Reaction of 1-Iodoalkynes with Tin Metal: A New Approach to the Sn–C sp Bond Formation

Article abstract of DOI:10.1134/S1070363220040088

Abstract: Tin iodoalkynylides were synthesized by the reaction of 1-iodoalkynes with tin metal. The scope of the reaction and the composition of the resulting mixtures were studied. The formation of tin iodoalkynylides was confirmed by counter synthesis v

Full text of DOI:10.1134/S1070363220040088

ISSN 1070-3632, Russian Journal of General Chemistry, 2020, Vol. 90, No. 4, pp. 610–613. © Pleiades Publishing, Ltd., 2020.
Russian Text © The Author(s), 2020, published in Zhurnal Obshchei Khimii, 2020, Vol. 90, No. 4, pp. 546–550.
Reaction of 1-Iodoalkynes with Tin Metal:
A New Approach to the Sn–Csp Bond Formation
A. R. Chikavaa, A. S. Levashova,*, and V. V. Konshina
a Kuban State University, Krasnodar, 350040 Russia
*e-mail: aslevashov@mail.ru
Received October 2, 2019; revised October 2, 2019; accepted October 7, 2019
Abstract—Tin iodoalkynylides were synthesized by the reaction of 1-iodoalkynes with tin metal. The scope of
the reaction and the composition of the resulting mixtures were studied. The formation of tin iodoalkynylides was
confirmed by counter synthesis via the reaction of disproportionation of tetra(phenylethynyl)tin with tin tetraiodide.
The compounds synthesized were characterized by means of 119Sn NMR spectroscopy.
Keywords: tin iodoalkynylides, tin tetraalkynylides, iodoalkynes
DOI: 10.1134/S1070363220040088
Alkynyl tin are widely used in organic synthesis as
reactants for the synthesis of alkenes [1] and conjugated
unsaturated compounds [2], as well as for construction
of carbo- and heterocycles [3, 4], including biologically
active substances [5]. The Stille reaction involving
tin alkynylides is a reliable tool for construction of
compounds with molecules of high complexity [6] and
self-assembling acetylene moieties [7]. Alkynyl tin
containing four acetylene moieties are suitable as atom-
economic reactants in the synthesis of aryl acetylenes
[8] and acetylenic ketones [9–11]. Widespread use of
alkynyl tin prompts the search for new synthetic routes
to these compounds, as discussed in a number of recent
publications [12–14].
affecting the equilibrium between the tin iodoalkynylides
being formed.
At the same time, the reaction proceeded very slowly
and required ca. 150 h for completion. Its acceleration
was achieved through the use of tin alloy containing
1.5% zinc, which allowed decreasing the reaction time
to 8 h. More active proceeding of the reaction was
observed when commercially available finely divided
tin powder (particle size 10 μm) was used, whereby the
reaction temperature was reduced to 100°C. We studied
the effect of the solvent on the reaction time and on the
composition of the resulting product mixtures (Table 1).
The progress of the reaction was monitored by GC/MS
via following the consumption of (iodoethynyl)benzene
1a with the use of hexadecane as an internal standard.
The reaction proceeded most rapidly in polar solvents
such as 1,4-dioxane and 1,2-dimethoxyethane, with
increases in the concentrations of the reactants from 25 to
40% accelerating the reaction only insignificantly. In all
the cases an induction period was observed, after which
the main interaction proceeded for ~1 h. The products
mixture changed most significantly by using toluene due
to low solubility of SnI4 in it. This caused a shift in the
equilibrium between compounds 2a–5a, resulting in the
lack of the SnI4 signal in the 119Sn NMR spectrum.
Direct synthesis of organotin compounds was the
subject of numerous studies [15–19], but there is no
information yet on the possibility of the Sn–Csp bond
formation by this method.
We presumed that 1-iodoalkynes may be reactive
toward tin metal. Indeed, heating (iodoethynyl)benzene
1a in aromatic solvents at 130–140°С with tin metal chips
(0.2–0.5 mm fraction) led to dissolution of the latter and
development of a color of the reaction mixture.According
to the 119Sn NMR spectroscopic data, the reaction gave a
mixture of tetra(phenylethynyl)tin 2a, tin iodoalkynylides
with different degrees of substitution 3a–5a, and tin
tetraiodide 6 (Scheme 1). The composition of the product
mixture was dependent on the solvent used, which is
attributable to the difference in the solubility of SnI4,
The reaction of 1-iodoalkynes containing substituents
in the benzene ring proceeded in a similar manner. For
example, 1-(iodoethynyl)-4-chlorobenzene 1b fully
reacted with tin metal in 1,4-dioxane at 100°C within 4 h
610

