Synthesis of 5-mercapto-1,2-dithiole-3-thiones and their transformation into 5-chloro-1,2-dithiol-3-ones

Article abstract of DOI:10.1007/s11172-006-0228-9

A number of 4-dialkylamino-5-mercapto-1,2-dithiole-3-thiones were synthesized by reactions of alkyl(diisopropyl)amines with S₂Cl ₂. Their reactions with S₂Cl₂-DABCO unexpectedly gave 5-chloro-4-dialkylamino-1,2-

Full text of DOI:10.1007/s11172-006-0228-9

Russian Chemical Bulletin, International Edition, Vol. 55, No. 1, pp. 147—151, January, 2006
147
Synthesis of 5ꢀmercaptoꢀ1,2ꢀdithioleꢀ3ꢀthiones
and their transformation into 5ꢀchloroꢀ1,2ꢀdithiolꢀ3ꢀones
L. S. Konstantinova, A. A. Berezin, K. A. Lysov, and O. A. Rakitinꢀ
N. D. Zelinsky Institute of Organic Chemistry, Russian Academy of Sciences,
47 Leninsky prosp., 119991 Moscow, Russian Federation.
Fax: +7 (495) 135 5328. Eꢀmail: orakitin@ioc.ac.ru
A number of 4ꢀdialkylaminoꢀ5ꢀmercaptoꢀ1,2ꢀdithioleꢀ3ꢀthiones were synthesized by reacꢀ
tions of alkyl(diisopropyl)amines with S2Cl2. Their reactions with S2Cl2—DABCO unexpectꢀ
edly gave 5ꢀchloroꢀ4ꢀdialkylaminoꢀ1,2ꢀdithiolꢀ3ꢀones.
Key words: sulfur monochloride, 1,2ꢀdithioleꢀ3ꢀthiones, 1,2ꢀdithiolꢀ3ꢀones, alkyl(diꢀ
isopropyl)amines, DABCO.
Scheme 1
Compounds containing 3Hꢀ1,2ꢀdithioleꢀ3ꢀthione
fragment have long been known1 and are at present under
intensive study because of a broad spectrum of their bioꢀ
logical activity. Oltipraz (4ꢀmethylꢀ5ꢀ(2ꢀpyrazinyl)ꢀ1,2ꢀ
dithioleꢀ3ꢀthione), which is the most known preparation
based on 1,2ꢀdithioles, has been clinically tested in China
as a chemotherapeutic agent against liver cancer,2 while
trithioanethol [5ꢀ(4ꢀmethoxyphenyl)ꢀ3Hꢀ1,2ꢀdithioleꢀ3ꢀ
thione] has been used as a cholagogue.3 4ꢀArylꢀ5ꢀchloroꢀ
3Hꢀ1,2ꢀdithioleꢀ3ꢀthione derivatives exhibit insecticidal
properties.4
Apart from biological activities, dithiolethiones are of
interest as starting reagents for creation of novel materiꢀ
als, e.g., for preparation of tetrathiafulvalene vinylogs with
enhanced characteristics or nonlinear optical properties,5
as πꢀdonors for the synthesis of photoconductors which
can be employed for recording holograms.6
Our synthesis of 1,2ꢀdithioleꢀ3ꢀthiones under unusuꢀ
ally mild conditions is exclusive among known relevant
methods1 and provides new wide possibilities for the study
of this promising class of chemical compounds. Comꢀ
pounds 2a and 3a and their analogs obtained can be of
interest as biologically active substances and serve as the
starting reagents for the synthesis of tricyclic bis[1,2]diꢀ
thiolo[1,4]thiazines with antitumor activities.12
Here we describe the synthesis of novel 4ꢀdialkylꢀ
aminoꢀ1,2ꢀdithioleꢀ3ꢀthiones from Nꢀsubstituted diisoꢀ
propylamines and their subsequent reactions with S2Cl2.
