Unexpected reaction of 2-chloro-1-propen-3-yl isothiuronium chloride with potassium ditelluride: the first example of vicinal elimination of chlorine and sulfur-bearing moieties

Article abstract of DOI:10.1080/17415993.2012.710909

2-Chloro-1-propen-3-yl isothiuronium chloride reacts with potassium ditelluride in hydrazine hydrate to afford elemental tellurium and allene. The latter is formed due to the vicinal elimination of chlorine and a sulfur-bearing moiety.

Full text of DOI:10.1080/17415993.2012.710909

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Unexpected reaction of 2-chloro-1-
propen-3-yl isothiuronium chloride with
potassium ditelluride: the first example
of vicinal elimination of chlorine and
sulfur-bearing moieties
Ekaterina P. Levanova a , Valentina A. Grabelnykh a , Alexander V.
Elaev a , Alexander I. Albanov a , Lyudmila V. Klyba a , Natalia V.
Russavskaya a , Olga A. Tarasova a , Igor B. Rozentsveig a & Nikolai
A. Korchevin a
a A.E. Favorsky Irkutsk Institute of Chemistry, Siberian Branch,
Russian Academy of Sciences, 1 Favorsky Street, Russia
Version of record first published: 17 Sep 2012.
To cite this article: Ekaterina P. Levanova, Valentina A. Grabelnykh, Alexander V. Elaev, Alexander
I. Albanov, Lyudmila V. Klyba, Natalia V. Russavskaya, Olga A. Tarasova, Igor B. Rozentsveig &
Nikolai A. Korchevin (2012): Unexpected reaction of 2-chloro-1-propen-3-yl isothiuronium chloride
with potassium ditelluride: the first example of vicinal elimination of chlorine and sulfur-bearing
moieties, Journal of Sulfur Chemistry, DOI:10.1080/17415993.2012.710909
To link to this article: http://dx.doi.org/10.1080/17415993.2012.710909
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Journal of Sulfur Chemistry
iFirst, 2012, 1–7
Unexpected reaction of 2-chloro-1-propen-3-yl isothiuronium
chloride with potassium ditelluride: the first example of vicinal
elimination of chlorine and sulfur-bearing moieties
Ekaterina P. Levanova, Valentina A. Grabelnykh, Alexander V. Elaev, Alexander I. Albanov,
Lyudmila V. Klyba, Natalia V. Russavskaya, Olga A. Tarasova, Igor B. Rozentsveig* and
Nikolai A. Korchevin
A.E. Favorsky Irkutsk Institute of Chemistry, Siberian Branch, Russian Academy of Sciences, 1 Favorsky
Street, Russia
(Received 29 May 2012; final version received 7 July 2012)
2-Chloro-1-propen-3-yl isothiuronium chloride reacts with potassium ditelluride in hydrazine hydrate to
afford elemental tellurium and allene. The latter is formed due to the vicinal elimination of chlorine and a
sulfur-bearing moiety.
Cl
NH2
K2Te2
–
S
Cl
+
H2C
C CH2
-Te
NH2
Keywords: isothiuronium salt; elimination; allene; hydrazine hydrate; tellurium
1. Introduction
The reaction of mild nucleophiles (e.g. chalcogene-containing anions) with 1,2-dihalogen deriva-
tivesofalkanesoralkenesmayinvolve, apartfromclassicalnucleophilicsubstitution, thereductive
elimination of both halogen atoms in the form of halogenide anions with simultaneous oxidation
of the attacking reagent. For tellurium-containing anions, the latter direction is preferable (1),
while for selenium and sulfur derivatives, the direction of the reaction (substitution or elimina-
tion) depends on the structure of the dihalogenide, the nature of the attacking anion, the solvent
employed (2), and the phase-transfer catalysts used, which in some cases can favor substitution (3)
and in other cases facilitates elimination (4). Halogen atoms attached to sp3-hybridized carbons
are known to undergo elimination most easily. However, we have shown that the reaction of potas-
sium ditelluride with 2,3-dichloro-1-propene can lead to the elimination of the chlorine atoms
from both the sp3-hybridized and sp2-hybridized carbons (5). Elimination can also be observed
*Corresponding author. Email: i_roz@irioch.irk.ru
ISSN 1741-5993 print/ISSN 1741-6000 online
© 2012 Taylor & Francis
http://dx.doi.org/10.1080/17415993.2012.710909
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2
E.P. Levanova et al.
in the presence of other leaving groups, such as halogen or oxygen incorporated into the oxirane
entity (6), tosylate moiety and oxirane fragment (7). It has even been reported (8) during the reac-
tion of potassium selenocyanate with 2-bromoethanol derivatives that the elimination of bromine
and the hydroxide anion occurs. To the best of our knowledge, examples of sulfur-containing
functional group elimination in reactions of this type are absent in the literature.
As part of our research exploring the reactivity of chlorine at sp2-hybridized carbon atoms in
derivatives of 2,3-dichloro-1-propene 1, we have synthesized isothiuronium salt 2 from compound
1.As expected, the salt is formed only by attack at the chlorine atom attached to the sp3-hybridized
carbon. Isothiuronium salts and their derivatives are known to possess unique biological and
chemical properties, and their biological activity is mainly determined by their ability to react
with the SH function of protein molecules (9).
2. Results and discussion
We have studied the behavior of isothiuronium salt 2 in the reaction with potassium ditelluride,
a milder nucleophile as compared to thiol derivatives. Potassium ditelluride was prepared from
elemental tellurium and potassium hydroxide in hydrazine hydrate, the Te:KOH molar ratio being
1:1 (10) (Scheme 1).
2K2Te2+N2+5H2O
4Te+4KOH+N2H4 H2O
Scheme 1. A synthesis of potassium ditelluride.
The addition of isothiuronium salt 2 to the reaction mixture formed during generation of
K2Te2 (Scheme 1) unexpectedly led to the quantitative regeneration of elemental tellurium and
formation of allene (the yield was 67% calculated by isothiuronium salt consumed) (Scheme 2).
The formation of allene and elemental tellurium under the mild conditions (see Section 4) used in
this reaction is indicative of an easy elimination of the chlorine and sulfur group in the vicinally
substituted propenyl fragment of compound 2.
S
Cl
NH2
+
NH2
H2N
NH2
K2Te2
-Te
Cl–
+
Cl
H2C
CH2
C
S
2
Cl
1
Scheme 2. A synthesis of isothiuronium salt 2 and allene.
Despiteallattempts, wefailedtodetectthioureaamongthereactionproducts.Afterseparationof
alleneandtellurium, thereactionmixturewastreatedwith1-iodobutane, whereupondibutylsulfide
3(yield14%calculatedbyisothiuroniumsaltconsumed), dibutyldisulfide 4(31%), butylhydrazine
5, and, presumably, dibutylhydrazines 6 (total yield 54% based on the amount of BuI consumed)
were formed. Butylhydrazine 5 was isolated from the reaction mixture and characterized by
NMR. The reaction of 1-iodobutane with thiourea, dissolved in hydrazine hydrate (blank run),
furnished sulfide 3 and disulfide 4 in trace amounts, in contrast to the larger amounts of substituted
butylhydrazines that were the major reaction products.