REACTION OF 1-IODOALKYNES WITH TIN METAL
611
Scheme 1.
to give the reaction products in the 2b : 3b : 4b : 5b : 6 =
5 : 35 : 33 : 23 : 4 ratio. 1-(Iodoethynyl)-4-methylbenzene
1c turned out to be more reactive; its complete
consumption within 2 h led to formation of the reaction
products in the 2c : 3c : 4c : 5c : 6=3 : 22 : 38 : 33 : 4 ratio.
Table 2 presents the 119Sn NMR chemical shifts, recorded
for compounds 2–5, 6 in various solvents.
chemical shifts for this type of organotin compounds. A
similar relationship was reported for (RC≡C)nSnI4–n at
n = 1–4 in [20].
Thus, we have demonstrated the possibility of
preparing tin iodoalkynylides by both direct synthesis
and disproportionation reaction.
EXPERIMENTAL
The counter synthesis of tin iodoalkynylides by the
reaction of disproportionation of tetra(phenylethynyl)tin
2a with tin tetraiodide 6 in 1,4-dioxane (Scheme 2) gave
a mixture dominated by certain products depending on
the ratio of the reactants (Fig. 1).
We used tin powder with particle size of 10 μm,
available from Aldrich, and tetra(phenylethynyl)tin
obtained by the technique from [14]. (Iodoethynyl)-
benzene 1a, 1-(iodoethynyl)-4-chlorobenzene 1b, and
1-(iodoethynyl)-4-methylbenzene 1c were synthesized
by the procedure similar to that described in [21].
The reaction proceeded similarly to the reaction
of disproportionation of tin tetraalkynylides with tin
tetrachloride [20]. It should be noted that the total
shielding constant of the substituents in (ArC≡C)nSnI4–n
exponentially varies with n. The linear relationship
ln (δ)–n thus observed allows predicting the 119Sn NMR
Scheme 2.
Table 1. Influence of various conditions on the time of the reaction of compound 1a with tin metal and on the composition of
the resulting mixture
Content,%
Run
no.
1
2
3
4
5
6
7
Reaction
Solvent
t, °С
time, ha
2a
3
3
–
21
6
3a
34
32
–
39
23
29
28
4a
35
35
–
28
33
33
31
5a
23
23
–
12
30
28
29
6
6
7
–
0
8
6
7
1,4-Dioxane
1,4-Dioxaneb
100
100
100
120
100
100
100
3
2.5
>20
6
5
3
Toluene
Toluene
1,2-Dichloroethane
1,2-Dimethoxyethane
1,2-Dimethoxyethaneb
4
5
2
a Reaction time indicates the time until compound 1a was completely consumed.
b The concentrations of the reactants were increased from 25 to 40%.
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612
CHIKAVA et al.
įSn, ppm
Fig. 1. 119Sn NMR spectra of the reaction mixture of tetra(phenylethynyl)tin with tin tetraiodide in 1,4-dioxane at (1) 3 : 1, (2) 1 : 1,
and (3) 1 : 3 ratio of the reactants.
119Sn NMR spectra were recorded on a JEOLECA400
the aqueous layer was extracted with diethyl ether–hexane
(1 : 1) mixture (2×10 mL). The combined organic layers
were dried over magnesium sulfate and then evaporated.
The residue was chromatographed (eluent—hexane–ethyl
acetate, 90 : 10, with 1% triethylamine addition). Yield
555 mg (92%), light yellow crystals. Mass spectrum (EI,
70 eV), m/z (Irel, %) : 264 (17) [M]+, 262 (100), 135 (23),
100 (16), 99 (84), 98 (12), 74 (77), 50 (18).
spectrometer. The reaction progress was monitored by gas
chromatography-mass spectrometry using a Shimadzu
GC-2010 instrument with a Shimadzu QP-2010 mass-
selective detector : Supelco 28064U column, 30 m,
temperature-programmed heating from 60 to 260°C at a
rate of 30°C/min.
1-(Iodoethynyl)-4-chlorobenzene (1b). A mixture
of 310 mg (2.3 mmol) of 4-chlorophenylacetylene,
7 mL of anhydrous acetone, 570 mg (2.53 mmol) of
N-iodosuccinimide, and 34 mg (0.2 mmol) of silver
nitrate was stirred at room temperature for 2 h. Thereupon,
20 mL of hexane and 15 mL of water were added to the
reaction mixture. The organic layer was separated, and
The spectral data correspond to those published in
[22].
1-(Iodoethynyl)-4-methylbenzene (1c) was obtained
in a similar manner from 0.32 mL (2.5 mmol) of
4-methylphenylacetylene, 7 mL of anhydrous acetone,
Table 2. Chemical shifts in the 119Sn NMR spectra of (ArC≡C)nSnI4–n in various solvents
δSn, ppm
Run
no.
Reactant
Solvent
1,4-Dioxane
n = 4
n = 3
n = 2
n = 1
n = 0
–1777.5
–1789.8
–1744.6
–
1a
1a
1a
1a
1b
1c
1
2
3
4
5
6
–351.2
–337.6
–335.3
–332.0
–355.3
–352.4
–502.9
–489.3
–473.2
–472.9
–508.8
–503.9
–792.6
–767.5
–739.9
–743.5
–797.7
–793.1
–1225.0
–1204.3
–1169.4
–1177.5
–1225.3
–1225.2
1,2-Dimethoxyethane
1,2-Dichloroethane
Toluene
1,4-Dioxane
–1777.5
–1777.3
1,4-Dioxane
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REACTION OF 1-IODOALKYNES WITH TIN METAL
613
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FUNDING
This study was financially supported by the Russian
Foundation for Basic Research (project no. р_а 19-43-
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Ministry of Education and Science of the Russian Federation
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CONFLICT OF INTEREST
No conflict of interest was declared by the authors.
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