Reductive Rearrangement of Tetraphenyldiphosphine Disulfide To Trigger the Bisthiophosphinylation of Alkenes and Alkynes

Article abstract of DOI:10.1002/chem.201900073

The facile synthesis of organophosphorus compounds is of great importance for the development of new synthetic methods by using air-stable sources of phosphorus. In this respect, a synthetic method that is based on a reductive rearrangement and is capable of converting air-stable pentavalent phosphorus compounds into reactive trivalent phosphorus compounds is a powerful tool. Tetraphenyldiphosphine disulfide, which is a shelf-stable solid, was the focus of this study, and it was shown to undergo reductive rearrangement to trigger the bisthiophosphinylation of a variety of alkenes, such as terminal, cyclic, internal, and branched alkenes, 1,3-dienes, and terminal alkynes when exposed to light without any catalyst, base, or additive.

Full text of DOI:10.1002/chem.201900073

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Accepted Article
Title: Reductive Rearrangement of Tetraphenyldiphosphine Disulfide to
Trigger the Bisthiophosphinylation of Alkenes and Alkynes
Authors: Yuki Sato, Misaki Nishimura, Shin-ichi Kawaguchi, Akihiro
Nomoto, and Akiya Ogawa
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Reductive Rearrangement of Tetraphenyldiphosphine Disulfide to
Trigger the Bisthiophosphinylation of Alkenes and Alkynes
Yuki Sato,[a] Misaki Nishimura,[a] Shin-ichi Kawaguchi,*[b] Akihiro Nomoto,[a] and Akiya Ogawa*[a]
Abstract: The facile synthesis of organophosphorus compounds is of
great importance for the development of new synthetic methods using
air-stable sources of phosphorus. In this respect, a synthetic method
based on reductive rearrangement and capable of converting air-
stable pentavalent phosphorus compounds into reactive trivalent
phosphorus compounds is a powerful tool. In this study, we focused
on tetraphenyldiphosphine disulfide, which is a shelf-stable solid, and
revealed that it undergoes reductive rearrangement to trigger the
bisthiophosphinylation of a variety of alkenes, such as terminal, cyclic,
internal, branched alkenes, and 1,3-dienes, and terminal alkynes
when exposed to light without any catalyst, base, or additive.
Inspired by the reductive rearrangement of TMDPO, we next
focused on the reductive rearrangement of diphosphine disulfides,
bearing PV(S)–PV(S) single bonds (Scheme 1b). We expected a
similar reductive rearrangement of several diphosphine disulfides
to proceed under radical conditions to afford reactive trivalent
phosphorus species in situ.
Diphosphines, bearing a PIII–PIII single bond, are important
phosphorus sources for the vic-bisphosphination of carbon-
carbon unsaturated bonds,[6],[7],[8] but they are difficult to handle
because they are highly sensitive to air and moisture. In contrast,
diphosphine disulfides[9],[10] are often sufficiently shelf-stable to be
stored in the presence of air for several months. Therefore,
diphosphine disulfides are attractive phosphorus sources for vic-
bisthiophosphinylation, yet limited examples of their addition
reactions to alkynes and alkenes[11] have been reported. The
reported addition reactions using diphosphines and their
analogues, which bear a PV–PIII single bond,[12] require a trivalent
phosphorus center because the ability to capture carbon radicals
is the key factor in these reactions. Therefore, we hypothesized
that the reductive rearrangements of diphosphine disulfides would
generate reactive trivalent phosphorus species in situ and would
enable the vic-bisthiophosphinylation of alkenes and alkynes.
Introduction
Organophosphorus compounds are widely used as ligands for
reactions catalyzed by transition metals, pharmaceuticals, and
physiologically active compounds.[1] The synthesis of these
compounds often requires the use of air- and moisture-sensitive
sources of phosphorus. Therefore, the development of new
synthetic methods involving air-stable sources of phosphorus,
such as pentavalent phosphorus compounds,[2] is of great
importance. Methods that employ the reductive rearrangement of
pentavalent to trivalent phosphorus compounds therefore
constitute a powerful tool, because they enable pentavalent
phosphorus compounds to be used efficiently. For instance, it is
known that (2,4,6-trimethylbenzoyl)phosphine oxide (TMDPO,
Scheme 1a), bearing a P(O)–C(O) single bond,[3] is transformed
into a reactive trivalent phosphorus compound (Ph2P–OC(O)Mes)
when exposed to light.[4] We previously reported the application of
this rearrangement to the synthesis of alkyl phosphines, which are
trivalent phosphorus compounds.[5] In this reaction, alkyl radicals,
generated in situ, efficiently react with the trivalent phosphorus
atom of Ph2P–OC(O)Mes to afford alkyl phosphines. In contrast,
alkyl radicals are not captured by the pentavalent phosphorus
atom of TMDPO at all because of its low radical capturing ability.
[a]
[b]
Y. Sato, M. Nishimura, Dr. A. Nomoto, Prof. Dr. A. Ogawa
Department of Applied Chemistry
Graduate School of Engineering, Osaka Prefecture University
1-1 Gakuen-cho, Nakaku, Sakai, Osaka 599-8531 (Japan)
E-mail: ogawa@chem.osakafu-u.ac.jp
Dr. S-i. Kawaguchi
Center for Education and Research in Agricultural Innovation
Faculty of Agriculture, Saga University
Scheme 1. Reductive rearrangement of TMDPO and diphosphine disulfide.