We found that the reactions of Nꢀalkyldiisopropylꢀ
amines 1 with S2Cl2 give 4ꢀalkyl(isopropyl)aminoꢀ5ꢀ
mercaptoꢀ1,2ꢀdithioleꢀ3ꢀthiones 2 as major products in
nearly all the reactions; their yields substantially depend
on the ratio 1 : S2Cl2 (Scheme 2). With compounds 1a—c
(R = Et (1a), CH2Ph (1b), and CH2CH2CO2Et (1c)) as
examples, we showed that the optimum ratio 1 : S2Cl2
is 2.2 : 1. With a decrease in the amine content (1 : S2Cl2 =
1.8 : 1), the yield of dithiolethione 2 was lowered to
15% (2a), 5% (2b), and 2% (2c). With an increase in the
Recently, we have shown that Nꢀalkyldiisopropylꢀ
amines can be easily converted by a singleꢀstep reaction
with sulfur monochloride and 1,4ꢀdiazabicyclo[2.2.2]ocꢀ
tane (DABCO) into complex thiaꢀ and azaheterocycles
such as bis[1,2]dithiolo[1,4]thiazines,7 bis[1,2]dithioloꢀ
pyrroles,8 [1,2]dithiolothiazines,9 and bis[1,2]dithiolylꢀ
amines.10 The suggested mechanism of these reactions
involve, as a key step, transformation of the isopropyl
groups into 3ꢀchlorodithiolium salts followed by nucleoꢀ
philic substitution of oxygen or sulfur atoms (depending
on the reagent used7) for the reactive Cl atom in posiꢀ
tion 3. Going further with investigations in this area, we
demonstrated that the reaction can be stopped at the step
of formation of monocyclic 1,2ꢀdithioles (Scheme 1). The
main conditions for the successful synthesis of monoꢀ
dithioles are a low reaction temperature (0 °C), use of an
excess of the starting amine 1a, and the absence of anꢀ
other base (DABCO).11
Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 1, pp. 143—147, January, 2006.
1066ꢀ5285/06/5501ꢀ0147 © 2006 Springer Science+Business Media, Inc.

148
Russ.Chem.Bull., Int.Ed., Vol. 55, No. 1, January, 2006
Konstantinova et al.
Scheme 3
amine content (1 : S2Cl2 = 2.5 : 1), the yield of product 2
did not decrease significantly; however, the formation of
considerable amounts of dithiolethiones 3 hinders chroꢀ
matographic isolation of the final products.
Scheme 2
Reagents and conditions: 1) 0 °C, 3 days; 2) HCO2H, ∆, 1 h.
Comꢀ
R
Yield (%)
pound
2a
2b
2c
2d
2e
Et
CH2Ph
CH2CH2CO2Et
CH2CH2CN
CH2CH2N3
22
24
37
13
11
The formation of thiones in this reaction is rather
unexpected since formic acid is known to transform
dithiolium salts into 1,2ꢀdithiolꢀ3ꢀones.7 This suggests
that 3ꢀchlorodithiolium salts 4 formed7 in reactions of
amines 1 with S2Cl2 are subsequently chlorinated with
S2Cl2 to 3,5ꢀdichlorodithiolium salts 5, which then are
sulfonated with nucleophilic species 6 (see Ref. 11) to
successively give chloro thione 7 and intermediate 8.
Treatment of the latter with HCO2H yields final mercaptoꢀ
dithiolethione 2 (Scheme 3).
Scheme 4
Interesting results were obtained in the reactions of
two other substituted diisopropylamines 1f,g with S2Cl2.
Instead of the expected mercaptodithiolethiones, we isoꢀ
lated dithiolothiazine 8 (Scheme 4). Presumably, the reꢀ
action intermediates are thiones 2f,g, which then convert
into bicyclic structure 9, via elimination of HCl or
phthalimide, respectively.
The structures of thiones 2 and dithiolothiazine 9 were
proven by elemental analysis data, 1H and 13C NMR, IR,
and mass spectra, and highꢀresolution mass spectra.
Mercaptodithiolethiones 2 were employed in reactions
with a mixture of S2Cl2 and DABCO under the condiꢀ
tions for the formation of tricyclic bis(dithiolo)thiazines
10 from substituted diisopropylamines 1 (see Ref. 7). Howꢀ
ever, contrary to the expectations, 5ꢀchlorodithiolꢀ3ꢀones
11 were obtained in high yields from all compounds but 2a
(R = Et) (Scheme 5).
