A simple route to dithiophosphinic esters and diesters from secondary phosphine sulfides and thiols or dithiols

Article abstract of DOI:10.1080/17415993.2013.853067

Secondary phosphine sulfides react easily at room temperature with aliphatic, aromatic and heteroaromatic thiols or dithiols in the oxidative medium Et₃N/CCl₄ to afford dithiophosphinic esters or diesters in 65-99% isolated yields(Equation Presented). 2013

Full text of DOI:10.1080/17415993.2013.853067

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A simple route to dithiophosphinic
esters and diesters from secondary
phosphine sulfides and thiols or dithiols
P.A. Volkova, N.I. Ivanovaa, N.K. Gusarovaa & B.A. Trofimova
a A. E. Favorsky Irkutsk Institute of Chemistry, Siberian Branch of
the Russian Academy of Sciences, 1 Favorsky Str., 664033 Irkutsk,
Russian Federation
Published online: 30 Oct 2013.
To cite this article: P.A. Volkov, N.I. Ivanova, N.K. Gusarova & B.A. Trofimov (2014) A simple route
to dithiophosphinic esters and diesters from secondary phosphine sulfides and thiols or dithiols,
Journal of Sulfur Chemistry, 35:3, 237-247, DOI: 10.1080/17415993.2013.853067
To link to this article: http://dx.doi.org/10.1080/17415993.2013.853067
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Journal of Sulfur Chemistry, 2014
Vol. 35, No. 3, 237–247, http://dx.doi.org/10.1080/17415993.2013.853067
A simple route to dithiophosphinic esters and diesters from
secondary phosphine sulfides and thiols or dithiols
P.A. Volkov, N.I. Ivanova, N.K. Gusarova and B.A. Trofimov∗
A. E. Favorsky Irkutsk Institute of Chemistry, Siberian Branch of the RussianAcademy of Sciences, 1 Favorsky
Str., 664033 Irkutsk, Russian Federation
(Received 13 June 2013; accepted 4 October 2013)
Secondary phosphine sulfides react easily at room temperature with aliphatic, aromatic and heteroaromatic
thiolsordithiolsintheoxidativemediumEt3N/CCl4 toafforddithiophosphinicestersordiestersin65–99%
isolated yields.
Keywords: secondary phosphine sulfides; thiols; dithiols; dithiophosphinic esters; dithiophosphinic
diesters
1. Introduction
Dithiophosphinic esters find application as RAFT-agents (Reversible Addition-Fragmentation
Chain Transfer) for controlled styrene polymerization,[1,2] flame retardants,[3] ligands for the
design of metal-complexes [4,5] and building blocks in organic and element-organic synthesis.
[6–11] Besides, they are prospective drug precursors,[12,13] and sulfur sources for the fabrication
of sulfur-containing nanoparticles.[14]
Conventionally, dithiophosphinic esters are prepared via a two-step method from chlorophos-
phines, thioles and elemental sulfur (Scheme 1).[15,16]
The synthesis of dithiophosphinic esters was also reported by alkylation of ammonium or alkali
metal salts of dithiophosphinic acids (Scheme 2).[17–19]
Dithiophosphinic acids are known to react with diverse alkenes to deliver Markovnikov or
anti-Markovnikov adducts (Scheme 3).[20–23]
The present paper discloses a novel convenient approach to dithiophosphinic esters and diesters
from secondary phosphine sulfides and thiols or dithiols.
∗Corresponding author. Email: boris_trofimov@irioch.irk.ru
© 2013 Taylor & Francis

238 P.A. Volkov et al.
Scheme 1. Synthesis of dithiophosphinic esters from diorganylchlorophosphine.
R1
R1
R1
R1
R1
R1
25-85 o
-H2O
C
R2Hal, 50-75 o
-MHal
C
S
S
+
2 S + MOH
P
P
P
H
SR2
SM
25-91%
70-99%
R1 = Alk, Ar, ArAlk; M = NH4, Na, K; R2= Alk, Ar, ArAlk
Scheme 2. Reaction of dithiophosphinates with organic halides.
Scheme 3. Reaction of dithiophosphinic acid with alkenes.
The starting secondary phosphine sulfides are readily synthesized by halogen-free protocol
from red phosphorus, styrenes and elemental sulfur (Scheme 4).[24,25]
R
R
R
R
Ph
KOH/DMSO
Ph
Ph
Ph
Ph
KOH/H2O
PhMe
S
H
S
R
Pred
PH3/H2
P
P
H
PhMe
R = H, Me
Scheme 4. Synthesis of secondary phosphine sulfides.
2. Results and discussion
We have shown that the reaction of secondary phosphine sulfides 1–3 with aliphatic 4, aromatic
5 and heteroaromatic 6–8 thiols (reactants molar ratio is 1:1) proceeds in the system Et3N/CCl4
at room temperature (1–24 h) to deliver dithiophosphinic esters 9a–g in 65–99% isolated yields
(Table 1).