In this context, the reductive rearrangement of diphosphine
disulfides and their addition reactions to alkenes and alkynes
were
investigated.
As
a
result,
we
found
that
152-1 Shonan-cho Karatsu, Saga 847-0021 (Japan)
E-mail: skawa@cc.saga-u.ac.jp
tetraphenyldiphosphine disulfide (1a) efficiently underwent
reductive rearrangement to form tetraphenyldiphosphathiane
monosulfide (Ph2P(S)–SPPh2) under light. This reductive
Supporting information for this article is given via a link at the end of
the document.
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rearrangement triggered the 1,2-addition of diphosphine disulfide
to a variety of alkenes and alkynes to afford bisthiophosphinylated
alkanes and alkenes, respectively (Scheme 1c). The reason why
not PIII-adducts but PV-adducts are obtained selectively is
described
in
detail
in
the
text.
Furthermore,
bis(thiophosphinyl)alkanes can be easily reduced to afford
bidentate bis(phosphino)alkane ligands,[8d, 12b] such as dppe (vic-
bis(diphenylphosphino)ethane).[13] Therefore, we focused on the
reductive rearrangement of diphosphine disulfides, and
investigated this bisthiophosphinylation process in detail.
Results and Discussion
We initiated our study by developing the synthetic method to
obtain diphosphine disulfide 1a. Diphosphine disulfide 1a is often
synthesized via disulfurization of tetraphenyldiphosphine,
prepared from diphenylphosphine and diphenylphosphine
chloride, with a reported total yield of 1a of 34%.[9d] We modified
the existing method to synthesize diphosphine monosulfide,
reported by Burford and Weigand et al.,[14] and successfully
synthesized 1a in 84% yield (12.9 g, Eq. 1) via a one-pot
sequence from diphenylphosphine chloride (70 mmol) and
bis(trimethylsilyl) sulfide (35 mmol). Diphosphine disulfide 1a is
shelf-stable solid, which does not undergo any noticeable
decomposition in ethanol and water.
Scheme 2. Photoinduced rearrangements of diphosphine dioxide 2 and
diphosphine disulfide 1a.
We confirmed the reversibility of the rearrangement between
1a and 3a by developing a novel synthetic method for 3a (Eq. 2).
nBuLi (1.6 M in nhexane) was added to diphenylphosphine
dissolved in THF followed by slow addition of two equivalents of
elemental sulfur at −78 °C. This mixture was allowed to warm to
room temperature slowly. Diphenylphosphine chloride was then
added to the mixture, which was stirred for 12 h to give 3a in 90%
yield as a crude mixture containing 1a (2%) and 5a (4%).
Next, we investigated the rearrangement of diphosphine
dioxide 2 and diphosphine disulfide 1a, both of which have a PV–
PV single bond. Diphosphine dioxide 2 was irradiated with a xenon
lamp (500 W) in a Pyrex NMR tube for 6 h (Scheme 2a), but the
rearrangement of diphosphine dioxide 2 did not proceed at all. In
the case of diphosphine disulfide 1a, a pair of doublet peaks (P =
20.6 ppm (JP-P = 78.0 Hz) and 65.4 ppm (JP-P = 78.0 Hz)) were
observed by 31P NMR spectroscopy of the mixture after irradiation
(Scheme 2b). These peaks were assigned to diphosphathiane
monosulfide 3a, which has both pentavalent and trivalent
phosphorus centers, and which was obtained in 42% yield.
After exposing 3a to irradiation by a xenon lamp for 1 h, the
conversion of 3a to 1a (14%), 4a (18%), and 5a (25%) was
observed by 31P NMR spectroscopy (Eq. 3). The ratio of the
phosphorus compounds generated from 3a was similar to the
result shown in Scheme 2b.
Additionally, diphosphine monosulfide 4a (P = −13.0 ppm (JP-P
=
251.4 Hz) and 45.1 ppm (JP-P = 251.4 Hz)) and dithiophosphinoic
anhydride 5a (P = 61.6 ppm) formed in yields of 22% and 20%,
respectively. These results indicate that 1a can undergo reductive
rearrangement to generate trivalent phosphorus compounds 3a
accompanied with the formation of 4a and 5a.
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When the mixture containing equal amounts of 4a and 5a was
also irradiated with a xenon lamp for 4 h, 4a and 5a were
transformed into 1a and 3a (Eq. 4). The ratio of the phosphorus
compounds generated from 4a and 5a was also similar to the
results shown in Scheme 2b and Eq. 3.
Scheme 3. Photoinduced rearrangements of diphosphine disulfides 1b and 1c.
Next, the radical addition reaction of diphosphine dioxide 2
and 1a to 1-dodecene (6a) was examined. The addition reaction
of 2 to 6a did not proceed at all under light (Eq. 5).
These results revealed that 1a and 3a–5a were reversibly
transformed to each other and they existed in the same molar
ratio under light (Figure 1): Homolytic cleavage of the P(S)–P(S)
single bond in 1a is reversibly induced by photoirradiation to
generate two diphenylthiophosphinyl radicals (Ph2P(S)·).[15] The
unpaired electron of Ph2P(S)· is delocalized on its phosphorus
and sulfur atoms, as shown in a single occupied molecular orbital
(SOMO) of Ph2P(S)· calculated at UB3LYP/6-31G++(2d,p) level.
