Peroxide promoted metal-free thiolation of phosphites by thiophenols/disulfides

Article abstract of DOI:10.1016/j.tet.2015.08.025

A metal-free oxidative P-S bonds coupling method for the synthesis of thiophosphates with DTBP as the oxidant is established. A wide range of functionalities are tolerated in the method. This method provides a facile way to synthesize thiophophates from readily available thiophenols/disulfides and phosphites.

Full text of DOI:10.1016/j.tet.2015.08.025

Tetrahedron 71 (2015) 7853e7859
Contents lists available at ScienceDirect
Tetrahedron
journal homepage: www.elsevier.com/locate/tet
Peroxide promoted metal-free thiolation of phosphites by
thiophenols/disulfides
*
*
Jichao Wang, Xin Huang, Zhangqin Ni, Sichang Wang, Yuanjiang Pan , Jun Wu
Department of Chemistry, Zhejiang University, Hangzhou 310027, People’s Republic of China
a r t i c l e i n f o
a b s t r a c t
Article history:
Received 18 June 2015
Received in revised form 24 July 2015
Accepted 10 August 2015
Available online 14 August 2015
A metal-free oxidative PeS bonds coupling method for the synthesis of thiophosphates with DTBP as the
oxidant is established. A wide range of functionalities are tolerated in the method. This method provides
a facile way to synthesize thiophophates from readily available thiophenols/disulfides and phosphites.
Ó 2015 Elsevier Ltd. All rights reserved.
Keywords:
Oxidative coupling
Thiophophate
Di-tert-butyl peroxide
Metal-free
Phosphites
1. Introduction
any bases or acids. Herein, we report a metal-free oxidative cou-
pling reaction between thiophenols (or disulfides) and phosphites
The formation of PeS bonds is one important tool in building
sulfur-contained organophosphorus compounds. Among them,
thiophosphates are prominent due to their promising biological
activities and applications in agricultural industry.1,2 Conventional
strategies for the synthesis of thiophosphates often started with
prefunctionalized substrates,3 which usually included multiple
steps and limited their applications. In the past year, the direct
thiolation of phosphites using readily accessible sulfur source has
made significant progress.4 For example, Zhao and co-workers
described an efficient copper iodide catalyzed PeS coupling re-
action between disulfides and dialkyl phosphites.4d In 2014, an
excellent thiophosphates synthesis work using thiols and dialkyl
phosphites in the presence of N-chlorosuccinimide has been re-
ported by Lee’s group.4f
Recently, the direct functionalization of SeH bonds under oxi-
dative conditions has received much attention.5 This atom and step
economy pathway has been applied in the synthesis of sulfur-
contained compounds, such as in the CeS bonds building of thio-
esters.6 In light of the precedent literature about phosphorous
radicals and our research on thiol chemistry,7,8 we designed an
oxidative PeS bonds coupling reaction for the synthesis of thio-
phosphates, which exhibited several advantages, including the use
of readily available substrates, high atom economy, and no use of
using di-tert-butyl peroxide (DTBP) as oxidant.
2. Results and discussion
We started our investigation by introducing thiophenol (1a) and
diethyl phosphite (2a) as the model substrates to optimize the re-
action conditions. Initially, 1a and 2a were added to DMSO in the
presence of TBHP and reacted at 60 ꢀC for 20 h (Table 1, entry 1).
Unfortunately, no desired product was detected. By elevating the
temperature to 80 ꢀC, product 3a could be obtained in 62%. We then
screened a wide range of the oxidant candidates, such as H2O2,
TBPB, DTBP, K2S2O8, and (PhCOO)2 (entries 3e7), among them,
DTBP was found to be the best choice, which furnished the desired
product in 92% yield (entry 5). Besides, a decreased yield was found
when the reaction was proceeded under air (entry 8). Furthermore,
the solvents effect was studied. A variety of solvents, including
dioxane, toluene, DMF, H2O, and ethyl acetate were tested and all of
them showed poor yields or not reacted at all (entries 9e13). On the
other hand, increasing the reaction temperature to 100 ꢀC or re-
ducing the amount of oxidant (entries 14 and 15) slightly reduced
the yields. Yet it was worth noting that, even without any oxidants,
3a could be obtained in 21% yield, which could be ascribed to the
weak oxidizability of DMSO.9
With the optimal reaction conditions in hand, the substrates
scope of thiophenols was explored later. As shown in Scheme 1,
a wide range of substituted thiophenols were subjected to our
* Corresponding authors. E-mail address: cheyjpan@zju.edu.cn (Y. Pan).
http://dx.doi.org/10.1016/j.tet.2015.08.025
0040-4020/Ó 2015 Elsevier Ltd. All rights reserved.

7854
J. Wang et al. / Tetrahedron 71 (2015) 7853e7859
Table 1
reaction conditions, and formed the corresponding thiophosphates
Optimization of the reaction conditiona
in good to excellent yields. Functionalities including alkyl, MeO,
AcNH, F, Br, Cl were well tolerated. To our delight, sensitive groups
such as NH2 and OH were well persevered under our oxidative
conditions and gave good yields (3j, 3k). Besides, thiophenols with
single electron-donating or electron-withdrawing group showed
no obvious differences in reactivity, for example, the yields of
meta-/para-methoxy substituted thiophenols (entries 3f, 3g) are
comparable to their chloro counterparts (3q, 3r). However, for the
thiophenol with double electron-withdrawing groups (entry 3s),
a reduced yield was found. Meanwhile, no desired product was
formed when using nitro-substituted thiophenol as substrate (3t).
Except for the electronic effect, steric effect also had a remarkable
influence on this reaction. The ortho-substituted substrates (3e, 3p)
revealed less reactivity when compared with their meta- or para-
analogs (3f, 3r). And such effect could also be found in the highly
substituted 2,6-dimethyl-benzenethiol (3d).
As we all know, disulfides were important sulfur source in
building PeS bonds, which proved to be more stable and bearing
less odor. Under this background, several disulfides substrates were
then employed to our reaction. The result was summarized in
Scheme 2. All disulfides were smoothly reacted with diethyl
phosphite and most of them afforded the corresponding thio-
phosphates with moderate to good yields. It could be found that
electron-withdrawing group such as chloro (3p, 3r) facilitated our
reaction, while disulfides with electron-donating groups (3u, 3e)
showed lower reactivity. Furthermore, disulfide that bearing strong
electron-withdraw group (NO2) could also be transformed to the
corresponding product (3v) though in low yield. Besides, steric
hindrance also exhibited significant influence. A reduced yield was
found in the case (3p) of ortho-substituted thiophosphate in con-
trast to its related para product (3r).