Under developed conditions, phosphine sulfides 1–3 also react with dithiol 10 (their molar ratio
is 2:1) in the Et3N/CCl4 system to give diesters 11a–c in high yield (88–98%) (Table 2).
Under the above conditions, the S-esters, R2P(S)SC6H4OC6H4SH 12, were not detected in the
resulting reaction mixture. However, in the example of phosphine sulfide 1, it was demonstrated
that, when the molar ratio of the starting reactants was 1:1, along with S-diester 11a S-ester 12
was formed in significant amount (Scheme 5).

Journal of Sulfur Chemistry 239
Table 1. Synthesis of dithiophosphinic esters 9a–ga.
Entry
1
R21P(S)H (1 mmol)
HSR2 (1 mmol)
Time (h)
4
Product
Yieldb (%)
65
1
4
9a
2
1
1
1
1
2
5
6
7
8
5
1
24
1.5
1.5
1
9b
9c
9d
9e
9f
94
86
83
91
90
3c
4
5
6
7
3
5
0.5
9g
99
aAll experiments were carried out under argon atmosphere in the presence of Et3N (1 mmol) and CCl4 (4 mL). Under these conditions,
triethylammonium chloride and chloroform are also formed.
bIsolated yield.
cThe heating (50–52◦C) decreases the reaction time to 7 h to afford ester 9e in 89% yield.
The synthesis of dithiophosphinic esters and diesters is assumed to be an oxidative cross-
coupling reaction between secondary phosphine sulfides and thiols or dithiols in the oxidative
system Et3N/CCl4. The process is trigged by the interaction of triethylamine with secondary
phosphine sulfides 1–3 to produce P, S-ambident thiophosphinite-anion A (Scheme 6). The latter
takes part in a one-electron transfer toward CCl4 (oxidizer) to deliver the free radical of secondary
phosphine sulfide B and anion radical C, which further are interconverted to give phosphinothioic

240 P.A. Volkov et al.
Table 2. Synthesis of dithiophosphinic diesters 11a–ca.
R2P(S)H
Time (h)
1.0
Product
Yieldb (%)
90
1
2
3
1.5
0.5
88
98
11c
aAll experiments were carried out under argon atmosphere in the presence of Et3N (1 mmol) and CCl4 (4 mL). Under
these conditions, triethylammonium chloride and chloroform are also formed.
bIsolated yield.
Scheme 5. Reaction of phosphine sulfide 1 with dithiol 10 (their molar ratio is 1:1).
chloride D and the −CCl3 carbanion. The reaction between chloride D and thiol in the presence of
triethylamine results in the target product 9 and triethylammonium chloride. The −CCl3 carbanion
is protonated by a triethylammonium cation to regenerate triethylamine and form chloroform
(Scheme 6).
Scheme 6. A tentative mechanism for the formation of dithiophosphinic esters.
Similar mechanism was previously discussed in the paper dedicated to the cross-coupling
reaction between secondary phosphine selenides and thiols or dithiols.[26]
Noteworthy, under the conditions of the reaction studied (Tables 1 and 2), the correspond-
ing diorganylphosphinothioic O-acid anhydrides 13a–c are formed as by-products in negligible
amounts. Their formation is likely due to hydrolysis of phosphinothioic chloride D with water,

Journal of Sulfur Chemistry 241
traces of which are present in the system. The resulted diorganylphosphinothioic O-acid E further
reacts with chloride D in the presence of Et3N to furnish anhydrides 13a–c (Scheme 7).
Scheme 7. A tentative mechanism for the formation of diorganylphosphinothioic O-acid
anhydrides 13a–c.
Scheme 7 is in agreement with experimental data. Indeed, we have shown that phosphine
sulfide 2 reacts easily (r.t., 11 h) with water in the system Et3N/CCl4 to give earlier unknown bis
(2-phenylpropyl)phosphinothioic O-acid anhydride 13b in almost quantitative yields (Scheme 8).
Scheme 8. Synthesis of bis(2-phenylpropyl)phosphinothioic O-acid anhydride 13b.
3. Conclusion
In summary, a novel convenient approach to dithiophosphinic esters and diesters from secondary
phosphine sulfides and thiols or dithiols has been developed. The method is based on the oxidative
transition-metal-free cross-coupling between diverse secondary phosphine sulfides and aliphatic,
aromatic and heteroaromatic thiols or dithiols, including thiols with pharmacophore groups such
as quinoline,[27] benzoxazole [28] and benzothiazole [29–31] moieties. The reaction readily
proceeds in the system Et3N/CCl4 at room temperature to afford in high yields hitherto 9a–f
and 10a–c or hardly available 9g dithiophosphinic esters and diesters which can be used as
RAFT-agents for pseudo-living radical polymerization, flame retardants, ligands for the design
of metal-complexes and potential drug candidates.