Thus, Ph2P(S)· partially coupled to form 3a, bearing a P(S)–S–P
structure, during the reversible homolytic cleavage of the P(S)–
P(S) single bond. The transfer of a sulfur atom[16] from 1a to 3a
also occurred to generate 4a and 5a, respectively.
In contrast, we previously reported that diphosphine monoxide
7, bearing a PV(O)–PIII single bond, adds to 6a and affords the
corresponding 1,2-adduct in 78% yield under the same conditions
as in Eq. 5.[12a] The addition reaction proceeds in three steps
(Figure 2): The photoinduced homolytic cleavage of the PV(O)–PIII
bond of 7 generates two phosphorus radicals, namely P(O)･ and
P･. The more electrophilic phosphorus radical (P(O)･) adds to an
alkene and the generated alkyl radical is captured by the more
electron-rich phosphorus group (P) of 7. In this reaction, the
diphenylphosphinyl group (P(O)) of 7 does not react with the alkyl
radical because of its low capturing ability to alkyl radical.
Figure 1. Reversible rearrangement between 1a and 3a–5a.
The influence of carbon substituents of diphosphine disulfides
on their rearrangement was investigated by irradiating
diphosphine disulfide 1b and 1c with a xenon lamp (Scheme 3).
Although diphosphine disulfide 1b was not consumed under light
at all (Scheme 3a), 1c was efficiently transformed to 3c (71%), 4c
(2%), and 5c (5%) (Scheme 3b).[17] These results indicated that
the bulkiness of the carbon substituents influences the product
ratio of 1 and 3–5 under light.
Figure 2. Model for radical addition of diphosphine monoxide 7 to alkenes under
light.
In the case of diphosphine dioxide 2 (Figure 3, top),
photoinduced homolytic cleavage of the PV(O)–PV(O) bond of 2
can be achieved but the generated alkyl radical was not captured
by the diphenylphosphinyl group (P(O)) of 2. In contrast,
diphosphine disulfide 1a (P(S)–P(S)) generates the trivalent
phosphorus species 3a (P(S)–SP) and 4a (P(S)–P), which are
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potentially good acceptors of alkyl radicals under exposure to UV
light (Figure 3, bottom). Therefore, we hypothesized that the
reductive rearrangement of 1a enables the bisthiophosphinylation
of alkenes.
the conversion of 1a and 3a–5a and the bisthiophosphinylation of
6a proceeded efficiently to generate the 1,2-adduct 7aa in 98%
yield. In particular, 1a and 3a were converted much faster than 4a
and 5a. The addition of 4a also occurred during the initial 1 h to 2
h but the 1,2-adduct of 4a was converted to 7aa after 2 h
accompanied with the slow consumption of 1a and 5a.[18] These
results indicate that 1a and 3a play a key role in this
bisthiophosphinylation reaction and the 1,2-adduct of 4a was
sulfurized by the transfer of a sulfur atom from 1a and 5a to
generate 7aa.
Figure 3. Model for radical addition of diphosphine dioxide 2 and diphosphine
disulfide 1a to alkenes under exposure to light.
Based on this hypothesis, the mixture of 1a and 3a–5a,
generated by exposing 1a to light (P,S-mixture-1a), was used as
the phosphorus source for the bisthiophosphinylation of alkene 6a
(Scheme 4). After P,S-mixture-1a and 6a was irradiated by light
for 4 h, interestingly, 1a and 3a–5a were almost completely
consumed and 1,2-bis(thiophosphinyl)alkane 7aa was generated
in 98% yield. In general, reactions consisting of four or more
substrates usually afford complex mixtures of many products. In
contrast, all components (1a and 3a–5a) of P,S-mixture-1a
converged to yield only one product 7aa, almost quantitatively.
Figure 4. Yields during the addition reactions of diphosphine disulfide 1a to
alkene 6a as a function of time, as monitored by 31P NMR spectroscopy.
The reaction progress of bisthiophosphinylation of alkene 6a
using diphosphine disulfide 1a or P,S-mixture-1a was monitored
1
by H NMR spectroscopy and compared (Figure 5). During the
initial 1 h, we found that the bisthiophosphinylation of 6a with P,S-
mixture-1a (86% yield) proceeded approximately five times faster
than the bisthiophosphinylation with 1a (17% yield). The results
summarized in Figures 4 and 5 strongly indicate that the formation
of 3a–5a is the induction step of the addition of 1a and this step
triggered the generation of 1,2-adduct 7aa.
Scheme 4. Bisthiophosphinylation of alkene 6a using the mixture of 1a and 3a–
5a.
The bisthiophosphinylation of 6a was investigated in detail by
monitoring the conversion of 1a and 3a–5a to the 1,2-adduct 7aa
by 31P NMR spectroscopy during the addition reaction, and the
results are summarized in Figure 4. During the initial 1 h, 1a was
mainly converted to 3a–5a. During the subsequent course of time,
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Figure 6. Plausible reaction pathways of bisthiophosphinylation of alkene 6
using the mixture of 1a and 3a–5a.
