Ph). MS (EI, 70 eV), m/z (Irel (%)):
276 [M – ArN=C]+ (60), 135 (100), 133 [ArN=C]+ (65), 100
(45), 90 (65). IR (KBr), ν/cm–1: 2950, 2828 (C—H), 1644, 1528,
1504, 1252 (C=S), 1032, 864, 680.
Phenyl 2ꢀ(chloro)ethaneꢀ2ꢀ{4ꢀ[(4ꢀnitrophenyl)imino]ꢀ1,3ꢀ
dithietanꢀ2ꢀylidene}dithioate (14d). The yield was 84%, yellow
crystals, m.p. 167—169 °C, Rf 0.70 (CH2Cl2). The reaction time
was 1 h. Found (%): C, 45.46; H, 2.14; N, 6.70. C16H9ClN2O2S4.
Calculated (%): C, 45.22; H, 2.13; N, 6.59. 1H NMR (CDCl3),
δ: 7.18 (d, 2 H, Ar, J = 8.8 Hz); 7.39 (d, 2 H, Ph, J = 5.5 Hz);
7.54 (m, 3 H, Ph); 8.30 (d, 2 H, Ar, J = 8.4 Hz). MS (EI, 70 eV),
m/z (Irel (%)): 276 [M – ArN=C]+ (47), 148 [ArN=C]+ (28),
135 (95), 100 (60), 77 (65), 51 (100). IR (KBr), ν/cm–1: 3096,
1584, 1512 (NO2), 1348 (NO2), 1208 (C=S), 1032, 744, 680.
4ꢀEthylꢀ5ꢀ[4({(4ꢀmethylphenyl)sulfonyl}methylimino)ꢀ1,3ꢀ
dithietanꢀ2ꢀylidene]ꢀ5,6ꢀdihydroꢀ3H,4Hꢀ[1,2]dithiolo[3,4ꢀb]ꢀ
[1,4]thiazine 3,6ꢀdithione (15a). The yield was 61%, black crysꢀ
tals, m.p. 59—61 °C, Rf 0.05 (CH2Cl2). The reaction time was
3 h. Found (%): C, 38.39; H, 2.54; N, 5.35. C17H14N2O2S8.
Calculated (%): C, 38.18; H, 2.64; N, 5.24. 1H NMR (CDCl3),
δ: 1.20 (t, 3 H, CH3CH2, J = 7.2 Hz); 2.46 (s, 3 H, CH3); 3.23
and 4.03 (both br.s, 1 H each, CH2CH3); 4.69 (br.s, 2 H, CH2);
7.39 and 7.81 (both d, 2 H each, Ph, J = 7.8 Hz). 13C NMR
(CDCl3), δ: 205.2 (C=S), 203.3 (C=S), 156.0, 155.2, 154.9,
2ꢀ(Chloro)ethaneꢀ2ꢀ[({(4ꢀmethylphenyl)sulfonyl}ꢀ
methylimino)ꢀ1,3ꢀdithietanꢀ2ꢀylidene]thioyl chloride (13a). The
yield was 92%, yellow crystals, m.p. 135—136 °C, Rf 0.38
(CH2Cl2). The reaction time was 3 h. Found (%): C, 36.38;
H, 2.00; S, 31.72; Cl, 17.54. C12H9Cl2NO2S4. Calculated (%):
1
C, 36.18; H, 2.28; S, 32.20; Cl, 17.80. H NMR (CDCl3), δ:
2.47 (s, 3 H, CH3); 4.70 and 4.78 (both s, 2 H); 7.40 (d, 2 H, Ar,
J = 8.1 Hz); 7.81 (d, 2 H, Ar, J = 8.8 Hz). MS (EI, 70 eV), m/z
(Irel (%)): 202 [M – ArN=C]+ (75), 155 [Ts]+ (80), 91 (100).
IR (KBr), ν/cm–1: 2984 (C—H), 1668, 1508, 1316, 1244 (C=S),
1144, 1008, 684.
2ꢀ(Chloro)ethaneꢀ2ꢀ[4ꢀ(phenylimino)ꢀ1,3ꢀdithietanꢀ
2ꢀylidene]thioyl chloride (13b). The yield was 72%, brown crysꢀ
tals, m.p. 99—101 °C, Rf 0.88 (CH2Cl2). The reaction time was
1 h. Found (%): C, 39.15; H, 1.51; N, 4.53. C10H5Cl2NS3.