4. Experimental
4.1. General
All reactions were carried out under an argon atmosphere. All solvents were dried and/or purified
according to standard procedures.[32] Secondary phosphine sulfides 1, 2 were prepared from
styrene or α-methylstyrene and elemental phosphorus.[24,25] Diphenylphosphine sulfide 3 was
prepared by oxidation of commercially available diphenylphosphine (Aldrich) with elemental
sulfur.[33]Thereactionwasmonitoredusing31P NMRspectrabythedisappearanceofpeaksofthe

242 P.A. Volkov et al.
initial bis(2-phenylethyl)phosphine sulfide 1 (δP 21.3 ppm), bis(2-phenylpropyl)phosphine sulfide
2 (δP 14.9, 15.5 and 17.5 ppm) and diphenylphosphine sulfide 3 (δP 23.5 ppm), and appearance of
new peaks corresponding to dithiophosphinic esters 9a–g (δP ∼ 66–84 ppm) and diesters 11a–c
(δP ∼ 66–75 ppm).
Bis(2-phenylethyl)phosphinothioic O-acid anhydride 13a was prepared by reaction of bis
(2-phenylethyl)phosphine sulfide 1 and water in the system Et3N/CCl4.[34] Diphenylphos-
phinothioic O-acid anhydride 13c was obtained from diphenylchlorophosphine, elemental sulfur
and water.[35] The 1H, 13C and 31P spectra were recorded on a Bruker DPX 400 and Bruker AV-
400 spectrometer (400.13, 100.61 and 161.98, respectively) in CDCl3 solutions and referenced to
Tetramethylsilane (1H NMR, 13C NMR) and H3PO4 (31P NMR). IR spectra were run on a Bruker
Vertex 70 instrument. Melting points (uncorrected) were measured on a Kofler micro hot-stage
apparatus. The microanalyses were performed on a Flash EA 1112 Series elemental analyzer.
Mass spectra of electron ionization (70 eV) were obtained on a Shimadzu GCMS–QP5050 A
(quadruple mass analyzer, the range of detected mass was from 34 to 650 Da); capillary column
SPB–5 ms (60 m × 0.25 mm × 0.25 μm), gas carrier helium, flow rate 0.7 mL min−1, tempera-
ture of injector and ion source 250◦C, pressure 100 kPa; temperature programming from 50◦C to
250◦C, 10◦ min−1
.
4.2. General procedure for the synthesis of dithiophosphinic esters 9a–g
A mixture of secondary phosphine sulfides 1–3 (1.0 mmol) and Et3N (1.0 mmol) in 4 mL of CCl4
was stirred at 20–22◦C for 10 min. The thiols 4–8 (1.0 mmol) were added, and the reaction mixture
was stirred at 20–22◦C for 0.5–24 h (see also Table 1). Chloroform (molecular mass 118 [M]+)
was identified qualitatively in the reaction mixture by chromato-mass spectrometry. The solvent
was removed under reduced pressure, and 1,4-dioxane (3 mL) was added. The precipitated white
solid [triethylammonium chloride, 0.131 g (96%)] was filtered, and 1,4-dioxane was evaporated.
Then hexane (2 mL) was added to the residue, and the resulting mixture was allowed to stand
for 12 h at 0–1◦C. The solution was removed from the precipitate by decantation, a solvent was
evaporated and the residue was dried under vacuum to give ester 9a. In the case of esters 9b–g, the
residue (after 1,4-dioxane was evaporated under vacuum) was washed with hexane (3 × 1 mL)
and dried in vacuum to afford 9b–g.
4.2.1. Bis(2-phenylethyl)dithiophosphinic ethyl ester (9a)
1
Waxy product; yield: 0.217 g (65%). H NMR (400 MHz, CDCl3): δ = 1.41 (t, 3JHH = 7.5 Hz,
3 H, Me), 2.34–2.40 (m, 4 H, CH2P), 2.93–3.12 (m, 6 H, PhCH2, CH2S), 7.21–7.25, 7.30–7.33
3
(m, 10 H, Ph). 13C NMR (100.61 Hz, CDCl3): δ = 16.70 (d, JPC = 4.6 Hz, Me), 25.93 (d,
2
1
2JPC = 2.3 Hz, SCH2), 28.94 (d, JPC = 2.7 Hz, PhCH2), 39.03 (d, JPC = 48.9 Hz, CH2P),
126.44 (Cp), 128.22 (Co), 128.63 (Cm), 140.35 (d, JPC = 16.4 Hz, Ci). 31P NMR (161.98 Hz,
3
CDCl3): δ = 73.9. IR (neat, ν, cm−1): 631 sh, 617 (P S). Anal. Calcd for C18H23PS2: C, 64.64;
=
H, 6.93; P, 9.26; S, 19.17. Found: C, 64.75; H, 6.89; P, 9.02; S, 19.12%.