Figure 5. Yields during the bisthiophosphinylation of alkene 6a using
diphosphine disulfide 1a or P,S-mixture-1a as a function of time, as monitored
by 1H NMR spectroscopy.
The capturing ability of alkyl radicals on 3a or 4a generated
from 1a was compared by conducting several experiments using
the secondary alkyl radical generated from bromoacetate 9a
under light (Scheme 5). Diphosphine disulfide 1a was irradiated
with a xenon lamp for 1 h followed by the addition of 9a. The
mixture was irradiated for 1 h. In this reaction, 3a–5a were
generated from 1a in situ by cleaving the P(S)–P(S) bond of 1a
under near-UV light in the first step, and the secondary alkyl
radical was then also formed by the cleavage of the carbon–
bromine bond in 9a in the second step. The generated alkyl
radical underwent homolytic substitution at the trivalent
phosphorus group of 3a and 4a to afford alkylphosphine sulfide
10a in 99% yield. Diphosphathiane monosulfide 3a also reacted
with 9a, quantitatively. In contrast to 3a, the reaction of 4a was
inefficient and alkylphosphine 11 was obtained in only 17% yield.
These results indicate that the capturing ability of 3a to the
secondary alkyl radical (involving the 3-methyl-2-butanoate
radicals) is higher than that of 4a.
Notably, the addition of 3a to 6a efficiently proceeded to afford
7aa, quantitatively, in an hour (Eq. 6). In our previous report, the
addition of 4a to 6a while exposed to light for an hour provided the
corresponding 1,2-adduct of 4a in 62% yield.[12b] These results
indicate that 3a behaves as the main active species of the addition
reaction to 6a.
Plausible reaction pathways for the present reaction are
illustrated in Figure 6. The bisthiophosphinylation proceeds via
three steps: the Ph2P(S)· attacks an alkene to afford the -
thiophosphinylated alkyl radical. The generated radical reacts
with the diphenylphosphino group of 3a and 4a to afford the 1,2-
bisthiophosphinylalkane
7a
and
1-thiophosphinyl-2-
phosphinoalkane 8a, respectively, accompanied with the release
of Ph2P(S)·. The sulfur atom was also transferred from 1a and 5a
to 8a to afford 7a accompanied by the regeneration of 4a and 3a,
respectively.
Scheme 5. Homolytic substitution reactions of 3a and 4a with the secondary
alkyl radical generated from bromoacetate 9a under light.
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The difference between the ability of 3a and 4a to capture alkyl
radicals can be attributed to the weakness of the phosphorus–
sulfur bond and the lower steric hindrance around the trivalent
phosphorus center of 3a. The capture of 3a to alkyl radicals can
proceed via an Arbuzov-type pathway: the alkyl radical undergoes
a nucleophilic attack by the lone pair of the trivalent phosphorus
atom of 3a accompanied with homolytic cleavage of the P(S)–SP
bond and formation of the P=S bond, as shown in Figure 7. In
contrast, 4a captures alkyl radicals via homolytic cleavage of the
relatively strong P(S)–P bond. In general, the bond dissociation
energy of the phosphorus–sulfur bond (442 ± 10 kJmol−1)[19] is
lower than that of the phosphorus–phosphorus bond (489 ± 10
kJmol−1).[19] In addition, the trivalent phosphorus center of 3a is
less sterically hindered than that of 4a because of the greater
distance maintained between the bulky thiophosphinyl group and
the trivalent phosphorus center of 3a by its sulfur bridge.
Table 1. Thiophosphinylation of several bromoacetates 9 with 1a.[a]
10a, 94%
10b, 95%
10c, 59%[b]
10d, 91%
10e, 6%[c]
Isolated yields. [a] Reaction conditions: 1a (0.3 mmol), 9 (0.3 mmol), CH2Cl2
(0.3 mL), 20 °C, xenon lamp (500 W), Pyrex, and 1 h. [b] Irradiation for 10
h. [c] The yield was determined by 1H NMR.
Photoredox reaction conditions were also available for this
reaction: under blue LED light (6.5 W), 0.5 mol% of fac-Ir(ppy)3
catalyzed the bisthiophosphinylation of 6a to generate 1,2-adduct
7aa in 91% yield (entry 5). In the presence of a catalytic amount
of the radical initiator V-40 (1,1’-azobis(cyclohexane-1-
carbonitrile)), 1a added to 6a, efficiently, and 1,2-adduct 7aa was
obtained in 95% yield (entry 6). In the absence of either light or
the radical initiator, 7aa was not observed by 1H NMR
spectroscopy under the same reaction conditions and 1a was
recovered quantitatively (entry 7).
Figure 7. Model for the difference between the ability of 3a and 4a to capture
alkyl radicals.
Homolytic substitution reactions of 3a and 4a, generated from
1a, with several bromoacetates 9 were examined to reveal the
scope of their ability to capture alkyl radicals (Table 1).
Diphosphine disulfide 1a efficiently reacts with aliphatic
secondary bromoacetates 9a and 9b to afford alkylphosphine
sulfides 10a and 10b, respectively, in excellent yields. The
reaction with tertiary bromoacetate 9c provided 10c, bearing a
quaternary carbon–phosphorus bond, in 59% yield. The alkyl
radical generated from 9d, bearing a cyclobutyl group, was also
captured by 3a and 4a efficiently, to give 10d in 94% yield. In
contrast, the benzyl radical generated from 9e could not be
captured by 3a and 4a. Considering the electron-withdrawing
from the ester groups of the acetate radicals generated from 9,
these results indicate that aliphatic and electron-rich alkyl radicals
are efficiently captured by 3a and 4a.
