Rhodium-catalyzed anti-markovnikov-type hydrophosphination of terminal alkynes with diphosphines and hydrosilanes in the presence of oxygen

Article abstract of DOI:10.1080/10426501003773423

A novel rhodium(I)-catalyzed hydrophosphination of terminal alkynes with diphosphines and hydrosilanes takes place regioselectively in the presence of small amounts of oxygen. After air-oxidation during workups, the corresponding anti-Markovnikov-type vinylic phosphine oxides were obtained in good yields. Copyright Taylor & Francis Group.

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Phosphorus, Sulfur, and Silicon and the
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Rhodium-Catalyzed Anti-
Markovnikov–Type Hydrophosphination
of Terminal Alkynes with Diphosphines
and Hydrosilanes in the Presence of
Oxygen
Shin-ichi Kawaguchi a , Mao Kotani a , Takashi Ohe a , Shoko Nagata a
, Akihiro Nomoto a , Motohiro Sonoda a & Akiya Ogawa a
a Department of Applied Chemistry, Graduate School of
Engineering , Osaka Prefecture University , Osaka, Japan
Published online: 27 May 2010.
To cite this article: Shin-ichi Kawaguchi , Mao Kotani , Takashi Ohe , Shoko Nagata , Akihiro
Nomoto , Motohiro Sonoda & Akiya Ogawa (2010) Rhodium-Catalyzed Anti-Markovnikov–Type
Hydrophosphination of Terminal Alkynes with Diphosphines and Hydrosilanes in the Presence
of Oxygen, Phosphorus, Sulfur, and Silicon and the Related Elements, 185:5-6, 1090-1097, DOI:
10.1080/10426501003773423
To link to this article: http://dx.doi.org/10.1080/10426501003773423
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Phosphorus, Sulfur, and Silicon, 185:1090–1097, 2010
Copyright ꢀC Taylor & Francis Group, LLC
ISSN: 1042-6507 print / 1563-5325 online
DOI: 10.1080/10426501003773423
RHODIUM-CATALYZED ANTI-MARKOVNIKOV–TYPE
HYDROPHOSPHINATION OF TERMINAL ALKYNES
WITH DIPHOSPHINES AND HYDROSILANES IN THE
PRESENCE OF OXYGEN
Shin-ichi Kawaguchi, Mao Kotani, Takashi Ohe, Shoko Nagata,
Akihiro Nomoto, Motohiro Sonoda, and Akiya Ogawa
Department of Applied Chemistry, Graduate School of Engineering,
Osaka Prefecture University, Osaka, Japan
Anovel rhodium(I)-catalyzed hydrophosphination of terminal alkynes with diphosphines and
hydrosilanes takes place regioselectively in the presence of small amounts of oxygen. After
air-oxidation during workups, the corresponding anti-Markovnikov–type vinylic phosphine
oxides were obtained in good yields.
Keywords Alkyne; anti-Markovnikov; diphosphine; hydrophosphination; hydrosilane;
rhodium catalyst
INTRODUCTION
Numerous studies of the additions of heteroatom compounds bearing a
heteroatom–heteroatom linkage such as B–B,1 Si–Si,2 Ge–Ge,3 Sn–Sn,4 S–S,5 and
Se–Se5 to alkynes catalyzed by transition metal catalysts have been reported.6 These
addition reactions provide useful tools to vicinally bifunctionalized vinylic compounds.
Recently, we reported the addition of tetraphenyldiphosphine as heteroatom compounds
bearing a P–P linkage, to terminal alkynes in the presence of palladium catalyst.7
Surprisingly, this reaction afforded not the corresponding bisphosphination8 product but a
Markovnikov-type hydrophosphination9–12 product (3), regioselectively, in the co-presence
of oxygen (Scheme 1).
Based on the result of the hydrophosphination using deuterized alkyne, it has been
apparent that the substrate alkynes also act as a hydrogen source in this hydrophosphina-
tion.7 Furthermore, we found that this hydrophosphination of alkynes proceeded efficiently
by the addition of hydrosilane as a hydrogen source in the presence of small amounts of
Received 3 December 2008; accepted 14 January 2009.
Dedicated to Professor Naomichi Furukawa on the occasion of his 70th birthday.
This research was supported by a Grant-in-Aid for Scientific Research on Priority Areas (Area 444, No.
19020061) and Scientific Research (B, 19350095), from the Ministry of Education, Culture, Sports, Science and
Technology, Japan.
Address correspondence to Akiya Ogawa, Department of Applied Chemistry, Graduate School of En-
gineering, Osaka Prefecture University, 1-1 Gakuen-cho, Nakaku, Sakai, Osaka 599-8531, Japan. E-mail:
ogawa@chem.osakafu-u.ac.jp
1090