Entry
Oxidant (equiv)
Solvent
T (ꢀC)
Yieldb (%)
1
2
3
4
5
6
TBHP (2)
TBHP (2)
H2O2 (2)
TBPB (2)
DTBP (2)
K2S2O8 (2)
(PhCOO)2 (2)
DTBP (2)
DTBP (2)
DTBP (2)
DTBP (2)
DTBP (2)
DTBP (2)
DTBP (2)
DTBP (1)
DMSO
DMSO
DMSO
DMSO
DMSO
DMSO
DMSO
DMSO
Dioxane
Toluene
DMF
60
80
80
80
80
80
80
80
80
80
80
80
80
100
80
80
N.D.
62
87
86
92
N.D.
29
85
7
N.D.
44
N.D.
N.D.
83
82
21
7
8c
9
10
11
12
13
14
15
16
H2O
EtOAc
DMSO
DMSO
DMSO
TBHP¼tert-butyl hydroperoxide, DTBP¼di-tert-butyl peroxide, TBPB¼tert-
butylperoxybenzoate.
a
Reaction conditions: thiophenol (1.0 mmol), diethyl phosphite (2.0 mmol), ox-
idant (2.0 mmol) were added in 2 mL solvent and heated under a nitrogen atmo-
sphere for 20 h.
b
Isolated yield.
Reaction in air condition.
c
Scheme 2. Coupling of diethyl phosphite with substituted disulfides.a
To further explore the substrate scope, reactions between thi-
ophenols and a range of dialkyl phosphites were also examined. As
depicted in Scheme 3, dialkyl phosphites with different alkyl chains
could be successfully converted to the related thiophosphates with
yields from 37% to 92%. Notably, variation of the chain length in the
dialkyl phosphite substrates significantly affected the reactivity.
When the straight carbon chains increased, an obvious trend of
decrease in yield was found (5ae5g). Besides, due to the steric ef-
fect, dialkyl phosphites with branched chains (5he5j) showed
lower yields when compared with their straight chain homologs
(5b,5c). For example, under our standard conditions, only traceable
5h could be obtained (Instead of DTBP, incorporating H2O2 as the
oxidant could improve the yield to 49%.).
Subsequently, a scale-up reaction was conducted to demon-
strate the utility of this DTBP promoted PeS bonds coupling re-
action. As shown in Scheme 4, under the standard conditions,
2.80 g (10.0 mmol) of 1r could be converted to 3r in 98% yield.
Scheme 1. Coupling of diethyl phosphite with substituted thiophenols.a

J. Wang et al. / Tetrahedron 71 (2015) 7853e7859
7855
Based on the above information, a plausible reaction mechanism
was proposed and presented in Scheme 6. Firstly, the tert-butoxy
radical was generated by homo-cleavage of DTBP. The tert-butoxy
radical then reacted with thiophenol and diethyl phosphite, re-
spectively, furnished the thiyl radical A and phosphorus radical B.
The former radical quickly formed disulfide by self-coupling, then
reacted with the phosphorus radical B through a substitution
process (pathway a) or directly added to radical B (pathway b) to
afford the product.
Scheme 6. Plausible mechanism.
Scheme 3. Coupling of dialkyl phosphites with thiophenol.a
3. Conclusions
In summary, we have developed a DTBP promoted direct PeS
bonds coupling reaction by utilizing simple thiophenols/disulfides
and dialkyl phosphites as substrates. The metal-free method has
exhibited a good functional compatibility, substituents such as
bromo, chloro, fluoro, amino, and hydroxyl were well tolerated in
our reaction conditions. Additionally, dialkyl phosphites with dif-
ferent chains were suitable substrates for our reaction. In all, our
reaction has provided a more attractive pathway for the synthesis
of biological and agricultural useful thiophosphate compounds.
Scheme 4. Gram-scale reaction.
On the basis of precedent reports and the following control
experiments,6f,7g,10 a preliminary mechanism study for the DTBP
promoted PeS bond coupling reaction was conducted. As depicted
in Scheme 5, when performed in the dark, the product 3a could also
be obtained in 91% yield, which implied that a photoirradiation
process was not involved. Then, the radical inhibitor (TEMPO) was
incorporated under our optimal reaction conditions. For thiophenol
(1a) substrate, a great reduction in yield was found (17%). And
TEMPO could even block this reaction when using disulfide (4a) as
substrate. Besides, in both control experiments, thiyl radical (PhSꢁ)
was captured by TEMPO and afforded 6a, which is the strong evi-
dence that a radical pathway may be involved.
4. Experimental section
4.1. General information
Reagents and solvents were purchased from commercial sup-
pliers and used without additional purification. Some dialkyl
phosphites substrates were synthesized according to the former
report.11 1H NMR and 13C NMR spectra were recorded on a Bruker
ARX-400. High-resolution mass spectra were performed on a TOF-
MS instrument with an ESI source. Melting points were measured
on SGW.X-4 (uncorrected).
4.2. General procedure of the coupling between thiophenol/
substituted thiophenols and dialkyl phosphites (3ae3t, 5ae5j)
A Schlenk tube was charged with thiophenol 1 (1.0 mmol),
dialkyl phosphites 2 (2.0 mmol), and DTBP (2.0 mmol), then 1.5 mL
DMSO was added as solvent. This reaction was performed under N2
atmosphere at 80 ꢀC for 20 h. After completion of the reaction, the
mixture was quenched with 20 mL Na2S2O4 solution (5%) then
extracted with ethyl acetate (15 mLꢂ3). The organic layer was
combined and dried with anhydrous Na2SO4. After the evaporation
in a vacuum, the crude product was purified by a gel column
chromatography using petroleum ether/ethyl acetate as eluent to
afford the desired products 3 and 5.
4.2.1. Thiophosphoric acid O,O0-diethyl ester S-phenyl ester
(3a). Colorless oil. Yield: 226.3 mg (92%). 1H NMR (CDCl3,
Scheme 5. Control experiments.