The yield of compound 9 was 33 (from 1f) and 21% (from 1g).
It should be noted that the transformations of
5ꢀmercaptoꢀ1,2ꢀdithioleꢀ3ꢀthiones into 5ꢀchloroꢀ1,2ꢀ
dithiolꢀ3ꢀones have not been reported hitherto. Apparꢀ
ently, the most probable precursor of compounds 11 can
be dichlorodithiolium salt 5, which reacts with HCO2H

Synthesis of 5ꢀmercaptoꢀ1,2ꢀdithioleꢀ3ꢀthiones
Russ.Chem.Bull., Int.Ed., Vol. 55, No. 1, January, 2006
149
Scheme 5
Experimental
1
H and 13C NMR spectra were recorded on Bruker WMꢀ250
and Bruker AMꢀ300 instruments (250 and 300 (1H) and 62.5
and 75 MHz (13C), respectively) in CDCl3. Chemical shifts are
given on the δ scale relative to Me4Si. Melting points were
determined on a Kofler hot stage and are given uncorrected.
Mass spectra were recorded on a Finnigan MAT INCOS 50
instrument (EI).
The starting substituted diisopropylamines 1b,14 1c,15 1d,16
1e,11 1f,11 and 1g (see Ref. 17) were prepared according to
available procedures.
Reactions of substituted diisopropylamines 1 with S2Cl2 (genꢀ
eral procedure). A solution of S2Cl2 (0.4 mL, 5 mmol) in chloroꢀ
form (2 mL) was added dropwise at –15 to –20 °C to a solution
of amine 1 in chloroform (12 mL). The mixture was left in a
refrigerator at 0 °C for 72 h. Formic acid (1.9 mL, 50 mmol) was
added dropwise at 0 °C and then the temperature was slowly
raised to 20 °C. The reaction mixture was refluxed for 1 h and
filtered and the precipitate was washed with CH2Cl2. The comꢀ
bined mother liquor was concentrated at reduced pressure and
the residue was chromatographed on Merck 60 silica gel with
CH2Cl2—light petroleum as the eluent.
4ꢀ[Ethyl(isopropyl)amino]ꢀ5ꢀmercaptoꢀ3Hꢀ1,2ꢀdithioleꢀ3ꢀ
thione (2a) was obtained as a yellow oil in 22% yield. Its spectroꢀ
scopic characteristics are identical with the literature data.11
4ꢀ[Benzyl(isopropyl)amino]ꢀ5ꢀmercaptoꢀ3Hꢀ1,2ꢀdithioleꢀ3ꢀ
thione (2b). The yield was 24%, m.p. 160—163 °C. Found (%):
C, 49.87; H, 5.14, N, 4.54. C13H15NS4. Calculated (%): C, 49.80;
H, 4.82; N, 4.47. 1H NMR (CDCl3), δ: 1.33, 1.73 (both d,
3 H each, CH3, J = 6.4 Hz); 4.61 (m, 1 H, CH2Ph); 5.11 (sept,
1 H, CHMe2, J = 6.4 Hz); 5.88 (m, 1 H, CH2Ph); 7.35 (m, 5 H,
Ar); 9.10 (s, 1 H, SH). 13C NMR (CDCl3), δ: 19.1 and 20.6
(2 Me); 54.2 (CH2Ph); 58.1 (CHMe2); 128.7, 130.3, and 130.5
(3 C—H); 128.6, 134.2, 194.0, and 198.9 (sp2 of the quaternary
C atoms). MS (EI, 70 eV), m/z (Irel (%)): 313 [M]+ (95), 270
(15), 222 (100), 91 (18). Found: m/z 313.0085 [M]+. C13H15NS4.
Calculated: 313.0087.
Reagents and conditions: 1) ∼20 °C, 3 days; 2) HCO2H, ∆, 1 h.