HYDROPHOSPHINATION OF TERMINAL ALKYNES
1091
cat. Pd(OAc)2
+ (Ph2P)2
R
or Pd(PPh3)4
1
2
R
R
[O]
Ph2P
3
Ph2P
4
O
< 79%
Scheme 1
oxygen (Scheme 2).13 Oxygen seems to oxidize appropriate amounts of tetraphenyldiphos-
phine to tetraphenyldiphosphine oxide, which inhibits the deactivation of the catalyst in
this hydrophosphination reaction.
+
R
(Ph2P)2
2
R3SiH
5
+
1
0.1 mmol
3 equiv
3 equiv
R
R
[O]
cat. Pd(PPh3)4
in the presence of O2
Ph2P
3
Ph2P
4
O
< 99%
Scheme 2
By switching the catalyst simply from palladium(0) to rhodium(I), anti-
Markovnikov–type hydrophosphination of terminal alkynes has been found to take
place regioselectively (Scheme 3). In this article, we report a novel rhodium-
catalyzed anti-Markovnikov–type hydrophosphination of terminal alkynes using a
diphosphine–hydrosilane binary system in the presence of oxygen.
Scheme 3

1092
S. KAWAGUCHI ET AL.
RESULTS AND DISCUSSION
In a sealed NMR tube under N2 atmosphere, 1-octyne (1a) (0.3 mmol), tetraphenyldi-
phosphine (2) (0.1 mmol), diethylmethylsilane (5) (0.3 mmol), tris(triphenylphosphine)
rhodium(I) chloride (0.005 mmol), and C6D6 (600 µl) were placed, and then a quarter equiv-
alent of oxygen (0.025 mmol) was introduced into the tube. Heating the resulting mixture at
80◦C for 18 h, and the subsequent air-oxidation during workups, afforded the corresponding
anti-Markovnikov–type hydrophosphination product, (E)-1-diphenylphosphinyl-1-octene
(7a), in 90% yield (Scheme 3).
In addition, the formation of silylphosphine oxide as a byproduct was observed by
31P NMR (Et2MeSiP(O)Ph2: 31P NMR (C6D6) δ 21.8 ppm).13
Since tetraphenyldiphosphine (2) may be oxidized by oxygen to the correspond-
ing oxide 8, we next examined this hydrophosphination of 1-octyne (1a) by adding
tetraphenyldiphosphine oxide (8) in the absence of oxygen. When a mixture of 1-octyne
(1a) (0.6 mmol), tetraphenyldiphosphine (2) (0.1 mmol), tetraphenyldiphosphine oxide
(8) (0.1 mmol), diethylmethylsilane (5) (0.6 mmol), and C6D6 (600 µl) in the presence
of tris(triphenylphosphine)rhodium(I) chloride (0.025 mmol) was heated under the same
conditions, the corresponding vinylphosphine as the hydrophosphination product and its
oxide 7a were formed. After air-oxidation during workups, vinylphosphine oxide 7a was
obtained in 83% yield (Scheme 4). (The yield was based on the sum of the mole numbers
of tetraphenyldiphosphine and tetraphenyldiphosphine oxide.)
Scheme 4
We next examined the hydrophosphination of several alkynes by using the methods
shown in Schemes 3 and 4 (Table I). Aromatic alkynes such as phenylacetylene underwent
the Rh(I)-catalyzed regioselective hydrophosphination, providing the corresponding (E)-
vinylic phosphine oxide (7b) in good yield (Table I, entry 3). Chloro and silyl substituents
are tolerant of the reaction (Table I, entries 4, 5, and 7). In the case of a conjugate enyne,
the corresponding phosphinyl diene (7d) was obtained in good yield (Table I, entry 6).
Although additional detailed experiments are required in order to clarify the reac-
tion mechanism of this rhodium(I)-catalyzed hydrophosphination, possible pathways13 are
shown in Scheme 5: (i) at first, oxidative addition of diphosphine oxide to rhodium(I) to
generate active species (9); (ii) regioselective phosphinorhodation of alkyne, to form vinyl-
rhodium intermediate (10); two possible pathways (path A and B) are considered: path A:
(iii) the reaction of vinylrhodium 10 with the hydrosilane to form vinylphosphine (6) and