400 MHz):
d 7.55e7.52 (m, 2H), 7.33e7.31 (m, 3H), 4.23e4.08 (m,

7856
J. Wang et al. / Tetrahedron 71 (2015) 7853e7859
4H), 1.29e1.25 (m, 6H); 13C NMR (CDCl3, 100 MHz):
d
134.5 (d,
J¼2.3 Hz), 64.0 (d, J¼6.2 Hz), 55.4, 16.1 (d, J¼7.1 Hz); 31P NMR
J¼5.0 Hz), 129.3 (d, J¼2.3 Hz), 129.0 (d, J¼2.8 Hz), 126.6 (d,
(CDCl3, 162 MHz): d 23.6; IR (neat): 3463, 2983, 1592, 1494, 1289,
J¼7.0 Hz), 64.1 (d, J¼6.13 Hz), 16.0 (d, J¼7.2 Hz); 31P NMR (CDCl3,
1249, 1162, 1015, 974, 829, 603 cmꢃ1; HRMS (ESI-TOF) m/z calcd for
162 MHz):
d
22.9; IR (neat): 3454, 2966, 1473, 1441, 1254, 1011, 747,
C
11H18O4PS [MþH]þ 277.0663, found 277.0671.
602 cmꢃ1; HRMS (ESI-TOF) m/z calcd for C10H16O3PS [MþH]þ
247.0558, found 247.0557.
4.2.8. Thiophosphoric acid O,O0-diethyl ester S-naphthalen-2-yl ester
(3h). Colorless oil. Yield: 263.1 mg (89%). 1H NMR (CDCl3,
4.2.2. Thiophosphoric acid O,O0-diethyl ester S-m-tolyl ester
400 MHz):
7.51e7.47 (m, 2H), 4.27e4.12 (m, 4H), 1.30e1.27 (m, 6H); 13C NMR
(CDCl3, 100 MHz):
d 8.06 (s, 1H), 7.82e7.77 (m, 3H), 7.60e7.57 (m, 1H),
(3b). Colorless oil. Yield: 236.0 mg (91%). 1H NMR (CDCl3,
400 MHz):
4.23e4.09 (m, 4H), 2.31 (s, 3H), 1.28 (m, 6H); 13C NMR (CDCl3,
100 MHz):
d
7.33 (m, 2H), 7.20 (m, 1H), 7.13 (d, J¼7.6 Hz, 1H),
d
134.4 (d, J¼6.7 Hz), 133.6 (d, J¼2.4 Hz), 133.1 (d,
J¼1.9 Hz), 130.9 (d, J¼4.0 Hz), 129.0 (d, J¼1.59 Hz), 127.7 (d,
J¼1.2 Hz), 127.7 (d, J¼0.85 Hz), 127.0 (d, J¼1.08 Hz), 126.7, 123.8 (d,
J¼7.4 Hz), 64.2 (d, J¼6.2 Hz), 16.0 (d, J¼7.1 Hz); 31P NMR (CDCl3,
d
139.2 (d, J¼2.3 Hz), 135.1 (d, J¼5.2 Hz), 131.5 (d,
J¼5.2 Hz),129.8 (d, J¼2.9 Hz),129.1 (d, J¼2.3 Hz),126.0 (d, J¼7.2 Hz),
64.0 (d, J¼6.1 Hz), 21.2, 16.0 (d, J¼7.3 Hz); 31P NMR (CDCl3,
162 MHz):
d 22.9; IR (neat): 3490, 3054, 2984, 2906, 1625, 1588,
162 MHz):
d
22.7; IR (neat): 3492, 2984, 1592, 1475, 1391, 1255,
1500, 1391, 1247, 1161, 1014, 941, 860, 816, 747, 602 cmꢃ1; HRMS
(ESI-TOF) m/z calcd for C14H18O3PS [MþH]þ 297.0714, found
297.0719.
1162, 1015, 974, 783, 690 cmꢃ1; HRMS (ESI-TOF) m/z calcd for
C
11H18O3PS [MþH]þ 261.0714, found 261.0719.
4.2.3. Thiophosphoric acid O,O0-diethyl ester S-(4-ethyl-phenyl) ester
4.2.9. Thiophosphoric acid S-(4-acetylamino-phenyl) ester O,O0-di-
(3c). Colorless oil. Yield: 241.6 mg (88%). 1H NMR (CDCl3,
ethyl ester (3i). White solid, mp: 132e133 ꢀC. Yield: 221.4 mg (73%).
400 MHz):
4.23e4.08 (m, 4H), 2.63e2.58 (m, 2H), 1.29e1.25 (t, J¼7.1 Hz, 6H),
1.21e1.17 (m, 3H); 13C NMR (CDCl3, 100 MHz):
d
7.44e7.42 (d, J¼8.2 Hz, 2H), 7.15e7.13 (d, J¼8.0 Hz, 2H),
1H NMR (DMSO-d6, 400 Hz):
d
10.13 (s, 1H), 7.63 (m, 2H), 7.47 (m,
2H), 4.21e4.02 (m, 4H), 2.06 (s, 3H), 1.21 (m, 6H); 13C NMR (DMSO-
d6, 100 MHz):
168.6, 140.3 (d, J¼2.9 Hz), 135.3 (d, J¼4.7 Hz), 119.6
d
145.5 (d, J¼3.1 Hz),
d
134.7 (d, J¼5.1 Hz), 128.9 (d, J¼2.4 Hz), 123.0 (d, J¼7.2 Hz), 64.0 (d,
(d, J¼2.0 Hz), 118.5 (d, J¼7.2 Hz), 63.6 (d, J¼6.1 Hz), 39.8, 39.6, 39.4,
J¼6.13 Hz), 28.5, 16.0 (d, J¼7.2 Hz), 15.3; 31P NMR (CDCl3, 162 MHz):
39.2, 23.9, 15.7 (d, J¼6.9 Hz); 31P NMR (DMSO-d6, 162 MHz):
d 21.8;
d
23.4; IR (neat): 3454, 2969, 1477, 1391, 1254, 1161, 1014, 973, 828,
IR (KBr): 3303, 2985, 1901, 1668, 1591, 1536, 1396, 1317, 1239, 1014,
969, 815, 747, 605 cmꢃ1; HRMS (ESI-TOF) m/z calcd for C12H19NO4PS
[MþH]þ 304.0772, found 304.0783.
790, 600 cmꢃ1; HRMS (ESI-TOF) m/z calcd for C12H20O3PS [MþH]þ
275.0871; found 275.0874.