Compound
R
Yield (%)
11b
11c
11d
11e
CH2Ph
80
94
91
77
CH2CH2CO2Et
CH2CH2CN
CH2CH2N3
to give chloro ketone 11 as has been described earlier.11
The formation of this salt seems to involve a double elecꢀ
trophilic attack of mercaptodithiolethione 2 and derived
chloro thione 7 by complex 12 (see Ref. 11; Scheme 6).
In the case of compound 2a (R = Et), we failed to
isolate the corresponding chloro ketone 11a. TLC analyꢀ
sis of the reaction mixture detected a product with an
Rf value close to those of ketones 11b—e; however, this
product decomposed on attempted isolation.
The chloro ketones 11 obtained are of interest as subꢀ
stances with potential biological (anticancer) activities
since they are structurally similar to biologically active
chloro ketones13 and as synthons for their subsequent
transformations, e.g., by nucleophilic substitution for the
Cl atom in position 5. We also found that mercaptoꢀ
dithiolethiones 2 cannot be intermediates in the synthesis
of tricyclic bis(dithiolo)thiazines 10 from substituted
diisopropylamines 1.
NꢀIsopropylꢀNꢀ(5ꢀmercaptoꢀ3ꢀthioxoꢀ3Hꢀ1,2ꢀdithiolꢀ4ꢀyl)ꢀ
βꢀalanine ethyl ester (2c). The yield was 37%, m.p. 40—42 °C.
Found (%): C, 40.67; H, 5.51, N, 4.29. C11H17NO2S4. Calcuꢀ
lated (%): C, 40.84; H, 5.30; N, 4.33. 1H NMR (CDCl3), δ: 1.26
Scheme 6

150
Russ.Chem.Bull., Int.Ed., Vol. 55, No. 1, January, 2006
Konstantinova et al.
(d, 6 H, (CH3)2CH), J = 6.6 Hz); 1.68 (d, 3 H, CH3CH2, J =
6.6 Hz); 2.53 (t, 2 H, CH2CH2, J = 3.9 Hz); 3.80 (m, 1 H,
CH2CH2); 4.17 (m, 2 H, CH2CH2); 5.03 (sept, 1 H, CHMe2,
J = 6.6 Hz); 5.07 (m, 1 H, CH2CH2); 8.90 (s, 1 H, SH).
13C NMR (CDCl3), δ: 14.1, 18.8 and 19.9 (3 Me); 29.3, 45.3,
and 61.8 (3 CH2); 58.4 (CHMe2); 133.6, 171.0, 193.9, and 199.6
(sp2 of the quaternary C atoms). MS (EI, 70 eV), m/z (Irel (%)):
323 [M]+ (100), 290 (37), 222 (25), 192 (45), 160 (40), 101 (42),
43 (88). Found: m/z 323.0131 [M]+. C11H17NO2S4. Calculated:
323.0142.
CH2Ph); 7.26 (m, 5 H, Ar). 13C NMR (CDCl3), δ: 21.6 (2 Me);
50.1 (CHMe2); 54.2 (CH2Ph); 127.1, 128.2, and 128.6 (3 C—H);
137.9, 139.1, 153.9, and 187.8 (sp2 of the quaternary C atoms).
MS (EI, 70 eV), m/z (Irel (%)): 299 [M]+ (8), 256 (18), 91
(100). Found: m/z 299.0197 [M]+. C13H14ClNOS2. Calculated:
299.0205.
Nꢀ(5ꢀChloroꢀ3ꢀoxoꢀ3Hꢀ1,2ꢀdithiolꢀ4ꢀyl)ꢀNꢀisopropylꢀβꢀalaꢀ
nine ethyl ester (11c), a yellow oil. The yield was 94%. Found (%):
C, 42.69; H, 5.42, N, 4.48. C11H16ClNO3S2. Calculated (%):
1
C, 42.64; H, 5.21; N, 4.52. H NMR (CDCl3), δ: 1.12 (d, 6 H,
3ꢀ[Isopropyl(5ꢀmercaptoꢀ3ꢀthioxoꢀ3Hꢀ1,2ꢀdithiolꢀ4ꢀyl)amiꢀ
no]propanenitrile (2d). The yield was 13%, m.p. 150—152 °C.