Table 2. Bisthiophosphinylation of 6a with 1a under various reaction
conditions conducive for generating radicals.[a]
Entry
Conditions
Yield
1
2
Xenon lamp ( > 300 nm, 500 W), rt, 6 h
>99%
95%
400 nm LED (4.5 W), rt, 20 h
Next, we investigated the ability of 1a to undergo an addition
reaction with alkenes under several radical conditions. The
bisthiophosphinylation reaction of alkene 6a proceeded efficiently
even under weak irradiation and radical initiators (Table 2). Under
400 nm LED light (4.5 W), 1a added to 6a in 95% yield (entry 2).
This reaction also proceeded under a 20 W fluorescent lamp to
give the 1,2-adduct 7aa in 51% yield (entry 3). The addition of 1a
was promoted by heating (80 °C) and the 1,2-adduct 7aa was
afforded in 95% yield under the 20 W fluorescent lamp (entry 4).
3
20 W Fluorescent lamp, rt, 20 h
20 W Fluorescent lamp, 80 °C, 20 h
Blue LED (6.5 W), fac-Ir(ppy)3 (0.5 mol%), rt, 20 h
Dark, V-40 (10 mol%), 80 °C, 20 h
Dark, 80 °C, 20 h
51%
95%
91%
95%
0%
4[b]
5
6[b]
7[b]
Yields were determined by 1H NMR. [a] Reaction conditions: 1a (0.3 mmol),
6a (0.3 mmol), and CH2Cl2 (0.3 mL). [b] Benzene (0.45 mL) was used
instead of CH2Cl2.
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The addition reactions of 1a to a variety of alkenes were
performed under light. This bisthiophosphinylation reaction was
effective for terminal and cyclic aliphatic alkenes 6a and 6c–6i as
well as the aromatic alkene 6b (Scheme 6). Diphosphine disulfide
1a was tolerated by the hydroxy- (6c) and chloro- (6d) group
under light and gave the desired product 7ac and 7ad,
respectively, in excellent yields. Diphosphines with a trivalent
phosphorus
center,
such
as
tetraphenyldisphosphine,
immediately decompose in the presence of alchohol, such as 6c.
In contrast, 1a is stable in the presence of alchohols, such as
ethanol and water solvent, and therefore it can efficiently add to
6c without decomposition. 4-Methoxystyrene (6b) was
transformed into the 1,2-adduct in 55% yield. The addition to
cyclic alkenes 6c–6h afforded the corresponding 1,2-adducts
7ae–7ai in excellent yields with excellent diastereoselectivities. In
particular, sufficiently pure 1,2-adducts 7aa and 7ag–7ai were
directly obtained, quantitatively, without any need for purification.
Scheme 7. Bisthiophosphinylation of several internal and branched alkenes 6
with 1a.
As
summarized
in
Schemes
6
and
7,
this
bisthiophosphinylation reaction is effective for relatively bulky
alkenes, such as branched alkene 6l–6o. In the case of
diphosphine monosulfide 4a, the attempted addition to 6o did not
proceed efficiently and gave the 1,2-adduct of 4a in 8% yield (Eq.
7). The difference in the reactivity between 1a and 4a supported
that 4a does not play a key role in the addition reaction of 1a to
alkenes.
Therefore, the 1,2-addition reaction of diphosphine disulfide
1a
is
a
general
synthetic
method
of
1,2-
bis(thiophosphinyl)alkanes which are the synthetic precursors of
1,2-bis(phosphino)alkane ligands. This reaction was also
effective for the synthesis of 1,4-bis(thiophosphinyl)alkanes which
are the synthetic precursor of 1,4-bis(phosphino)alkane ligands,
Scheme 6. Bisthiophosphinylation of several terminal and cyclic alkenes 6 with
1a.
such
as
dppb
(1,4-bis(phosphino)butane):
the
The higher capturing ability of 3a to bulky alkyl radicals
enabled efficient 1,2-additions to internal and branched alkenes.
Therefore, the scope of internal and branched alkenes was also
investigated (Scheme 7). For internal alkenes, such as vinyl ether
6j and acrylate 6k, the desired products 7aj and 7ak were
generated in 95% and 91% yield, respectively, with good
stereoselectivities. In general, 1,2-addition of diphosphines and
their analogues, bearing a phosphorus–phosphorus single bond,
to branched alkenes is difficult because of the bulkiness of their
phosphorus groups. However, 1a successfully added to branched
alkenes 6l–6o to afford the corresponding 1,2-adducts 7al–7ao,
bearing a quaternary carbon center, in good yields. These results
demonstrate the high substrate generality of this reaction.
bisthiophosphinylation of 1,3-dienes 6p and 6q with 1a gave the
corresponding 1,4-adducts 7ap and 7aq, respectively, in good
yields with good stereoselectivities (Scheme 8).