Calculated (%): C, 39.22; H, 1.65; N, 4.57. 1H NMR (CDCl3),
δ: 7.07 (d, 2 H, Ph, J = 7.3 Hz); 7.29 (t, 1 H, Ph, J = 7.3 Hz);
7.43 (t, 2 H, Ph, J = 7.8 Hz). MS (EI, 70 eV), m/z (Irel (%)):
202 [M – PhN=C]+ (25), 135 (30), 103 [PhN=C]+ (100), 76
(80). IR (KBr), ν/cm–1: 1680, 1644, 1500, 1256 (C=S), 1004,
748, 688.
2ꢀ(Chloro)ethaneꢀ2ꢀ{4ꢀ[(4ꢀmethoxyphenyl)imino]ꢀ1,3ꢀdiꢀ
thietanꢀ2ꢀylidene}thioyl chloride (13c). The yield was 72%, brown
crystals, m.p. 117—120 °C, Rf 0.80 (CH2Cl2). The reaction time
was 15 min. Found (%): C, 39.09; H, 1.97; N, 4.03. C11H7Cl2NOS3.
Calculated (%): C, 39.29; H, 2.10; N, 4.17. 1H NMR (CDCl3),
δ: 3.83 (s, 3 H); 6.94 (d, 2 H, Ar, J = 8.8 Hz); 7.04 (d, 2 H, Ar,
J = 9.3 Hz). MS (EI, 70 eV), m/z (Irel (%)): 202 [M – ArN=C]+
(87), 133 [ArN=C]+ (90), 103 (100), 90 (95). IR (KBr), ν/cm–1
:
2
2960, 2836 (C—H), 1648, 1596, 1496, 1244 (C=S), 1004, 864, 680.
2ꢀ(Chloro)ethaneꢀ2ꢀ{4ꢀ[(4ꢀnitrophenyl)imino]ꢀ1,3ꢀdithietanꢀ
2ꢀylidene}thioyl chloride (13d). The yield was 85%, brown crysꢀ
tals, m.p. 154—156 °C, Rf 0.75 (CH2Cl2). The reaction time was
30 min. Found (%): C, 34.24; H, 1.03; N, 7.67. C10H4Cl2N2O2S3.
Calculated (%): C, 34.19; H, 1.15; N, 7.98. 1H NMR (CDCl3),
δ: 7.18 and 8.30 (both d, 2 H each, Ar, J = 8.8 Hz). MS (EI,
70 eV), m/z (Irel (%)): 202 [M – ArN=C]+ (40), 148 [ArN=C]+
(30), 103 (85), 64 (95), 35 (100). IR (KBr), ν/cm–1: 3096 (C—H),
1584, 1508 (NO2), 1348 (NO2), 1244 (C=S), 1020, 752, 688.
Phenyl 2ꢀ(chloro)ethaneꢀ2ꢀ[4({(4ꢀmethylphenyl)sulfonyl}ꢀ
methylimino)ꢀ1,3ꢀdithietanꢀ2ꢀylidene]dithioate (14a). The yield
was 84%, brown crystals, m.p. 137—138 °C, Rf 0.33 (CH2Cl2).
The reaction time was 5 h. Found (%): C, 45.76; H, 2.88;
N, 2.94. C18H14ClNO2S5. Calculated (%): C, 45.79; H, 2.99;
145.6, 143.8, 134.2, 133.9 (7 Csp ), 129.9 and 128.9 (2 C—HAr),
73.6 (CH2), 48.8 (CH2CH3), 21.6 (CH3), 13.5 (CH2CH3).
MS (EI, 70 eV), m/z (Irel (%)): 339 [M – ArCH2N=C]+ (20),
195 (15), 155 (40), 91 (100). IR (KBr), ν/cm–1: 2943 (C—H),
1505, 1324, 1281, 1259 (C=S), 1121, 765.
4ꢀEhylꢀ5ꢀ[4ꢀ(phenylimino)ꢀ1,3ꢀdithietanꢀ2ꢀylidene]ꢀ5,6ꢀ
dihydroꢀ3H,4Hꢀ[1,2]dithiolo[3,4ꢀb][1,4]thiazine 3,6ꢀdithione
(15b). The yield was 42%, black crystals, m.p. 49—51 °C, Rf 0.80
(CH2Cl2). The reaction time was 2 h. Found (%): C, 40.81;
H, 2.32; N, 6.48. C15H10N2S7. Calculated (%): C, 40.69;
H, 2.28; N, 6.33. 1H NMR (CDCl3), δ: 1.21 (t, 3 H, CH2CH3,
J = 7.2 Hz); 3.29 (br.s, 2 H, CH2CH3); 7.05 (d, 2 H, Ph,
J = 7.2 Hz); 7.25 (t, 1 H, Ph, J = 7.5 Hz); 7.40 (d, 2 H, Ph,
J = 7.5 Hz). MS (EI, 70 eV), m/z (Irel (%)): 339 [M – PhN=C]+
(10), 135 (90), 77 (100). IR (KBr), ν/cm–1: 2965, 2925 (C—H),
1498, 1310, 1283, 1265 (C=S), 1011, 781.