Found (%): C, 39.12; H, 4.35, N, 10.17. C9H12N2S4. Calcuꢀ
(CH3)2CH, J = 6.6 Hz); 1.26 (d, 3 H, CH3CH2, J = 6.6 Hz);
2.34 (t, 2 H, CH2, J = 6.6 Hz); 3.40 (sept, 1 H, CHMe2, J =
6.6 Hz); 3.45, 4.11 (both t, 2 H each, CH2, J = 7.3 Hz). 13C NMR
(CDCl3), δ: 14.3 and 21.6 (3 Me); 35.0, 41.8, and 60.5 (3 CH2);
53.9 (CHMe2); 137.3, 154.6, 172.1, and 187.6 (sp2 of the quaꢀ
ternary C atoms). MS (EI, 70 eV), m/z (Irel (%)): 309 [M]+ (72),
294 (95), 222 (100), 180 (97), 101 (56). Found: m/z 309.0256
[M]+. C11H16ClNO3S2. Calculated: 309.0260.
3ꢀ[5ꢀChloroꢀ3ꢀoxoꢀ3Hꢀ1,2ꢀdithiolꢀ4ꢀyl(isopropyl)amiꢀ
no]propanenitrile (11d), a yellow oil. The yield was 91%.
Found (%): C, 41.25; H, 4.41, N, 10.57. C9H11ClN2OS2. Calꢀ
culated (%): C, 41.14; H, 4.22; N, 10.66. 1H NMR (CDCl3), δ:
1.15 (d, 6 H, (CH3)2CH, J = 5.9 Hz); 2.36 (t, 2 H, CH2, J =
6.6 Hz); 3.39 (sept, 1 H, CHMe2, J = 5.9 Hz); 3.43 (t, 2 H,
CH2, J = 6.6 Hz). 13C NMR (CDCl3), δ: 19.2 (Me); 29.7 and
42.2 (2 CH2); 54.2 (CHMe2); 118.3 (CN); 136.7, 156.1, and
187.8 (sp2 of the quaternary C atoms). MS (EI, 70 eV),
m/z (Irel (%)): 262 [M]+ (36), 247 (48), 180 (76), 79 (79), 41
(100). Found: m/z 262.0003 [M]+. C9H11ClN2OS2. Calculated:
262.0001.
4ꢀ[2ꢀAzidoethyl(isopropyl)amino]ꢀ5ꢀchloroꢀ3Hꢀ1,2ꢀdithiolꢀ
3ꢀone (11e), a yellow oil. The yield was 77%. Found (%):
C, 41.32; H, 4.05, N, 20.46. C8H11ClN4OS2. Calculated (%):
C, 41.14; H, 3.98; N, 20.10. 1H NMR (CDCl3), δ: 1.12 (d,
6 H, (CH3)2CH, J = 6.5 Hz); 3.17, 3.29 (both m, 2 H each,
CH2); 3.35 (sept, 1 H, CHMe2, J = 6.5 Hz). 13C NMR (CDCl3),
δ: 21.5 (Me); 45.0 and 50.8 (2 CH2); 54.3 (CHMe2); 137.0,
154.9, and 187.4 (sp2 of the quaternary C atoms). MS (EI,
70 eV), m/z (Irel (%)): 278 [M]+ (10), 222 (69), 180 (100).
Found: m/z 278.0060 [M]+. C8H11ClN4OS2. Calculated:
278.0063.
1
lated (%): C, 39.10; H, 4.37; N, 10.13. H NMR (CDCl3), δ:
1.22 (d, 6 H, (CH3)2CH, J = 6.6 Hz); 2.53 (t, 2 H, CH2, J =
6.6 Hz); 3.25 (m, 1 H, CH2); 3.81 (sept, 1 H, CHMe2, J =
6.6 Hz); 4.18 (m, 1 H, CH2); 8.95 (s, 1 H, SH). 13C NMR
(CDCl3), δ: 19.2 (Me); 29.7 and 43.6 (2 CH2); 53.3 (CHMe2);
118.7 (CN); 147.5, 174.3, and 208.0 (sp2 of the quaternary
C atoms). MS (EI, 70 eV), m/z (Irel (%)): 276 [M]+ (76),
240 (20), 192 (56), 160 (45), 100 (54), 43 (100). Found:
m/z 275.9878 [M]+. C9H12N2S4. Calculated: 275.9883.