4.2.2. Bis(2-phenylethyl)dithiophosphinic phenyl ester (9b )
White powder; yield: 0.36 g (94%); mp 69–70◦C (hexane).1H NMR (400.13 MHz, CDCl3):
δ = 2.24–2.38 (m, 4 H, CH2P), 3.01–3.10 (m, 4 H, PhCH2), 7.17–7.25 (m, 6 H, Ho, Hp, Ph),
3
3
7.30 (dd, JHH = 7.6 Hz, JHH = 8.3 Hz, 4 H, Hm, Ph), 7.38–7.46 (m, 3 H, Hm, Hp, SPh), 7.59
(d, 3JHH = 6.8 Hz, 2 H, Ho, SPh). 13C NMR (100.61 Hz, CDCl3): δ = 28.93 (d, 2JPC = 3.2 Hz,
PhCH2), 36.91 (d, 1JPC = 47.1 Hz, CH2P), 126.54 (Cp, Ph), 127.10 (d, 2JPC = 6.4 Hz, Ci, SPh),

Journal of Sulfur Chemistry 243
128.27 (Co, Ph), 128.69 (Cm, Ph), 129.45 (d, 4JPC = 2.4 Hz, Cm, SPh), 129.92 (d, 5JPC = 2.8 Hz,
3
3
Cp, SPh), 136.29 (d, JPC = 3.2 Hz, Co, SPh), 140.29 (d, JPC = 16.4 Hz, Ci, Ph). 31P NMR
(161.98 Hz, CDCl3): δ = 75.3. IR (KBr,ν, cm−1): 612 (P S). Anal. Calcd for C22H23PS2: C,
=
69.08; H, 6.06; P, 8.10; S, 16.77. Found: C, 68.97; H, 6.09; P, 8.02; S, 16.68%.
4.2.3. Bis(2-phenylethyl)dithiophosphinic 2-quinolinyl ester (9c)
1
Yellow powder; yield: 0.373 g (86%); mp 75–76◦C (hexane). H NMR (400.13 MHz, CDCl3):
δ = 2.57–2.62 (m, 2 H, CH2P), 3.04–3.24 (m, 6 H, CH2P, PhCH2), 7.14–7.27 (m, 10 H, Ph),
7.41 (d, 3JHH = 8.6 Hz, 1 H, H-3, Quinoline), 7.57 (dd, 3JHH = 8.3 Hz, 3JHH = 7.5 Hz, 1 H, H-6,
Quinoline), 7.74(dd, 3JHH = 8.6 Hz, 3JHH = 7.5 Hz, 1H, H-7, Quinoline), 7.83(d, 3JHH = 8.3 Hz,
1 H, H-5, Quinoline), 7.93 (d, 3JHH = 8.6 Hz, 1 H, H-8, Quinoline), 8.09 (d, 3JHH = 8.6 Hz, 1 H,
H-4, Quinoline). 13C NMR (100.61 Hz, CDCl3): δ = 28.55 (d, JPC = 3.0 Hz, PhCH2), 37.26
2
(d, 1JPC = 46.1 Hz, CH2P), 115.58 (C-3, Quinoline), 123.17 (C-6, Quinoline), 126.35 (Cp, Ph),
126.67 (C-10, Quinoline), 126.98 (C-8, Quinoline), 127.90, 128.22 (Co, Ph), 128.36, 128.58
4
(Cm, Ph), 130.45 (C-5, Quinoline), 131.55 (d, JPC = 11.6 Hz, C-4, Quinoline), 137.14 (C-8,
Quinoline), 140.65(d, 3JPC = 17.7 Hz, Ci, Ph), 148.33(C-9, Quinoline), 155.89(d, 2JPC = 6.0 Hz,
C-2, Quinoline). 31P NMR (161.98 Hz, CDCl3): δ = 79.1. IR (KBr, ν, cm−1): 609 (P S). Anal.
=
Calcd for C25H24NPS2: C, 69.25; H, 5.58; N, 3.23; P, 7.14; S, 14.79. Found: C, 68.91; H, 5.55;
N, 3.19; P, 7.05; S, 14.52%.
4.2.4. Bis(2-phenylethyl)dithiophosphinic 1,3-benzoxazol-2-yl ester (9d)
Waxy product; yield: 0.351 g (83%). 1H NMR (400.13 MHz, CDCl3): δ = 2.38–2.47, 2.85–2.96
(m, 4 H, CH2P), 3.02–3.12 (m, 4 H, PhCH2), 7.07–7.11, 7.14–7.18 (m, 10 H, Ph), 7.25–7.27
(m, 2 H, H-5, H-6, Benzoxazol), 7.40–7.43 (m, 1 H, H-4, Benzoxazol), 7.57–7.59 (m, 1 H,
H-7, Benzoxazol). 13C NMR (100.61 Hz, CDCl3): δ = 28.44 (PhCH2), 37.36 (d, 1JPC = 44.7 Hz,
CH2P), 110.58 (C-7, Benzoxazol), 119.75 (C-4, Benzoxazol), 124.99 (C-6, Benzoxazol), 125.75
(C-5, Benzoxazol), 126.63 (Cp, Ph), 128.43 (Co, Ph), 128.72 (Cm, Ph), 140.03 (d, 3JPC = 16.1 Hz,
2
Ci, Ph), 140.88 (C-9, Benzoxazol), 151.05 (C-8, Benzoxazol), 157.12 (d, JPC = 9.0 Hz, C-2,
Benzoxazol). 31P NMR (161.98 Hz, CDCl3): δ = 84.3. IR (neat, ν, cm−1): 614 (P S). Anal.