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In the case of unsymmetrical diphosphine disulfide 1d, 1,2-
adduct 12de was obtained in 60% yield (Scheme 10a). In this
reaction, symmetrical 1,2-adducts 7ae (20% yield) and 7ee (16%
yield) were also generated because of the presence of the two
competing phosphorus radicals, Ph2P(S)· and (EtO)2P(S)·. In
contrast, the addition of 3d selectively afforded 12de in 88% yield
(Scheme 10b). Interestingly, 3d added to alkene 6h
regioselectively, and the 1,2-adduct 12dh was obtained in 72%
yield (Scheme 10c). In these reactions, 1d was efficiently
converted to 3d–5d (Scheme 10a) but the conversion of 3d was
relatively slower than 1d (Scheme 10b and 10c). We concluded
that the slow release of the thiophosphoryl radical from 3d and its
relatively fast ability to capture carbon radicals prevented the
scramble for the two phosphorus radicals (EtO)2P(S)· and
Ph2P(S)· (Figure 8).
Scheme 8. Bisthiophosphinylation of several 1,3-dienes 6 with 1a.
The influence of the substituents at phosphorus atoms of
diphosphine disulfides on their addition to alkenes was
investigated by irradiating a mixture of diphosphine disulfide 1b
and 6e under light for 20 h but the addition reaction did not
proceed at all (Scheme 9a). Diphosphine disulfide 1b did not
undergo the reductive rearrangement under light as shown in
Scheme 3a. Thus, we hypothesized that 1b could be activated by
other trivalent phosphorus species, such as 3a and 4a, followed
by the generation of the unsymmetrical coupled products, such as
Me2P(S)–P(S)Ph2, and they could react with alkenes. When the
mixture of 1a and 1b was irradiated under light for 10 h (Scheme
9b), the conversion of 1a and 1b to more than 11 phosphorus
species (P,S-mixture-1a+1b), including Me2P(S)–P(S)Ph2 (56%),
Me2P(S)–SPPh2 (11%), Me2P(S)–PPh2 (2%), and Me2P(S)–
SP(S)Ph2 (25%), was observed by 31P NMR spectroscopy. After
addition of alkene 6e and irradiation under light for 10 h,
unsymmetrical 1,2-adduct 12be was obtained in 34% yield
accompanied with the generation of 7ae (40%) and 7be (5%).
Scheme 10. Selectivity in bisthiophosphinylation reaction of 6e and 6h using
unsymmetrical diphosphine disulfide 1d and diphosphathiane monosulfide 3d.
Scheme 9. Radical addition of diphosphine disulfide 1b to alkene 6e
with/without 1a.
Figure 8. Model for regioselective 1,2-addition of diphosphathiane monosulfide
3d to alkenes.
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The bisthiophosphinylation reaction of a variety of alkynes 13
also proceeded efficiently to afford (E)-1,2-bisthiophosphinylated
alkenes 14 with good stereoselectivities (Table 3). Diphosphine
disulfide 1a efficiently added to aliphatic alkynes with a long
carbon chain (13a), cyclohexyl (13b), and trimethylsilyl groups
(13c), and the desired products 14a–14c were obtained in good
yield with good stereoselectivities. The addition to
phenylacetylene (13d) gave the 1,2-adduct 14ad in 85% yield with
good stereoselectivity. Both alkynes with an electron-donating
group (13e) and electron-withdrawing group (13f) were available
for this reaction and the corresponding 1,2-adducts 14ae and 14af
were obtained in good yield with good stereoselectivities,
respectively.
for the bisthiophosphinylation reaction of a variety of alkenes and
alkynes. This reaction readily affords
a
variety of
bis(thiophosphinyl)alkanes without the need for a catalyst, base,
or additive. We believe this work provides a powerful tool for the
synthesis of bis(phosphino)alkane ligands, such as dppe, which
can easily be obtained by the desulfurization of
bis(thiophosphinyl)alkanes.
Experimental Section
The general procedures for the bisthiophosphinylations of alkenes and
alkynes with diphosphine disulfides were as follows. Diphosphine disulfide
1a (0.3 mmol) and alkene 6 or alkyne 13 (0.3 mmol) in degassed dry
CH2Cl2 (0.3 mL) were placed in a sealed Pyrex NMR tube under argon
atmosphere and the mixture was irradiated with a xenon short arc lamp for
the specified time at room temperature. The desired product was obtained
after isolation by silica gel chromatography (n-hexane/AcOEt/CHCl3).
Further details of the experimental procedures and characterization data
for the new compounds are included as supporting information.
Table 3. Bisthiophosphinylation of several alkynes 13 with 1a.[a]
Acknowledgements
This research was supported by JSPS KAKENHI Grant Number
16H04138, A.O., H18J15153, Y.S.
14aa, 92% (71%)
[E/Z = 82/18]
14ab, 86% (65%)
[E/Z = 80/20]
14ac, 82% (64%)
[E/Z = 82/18]
Conflict of interest
The authors declare no conflict of interest.
Keywords: Phosphanes • Phosphorylation • Radical reactions •
Rearrangements
14ad, 85% (62%)
[E/Z = 75/25]
14ae, 93% (68%)
[E/Z = 76/24]
14af, 80% (54%)
[E/Z = 75/25][b]
[1]
[2]
L. D. Quin, A Guide to Organophosphorus Chemistry, John Wiley & Sons,
New York, 2000.