Journal of Sulfur Chemistry
3
Several alternative ways for allene formation are shown in Schemes 3–9. They differ in the
direction of the nucleophilic attack by Te22−-nucleophile. The possible electrophilic centers in the
structure of isothiuronium salt 2 are the carbon atoms bonded to the sulfur atom (ways a and b,
Scheme 3) and the chlorine atom conjugated with the unsaturated bond (way c, Scheme 3).
c
b
Cl
NH2
+
NH2
Cl–
S
2
a
Scheme 3. The possible directions of the nucleophilic attack by Te22−-nucleophile.
If Te22−-nucleophile attacks the carbon atom of CH2–S – fragment (direction a), a molecule of
thiourea is expected to be eliminated followed by an intramolecular cyclization of intermediate
anion 7 into unstable methylenetellurirane 8 or methyleneditelluretane 9, which in turn eliminate
tellurium to produce allene (Scheme 4).
H2C
H2C
C
CH2
CH2
– Te
– Cl–
Te
–Te
Cl
Te22–
Te22–
2
8
–SC(NH2)2, – Cl–
7
C
– Cl–
–2Te
Te–Te
9
Scheme 4. The formation of allene according to the direction a.
A similar mechanism of elimination is discussed in the papers (7, 8). However, the formation
of heterocycles 8 and 9 from intermediate 7 requires a stage of a nucleophilic substitution of the
chlorine atom bonded to sp2-hybridized carbon atom. A substitution of such type is known to
proceed with difficulty. So, one can suggest another path of allene formation from intermediate
7: intramolecular halophilic attack of the chlorine atom with the tellurane moiety, as shown in
Scheme 5.
Te–
Cl
–
Te2Cl
+H2C=
C=CH2
7
Te
Scheme 5. Intramolecular halophilic attack of the chlorine atom with the tellurane moiety.
As opposed to the direction a, we determined by an independent experiment that the formation
of thiourea could not lead to the essential quantity of dibutylsulfide 3 and dibutyldisulfide 4 under
the action of 1-iodobutane on the reaction mixture after separation of allene and tellurium.
The attack of Te22− at the carbon atom of isothiuronium moiety (direction b) is expected to
result in the formation of tellurourea, tellurium, and intermediate thiolate anion 10 (Scheme 6).
The same thiolate 10 can be produced also under the action of a base on isothiuronium salt 2
(a classical cleavage) (Scheme 7).