4.2.4. Thiophosphoric acid S-(2,6-dimethyl-phenyl) ester O,O0-diethyl
4.2.10. Thiophosphoric acid S-(2-amino-phenyl) ester O,O0-diethyl
ester (3d). Colorless oil. Yield: 213.6 mg (78%). 1H NMR (CDCl3,
ester (3j). Colorless oil. Yield: 201.2 mg (77%). 1H NMR (CDCl3,
400 MHz):
d
7.18e7.10 (m, 3H), 4.16e4.05 (m, 4H), 2.58 (s, 6H),
143.3 (d, J¼4.7 Hz),
400 MHz):
2H), 4.19e4.08 (m, 4H), 3.73 (br, 2H), 1.29e1.25 (m, 6H); 13C NMR
(CDCl3, 100 MHz):
149.1, 137.5 (d, J¼4.2 Hz), 131.2 (d, J¼3.2 Hz),
d 7.37e7.35 (m, 1H), 7.16e7.12 (m, 1H), 6.75e6.66 (m,
1.29e1.25 (m, 3H); 13C NMR: (CDCl3, 100 MHz)
d
129.4 (d, J¼3.6 Hz), 128.4 (d, J¼3.2 Hz), 124.8 (d, J¼7.9 Hz), 64.2 (d,
d
J¼7.3 Hz), 22.5,16.1 (d, J¼6.8 Hz); 31P NMR (CDCl3,162 MHz):
d
23.1;
119.0 (d, J¼2.6 Hz), 116.2 (d, J¼2.6 Hz), 108.4 (d, J¼7.5 Hz), 64.5 (d,
IR (neat): 3489, 3056, 2982, 2930, 2736, 1939, 1774, 1630, 1460,
1390, 1252, 1163, 1016, 968, 774, 605 cmꢃ1; HRMS (ESI-TOF) m/z
calcd for C12H20O3PS [MþH]þ 275.0871; found 275.0872.
J¼6.9 Hz), 16.1 (d, J¼6.9 Hz); 31P NMR (CDCl3, 162 MHz):
d 22.8; IR
(neat): 3345, 2982, 1615, 1479, 1392, 1297, 1209, 1099, 818, 752,
549 cmꢃ1; HRMS (ESI-TOF) m/z calcd for C10H17NO3PS [MþH]þ
262.0667, found 263.0669.
4.2.5. Thiophosphoric acid O,O0-diethyl ester S-(2-methoxy-phenyl)
ester (3e). Colorless oil. Yield: 88.3 mg (32%). 1H NMR (CDCl3,
4.2.11. Thiophosphoric acid O,O0-diethyl ester S-(3-hydroxy-phenyl)
400 MHz):
2H), 4.26e4.12 (m, 4H), 3.86 (s, 3H), 1.29e1.26 (m, 6H); 13C NMR
(CDCl3, 100 MHz):
d
7.58e7.55 (m, 1H), 7.33e7.23 (m, 1H), 6.93e6.87 (m,
ester (3k). Colorless oil. Yield: 222.7 mg (85%); 1H NMR (CDCl3,
400 MHz):
1H), 4.24e4.10 (m, 4H), 1.31e1.28 (m, 6H); 13C NMR (CDCl3,
100 MHz):
157.5 (d, J¼2.0 Hz), 125.9 (d, J¼2.4 Hz), 125.7 (d,
d 7.12e7.08 (m, 2H), 6.99e6.97 (m, 1H), 6.77e6.75 (m,
d
159.4 (d, J¼7.9 Hz), 136.9 (d, J¼4.4 Hz), 130.9 (d,
J¼2.9 Hz), 121.3 (d, J¼2.5 Hz), 114.5 (d, J¼7.1 Hz), 114.4 (d,
d
J¼10.0 Hz), 63.8 (d, J¼5.7 Hz), 55.8; 16.0 (d, J¼7.6 Hz); 31P NMR
J¼5.5 Hz), 121.9 (d, J¼6.9 Hz), 116.9 (d, J¼5.0 Hz), 64.6 (d, J¼6.6 Hz),
(CDCl3, 162 MHz):
d
22.9; IR (neat): 3442, 2984, 2939, 2415, 1639,
16.0 (d, J¼7.1 Hz); 31P NMR (CDCl3, 162 MHz):
d 20.8; IR (neat):
1583, 1479, 1392, 1250, 1018, 977, 795, 755, 575 cmꢃ1; HRMS (ESI-
3228, 2986, 2926, 1583, 1475, 1443, 1219, 1160, 1219, 1014, 978, 885,
609 cmꢃ1; HRMS (ESI-TOF) m/z calcd for C10H16O4PS [MþH]þ
263.0507, found 263.0507.
TOF) m/z calcd for C11H18O4PS [MþH]þ 277.0663, found 277.0667.
4.2.6. Thiophosphoric acid O,O0-diethyl ester S-(3-methoxy-phenyl)
ester (3f). Colorless oil. Yield: 234.8 mg (85%). 1H NMR (CDCl3,
4.2.12. Thiophosphoric acid O,O0-diethyl ester S-(3-fluoro-phenyl)
ester (3l). Colorless oil. Yield: 190 mg (72%). 1H NMR (CDCl3,
400 MHz):
1H), 4.26e4.13 (m, 4H), 3.81 (s, 3H), 1.33e1.30 (m, 6H); 13C NMR
(CDCl3, 100 MHz):
d 7.27e7.25 (m, 1H), 7.15e7.12 (m, 2H), 6.91e6.89 (m,
400 MHz):
d
7.34e7.26 (m, 3H), 7.07e7.01 (m, 1H), 4.25e4.10 (m,
163.7 (d,
d
159.8 (d, J¼2.1 Hz), 130.0 (d, J¼2.2 Hz), 127.4 (d,
4H), 1.31e1.27 (m, 6H); 13C NMR (CDCl3, 100 MHz):
d
J¼6.9 Hz),126.6 (d, J¼5.5 Hz), 119.6 (d, J¼5.2 Hz),115.0 (d, J¼2.6 Hz),
J¼2.2 Hz), 161.2 (d, J¼2.3 Hz), 130.5 (dd, J1¼8.2 Hz, J2¼2.1 Hz), 130
(dd, J1¼5.6 Hz, J2¼3.2 Hz), 128.6 (t, J¼7.8 Hz), 121.4 (dd, J1¼22.7 Hz,
J2¼5.2 Hz), 116.3 (dd, J1¼20.1 Hz, J2¼2.6 Hz), 64.3 (d, J¼6.2 Hz), 16.0
64.1 (d, J¼6.2 Hz), 55.3, 16.0 (d, J¼7.2 Hz); 31P NMR (CDCl3,
162 MHz):
d 22.8; IR (neat): 3490, 2984, 2938, 2070, 1590, 1478,
1250, 1161, 1013, 973, 857, 788, 687, 606 cmꢃ1; HRMS (ESI-TOF) m/z
calcd for C11H18O4PS [MþH]þ 277.0663, found 277.0665.