4ꢀ[2ꢀAzidoethyl(isopropyl)amino]ꢀ5ꢀmercaptoꢀ3Hꢀ1,2ꢀdiꢀ
thioleꢀ3ꢀthione (2e). The yield was 11% (yellow oil). Found (%):
C, 32.72; H, 4.18, N, 19.33. C8H12N4S4. Calculated (%):
C, 32.86; H, 4.14; N, 19.16. 1H NMR (CDCl3), δ: 1.16 (d, 6 H,
(CH3)2CH, J = 6.6 Hz); 3.25, 3.32 (both q, 2 H each, CH2CH2,
J = 5.9 Hz); 3.91 (sept, 1 H, CHMe2, J = 6.6 Hz); 7.92 (s, 1 H,
SH). 13C NMR (CDCl3), δ: 18.7 and 20.0 (2 Me); 30.0 and 46.6
(2 CH2); 59.0 (CHMe2); 134.2, 194.1, and 199.2 (sp2 of the
quaternary C atoms). MS (EI, 70 eV), m/z (Irel (%)): 292 [M]+
(100), 236 (21), 206 (54), 194 (75), 160 (28). Found:
m/z 291.9934 [M]+. C8H12N4S4. Calculated: 291.9944.
4 ꢀ I s o p r o p y l ꢀ 5 , 6 ꢀ d i h y d r o ꢀ 3 H , 4 H ꢀ [ 1 , 2 ] d i t h i o ꢀ
lo[3,4ꢀb][1,4]thiazineꢀ3ꢀthione (9), a yellow oil. The yield was
33 (from 1f) and 21% (from 1g). Found (%): C, 38.75; H, 4.38,
N, 5.51. C8H11NS4. Calculated (%): C, 38.52; H, 4.45; N, 5.62.
1H NMR (CDCl3), δ: 1.16 (d, 6 H, Me2C H, J = 6.7 Hz);
2.92, 3.40 (both t, 2 H each, CH2, J = 4.9 Hz); 4.59 (sept,
1 H, CHMe2, J = 6.7 Hz). 13C NMR (CDCl3), δ: 22.0 (2 Me);
24.6 and 41.3 (2 CH2); 50.0 (CHMe2); 145.0, 153.4 and
205.3 (sp2 of the quaternary C atoms). MS (EI, 70 eV),
m/z (Irel (%)): 249 [M]+ (65), 234 (28), 206 (90), 149 (58),
41 (100).
We are grateful to Prof. C. W. Rees (Imperial College,
London, UK) for discussing the results obtained.
This work was financially supported by the Russian
Foundation for Basic Research (Project No. 05ꢀ03ꢀ
32032).
Reactions of dithiolethiones 2 with S2Cl2 and DABCO (genꢀ
eral procedure). A solution of S2Cl2 (0.16 mL, 2 mmol) in chloꢀ
roform (1 mL) was added dropwise at –40 to –45 °C to a soluꢀ
tion of amine 1 (0.2 mmol) and DABCO (0.11 g, 1 mmol) in
chloroform (7 mL). The mixture was left at room temperature
for 72 h. Formic acid (0.375 mL, 10 mmol) was added dropwise
at 0 °C and the temperature was slowly raised to 20 °C. Then the
mixture was refluxed for 1 h and filtered and the precipitate was
washed with CH2Cl2. The combined mother liquor was concenꢀ
trated at reduced pressure and the residue was chromatographed
on Merck 60 silica gel with CH2Cl2—light petroleum as the
eluent.
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Synthesis of 5ꢀmercaptoꢀ1,2ꢀdithioleꢀ3ꢀthiones
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Received October 28, 2005;
in revised form December 19, 2005