4
E.P. Levanova et al.
Cl
Te22–
–Te
NH2
NH2
S–
Te
+
2
10
Scheme 6. The attack of Te22− on the carbon atom of isothiuronium moiety according to the
direction b.
H2O,base
–NH3,– CO2,– Cl–
10
2
Scheme 7. A cleavage of isothiuronium salt 2 under the action of a base.
A further intramolecular cyclization of thiolate 10 via nucleophilic substitution of the chlorine
atom at double bond could lead to intermediate methylenethiirane 11 followed by an elimination
of sulfur to produce allene (Scheme 8).
H2C=C=CH2
10
–Cl–
–S
S
11
Scheme 8. A formation of allene via methylenethiirane intermediate 11.
A halophilic attack of Te22− (direction c) is expected to proceed via elimination of thiourea and
formation of allene in one stage (Scheme 9). Such a mechanism is most commonly used for an
explanation of 1,2-elimination (5, 6, 11, 12).
Te22–
Cl
NH2
+
NH2
–
Cl–
Te2Cl
S
+H2C=C=CH2
-SC(NH2)2, –Cl–
2
Cl–+Te4
2–
Te2Cl–+Te22–
2–
Te22–+Te
Te4
Scheme 9. A halophilic attack with Te22−
.
A further participation of Te24− anions in a halophilic attack could finally lead to elemental
tellurium. But, as mentioned above, the elimination of thiourea cannot explain the formation of
dibutylsulfide 3 and dibutyldisulfide 4 under the action of 1-iodobutane.
If cleavage of isothiuronium salt 2 runs sufficiently fast, intermediate thiolate 10 can undergo
a halophilic attack (Scheme 10).
Cl
Te22–
H2C C CH2
+
S–
–Te2Cl– ; –S2–
10
Scheme 10. The halophilic attack of thiolate 10 under the action of Te22−
.