(d, J¼7.1 Hz); 31P NMR (CDCl3, 162 MHz):
d 21.9; IR (neat): 3494,
3070, 2986, 1581, 1474, 1422, 1251, 1161, 1048, 976, 876, 786, 682,
603 cmꢃ1; HRMS (ESI-TOF) m/z calcd for C10H15FO3PS [MþH]þ
265.0464, found 265.0468.
4.2.7. Thiophosphoric acid O,O0-diethyl ester S-(4-methoxy-phenyl)
ester (3g). Colorless oil. Yield: 265.1 mg (96%). 1H NMR (CDCl3,
400 MHz):
4H), 3.77 (s, 3H), 1.29e1.26 (m, 6H); 13C NMR (CDCl3, 100 MHz):
160.5 (d, J¼2.9 Hz), 136.4 (d, J¼4.7 Hz), 116.6 (d, J¼7.4 Hz), 115.0 (d,
d
7.45e7.43 (m, 2H), 6.85e6.83 (m, 2H), 4.19e4.10 (m,
4.2.13. Thiophosphoric acid O,O0-diethyl ester S-(4-fluoro-phenyl)
ester (3m). Colorless oil. Yield: 227 mg (86%). 1H NMR (CDCl3,
400 MHz): d 7.54e7.50 (m, 2H), 7.04e7.00 (m, 2H), 4.23e4.08 (m,
d

J. Wang et al. / Tetrahedron 71 (2015) 7853e7859
7857
4H), 1.30e1.26 (m, 6H); 13C NMR (CDCl3, 100 MHz):
d
164.6 (dd,
J¼3.3 Hz), 133.6 (d, J¼5.1 Hz), 133.2 (d, J¼2.5 Hz), 131.0 (d, J¼2.2 Hz),
126.7 (d, J¼7.1 Hz), 64.5 (d, J¼6.4 Hz), 16.0 (d, J¼7.0 Hz); 31P NMR
J1¼248 Hz, J2¼3.2 Hz), 136.7 (dd, J1¼8.5 Hz, J2¼5.3 Hz), 121.7 (dd,
J1¼7.3 Hz, J2¼3.5 Hz), 116.7 (dd, J1¼22.0 Hz, J2¼2.4 Hz), 64.2 (d,
(CDCl3, 162 MHz):
d 21.3; IR (neat): 2455, 2985, 1630, 1476, 1366,
J¼6.3 Hz), 16.0 (d, J¼7.1 Hz); 31P NMR (CDCl3, 162 MHz):
d
22.6; IR
1258, 1162, 1012, 976, 810, 602 cmꢃ1; HRMS (ESI-TOF) m/z calcd for
(neat): 3491, 2985, 2908, 1589, 1490, 1393, 1255, 1159, 1014, 976,
835, 791, 601 cmꢃ1; HRMS (ESI-TOF) m/z calcd for C10H15FO3PS
[MþH]þ 265.0464, found 265.0463.
C
10H14Cl2O3PS [MþH]þ 314.9778, found 314.9786.
4.2.20. Thiophosphoric acid O,O0-dimethyl ester S-phenyl ester
(5a). Colorless oil. Yield: 196 mg (90%). 1H NMR (CDCl3, 400 MHz):
4.2.14. Thiophosphoric acid S-(3-bromo-phenyl) ester O,O0-diethyl
d C
7.54e7.51 (m, 2H), 7.33e7.32 (m, 3H), 3.80 (s, 3H), 3.77 (s, 3H); 13
ester (3n). Colorless oil. Yield: 245.5 mg (76%). 1H NMR (CDCl3,
NMR (CDCl3, 100 MHz):
d
134.6 (d, J¼5.2 Hz), 129.5 (d, J¼2.3 Hz),
400 MHz):
d
7.69 (m, 1H), 7.50e7.44 (m, 2H), 7.21e7.17 (m, 1H),
136.9
129.2 (d, J¼2.9 Hz), 125.9 (d, J¼7.2 Hz), 54.2 (d, J¼6.1 Hz); 31P NMR
4.26e4.07 (m, 4H), 1.30 (m, 6H); 13C NMR (CDCl3, 100 MHz):
d
(CDCl3, 162 MHz): d 26.2; IR (neat): 3455, 2954, 1712, 1640, 1474,
(d, J¼5.4 Hz), 133.0 (d, J¼5.2 Hz), 132.1 (d, J¼2.8 Hz), 130.5 (d,
1441,1257,1181,1020, 830, 795, 691, 600 cmꢃ1; HRMS (ESI-TOF) m/z
calcd for C8H12O3PS [MþH]þ 219.0245, found 219.0246.
J¼2.2 Hz), 128.8 (d, J¼7.2 Hz), 122.7 (d, J¼2.6 Hz), 64.3 (d, J¼6.3 Hz),
16.0 (d, J¼7.2 Hz); 31P NMR (CDCl3, 162 MHz):
d 21.8; IR (neat):
3491, 3058, 2984, 2906, 1764, 1573, 1459, 1395, 1258, 1162, 1013,
4.2.21. Thiophosphoric acid S-phenyl ester O,O0-dipropyl ester
975, 877, 783, 748, 600 cmꢃ1; HRMS (ESI-TOF) m/z calcd for
(5b). Colorless oil. Yield: 225 mg (82%). 1H NMR (CDCl3, 400 MHz):
C
10H15BrO3PS [MþH]þ 324.9663, found 324.9660.
d
7.55 (m, 2H), 7.38e7.27 (m, 3H), 4.14e3.95 (m, 4H), 1.65 (m, 4H),
0.88 (m, 6H); 13C NMR (CDCl3,100 MHz):
d
134.5 (d, J¼5.3 Hz),129.3
4.2.15. Thiophosphoric acid S-(4-bromo-phenyl) ester O,O0-diethyl
(d, J¼2.1 Hz), 128.9 (d, J¼2.7 Hz), 126.6 (d, J¼7.1 Hz), 69.5 (d,
ester (3o). Colorless oil. Yield: 301 mg (93%). 1H NMR (CDCl3,
J¼6.7 Hz), 23.5 (d, J¼7.2 Hz), 9.9; 31P NMR (CDCl3, 162 MHz):
d 22.7;
400 MHz):
d
7.49e7.42 (m, 2H), 7.45e7.42 (m, 2H), 4.27e4.11 (m,
136.0 (d,
IR (neat): 3451, 2969, 1640, 1473, 1440, 1260, 1052, 994, 748,
602 cmꢃ1; HRMS (ESI-TOF) m/z calcd for C12H20O3PS [MþH]þ
275.0871, found 275.0870.
