Microwave activation of the reaction of red phosphorus with alkanethiolate anions

Full text of DOI:10.1134/S1070363209110309

ISSN 1070-3632, Russian Journal of General Chemistry, 2009, Vol. 79, No. 11, pp. 2453–2455. © Pleiades Publishing, Ltd., 2009.
Original Russian Text © B.А. Trofimov, N.K. Gusarova, S.I. Verkhoturova, V.L. Mikhailenko, T.I. Kazantseva, S.N. Arbuzova, 2009, published in Zhurnal
Obshchei Khimii, 2009, Vol. 79, No. 11, pp. 1928–1929.
LETTERS
TO THE EDITOR
Microwave Activation of the Reaction of Red Phosphorus
with Alkanethiolate Anions
B. А. Trofimov, N. K. Gusarova, S. I. Verkhoturova,
V. L. Mikhailenko, T. I. Kazantseva, and S. N. Arbuzova
Favorskii Irkutsk Institute of Chemistry, Siberian Branch, Russian Academy of Sciences,
ul. Favorskogo 1, Irkutsk, 664033 Russia
e-mail: arbuzova@irioch.irk.ru
Received June 3, 2009
DOI: 10.1134/S1070363209110309
The direct phosphorylation of organic compounds
with elemental phosphorus and, first of all, with non-
combustible and non-toxic red phosphorus, is a
convenient method of the C–P bond formation, which
has advantages over the methods of synthesis of
organophosphorus compounds based on the use of toxic,
aggressive and less available phosphorus halides.
Nowadays, to activate red phosphorus, superbasic media
[1] like alkali metal hydroxide–polar nonhydroxylic
solvent (DMSO, HMPTA) or aqueous solution of
alkali metal hydroxide–organic solvent–phase transfer
catalyst [2–4] are widely used. Polyphosphide and
polyphosphinite ions generated in these media by
successive rupture of the P–P bonds in macro-
molecules of red phosphorus under the action of
hydroxide anion react with versatile electrophiles
(electrophilic alkenes, acetylenes, organyl halides,
oxiranes) to form organic phosphines and phosphine
oxides [1–7]. Recently, short communications
appeared reporting the splitting of the macromolecule
of red phosphorus in the presence of sulfur-centered
nucleophiles (sodium hydrosulfide [8] or alkane-
thiolate anions [9]). In particular, the reaction of red
phosphorus with alkanethiolate anions (generated in
situ from alkanethiols in the system KOH–DMSO)
proceeds upon heating (125–128°C) and leads in 4 h to
the earlier unknown O-potassium S,S-dialkyl trithio-
phosphates in 13–15% yield.
thiolates generated from alkanethiols Ia, Ib and KOH
in DMSO resulted in the reduction of the time of the
reaction to 5 min (that is, almost 50-fold) and in the
formation of potassium dialkyl trithiophosphates in
19–20% yield [the yield was calculated with respect to
the reacted alkanethiol Ia, Ib whose conversion was
98–99%].
DMSO
RSH + KOH
RSK + H2O
Iа, Ib
RS
S
DMSO (H2O)
Pred + RSK
P
MW (300 Wt, 5 min)
RS
OK
IIа, IIb
R = Bu (a), C7H15 (b).
Possible routes of formation of salts IIa, IIb were
discussed in [9].
In the reaction mixture were identified the cor-
responding trialkyltetrathiophosphates (31P NMR) as
well as dialkyldisulfides (the products of oxidation of
alkanethiols) and alkyl methyl sulfides (the GLC and
mass spectrometry data). The sulfides appear as a
result of the reaction of thiols with the system KOH–
DMSO [10].
Therefore, we have proved the effect of microwave
activation of the new reaction of splitting the three-
dimensional macromolecule of red phosphorus under
the action of sulfur-centered nucleophiles (alkane-
thiolate anions) leading to the formation of the P–S
bonds and O-potassium S,S-dialkyl trithiophosphates,
In the present communication we report the results
of activation of this new reaction under the conditions
of microwave irradiation. It turned out that microwave
irradiation (Samsung M181DNR, 300 Wt) of the
mixture of red phosphorus and potassium alkane-
2453