=
Calcd for C23H22NOPS2: C, 65.22; H, 5.24; N, 3.31; P, 7.31; S, 15.14. Found: C, 65.13; H, 5.21;
N, 3.28; P, 7.22; S, 15.08%.
4.2.5. Bis(2-phenylethyl)dithiophosphinic 1,3-benzothiazol-2-yl ester (9e)
White solid; yield: 0.400 g (91%); mp 69–70◦C (hexane). H NMR (400.13 MHz, CDCl3):
1
δ = 2.31–2.41 (m, 2 H, CH2P), 2.74–2.86, 2.98–3.13 (m, 6 H, CH2P, PhCH2), 7.07–7.10,
3
3
7.14–7.18 (m, 10 H, Ph), 7.33 (dd, JHH = 8.0 Hz, JHH = 7.3 Hz, 1 H, H-6, Benzothiazol),
7.40 (dd, 3JHH = 7.9 Hz, 3JHH = 7.3 Hz, 1 H, H-5, Benzothiazol), 7.75 (d, 3JHH = 7.9 Hz, 1 H,
3
H-4, Benzothiazol), 7.88 (d, JHH = 8.0 Hz, 1 H, H-7, Benzothiazol). 13C NMR (100.61 Hz,
2
1
CDCl3): δ = 28.47 (d, JPC = 2.7 Hz, PhCH2), 37.43 (d, JPC = 44.7 Hz, CH2P), 121.31 (C-6,
Benzothiazol), 122.89 (C-4, Benzothiazol), 125.90 (C-5, Benzothiazol), 126.47 (Cp, Ph), 126.61
(C-7, Benzothiazol), 128.33 (Co, Ph), 128.60 (Cm, Ph), 136.67 (C-8, Benzothiazol), 140.10 (d,
3JPC = 16.8 Hz, Ci, Ph), 153.21 (C-2, Benzothiazol), 157.43 (d, 2JPC = 6.1 Hz, C-9, Benzothia-
zol). 31P NMR (161.98 Hz, CDCl3): δ = 83.4. IR (KBr, ν, cm−1): 613 (P S). Anal. Calcd for
=
C23H22NPS3: C, 62.84; H, 5.04; N, 3.19; P, 7.05; S, 21.88. Found: C, 62.42; H, 4.99; N, 3.17; P,
6.92; S, 21.81%.

244 P.A. Volkov et al.
4.2.6. Bis(2-phenylpropyl)dithiophosphinic phenyl ester (9f)
Waxy product; yield: 0.37 g (90%). 1H NMR (400.13 MHz, CDCl3): δ = 1.24, 1.32, 1.34, 1.38,
1.39 (5 d, 3JHH = 7.0 Hz, 3JHH = 6.9 Hz, 3JHH = 7.0 Hz, 3JHH = 7.1 Hz, 3JHH = 7.1 Hz, 6 H, Me,
respectively), 1.97–2.13, 2.19–2.24, 2.27–2.35 (m, 4 H, CH2P), 3.13–3.19, 3.25–3.37, 3.38–3.51
(m, 2 H, PhCH), 7.09–7.16, 7.18–7.28, 7.30–7.35, 7.37–7.46, 7.51–7.55 (m, 15 H, Ph, SPh). 13
C
NMR (100.61 Hz, CDCl3): δ = 23.76, 24.21, 24.35, 24.41 (4 d, 3JPC = 10.3 Hz, 3JPC = 12.6 Hz,
3JPC = 8.8 Hz, 3JPC = 8.2 Hz, Me, respectively), 35.00, 35.27, 35.48, 35.58 (4 d, 2JPC = 3.7 Hz,
2
2
2JPC = 3.2 Hz, JPC = 2.9 Hz, JPC = 3.7 Hz, PhCH, respectively), 42.60, 43.74, 44.06, 44.87
1
1
1
1
(4 d, JPC = 45.7 Hz, JPC = 45.9 Hz, JPC = 45.5 Hz, JPC = 46.9 Hz, CH2P, respectively),
126.53, 126.81, 127.08–127.52 (m, Co, Ph; Ci, SPh), 128.53–128.71 (m, Cm, Ph), 129.11,
4
4
4
129.17, 129.21 (3 d, JPC = 2.5 Hz, JPC = 2.3 Hz, JPC = 2.3 Hz, Cm, SPh), 129.62, 129.67,
5
5
5
129.76 (3 d, JPC = 2.9 Hz, JPC = 2.8 Hz, JPC = 2.7 Hz, Cp, SPh), 136.30, 136.40, 136.51
(3 d, 3JPC = 3.5 Hz, Co, SPh), 145.74, 145.88, 146.32, 146.60 (4 d, 3JPC = 6.4 Hz, 3JPC = 8.2 Hz,
3
3JPC = 8.8 Hz, JPC = 9.1 Hz, Ci, Ph). 31P NMR (161.98 Hz, CDCl3): δ = 74.2, 74.6, 75.6. IR
(neat, ν, cm−1): 617 (P S). Anal. Calcd for C24H27PS2: C, 70.21; H, 6.63; P, 7.54; S, 15.62.