1
N, 2.97. H NMR (CDCl3), δ: 2.46 (s, 3 H, CH3); 4.68 and
4.74 (both s, 2 H); 7.40 (m, 4 H, Ar); 7.54 (m, 3 H, Ar); 7.79
(d, 2 H, Ar, J = 8.8 Hz). MS (EI, 70 eV), m/z (Irel (%)): 276
[M – ArN=C]+ (30), 155 [Ts]+ (50), 135 (40), 91 (100). IR
(KBr), ν/cm–1: 2944 (C—H), 1672, 1536, 1324, 1288 (C=S),
1148, 1008, 676.
Phenyl 2ꢀ(chloro)ethaneꢀ2ꢀ[4ꢀ(phenylimino)ꢀ1,3ꢀdithietanꢀ
2ꢀylidene]dithioate (14b). The yield was 73%, yellow crystals,
m.p. 87—89 °C, Rf 0.78 (CH2Cl2). The reaction time was 2 h.
Found (%): C, 50.68; H, 2.54; N, 3.72. C16H10ClNS4. Calcuꢀ
lated (%): C, 50.57; H, 2.65; N, 3.69. 1H NMR (CDCl3), δ: 7.07
(d, 2 H, Ph, J = 7.3 Hz); 7.41 (m, 5 H, Ph); 7.54 (m, 3 H, Ph).
Ethyl Nꢀ[4ꢀethylꢀ4ꢀ(3,6ꢀdithioxoꢀ3H,4Hꢀ[1,2]dithioloꢀ
[3,4ꢀd][1,4]thiazinꢀ5(6H)ꢀylidene)ꢀ1,3ꢀdithietanꢀ2ꢀylidene]ꢀ
glycinate (15e). The yield was 39%, black crystals, m.p. 48—50 °C,
Rf 0.30 (CH2Cl2). The reaction time was 3 h. Found (%):
C, 34.61; H, 2.73; N, 6.32. C13H12N2O2S7. Calculated (%):
1
C, 34.49; H, 2.67; N, 6.19. H NMR (CDCl3), δ: 1.20 (t, 3 H,
CH2CH3, J = 7.2 Hz); 1.30 (t, 3 H, CH2CH3, J = 6.9 Hz); 3.99
(m, 2 H, CH2CH3); 4.21 (s, 2 H, CH2); 4.27 (m, 2 H, CH2CH3).
13C NMR (CDCl3), δ: 204.5 (C=S), 203.5 (C=S), 167.6, 155.4,
2
149.4, 148.9, 144.1, 134.1 (6 Csp ), 61.8 (CH2), 55.2 (CH2),
48.8 (CH2), 14.1 (CH3), 13.7 (CH3). MS (EI, 70 eV), m/z

436
Russ.Chem.Bull., Int.Ed., Vol. 58, No. 2, February, 2009
Ogurtsov et al.
Table 4. Principal crystallographic characteristics and the Xꢀray
data collection and refinement statistics for compound 14a
2. U. Zoller, in Comprehensive Heterocyclic Chemistry II, Ed. A.
Padwa, Pergamon, Oxford, 1996, 1, Ch. 1.35, 1113.
3. S. Ohya, T. Miyadera, M. Yamazaki, Antimicrob. Agents
Chemother., 1982, 21, 613.
Parameter
14а
4. U. Zoller, in Small Ring Heterocycles, Ed. A. Hassner, Wiley,
New York, 1983, 42, Ch. 11, Part 1, 596.
5. M. Iwanami, T. Maeda, M. Fujimoto, Y. Nagano, N.
Nagano, A. Yamazaki, T. Shibanuma, K. Tamazawa, K.
Yano, Chem. Pharm. Bull., 1980, 28, 2629.
Molecular formula
Molecular weight
T/K
Crystal system
Space group
Z
C
18H14ClNO2S5
472.05
120
Monoclinic
P21/n
6. K. Naka, Macromolecules, 2002, 35, 3806; K. Naka,
Macromol. Rapid. Commun., 2006, 27, 2113.