2454
TROFIMOV et al.
promising precursors for preparation of S,S,S-trial-
kylthiophosphates [9].
ppm: 85.6. IR spectrum (KBr, cm–1): 645 (Р=S).
Found, %: С 32.28, Н 6.40, Р 9.95, S 32.17.
С8H18KOPS3. Calculated, %: C 32.41, Н 6.12, P 10.45,
S 32.44.
O-Potassium S,S-dibutyltrithiophosphate (IIа).
The mixture of 2.13 g (32.7 mmol) of the ground
KOH·0.5Н2О and 2.95 g (32.7 mmol) of BuSH in
35 ml of DMSO was heated (60°C) at stirring to full
homogenization. The obtained solution was cooled to
40°C, 0.63 g (20.3 mmol) of red phosphorus was
added, the reaction mixture was irradiated in a
domestic microwave oven (Samsung M181DNR, 300 Wt
power) during 5 min, cooled, filtered, the precipitate
was washed successively with DMSO (10 ml), H2O
(10 ml), acetone (10 ml), ether (10 ml), and dried in a
vacuum to obtain 0.22 g of red phosphorus (conversion
65%). The filtrate was combined with the DMSO and
water washing solutions and analyzed (NMR, GLC).
In the 31Р NMR spectrum (δР, ppm) the signals were
observed at 3.4 t (1JPH 464 Hz), 73.6, and 98.1 ppm in
the ratio of 3:9:1, belonging, respectively, to KH2PO2,
Bu2P(S)OK IIb, and Bu3P(S). According to the GLC
data (xylene as a standard, temperature of column 50°C,
of injector 200°C), the filtrate also contains 0.01 g of
Me2S, 0.03 g of BuSH (conversion 99%), and 0.39 g of
BuSMe (12%, hereinafter the yield is calculated with
due regard to the conversion of the thiol) (all
compounds were identified by com-parison with
authentic samples). The filtrate was diluted with water
(1 : 1), extracted with ether (3×30 ml), the extract was
washed with water (3×30 ml), dried over K2CO3, ether
was removed at the atmospheric pressure, BuSH and
BuSMe, at 2 mm Hg (for BuSMe m/z = 104 [M]+·), the
residue in the flask was dibutyldisulfide, 0.87 g (30%)
(its spectra were identical to those of the authentic
sample). Found, %: С 53.59; Н 9.95; S 35.49. C8H18S2.
Calculated, %: С 53.87; Н 10.17; S 35.96. The
aqueous solution after the extraction with ether was
combined with washings of the ether extract, 5%
aqueous solution of HCl was added to рН 4, the water
solution was extracted with ether (3×30 ml), the
extract was washed with water (3×30 ml), and dried
over K2CO3. Ether was removed at the atmospheric
pressure, the residue was dried in a vacuum, and
washed with hexane to obtain 0.64 g (20%) of O-
potassium S,S-dibutyl trithiophosphate (IIа), white
O-Potassium S,S-diheptyltrithiophosphate (IIb)
was prepared similarly to salt (IIa) at the microwave
irradiation (300 Wt, 5 min) of 36.6 mmol of potassium
heptanethiolate and 0.71 g (22.9 mmol) of red
phosphorus in 50 ml of DMSO. Yield 0.87 g (19% at
98% conversion of heptanethiol), white crystals, mp
1
114–116°C (hexane). H NMR spectrum (CDCl3), δ,
3
ppm: 0.89 t (6H, Me, JHH 6.72 Hz), 1.20–1.45 m
(16H, CH2), 1.68 m (4Н, CH2CH2S), 2.88 m (4Н,
31
CH2S). Р NMR spectrum (CDCl3), δР, ppm: 86.5. IR
spectrum (KBr, cm–1): 635 (Р=S). Found, %: С 44.45,
Н 7.89, Р 7.51, S 24.81. С14H30KOPS3. Calculated, %:
C 44.17, Н 7.94, Р 8.14, S 25.27. Conversion of red
phosphorus was 55%, yield of C7H15SMe 21%, yield
of diheptyldisulfide 27%.
1H, 13С, and 31P NMR spectra were registered on a
Bruker 400 DPX spectrometer (at 400.13, 100.69, and
161.98 MHz, respectively), internal standard HMDS,
external standard 85% Н3РО4. IR spectra were
recorded on a Bruker ISF 25 instrument. Electron
impact (70 eV) mass spectra were obtained on a
GCMS-QP5050A SHIMADZU instrument (quadruple
mass analyzer, the range of detected masses 34–450 D,
capillary column, stationary phase SPB-5). GLC
analysis was performed on an LKhM 8MD instrument
(column 1.2 m×3 mm, 1% of PEG 20000 on NaCl,
carrier gas helium, 2 l h–1).
ACKNOWLEDGMENTS
This work was financially supported by the Russian
Foundation for Basic Research (grant no. 08-03-
98012-р_sibir_а).
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