Journal of Sulfur Chemistry
5
Dehalogenation reactions for vicinal dihaloalkanes under the action of mild nucleophiles pro-
ceed via halophilic attack (12). In the process studied, the attack of Te22− at the negatively charged
sulfur atom in thiolate 10 seems to be improbable. Consequently, the reaction is realized as a
result of the halophilic attack at the chlorine atom attached to the sp2-hybridized carbon. The
process takes place under the mild conditions, as noted previously, and is remarkably facile.
The reaction of 2,3-dichloropropene 1 with ditelluride anions was previously shown to result in
allene formation (5). This brings up the question: at which chlorine atom does the halophilic attack
occur? It is tempting to suggest, given the results of the present work, that the halophilic attack is
directed at the chlorine atom attached to sp2-hybridized carbon both for 2,3-dichloropropene and
thiolate 10.
Sulfide anions, formed according to Scheme 10, are partially alkylated by 1-iodobutane to
deliver sulfide 3 (Scheme 11). In the absence of free alkali (13), the sulfide anions are also
oxidized by hydrazine to generate disulfide anions (Scheme 11).
2BuI+S2–
Bu2S
3
–2I–
2S2–+N2H4+2H2O
S22–+2NH3+2OH–
2–
2BuI+S2
Bu2S2
4
Scheme 11. A formation of dibutylsulfide 3 and dibutyldisulfide 4.
High reactivity of 1-iodobutane as an electrophile and the low concentrations of S2− and
S22− anions in the reaction mixture containing excess hydrazine also allow formation of
butyl derivatives of hydrazine. Consistent with this suggestion, butylhydrazines 5 and N,N-
dibutylhydrazine 6 have been prepared independently by the reaction of BuI with hydrazine
hydrate.
So, in our opinion, Scheme 10 is more preferable, since it provides an explanation for the
formation of allene, dibutylsulfide 3, and dibutyldisulfide 4.
3. Conclusion
Inconclusion, thereactionof2-chloro-1-propen-3-ylisothiuroniumsaltwithpotassiumditelluride
in the presence of hydrazine hydrate leads to reductive elimination of a chlorine atom and a sulfur-
bearing functional group. This fact complements and expands fundamental knowledge on the
elimination reactions in the synthesis of chalcogene-containing compounds, especially polymers
which possess valuable electro-physical and other properties (14).
4. Experimental
4.1. General
1
IR spectra were recorded on a Bruker IFS instrument. H and 13C NMR spectra were run on
a Bruker DPX-400 spectrometer (400.13 and 100.61 MHz, respectively) in CDCl3, DMSO-d6.
Chemical shifts (δ) are expressed in ppm downfield from tetramethylsilane as an internal stan-
dard. Mass spectra were recorded on a Shimadzu GCMS-QP5050A spectrometer (SPB-5 column,