4
7. P. Metzner, J. Vialle, A. Vibet, Tetrahedron, 1978, 34, 2289.
8. J. C. Martin, P. G. Gott, R. H. Meen, P. W. Raynolds, J.
Org. Chem., 1981, 46, 3911.
9. W. J. Middleton, E. G. Howard, W. H. Sharkey, J. Org.
Chem., 1965, 30, 1375.
10. J. W. Greidanus, Can. J. Chem., 1970, 48, 3530.
11. C. Th. Pedersen, Sulfur Reports, 1995, 16, 173; D. M.
McKinnon, in Comprehensive Heterocyclic Chemistry II, Ed.
I. Shinkai, Pergamon, Oxford, 1996, 3, Ch. 3.11, 593.
12. Khimicheskaya entsiklopediya [Encyclopedia of Chemistry],
Ed. I. L. Knunyants, Sovetskaya entsiklopediya, Moscow,
1990, 2, 190 (in Russian); G. D. Hartman, L. M. Weinstock,
Synthesis, 1976, 681; K. Hartke, A. Kumar, G. Henssen,
Chem. Ber., 1982, 115, 3107.
13. S. Barriga, P. Fuertes, C. F. Marcos, D. Miguel, O. A.
Rakitin, C. W. Rees, T. Torroba, J. Org. Chem., 2001, 66,
5766.
14. A. N. Vereshchagin, Induktivnyi effekt [Inductive Effect],
Nauka, Moscow, 1988, 111 p. (in Russian); C. Hansch, A.
Leo, R. W. Taft, Chem. Rev., 1991, 91, 165; M. Charton,
Progr. Phys. Org. Chem., 1981, 13, 119.
a/Å
b/Å
c/Å
β/deg
20.6834(15)
5.1168(4)
20.7833(15)
113.784(5)
2012.8(3)
1.558
3
V/Å
dcalc/g cm–3
μ/cm–1
7.23
F(000)
968
2θmax/deg
Number of measured reflections
Number of independent reflections
Number of reflections with
I > 2σ(I)
Number of refined parameters
R1
wR2
58
21008
5325
3392
245
0.0498
0.1221
1.001
GOOF
Residual electron density,
0.746/–0.397
e Å–3 (dmin/dmax
)
15. Cambridge Crystallographic Database, release 2004.
16. S. Barriga, P. Fuertes, C. F. Marcos, O. A. Rakitin, C. W.
Rees, T. Torroba, J. Org. Chem., 2002, 67, 6439.
17. L. W. Herman, V. Sharma, J. F. Kronauge, E. Barbarics, L.
A. Herman, D. PiwnicaꢀWorms, J. Med. Chem., 1995, 38,
2955.
18. R. Obrecht, R. Hermann, I. Ugi, Synthesis, 1985, 400.
19. C. W. Rees, A. J. P. White, D. J. Williams, O. A. Rakitin, C.
F. Marcos, C. Polo, T. Torroba, J. Org. Chem., 1998, 63,
2189.
20. G.ꢀJ. Wentrup, M. Koepke, F. Boberg, Synthesis, 1975, 525.
21. L. Legrand, Y. Mollier, N. Lozach, Bull. Soc. Chim. Fr.,
1953, 327.
22. G. M. Sheldrick, SHELXTLꢀ97, Version 5.10, Bruker AXS
Inc., Madison, WIꢀ53719, USA.
(Irel (%)): 339 [M – EtOCOCH2N=C]+ (100), 306 (45), 174
(50), 145 (55), 100 (90), 72 (70). IR (KBr), ν/cm–1: 2964
(C—H), 1693 (C=O), 1510, 1315, 1282, 1268 (C=S), 1080, 773.
Xꢀray diffraction study. The Xꢀray diffraction data for comꢀ
pound 14a were collected on a SMART 1000 CCD diffractoꢀ
meter (MoꢀKα radiation, graphite monochromator, ωꢀscanning
technique). Principal crystallographic characteristics and the
Xꢀray data collection and refinement statistics are given in Table 4.
The structure was solved by direct methods and refined anisoꢀ
tropically by the fullꢀmatrix leastꢀsquares method based on F 2hkl
.
The hydrogen atoms were positioned geometrically. All hydroꢀ
gen atoms were refined isotropically using a riding model. All
calculations were carried out on a PC using the SHELXTL
PLUS program package.22
References
1. A. Behr, Ber. Dtsch. Chem. Ges., 1872, 5, 970; W. Ried, H.
Klug, Chem. Ber., 1961, 94, 368.
Received June 21, 2008;
in revised form February 5, 2009