4H), 1.34e1.30 (m, 6H); 13C NMR (CDCl3, 100 MHz):
d
J¼5.18 Hz), 132.5 (d, J¼2.2 Hz), 125.8 (d, J¼7.2 Hz), 123.7 (d,
J¼3.5 Hz), 64.3 (d, J¼6.3 Hz), 16.0 (d, J¼7.0 Hz); 31P NMR (CDCl3,
162 MHz):
d
21.9; IR (neat): 3492, 3082, 2984, 2906, 1901, 1634,
4.2.22. Thiophosphoric acid O,O0-dibutyl ester S-phenyl ester
1565, 1388, 1257, 1162, 1087, 1008, 975, 817, 753, 600 cmꢃ1; HRMS
(ESI-TOF) m/z calcd for C10H15BrO3PS [MþH]þ 324.9663, found
324.9660.
(5c). Colorless oil. Yield: 278 mg (92%). 1H NMR (CDCl3, 400 MHz):
d
7.63e7.52 (m, 2H), 7.35 (m, 3H), 4.21e4.02 (m, 4H), 1.67e1.57 (m,
4H), 1.42e1.29 (m, 4H), 0.91e0.88 (m, 6H); 13C NMR (CDCl3,
100 MHz):
134.5 (d, J¼5.3 Hz), 129.3 (d, J¼2.1 Hz), 128.9 (d,
J¼2.8 Hz), 126.6 (d, J¼7.1 Hz), 67.7 (d, J¼6.7 Hz), 32.1 (d, J¼7.2 Hz),
18.6, 13.5; 31P NMR (CDCl3, 162 MHz):
22.9; IR (neat): 3489, 3060,
d
4.2.16. Thiophosphoric acid S-(2-chloro-phenyl) ester O,O0-diethyl
ester (3p). Colorless oil. Yield: 227 mg (81%). 1H NMR (CDCl3,
d
400 MHz):
2H), 4.26e4.08 (m, 4H), 1.30e1.26 (m, 6H); 13C NMR (CDCl3,
100 MHz):
d
7.73e7.70 (m, 1H), 7.43e7.40 (m, 1H), 7.28e7.19 (m,
2960, 2873, 1631, 1581, 1471, 1383, 1258, 1021, 987, 900, 758, 747,
692, 603 cmꢃ1; HRMS (ESI-TOF) m/z calcd for C14H24O3PS [MþH]þ
303.1184, found 303.1184.
d
137.9 (d, J¼6.9 Hz), 136.8 (d, J¼4.4 Hz), 130.3 (d,
J¼2.7 Hz),130.2 (d, J¼2.3 Hz),127.4 (d, J¼2.3 Hz),126.3 (d, J¼6.8 Hz),
64.4 (d, J¼6.2 Hz), 16.0 (d, J¼7.3 Hz); 31P NMR (CDCl3, 162 MHz):
4.2.23. Thiophosphoric acid O,O0-dipentyl ester S-phenyl ester
d
21.3; IR (neat): 3493, 2984, 2907, 1631, 1453, 1391, 1255, 1162,
(5d). Colorless oil. Yield: 175 mg (53%). 1H NMR (CDCl3, 400 MHz):
1015, 976, 756, 599 cmꢃ1
;
HRMS (ESI-TOF) m/z calcd for
d
7.55 (m, 2H), 7.41e7.27 (m, 3H), 4.14e4.02 (m, 4H), 1.67e1.56 (m,
4H), 1.33e1.23 (m, 8H), 0.86 (m, 6H); 13C NMR (CDCl3, 100 MHz):
134.4 (d, J¼5.3 Hz), 129.3 (d, J¼2.0 Hz), 128.9 (d, J¼2.7 Hz), 126.7
(d, J¼7.0 Hz), 68.1 (d, J¼6.6 Hz), 29.84 (d, J¼7.1 Hz), 27.5, 22.1, 13.9;
C
10H15ClO3PS [MþH]þ 281.0168, found 281.0168.
d
4.2.17. Thiophosphoric acid S-(3-chloro-phenyl) ester O,O0-diethyl
ester (3q). Colorless oil. Yield: 249 mg (89%). 1H NMR (CDCl3,
31P NMR (CDCl3, 162 MHz):
d 22.9; IR (neat): 3490, 3061, 2958,
400 MHz):
1H), 7.27e7.25 (m, 1H), 4.25e4.10 (m, 4H), 1.31e1.28 (m, 6H); 13C
NMR (CDCl3, 100 MHz):
d
7.54e7.53 (m, 1H), 7.45e7.42 (m, 1H), 7.33e7.30 (m,
2871, 1582, 1441, 1381, 1260, 1044, 990, 831, 690, 603 cmꢃ1; HRMS
(ESI-TOF) m/z calcd for C16H28O3PS [MþH]þ 331.1497, found
331.1501.
d
134.8 (d, J¼2.5 Hz), 134.1 (d, J¼5.4 Hz),
132.5 (d, J¼5.2 Hz), 130.3 (d, J¼2.2 Hz), 129.2 (d, J¼2.7 Hz), 128.5 (d,
J¼7.0 Hz), 64.3 (d, J¼6.2 Hz), 16.0 (d, J¼7.1 Hz); 31P NMR (CDCl3,
4.2.24. Thiophosphoric acid O,O0-dihexyl ester S-phenyl ester
162 MHz):
d
21.8; IR (neat): 3475, 2984, 1574, 1461, 1401, 1256, 1162,
(5e). Colorless oil. Yield: 197 mg (55%). 1H NMR (CDCl3, 400 MHz):
1013, 777, 680, 600 cmꢃ1
;
HRMS (ESI-TOF) m/z calcd for
d
7.58e7.55 (m, 2H), 7.39e7.29 (m, 3H), 4.16e4.10 (m, 4H),1.71e1.60
(m, 4H), 1.34e1.22 (m, 12H), 0.89e0.86 (m, 6H); 13C NMR (CDCl3,
100 MHz):
C
10H15ClO3PS [MþH]þ 281.0168, found 281.0166.
d
134.4 (d, J¼5.3 Hz), 129.3 (d, J¼2.0 Hz), 128.9 (d,
4.2.18. Thiophosphoric acid S-(4-chloro-phenyl) ester O,O0-diethyl
J¼2.7 Hz), 126.7 (d, J¼7.0 Hz), 68.1 (d, J¼6.7 Hz), 31.3 (d, J¼6.6 Hz),
ester (3r). Colorless oil. Yield: 288 mg (97%). 1H NMR (CDCl3,
30.1 (d, J¼7.2 Hz), 25.1 (d, J¼4.0 Hz), 22.5 (d, J¼4.2 Hz), 13.9; 31P
400 MHz):
d
7.48e7.46 (m, 2H), 7.30e7.29 (m, 2H), 4.23e4.09 (m,
135.7 (d,
NMR (CDCl3, 162 MHz): d 22.9; IR (neat): 2474, 3061, 2957, 2930,
4H), 1.30e1.27 (m, 6H); 13C NMR (CDCl3, 100 MHz):
d
2859, 1468, 1257, 994, 746, 690, 603 cmꢃ1; HRMS (ESI-TOF) m/z
calcd for C18H32O3PS [MþH]þ 359.1810, found 359.1819.
