Reactions of sodium 2ꢀpyridylchalcogenolates
Russ.Chem.Bull., Int.Ed., Vol. 65, No. 12, December, 2016
2983
increased up to 90% by performing the reaction in refluxꢀ
ing EtOH for 5 h instead of room temperature.
Selenide 2 is a newly synthesized compound; while
synthesis of sulfide 3 has been earlier described.13,14
According to the authors of work,14 sulfide 3 has antituꢀ
mor activity.
spectrum, the carbon atoms of the allenyl group of telluꢀ
ride 1 resonate at δ 54.22 (TeCH=), 72.31 (=CH2), and
210.44 (=C=).
In summary, the nature of the chalcogen atom has
been shown to play a decisive role in determining the
direction of nucleophilic substitution reaction between
2ꢀpyridyl chalcogenolate anions and propargyl halides.
Sodium 2ꢀpyridyl tellurolate selectively reacts with proꢀ
pargyl halides following 1,3ꢀnucleophilic substitution
mechanism to afford allenyl telluride 1. At the same
time, sodium 2ꢀpyridyl selenolate and 2ꢀpyridyl thiolate
react with propargyl halides under similar conditions to
give propargyl selenide 2 and propargyl sulfide 3. The
newly synthesized telluride 1 and selenide 2 can find
applications as intermediates and building blocks in orꢀ
ganic synthesis, for instance, for the synthesis of subꢀ
stances with promising biological activity.
Sodium 2ꢀpyridyl tellurolate and 2ꢀpyridyl selenoꢀ
late react with propargyl chloride under similar condiꢀ
tions to give the same products 1 and 2. However, in this
case the yields of compounds 1 and 2 were lower (68 and
72%, respectively) than in the reactions with propargyl
bromide.
The obtained results indicate that sodium 2ꢀpyridyl
tellurolate reacts with propargyl halides following
1,3ꢀnucleophilic substitution mechanism; while reactions
of sodium 2ꢀpyridyl selenolate and 2ꢀpyridyl thiolate
proceed via general 1,1ꢀnucleophilic substitution patꢀ
tern. Apparently, for bulky and highly nucleophilic
2ꢀpyrydil tellurolate the attack at the terminal C atom of
the triple bond of propargyl bromide is more energetiꢀ
cally favorable than at the substituted C atom of the
CH2Hal moiety. Nucleophilic attack of 2ꢀpyridyl telluꢀ
rolate at the terminal C atom of the triple bond is accomꢀ
panied with a shift of six electrons to produce the allenyl
fragment and halide anion. This process may occur in a
concerted mode (Scheme 2).
Experimental
NMR spectra were recorded with a Bruker DPXꢀ400 instruꢀ
ment in CDCl3 relative to hexamethyldisiloxane; the working freꢀ
quencies were 400.13 (1H) and 100.61 MHz (13C). Anhydrous
EtOH and commercial (Alfa Aesar) sodium borohydride (97%,
granules, 10—40 mesh) and bis(2ꢀpyridyl)disulfide (98%) were
used. Bis(2ꢀpyridyl)diselenide15 and bis(2ꢀpyridyl)ditelluride16
were synthesized by the known procedures from 2ꢀbromopyridine
and selenium or tellurium. Propargyl bromide was synthesized as
earlier described from propargyl alcohol and phosphorus tribroꢀ
mide.17 Elemental analyses were performed with a THERMO
Flash EA1112 elemental analyzer.
Scheme 2
Allenyl 2ꢀpyridyl telluride (1). To a solution of bisꢀ
(2ꢀpyridyl)ditelluride (0.206 g, 0.5 mmol) and propargyl bromide
(0.143 g, 1.2 mmol) in EtOH (5 mL), sodium borohydride (0.1 g,
2.6 mmol) was added by small portions under argon. The mixture
was stirred at room temperature for 16 h under argon, diluted with
degassed water (15 mL), and extracted with benzene (3×10 mL).
The combined organic layers were dried with Na2SO4, filtered, and
concentrated in vacuo to give 0.22 g (90%) of telluride 1, yellowish
liquid. Found (%): C, 39.38; H, 3.02; N, 5.43. C8H7NTe. Calcuꢀ
lated (%): C, 39.26; H, 2.88; N, 5.72. 1H NMR, δ: 4.70 (d, 2 H,
4
=CH2, J = 6.4 Hz); 6.45 (t, 1 H, TeCH=, 4J = 6.4 Hz); 7.02
(m, 1 H, Py); 7.35—7.48 (m, 2 H, Py); 8.46 (m, 1 H, Py).
13C NMR, δ: 54.22 (TeCH=); 72.31 (=CH2); 120.78 (Py); 129.55
(Py); 135.36 (Py); 145.23 (Py); 150.67 (Py), 210.44 (=C=).
Propargyl 2ꢀpyridyl selenide (2) was synthesized similarly to
telluride 1 in the yield of 94%. Found (%): C, 48.86; H, 3.52;
N, 7.46. C8H7NSe. Calculated (%): C, 49.00; H, 3.60; N, 7.14.
1H NMR, δ: 2.15 (t, 1 H, CH, 4J = 2.7 Hz); 3.80 (d, 2 H, CH2,
4J = 2.7 Hz); 7.01 (m, 1 H, CH, Py); 7.28 (m, 1 H, Py); 7.42 (m, 1 H,
CH, Py); 8.40 (m, 1 H, CH, Py). 13C NMR, δ: 10.04 (CH2), 71.09
(CH), 81.02 (C), 120.55 (Py), 124.99 (Py), 136.07 (Py), 150.07
(Py) 154.21 (Py).
X = Se (2), S (3); Hal = Br, Cl
Reactions of bis(2ꢀpyridyl)dichalcogenides with proꢀ
pargyl bromide using basic reducing system DMF—
KOH—hydrazine hydrate—H2O give lower yields of telꢀ
luride 1 and selenide 2 (67 and 73%) and accompanied
with the side product formation.
Structures of compounds 1 and 2 were established by
1H and 13C NMR spectroscopy and confirmed by eleꢀ
1
Spectral studies were performed using the equipment
and facilities of the Baikal Analytical Center for collecꢀ
tive use of the Siberian Branch of the Russian Academy
of Sciences.
mental analysis. H NMR spectrum of telluride 1 exhibꢀ
its signals typical of the allenyl fragment: doublet at
δ 4.70 (=CH2) and triplet at δ 6.45 (TeCH=) with spinꢀ
spin coupling constants of 4J = 6.4 Hz. In 13C NMR
Musalova