NMR yield of E/Z mixture (Isolated yield of E-isomer). The NMR yields were
determined by 31P NMR. The E/Z ratios were determined by 31P NMR of the
crude mixture. [a] Reaction conditions: 1a (0.3 mmol), 13 (0.3 mmol), CH2Cl2
(0.3 mL), 20 °C, xenon lamp (500 W), and 20 h. [b] Irradiation for 30 h.
a) Q. Xu, L.-B. Han, J. Organomet. Chem. 2011, 696, 130-140; b) T.
Bunlaksananusorn, P. Knochel, Tetrahedron Lett. 2002, 43, 5817-5819;
c) V. P. Ananikov, J. V. Ivanova, L. L. Khemchyan, I. P. Beletskaya, Eur.
J. Org. Chem. 2012, 2012, 3830-3840.
[3]
[4]
a) P. Lechtken, I. Buethe, A. Hesse (BASF SE), US-A 4324744, 1982; b)
P. Lechtken, I. Buethe, M. Jacobi, W. Trimborn (BASF SE), US-A
4710523, 1987; c) T. Sumiyoshi, M. Katayama, W. Schnabel, Chem. Lett.
1985, 14, 1647-1650; d) T. Sumiyoshi, W. Schnabel, A. Henne, P.
Lechtken, Polymer 1985, 26, 141-146.
Conclusions
a) G. W. Sluggett, C. Turro, M. W. George, I. V. Koptyug, N. J. Turro, J.
Am. Chem. Soc. 1995, 117, 5148-5153; b) U. Kolczak, G. Rist, K.
Dietliker, J. Wirz, J. Am. Chem. Soc. 1996, 118, 6477-6489; c) C. S.
Colley, D. C. Grills, N. A. Besley, S. Jockusch, P. Matousek, A. W. Parker,
M. Towrie, N. J. Turro, P. M. W. Gill, M. W. George, J. Am. Chem. Soc.
2002, 124, 14952-14958.
In conclusion, we developed a simple and facile synthetic method
for the preparation of bis(thiophosphinyl)alkanes and
bis(thiophosphinyl)alkenes. Diphosphine disulfides are promising
sources of phosphorus because of their facile preparation and
because they are shelf-stable solids. However, previous
examples of addition reactions involving diphosphine disulfides
were limited. Our results showed that diphosphine disulfides
underwent reductive rearrangement to reactive trivalent
phosphorus species, such as diphosphathiane monosulfide,
which has a P(S)–SP single bond, when exposed to light. In
addition, this rearrangement triggered the efficient radical chain
[5]
[6]
a) Y. Sato, S-i. Kawaguchi, A. Ogawa, Chem. Commun. 2015, 51,
10385-10388; b) Y. Sato, S-i. Kawaguchi, A. Nomoto, A. Ogawa,
Synthesis 2017, 49, 3558-3567.
For addition reactions of diphosphines to alkynes, see: a) A. Tzschach,
S. Baensch, J. Prakt. Chem. 1971, 313, 254-258; b) A. Sato, H. Yorimitsu,
K. Oshima, Angew. Chem. Int. Ed. 2005, 44, 1694-1696; c) D. L. Dodds,
M. F. Haddow, A. G. Orpen, P. G. Pringle, G. Woodward,
Organometallics 2006, 25, 5937-5945; d) S-i. Kawaguchi, S. Nagata, T.
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10.1002/chem.201900073
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Shirai, K. Tsuchii, A. Nomoto, A. Ogawa, Tetrahedron Lett. 2006, 47,
3919-3922; e) Y. Okugawa, K. Hirano, M. Miura, Org. Lett. 2017, 19,
2973-2976.
Yamaguchi, Chem. Commun. 2016, 52, 13580-13583; f) M. Arisawa, T.
Tazawa, W. Ichinose, H. Kobayashi, M. Yamaguchi, Adv. Synth. Catal.
2018, 360, 3488-3491.
[7]
[8]
[9]
For addition reactions of diphosphines to alkenes, see: a) A. B. Burg, J.
Am. Chem. Soc. 1961, 83, 2226-2231; b) K. W. Morse, J. G. Morse, J.
Am. Chem. Soc. 1973, 95, 8469-8470; c) J. G. Morse, K. W. Morse, Inorg.
Chem. 1975, 14, 565-569; d) M. Drieß, G. Haiber, Z. Anorg. Allg. Chem.
1993, 619, 215-219; e) S. Burck, D. Gudat, M. Nieger, Angew. Chem. Int.
Ed. 2004, 43, 4801-4804; f) I. Hajdók, F. Lissner, M. Nieger, S. Strobel,
D. Gudat, Organometallics 2009, 28, 1644-1651; g) N. Otomura, Y.
Okugawa, K. Hirano, M. Miura, Synthesis 2018, 50, 3402-3407; h) N.
Otomura, K. Hirano, M. Miura, Org. Lett. 2018, 20, 7965-7968.
[11] a) G. W. Parshall, J. Inorg. Nucl. Chem. 1960, 14, 291-292; b) R.
Schmutzler, Inorg. Chem. 1964, 3, 421-428.
[12] a) Y. Sato, S-i. Kawaguchi, A. Nomoto, A. Ogawa, Angew. Chem. Int. Ed.
2016, 55, 9700-9703; b) Y. Sato, S-i. Kawaguchi, A. Nomoto, A. Ogawa,
Chem. Eur. J. 2019, 25, 2295-2302.