J¼5.2 Hz),135.5 (d, J¼3.4 Hz),129.5 (d, J¼2.3 Hz),125.1 (d, J¼3.3 Hz),
64.2 (d, J¼6.3 Hz), 16.0 (d, J¼7.1 Hz); 31P NMR (CDCl3, 162 MHz):
d
22.1; IR (neat): 3492, 3064, 2984, 2932, 1639, 1572, 1476, 1443,
4.2.25. Thiophosphoric acid O,O0-dioctyl ester S-phenyl ester
1391, 1254, 1091, 1013, 822, 791, 600 cmꢃ1; HRMS (ESI-TOF) m/z
(5f). Colorless oil. Yield: 153 mg (37%). 1H NMR (CDCl3, 400 MHz):
calcd for C10H15ClO3PS [MþH]þ 281.0168, found 281.0166.
d
7.55e7.53 (M, 2H), 7.37e7.28 (m, 3H), 4.16e4.01 (m, 4H),
1.65e1.57 (m, 4H), 1.33e1.17 (m, 20H), 0.86 (m, 6H); 13C NMR
(CDCl3, 100 MHz):
4.2.19. Thiophosphoric acid S-(3,4-dichloro-phenyl) ester O,O0-di-
d
134.4 (d, J¼5.3 Hz), 129.3 (d, J¼2.0 Hz), 128.9 (d,
ethyl ester (3s). Colorless oil. Yield: 234.1 mg (75%). 1H NMR (CDCl3,
J¼2.7 Hz), 126.7 (d, J¼7.1 Hz), 68.1 (d, J¼6.7 Hz), 31.7, 30.1 (d,
400 MHz):
d
7.62 (s, 1H), 7.38 (m, 1H), 4.25e4.09 (m, 4H), 1.32e1.28
135.8 (d, J¼5.4 Hz), 133.8 (d,
J¼7.1 Hz), 29.1 (d, J¼9.3 Hz), 25.4, 22.6, 14.1; 31P NMR (CDCl3,
(m, 6H); 13C NMR (CDCl3, 100 MHz):
d
162 MHz): d 22.9; IR (neat): 3473, 3061, 2926, 2855, 1582, 1467,

7858
J. Wang et al. / Tetrahedron 71 (2015) 7853e7859
1378, 1261, 996, 746, 689, 603 cmꢃ1; HRMS (ESI-TOF) m/z calcd for
C
(CDCl3, 100 MHz):
d
139.2 (d, J¼3.1 Hz), 134.6 (d, J¼5.1 Hz), 130.1 (d,
22H40O3PS [MþH]þ 415.2436, found 415.2450.
J¼2.3 Hz), 122.8 (d, J¼7.3 Hz), 63.9 (d, J¼6.2 Hz), 21.1, 16.0 (d,
J¼7.2 Hz); 31P NMR (CDCl3, 162 MHz):
d 23.3; IR (neat): 3491, 2983,
4.2.26. Thiophosphoric acid O,O0-bis-[2-(2-chloro-ethoxy)-ethyl] es-
1492, 1443, 1391, 1254, 1161, 1014, 973, 810, 601 cmꢃ1; HRMS (ESI-
ter S-phenyl ester (5g). Colorless oil. Yield: 165 mg (41%). 1H NMR
TOF) m/z calcd for C11H18O3PS [MþH]þ 261.0714, found 261.0708.
(CDCl3, 400 MHz):
4.29e4.20 (m, 4H), 3.67e3.66 (m, 8H), 3.57e3.55 (m, 4H); 13C NMR
(CDCl3, 100 MHz):
134.7 (d, J¼5.3 Hz), 129.4 (d, J¼2.3 Hz), 129.2 (d,
d 7.60e7.58 (m, 2H), 7.34e7.32 (m, 3H),
4.3.2. Thiophosphoric acid O,O0-diethyl ester S-(2-nitro-phenyl) ester
d
(3v). Yellow oil. Yield: 78.7 mg (27%). 1H NMR (CDCl3, 400 MHz):
J¼2.9 Hz), 125.9 (d, J¼7.2 Hz), 71.3, 69.8 (d, J¼7.4 Hz), 66.8 (d,
d
7.99e7.96 (m, 1H), 7.90e7.88 (m, 1H), 7.57e7.53 (m, 1H),
7.48e7.44 (m, 1H), 4.24e4.09 (m, 4H), 1.31e1.27 (m, 6H); 13C NMR
(CDCl3, 100 MHz):
J¼6.5 Hz), 42.7; 31P NMR (CDCl3, 162 MHz):
d 24.1; IR (neat): 3456,
3060, 2958, 2871, 1631, 1581, 1473, 1299, 1256, 1135, 1024, 749, 665,
606 cmꢃ1; HRMS (ESI-TOF) m/z calcd for C14H22Cl2O5PS [MþH]þ
403.0303, found 403.0313.
d
151.7 (d, J¼4.3 Hz), 136.1 (d, J¼4.8 Hz), 132.8 (d,
J¼1.6 Hz), 129.2 (d, J¼1.9 Hz), 125.2 (d, J¼1.5 Hz), 123.1 (d, J¼6.3 Hz),
64.9 (d, J¼6.7 Hz), 16.0 (d, J¼7.0 Hz); 31P NMR (CDCl3, 162 MHz):
d
19.9; IR (neat): 3489, 2986, 2908, 1529, 1355, 1258, 1162, 1012,
4.2.27. Thiophosphoric acid O,O0-diisopropyl ester S-phenyl ester
853, 782, 738, 651, 598 cmꢃ1; HRMS (ESI-TOF) m/z calcd for
(5h). Colorless oil. Yield: 134 mg (49%). 1H NMR (CDCl3, 400 MHz):
C
10H15NO5PS [MþH]þ 292.0409, found 292.0404.