6
E.P. Levanova et al.
60, 000 × 0.25 mm) operating at an ionization potential of 70 eV, quadruple mass analyzer,
temperature of ion source 190◦C, range of detected masses 34-650 D.
4.1.1. 2-Chloro-1-propen-3-yl isothiuronium chloride 2
2,3-Dichloropropene 1 (200 mmol, 22.20 g), thiourea (200 mmol, 15.20 g) in ethanol (120 ml)
were boiled for 17.5 h. The reaction mixture was diluted with diethyl ether (50 ml), the precipitate
of salt 2 was filtered off, washed with ether and dried in vacuum. Colorless solid; yield: 33.60 g
(90%); m.p. 135–137◦C. IR (KBr, ν, cm−1): 3274, 3187, 3046, 2969, 2929, 2707, 1655, 1544,
1423, 1385, 1252, 1212, 1125, 1079, 900, 720, 629, 593, 456. 1H NMR (DMSO-d6): δ = 4.45 (s,
2H, SCH2), 5.46 (d, 2JH−H = 1.3 Hz, 1H, C H), 5.81 (d, JH−H = 1.3 Hz, C H), 9.41 (br.
2
= −
= −
13
=
s, 2H, NH2), 9.54 (br. s, 2H, NH2). C NMR (DMSO-d6): δ = 37.9 (CH2S), 118.05 ( CH2),
=
=
135.61 ( CCl), 168.64 (C N). Anal. calcd. for C4H8Cl2N2S: C, 25.68; H, 4.31; N, 14.97; Cl,
37.90; S, 17.14. Found: C, 25.61; H, 4.27; N, 15.07; Cl, 37.86; S, 17.24.
4.1.2. The reaction of isothiuronium salt 2 with potassium ditelluride
Potassiumhydroxide(37.4 mmol, 2.09 g)wasdissolvedinhydrazinehydrate(40 ml)andtellurium
(37.4 mmol, 4.78 g) was added portion-wise to the solution obtained (5). The reaction mixture
was heated for 2 h. The flask was connected to two traps (temperatures of the traps were −30◦C
and −80◦C, respectively). Isothiuronium salt 2 (28 mmol, 5.25 g) was added to the flask at 25◦C
and the mixture was stirred for 4.5 h at 35–45◦C. Allene was collected in the second trap. Yield:
0.75 g (67% calculated by the isothiuronium salt 2 consumed). 1H NMR (CDCl3): δ = 4.72 (s, 4H,
13
=
=
= =
CH2) (cf. (5)). C NMR (CDCl3): δ = 73.91 ( CH2), 212.61 ( C ). Tellurium was filtered off
from the remaining reaction mixture.Yield of tellurium: 4.45 g (100%).The filtrate after separation
of tellurium was treated with 1-iodobutane (37.8 mmol, 6.95 g). The mixture was stirred for 3 h at
40–50◦C. The organic layer was separated and dried over MgSO4 to give 1.92 g of the light-yellow
oil, containing sulfide 3 (0.61 g), MS: 146 (M+), calcd. for C8H18S (146.29), disulfide 4 (0.81 g),
MS: 178 (M+), calcd. for C8H18S2 (178.35), and N,N-dibutylhydrazine 6 (0.50 g), which were
identified, using gas-liquid chromatography (GLC) and chromato-mass spectrometry techniques
in comparison with standards. Yield was calculated in according with GLC data. The residue
obtained after separation of the organic layer was extracted with dichloromethane (2 × 50 ml),
the extracts were combined and dried over MgSO4 to give practically pure (after removal of
the solvent) butylhydrazine 5. Yield 1.20 g (36%); b.p. 79◦C (80Torr), reference data (15): b.p.
141–142◦C (750Torr). 1H NMR (CDCl3): δ = 0.91 (t, 3JH−H = 7.3 Hz, 3H, CH3), 1.35 (m, 2H,
CH2), 1.46 (m, 2H, CH2), 2.75 (t, 3JH−H = 7.0 Hz, 2H, CH2N), 3.14 (br. s, 3H, HN–NH2). 13
NMR (CDCl3): δ = 13.80 (CH3), 20.16 (CH2), 29.65 (CH2), 55.99 (NCH2).
C
4.1.3. Reaction of 1-iodobutane with thiourea in hydrazine hydrate
Thiourea (28 mmol, 2.14 g) was added to hydrazine hydrate (40 ml) at 50◦C. Then 1-iodobutane
(38 mmol, 6.95 g) was added to the reaction mixture dropwise at 40–45◦C for 1.5 h. The
mixture was stirred for 3 h at 40◦C. The light-yellow organic layer (0.55 g), containing N,N-
dibutylhydrazine 6 and traces of sulfide 3 and disulfide 4, was separated. Compounds 3 and
4 were identified, using GLC and chromato-mass spectrometry techniques in comparison with
standards without isolation in a pure form. The residue was extracted with dichloromethane
(2 × 50 ml), the extract was dried over MgSO4, and the solvent was removed to give 1.70 g
(51%) of butylhydrazine 5.

Journal of Sulfur Chemistry
7
4.1.4. Reaction of 1-iodobutane with hydrazine
1-Iodobutane (37.8 mmol, 6.95 g) was added to hydrazine hydrate (40 ml) and the reaction mixture
was stirred for 3 h at 40–45◦C. The reaction products were extracted with diethyl ether (2 × 50 ml),
the extract was dried over MgSO4, and the solvent was removed to afford 3.46 g of light-yellow oil
containing butylhydrazine 5. Products of a reaction of 1-iodobutane with water were not found.
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