HYDROPHOSPHINATION OF TERMINAL ALKYNES
1093
Table I Rhodium(I)-catalyzed hydrophosphination of alkynes using diphosphine-hydrosilane binary systems
Entry
Alkyne
Condition
Product
Yield%b
1
2
A
B
7a
7b
90%
83%
3
A
82%d
4
5
A
B
7c
80%
63%
6
A
7d
90%d
7c
A
7e
71%
aReaction condition A: alkyne (0.3 mmol), (Ph2P)2 (0.1 mmol), Et2MeSiH (0.3 mmol), oxygen (0.025 mmol),
RhCl(PPh3)3 (0.005 mmol). Reaction condition B: alkyne (0.6 mmol), (Ph2P)2 (0.1 mmol), Ph2PP(O)Ph2
(0.1 mmol), Et2MeSiH (0.6 mmol), RhCl(PPh3)3 (0.01 mmol).
bDetermined by 1H NMR.
cRhCl(PPh3)3 (10 mol%, 0.02 mmol) was used.
dThe yield of this Rh-catalyzed reaction was higher compared with that of the Pd(PPh3)4-catalyzed hydrophos-
phination,13 in which some minor byproducts were formed concomitantly.
silylphosphinylrhodium species (11) and (iv) exchange reaction of the silyl group of 11
with the phosphino group of tetraphenyldiphosphine to regenerate Rh species 9 with the
concomitant formation of silylphosphine as a byproduct; path B: (iii) exchange of phophinyl
group with hydride group to form vinylrhodium hydride species (12) and silylphosphine
oxide and (iv) reductive elimination to give vinylphosphine 6 and addition of diphosphine
oxide to regenerate 9.
An alternative pathway may involve the formation of phosphinylrhodium hydride
(13) (Scheme 6): (i) the reaction of rhodium species 9 with the hydrosilane to generate
phosphinylrhodium hydride 1314; (ii) hydrorhodation of alkyne to generate vinylrhodium
hydride (14); (iii) the reaction of 14 with the diphosphine to give vinylphosphine 6 along
with the regeneration of 9.
In summary, rhodium-catalyzed highly regioselective hydrophosphination of termi-
nal alkynes has been developed by using diphosphine-hydrosilane binary systems, which
affords the anti-Markovnikov–type addition products. This reaction is regiocomplementary
with the palladium-catalyzed Markovnikov-type hydrophosphination reported previously.

1094
S. KAWAGUCHI ET AL.
R
R
PPh2
O
7
R'3SiPPh2
O
Rh(I)
[O]
Ph2PPPh2
O
[O]
PPh2
R'3SiPPh2
6
Ph2PPPh2
Ph2P Rh
O PPh2
O
(Ph2P)2
9
R
Ph2P Rh
PPh2
path B
R
path A
O
SiR'3
Rh
11
H
12
R
PPh2
Rh
O
Ph2P
R'3SiPPh2
O
R
R'3SiH
R'3SiH
PPh2
6
10
[O]
R
PPh2
O
7
Scheme 5
EXPERIMENTAL
General Procedure for Rhodium-Catalyzed Hydrophosphination
of Alkynes Using Diphosphine-Hydrosilane Binary Systems
Condition A. (Ph2P)2 (37.0 mg, 0.1 mmol), Ph2PP(O)Ph2 (38.6 mg, 0.1 mmol),
RhCl(PPh3)3 (9.3 mg, 0.01 mmol), alkyne (0.6 mmol), Et2MeSiH (87 µl, 0.6 mmol), and
C6D6 (0.6 mL) were placed in a sealed Pyrex glass NMR tube under a nitrogen atmosphere.
The mixture was stirred for 30 sec, and the tube was covered with aluminum foil. The
mixture was heated under reflux for 18 h, and then was left under air overnight. Purification
of the crude materials was performed by preparative TLC.
Condition B. (Ph2P)2 (37.0 mg, 0.1 mmol), RhCl(PPh3)3 (4.6 mg, 0.005 mmol),
alkyne (0.3 mmol), Et2MeSiH (43 µl, 0.3 mmol), and C6D6 (0.6 mL) were placed in a
sealed Pyrex glass NMR tube. Next, oxygen (0.6 mL, 0.025 mmol) was introduced into the
tube. The mixture was stirred for 30 sec, and the tube was covered with aluminum foil. The
mixture was heated under reflux for 18 h, and was left under air overnight. Purification of
the crude products was performed by preparative TLC.
(E)-1-(Diphenylphosphinyl)-1-octene (7a). Colorless oil; 1H NMR (400 MHz,
CDCl3) δ 7.18–7.72 (m, 10H), 6.73 (ddt, J = 6.5, 16.9, JHP = 19.4 Hz, 1H), 6.22 (dd, J =
17.0, JHP = 24.7 Hz, 1H), 2.30 (q, 2H), 1.28–1.50 (m, 8H), 0.86 (t, 3H); 13C NMR (100

HYDROPHOSPHINATION OF TERMINAL ALKYNES
1095
Rh(I)
R
PPh2
Ph2PPPh2
O
O
7
[O]
Ph2P Rh
O PPh2
R
PPh2
R'3SiH
6
9
(Ph2P)2
R'3SiPPh2
[O]
R'3SiPPh2
O
O
R
Rh PPh2
Ph2P Rh
H
O
H
14
13
R
Scheme 6
MHz, CDCl3) δ 153.0, 133.2 (JCP = 104.5 Hz), 131.6 (JCP = 2.5 Hz), 131.3 (JCP = 9.9
Hz), 128.5 (JCP = 12.3 Hz), 121.5 (JCP = 102.8 Hz), 34.5 (JCP = 16.5 Hz), 31.5, 28.8,
27.8, 22.5, 14.0; 31P NMR (200 MHz, CDCl3) δ 24.2.
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