d
7.61e7.51 (m, 2H), 7.30 (m, 3H), 4.86e4.62 (m, 2H), 1.30 (d,
J¼6.2 Hz, 6H), 1.22 (d, J¼6.2 Hz, 6H); 13C NMR (CDCl3, 100 MHz):
4.4. TEMPO trapping experiment (6a)
d
134.2 (d, J¼5.5 Hz), 129.2 (d, J¼2.0 Hz), 128.6 (d, J¼2.6 Hz), 127.3
(d, J¼7.0 Hz), 73.3 (d, J¼6.8 Hz), 23.8 (d, J¼4.1 Hz), 23.5 (d,
A Schlenk tube was charged with disulfide 4 (0.5 mmol), dialkyl
phosphite 2 (2.0 mmol), DTBP (2.0 mmol) and TEMPO (2.0 mmol),
then 1.5 mL DMSO was added as solvent. This reaction was per-
formed under N2 atmosphere at 80 ꢀC for 20 h. After completion of
the reaction, the mixture was quenched with 20 mL Na2S2O4 so-
lution (5%) then extracted with ethyl acetate (15 mLꢂ3). The or-
ganic layer was combined and dried with anhydrous Na2SO4. After
the evaporation in a vacuum, the crude product was purified by
a gel column chromatography using petroleum ether as eluent to
afford the desired product 6a.
J¼5.7 Hz); 31P NMR (CDCl3, 162 MHz):
d 20.4; IR (neat): 3476, 3061,
2981, 2934, 1958, 1882, 1725, 1632, 1581, 1474, 1386, 1329, 1254,
1145, 982, 747, 689, 596 cmꢃ1; HRMS (ESI-TOF) m/z calcd for
C
12H20O3PS [MþH]þ 275.0871, found 275.0879.
4.2.28. Thiophosphoric acid O,O0-diisobutyl ester S-phenyl ester
(5i). Colorless oil. Yield: 263 mg (87%). 1H NMR (CDCl3, 400 MHz):
d
7.56e7.53 (m, 2H), 7.36e7.27 (m, 3H), 3.91e3.78 (m, 4H),
1.96e1.82 (m, 2H), 0.87 (m, 12H); 13C NMR (CDCl3, 100 MHz):
d
134.5 (d, J¼5.3 Hz), 129.2 (d, J¼2.1 Hz), 128.9 (d, J¼2.8 Hz), 126.6
(d, J¼7.0 Hz), 73.86 (d, J¼7.2 Hz), 29.0 (d, J¼7.4 Hz), 18.6; 31P NMR
4.4.1. 2,2,6,6-Tetramethyl-1-(phenylthiooxy)piperidine (6a). White
solid, mp: 63e64 ꢀC. Yield: 58 mg (22%). 1H NMR (CDCl3, 400 MHz):
(CDCl3, 162 MHz):
d 22.7; IR (neat): 3492, 3061, 2962, 2875, 1630,
1582, 1471, 1395, 1255, 998, 863, 817, 747, 690, 604 cmꢃ1; HRMS
(ESI-TOF) m/z calcd for C14H24O3PS [MþH]þ 303.1184, found
303.1188.
d
7.70e7.63 (m, 2H), 7.46e7.39 (m, 2H), 7.39e7.33 (m, 1H), 1.82 (s,
1H), 1.62 (m, 5H), 1.49 (m, 8H), 1.35 (s, 1H), 0.88 (s, 3H); 13C NMR
(CDCl3, 100 MHz): 150.4, 129.4, 128.7, 126.1, 77.5, 77.2, 76.9, 61.4,
d
59.0, 43.6, 41.5, 35.5, 32.7, 29.9, 17.4; IR (KBr): 3446, 2933, 1650,
1534, 1441, 1301, 1242, 1178, 1128, 1080, 1052, 908, 749, 698, 555,
453 cmꢃ1; HRMS (ESI-TOF) m/z calcd for C15H24NOS [MþH]þ
266.1579, found 266.1588.
4.2.29. Thiophosphoric acid O,O0-di-sec-butyl ester S-phenyl ester
(5j). Colorless oil. Yield: 169 mg (56%). 1H NMR (CDCl3, 400 MHz):
d
7.63e7.54 (m, 2H), 7.36e7.26 (m, 3H), 4.64e4.41 (m, 2H),
1.71e1.46 (m, 4H), 1.29e1.27 (m, 3H), 1.22e1.20 (m, 3H), 0.85 (m,
6H); 13C NMR (CDCl3, 100 MHz):
d
134.2 (d, J¼5.5 Hz), 129.1 (d,
Acknowledgements
J¼1.9 Hz), 128.6 (d, J¼2.0 Hz), 127.4 (d, J¼2.7 Hz), 30.2 (d, J¼5.8 Hz),
21.0 (d, J¼2.9 Hz), 20.7 (d, J¼4.2 Hz), 9.3 (d, J¼4.4 Hz); 31P NMR
The authors gratefully acknowledge financial support from the
National Natural Science Foundation of China (21025207).
(CDCl3, 162 MHz):
d 20.8; IR (neat): 3488, 3061, 2974, 2880, 2740,
1958, 1724, 1631, 1463, 1381, 1256, 1125, 1027, 811, 697, 604 cmꢃ1
;
HRMS (ESI-TOF) m/z calcd for C14H24O3PS [MþH]þ 303.1184, found
Supplementary data
303.1188.
Supplementary data associated with this article can be found in
the online version, at http://dx.doi.org/10.1016/j.tet.2015.08.025.
4.3. General procedure of the coupling between disulfides
and diethyl phosphite (3a, 3e, 3p, 3r, 3u, 3v)
References and notes
A Schlenk tube was charged with disulfide 4 (0.5 mmol), dialkyl
phosphite 2 (2.0 mmol), and DTBP (2.0 mmol), then 1.5 mL DMSO
was added as solvent. This reaction was performed under N2 at-
mosphere at 80 ꢀC for 20 h. After completion of the reaction, the
mixture was quenched with 20 mL Na2S2O4 solution (5%) then
extracted with ethyl acetate (15 mLꢂ3). The organic layer was
combined and dried with anhydrous Na2SO4. After the evaporation
in a vacuum, the crude product was purified by a gel column
chromatography using petroleum ether/ethyl acetate as eluent to
afford the desired product 3.
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