[13] a) E. R. Fruchey, B. M. Monks, S. P. Cook, J. Am. Chem. Soc. 2014, 136,
13130-13133; b) J.-H. Fan, W.-T. Wei, M.-B. Zhou, R.-J. Song, J.-H. Li,
Angew. Chem. Int. Ed. 2014, 53, 6650-6654; c) S. Uesugi, Z. Li, R.
Yazaki, T. Ohshima, Angew. Chem. Int. Ed. 2014, 53, 1611-1615; d) M.
Arisawa, T. Ichikawa, M. Yamaguchi, Chem. Commun. 2015, 51, 8821-
8824.
For bisphosphination reactions of alkenes and alkynes, see: a) K. Hirano,
M. Miura, Tetrahedron Lett. 2017, 58, 4317-4322; b) L. L. Khemchyan, J.
V. Ivanova, S. S. Zalesskiy, V. P. Ananikov, I. P. Beletskaya, Z. A.
Starikova, Adv. Synth. Catal. 2014, 356, 771-780; c) A. Yoshimura, Y.
Saga, Y. Sato, A. Ogawa, T. Chen, L.-B. Han, Tetrahedron Lett. 2016,
57, 3382-3384; d) Y. Okugawa, K. Hirano, M. Miura, Angew. Chem. Int.
Ed. 2016, 55, 13558-13561; e) N. Otomura, Y. Okugawa, K. Hirano, M.
Miura, Org. Lett. 2017, 19, 4802-4805; f) H. Guo, A. Yoshimura, T. Chen,
Y. Saga, L.-B. Han, Green Chem. 2017, 19, 1502-1506.
[14] S. Yogendra, S. S. Chitnis, F. Hennersdorf, M. Bodensteiner, R. Fischer,
N. Burford, J. J. Weigand, Inorg. Chem. 2016, 55, 1854-1860.
[15] a) H. Karlsson, C. Lagercrantz, Acta Chem. Scand 1970, 24, 3411-3413;
b) R. E. Medsker, A. Sebenik, H. J. Harwood, Polym. Bull. 2002, 48, 17-
23.
[16] M. Kullberg, J. Stawinski, J. Organomet. Chem. 2005, 690, 2571-2576.
[17] When the solution of 1b (0.4 mmol) dissolved in CD2Cl2 (0.4 mL) was
irradiated with a xenon lamp (500 W) in a quartz NMR tube for 10 h, 1b
(89%), Me2P(S)–SPMe2 (1%), Me2P(S)–PMe2 (3%), Me2P(S)–S–
P(S)Me2 (3%), and three unidentified products were observed by 31P
NMR spectroscopy.
For synthetic methods of diphosphine disulfides, see: a) L. Mayer, Chem.
Ber. 1961, 94, 3051-3055; b) N. K. Patel, H. J. Harwood, J. Org. Chem.
1967, 32, 2999-3003; c) G. Hägele, G. Tossing, W. Kückelhaus, J. Seega,
Z. Naturforsch. B 1984, 39, 1574; d) K. Hahn, O. Kriha, I. Bellin, P. Spies,
S. Fuchs, P. Deglmann, K. Massonne, H. Denecke, C. Fleckenstein, G.
Janssens (BASF SE), US-A 20120178842, 2012.
[18] Diphosphine disulfide 1a (0.3 mmol) and 1,2-adduct of 4a to 6a ((1-
diphenylthiophosphinyl-2-diphenylphosphino)dodecane) dissolved in
CD2Cl2 (0.3 mL) were exposed to photoirradiation conditions for 6 h. Most
of the 1,2-adduct of 4a was sulfurized to afford 7aa, quantitatively.
[19] Luo, Y. R. Comprehensive Handbook of Chemical Bond Energies, CRC
Press, Boca Raton, 2007.
[10] For reactions using diphosphine disulfides, see: a) T. Emoto, R. Okazaki,
N. Inamoto, Bull. Chem. Soc. Jpn. 1973, 46, 898-901; b) M. Arisawa, M.
Yamaguchi, Tetrahedron Lett. 2009, 50, 3639-3640; c) M. Arisawa, T.
Yamada, M. Yamaguchi, Tetrahedron Lett. 2010, 51, 4957-4958; d) M.
Arisawa, T. Watanabe, M. Yamaguchi, Tetrahedron Lett. 2011, 52, 2410-
2412; e) M. Arisawa, T. Yamada, S. Tanii, Y. Kawada, H. Hashimoto, M.
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Entry for the Table of Contents
FULL PAPER
Synthetic methods involving reductive
rearrangement to convert air-stable
pentavalent phosphorus compounds
to reactive trivalent phosphorus
compounds constitute a powerful tool.
We focused on
tetraphenyldiphosphine disulfide,
which is a shelf-stable solid, and
revealed that its reductive
Yuki Sato, Misaki, Nishimura, Shin-ichi
Kawaguchi,* Akihiro Nomoto, and Akiya
Ogawa*
Page No. – Page No.
Title
Reductive Rearrangement of
Tetraphenyldiphosphine Disulfide to
Trigger the Bisthiophosphinylation of
Alkenes and Alkynes
rearrangement triggers vic-
bisthiophosphinylation of a variety of
alkenes and alkynes when exposed to
light without requiring any catalyst,
base, or additive.
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