=
Found: C, 70.14; H, 6.59; P, 7.42; S, 15.48%.
4.2.7. Diphenyldithiophosphinic phenyl ester (9g)
1
White powder; yield: 0.323 g (99%); mp 59–60◦C (ethanol) (Lit. [36] 57–59◦C). H NMR
(400.13 MHz, CDCl3): δ = 7.21–7.26, 7.31–7.36 (m, 5 H, SPh), 7.45–7.53 (m, 6 H, Hm, Hp,
Ph), 7.95–8.01 (m, 4 H, Ho, Ph). 13C NMR (100.61 Hz, CDCl3): δ = 128.80 (d, 2JPC = 5.2 Hz,
3
3
Ci, SPh), 128.45 (d, JPC = 13.4 Hz, Cm, Ph), 128.88 (d, JPC = 2.2 Hz, Cm, SPh), 129.57
(d, 4JPC = 3.0 Hz, Cp, SPh), 131.76(d, 2JPC = 11.2 Hz, Co, Ph), 131.99(d, 4JPC = 3.0 Hz, Cp, Ph),
133.64 (d, 1JPC = 83.6 Hz, Ci, Ph), 136.38 (d, 3JPC = 3.94 Hz, Co, SPh). 31P NMR (161.98 Hz,
CDCl3): δ = 65.5 (Lit. [37] 65.3). IR (KBr, ν, cm−1): 653 (P S). Anal. Calcd for C18H15PS2: C,
=
66.23; H, 4.63; P, 9.49; S, 19.65. Found: C, 66.11; H, 4.59; P, 9.21; S, 19.48%.
4.3. General procedure for the synthesis of dithiophosphinic diesters 11a–c
A mixture of secondary phosphine sulfides 1–3 (1.0 mmol) and Et3N (1.0 mmol) in CCl4 (4 mL)
was stirred at 20–22◦C for 10 min. The 4-(4-sulfanylphenoxy)benzenethiol 10 (0.5 mmol) was
added, and the reaction mixture was stirred at 20–22◦C for 0.5–1.5 h (see alsoTable 2). Chloroform
(molecular mass 118 [M]+) was identified qualitatively in the reaction mixture by chromato-mass
spectrometry. The solvent was removed under reduced pressure, and 1,4-dioxane (3 mL) was
added. The precipitated white solid [triethylammonium chloride, 0.131 g (96%)] was filtered, and
1,4-dioxane was evaporated. The residue was re-precipitated from chloroform (1 mL) into hexane
(10 mL) to give dithiophosphinic diesters 11a–c.
4.3.1. 4-4-[(Diphenethylphosphorothioyl)sulfanyl]phenoxyphenyl
diphenethyl-phosphinodithioate (11a)
1
Waxy product; yield: 0.351 g (90%). H NMR (400.13 MHz, CDCl3): δ = 2.28–2.38 (m, 8 H,
3
CH2P), 2.96–3.09 (m, 8 H, PhCH2), 7.03 (d, JHH = 7.7 Hz, 4 H, H-3,5, SC6H4), 7.17–7.32
3
(m, 20 H, Ph), 7.54 (d, JHH = 7.74 Hz, 4 H, H-2,6, SC6H4). 13C NMR (100.61 Hz, CDCl3):
δ = 29.02 (d, 2JPC = 2.7 Hz, PhCH2), 37.06 (d, 1JPC = 46.8 Hz, CH2P), 119.82 (C-3,5, SC6H4),
121.35 (d, 2JPC = 6.1 Hz, C-1, SC6H4), 126.59 (Cp, Ph), 128.26 (Co, Ph), 128.72 (Cm, Ph), 138.12
(d, 3JPC = 2.7 Hz, C-2,6, SC6H4), 140.21 (d, 3JPC = 15.7 Hz, Ci, Ph), 158.04 (d, 5JPC = 2.3 Hz,

Journal of Sulfur Chemistry 245
C-4, SC6H4). 31P NMR (161.98 Hz, CDCl3): δ = 75.5. IR (neat, ν, cm−1): 631 sh, 616 (P S).
=
Anal. Calcd for C44H44OP2S4: C, 67.84; H, 5.69; P, 7.95; S, 16.46. Found: C, 67.61; H, 5.66; P,
7.81; S, 16.39%.
4.3.2. 4-4-[(Di-(2-phenylpropyl)phosphorothioyl)sulfanyl]phenoxyphenyl
di-(2-(phenylpropyl)phosphinodithioate (11b)
1
Waxy product, yield: 0.367 mg (88%). H NMR (400.13 MHz, CDCl3): δ = 1.23, 1.31, 1.34,
3
3
3
3
3
1.38, 1.40 (5 d, JHH = 7.0 Hz, JHH = 6.9 Hz, JHH = 7.5 Hz, JHH = 5.1 Hz, JHH = 5.9 Hz,
12 H, Me, respectively), 2.00–2.14, 2.18–2.35 (m, 8 H, CH2P), 3.11–3.16, 3.23–3.32, 3.38–3.49
(m, 4 H, PhCH), 6.88–7.04 (m, 4 H, H-3,5, SC6H4), 7.10–7.15, 7.18–7.26, 7.29–7.34 (m, 20
H, Ph; 2 H, H-2,6, SC6H4), 7.44–7.52 (2 H, H-2,6, SC6H4). 13C NMR (100.61 Hz, CDCl3):
δ = 23.72, 24.13, 24.27, 24.29 (4 d, 3JPC = 10.3 Hz, 3JPC = 12.9 Hz, 3JPC = 9.1, 3JPC = 8.6 Hz,
Me, respectively), 34.92, 35.23, 35.45, 35.50 (4 d, 2JPC = 3.5 Hz, 2JPC = 3.0 Hz, 2JPC = 2.64 Hz,
1
2JPC = 3.5 Hz, PhCH, respectively), 42.50, 43.72, 44.01, 44.91, 44.96 (5 d, JPC = 45.3 Hz,
1JPC = 45.3 Hz, 1JPC = 45.3 Hz, 1JPC = 46.6 Hz, 1JPC = 46.9 Hz, CH2P, respectively), 118.90–
118.98, 119.35–119.51, 120.00–120.09 (3 m, C-3,5, SC6H4), 121.23–121.53 (m, C-1, SC6H4),
126.47, 126.52, 126.65, 126.74 (4 s, Cp, Ph), 126.98, 127.03, 127.09, 127.31 (4 s, Co, Ph),
128.46, 128.62 (2 s, Cm, Ph), 138.01–138.18 (m, C-2,6, SC6H4), 145.61, 145.73, 146.15, 146.41
(4 d, 3JPC = 6.0 Hz, 3JPC = 8.24 Hz, 3JPC = 9.1 Hz, 3JPC = 8.6 Hz, Ci, Ph), 157.77, 157.92 (2 d,
5JPC = 2.2 Hz, JPC = 3.0 Hz, C-4, SC6H4). 31P NMR (161.98 Hz, CDCl3): δ = 74.16–74.48,
5
75.37–75.42 m. IR (neat, ν, cm−1): 633 sh, 618 (P S). Anal. Calcd for C48H52OP2S4: C, 69.03;
=
H, 6.28; P, 7.42; S, 15.36. Found: C, 68.91; H, 6.26; P, 7.28; S, 15.29%.
4.3.3. 4-4-[(Diphenylphosphorothioyl)sulfanyl]phenoxyphenyl diphenylphosphino-dithioate
(11c)
Waxy product; yield: 0.327 g (98%). 1H NMR (400.13 MHz, CDCl3): δ = 6.82 (d, 3JHH = 8.6 Hz,
4 H, H-3,5, SC6H4), 7.30 (2 d, 3JHH = 8.6 Hz, 4JPH = 1.8 Hz, 4 H, H-2,6, SC6H4), 7.45–7.55 (m,
12 H, Hm, Hp, Ph), 7.94–7.99 (m, 8 H, Ho, Ph). 13C NMR (100.61 Hz, CDCl3): δ = 119.504 (C-3,5,
2
2
SC6H4), 121.11 (d, JPC = 5.2 Hz, C-1, SC6H4), 128.65 (d, JPC = 13.3 Hz, Cm, Ph), 131.91
3
4
1
(d, JPC = 10.8 Hz, Co, Ph), 132.13 (d, JPC = 1.5 Hz, Cp, Ph), 133.60 (d, JPC = 83.5 Hz, Ci,
Ph), 138.25 (d, 3JPC = 2.8 Hz, C-2,6, SC6H4), 158.10 (d, 5JPC = 2.2 Hz, C-4, SC6H4). 31P NMR
(161.98 Hz, CDCl3): δ = 66.7. IR (neat, ν, cm−1): 652 (P S). Anal. Calcd for C36H28OP2S4: C,
=
64.84; H, 4.23; P, 9.29; S, 19.24. Found: C, 64.71; H, 4.24; P, 9.16; S, 19.08%.
4.4. Reaction of phosphine sulfide 1 with dithiol 10 in molar ratio 1:1
A mixture of secondary phosphine sulfides 1 (1.0 mmol) and Et3N (1.0 mmol) in CCl4 (4 mL) was
stirred at 20–22◦C for 10 min. The 4-(4-sulfanylphenoxy)benzenethiol 10 (1 mmol) were added,
and the reaction mixture was stirred at 20–22◦C for 1 h. According to 31P NMR data, the reac-
tion mixture contains dithiophosphinic ester 12 (31%) and dithiophosphinic diester 11a (69%).
The solvent was removed under reduced pressure, and 1,4-dioxane (3 mL) was added. The pre-
cipitated white solid (triethylammonium chloride) was filtered, and 1,4-dioxane was evaporated.
The residue was re-precipitated from CHCl3 (1 mL) to hexane (10 mL). The hexane solution was
distilled by decantation from the precipitated viscous residue [mixture of ester 12 and diester 11a
(31P NMR data)] and evaporated under reduced pressure to give a mixture of initial benzenethiol
10 and dithiophosphinic ester 12.

246 P.A. Volkov et al.
4.4.1. 4-(4-Sulfanylphenoxy)phenyl bis(2-phenylethyl)phosphinodithioate (12)
13C NMR (100.61 Hz, CDCl3): δ = 28.85 (d, 2JPC = 3.0 Hz, PhCH2), 36.72 (d, 1JPC = 46.6 Hz,
CH2P), 118.56 (C-3,5, SC6H4), 119.94 (d, 2JPC = 6.5 Hz, C-1, SC6H4), 120.57 (C-13,15, SC6H4),
125.46 (C-14, SC6H4), 126.46 (Cp, Ph), 128.15 (Co, Ph), 128.59 (Cm, Ph), 131.61 (C-12,16,
3
3
SC6H4), 137.82 (d, JPC = 3.0 Hz, C-2,6, SC6H4), 140.13 (d, JPC = 15.9 Hz, Ci, Ph), 154.08
(C-11, SC6H4), 159.20 (d, 5JPC = 2.6 Hz, C-4, SC6H4). 31P NMR (161.98 Hz, CDCl3): δ = 75.1.
4.5. Synthesis of bis(2-phenylpropyl)phosphinothioic O-acid anhydride (13b)
A mixture of bis(2-phenylpropyl)phosphine sulfide 2 (1.0 mmol) and Et3N (1.0 mmol) in 3 mL of
CCl4 was stirred at 20–22◦C for 10 min. Then H2O (0.5 mmol) in 1 mL of 1,4-dioxane was
added, and the reaction mixture was stirred at 20–22◦C for 11 h. The solvent was removed
under the reduced pressure, and 1,4-dioxane (3 mL) was added. The precipitated white solid
(triethylammonium chloride) was filtered, and 1,4-dioxane was evaporated under vacuum to
give bis(2-phenylpropyl)phosphinothioic O-acid anhydride (13b). White powder, yield 0.248 g
1
(80%), mp 120–121◦C (re-precipitated CHCl3-hexane). H NMR (400.13 MHz, CDCl3): δ =
0.90, 0.95, 0.96, 1.041, 1.044, 1.10, 1.11, 1.20, 1.22, 1.23, 1.25, 1.26, 1.27, 1.32, 1.34,
1.40, 1.41 (17 d, 3JHH = 7.0 Hz, 3JHH = 6.9 Hz, 3JHH = 6.9 Hz, 3JHH = 7.1 Hz, 3JHH = 6.9 Hz,
3
3
3
3
3
3JHH = 5.9 Hz, JHH = 6.9 Hz, JHH = 6.9 Hz, JHH = 5.5 Hz, JHH = 7.2 Hz, JHH = 5.1 Hz,
3
3
3
3
3
3JHH = 4.8 Hz, JHH = 5.5 Hz, JHH = 6.6 Hz, JHH = 5.0 Hz, JHH = 7.1 Hz, JHH = 7.1 Hz,
12 H, Me, respectively), 1.47–1.78, 1.83–2.22, 2.24–2.53, 2.56–2.69 (m, 8 H, CH2P), 2.82–2.91,
2.97–3.30, 3.31–3.47 (m, 4 H, PhCH), 6.94–7.03, 7.07–7.10, 7.15–7.33 (m, 20 H, Ph). 31P NMR
(161.98 Hz, CDCl3): δ = 102.1–102.9, 103.9–104.4, 104.9–105.3, 105.9–106.2 m. Anal. Calcd
for C36H44OP2S2: C, 69.87; H, 7.17; P, 10.01; S, 10.36. Found: C, 69.76; H, 7.13; P, 9.78; S,
10.29%.
Funding
This work was supported by leading scientific schools by the President of the Russian Federation [grant number NSh-
1550.2012.3] and Russian Fund for Basic Research [grant number 12-03-31631].
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