A highly regioselective palladium-catalyzed hydrophosphination of alkynes using a diphosphine-hydrosilane binary system

Article abstract of DOI:10.1021/jo801267y

(Chemical Equation Presented) A novel transition-metal-catalyzed hydrophosphination of terminal alkynes using a diphosphine-hydrosilane binary system takes place regioselectively to provide vinylic phosphines, which undergo air oxidation during workup, affording the corresponding vinylphosphine oxides in good yields. In this hydrophosphination, hydrosilanes act as a useful hydrogen source, and furthermore, small amounts of oxygen is required to accomplish the reaction efficiently.

Full text of DOI:10.1021/jo801267y

A Highly Regioselective Palladium-Catalyzed Hydrophosphination of
Alkynes Using a Diphosphine-Hydrosilane Binary System
Shin-ichi Kawaguchi, Shoko Nagata, Akihiro Nomoto, Motohiro Sonoda, and
Akiya Ogawa*
Department of Applied Chemistry, Graduate School of Engineering, Osaka Prefecture UniVersity,
1-1 Gakuen-cho, Nakaku, Sakai, Osaka 599-8531, Japan
ogawa@chem.osakafu-u.ac.jp
ReceiVed June 13, 2008
A novel transition-metal-catalyzed hydrophosphination of terminal alkynes using a diphosphine-hydrosilane
binary system takes place regioselectively to provide vinylic phosphines, which undergo air oxidation during
workup, affording the corresponding vinylphosphine oxides in good yields. In this hydrophosphination,
hydrosilanes act as a useful hydrogen source, and furthermore, small amounts of oxygen is required to
accomplish the reaction efficiently.
Introduction
hydrogen source is attractive. In this paper, we wish to report
a highly selective transition-metal-catalyzed hydrophosphination
of alkynes by the novel combination of diphosphine and hydro-
silane (eq 3).
Transition-metal-catalyzed addition of heteroatom compounds
bearing heteroatom-heteroatom linkage (E-E) to carbon-carbon
unsaturated bonds is one of the most straightforward and highly
atom-economical methods for the synthesis of vicinally bifunc-
tionalized heteroatom compounds1 (eq 1).
(1) (a) Beletskaya, I. P.; Moberg, C. Chem. ReV. 2006, 106, 2320. (b) Horn, K. A.
Chem. ReV. 1995, 95, 1317. (c) Sharma, H. K.; Pannell, K. H. Chem. ReV. 1995, 95,
1351. (d) Beletskaya, I.; Moberg, C. Chem. ReV. 1999, 99, 3435. (e) Han, L.-B.; Tanaka,
M. Chem. Commun. 1999, 395. (f) Suginome, M.; Ito, Y. Chem. ReV. 2000, 100, 3221.
(g) Ogawa, A. J. Organomet. Chem. 2000, 611, 463.
Indeed, group 13, 14, and 162 heteroatom compounds have been
employed successfully for this purpose. In sharp contrast, however,
there has been no report concerning transition-metal-catalyzed
addition of group 15 heteroatom compounds bearing E-E linkage
to carbon-carbon unsaturated bonds.3-7 Very recently, we have
reported the first example of transition-metal-catalyzed addition
of tetraphenyldiphosphine to alkynes, which surprisingly dose not
afford the expected bisphosphination products but hydrophosphi-
nation ones with excellent selectivity8 (eq 2).
(2) For the metal-catalyzed addition of E-E (E ) group 16) to carbon-
carbon unsaturated bonds, see: (a) Kuniyasu, H.; Ogawa, A.; Miyazaki, S.; Ryu, I.;
Kambe, N.; Sonoda, N. J. Am. Chem. Soc. 1991, 113, 9796. (b) Kondo, T.; Uenoyama,
S.; Fujita, K.; Mitsudo, T. J. Am. Chem. Soc. 1999, 121, 482. (c) Arisawa, M.;
Yamaguchi, M. Org. Lett. 2001, 3, 763. (d) Kuniyasu, H. In Catalytic Heterofunction-
alization; Togni, A.; Gru¨tzmacher, H., Eds.; Wiley-VCH: Weinheim, Germany, 2001;
Chapter 7. (e) Ogawa, A. In Handbook of Organopalladium Chemistry for Organic
Synthesis; Negishi, E., Ed.; Wiley-Interscience:New York, 2002; Chapter VII.6. (f)
Ananikov, V. P.; Kabeshov, M. A.; Beletskaya, I. P.; Aleksandrov, G. G.; Eremenko,
I. L. J. Organomet. Chem. 2003, 687, 451. (g) Arisawa, M.; Kozuki, Y.; Yamaguchi,
M. J. Org. Chem. 2003, 68, 8964. (h) Usugi, S.; Yorimitsu, H.; Shinokubo, H.; Oshima,
K. Org. Lett. 2004, 6, 601. (i) Ananikov, V. P.; Beletskaya, I. P. Org. Biomol. Chem.
2004, 2, 284. (j) Ogawa, A. In Main Group Metals in Organic Synthesis; Yamamoto,
H.; Oshima, K., Eds.; Wiley-VCH: Weinheim, Germany, 2004; Vol. 2, Chapter 15.
(k) Moro, A. V.; Nogueira, C. W.; Barbosa, N. B. V.; Menezes, P. H.; da Rocha, J. B. T.;
Zeni, G. J. Org. Chem. 2005, 70, 5257. (l) Ananikov, V. P.; Kabeshov, M. A.;
Beletskaya, I. P. Synlett 2005, 1012.
(3) For reviews concerning transition-metal-catalyzed hydrophosphination and
hydrophosphinylation to carbon-carbon unsaturated bonds, see: Wicht, D. K.;
Glueck, D. S. In Catalytic Heterofunctionalization; Togni, A.; Gru¨tzmacher, H.,
Eds.; Wiley-VCH: Weinheim, Germany, 2001; Chapter 5.
In this reaction, it becomes apparent that the hydrogen source
of the hydrophosphination product comes from alkynic hydro-
gen. To increase the atom-economy of alkynes, the addition of
7928 J. Org. Chem. 2008, 73, 7928–7933
10.1021/jo801267y CCC: $40.75 2008 American Chemical Society
Published on Web 09/18/2008

Palladium-Catalyzed Hydrophosphination of Alkynes
TABLE 1. Pd-Catalyzed Hydrophosphination of 1-Octyne with
(Ph2P)2 and Hydrosilanes
TABLE 2. Pd(PPh3)4-Catalyzed Hydrophosphination of Alkynes
with (Ph2P)2 and Et2MeSiHa
entry
catalyst
silane
yield %a
1
Pd(OAc)2
Pd(OAc)2
Pd(PPh3)4
Pd(PPh3)4
Pd(PPh3)4
Pd(PPh3)4
Et2MeSiH
Et2MeSiH
Et2MeSiH
Et3SiH
PhSiH3
(TMS)3SiH
84
64
95
92
trace
7
2b
3
4
5
6
a Determined by 1H NMR. b The reaction condition: 1-octyne (1 equiv),
Et2MeSiH (1 equiv).
Results and Discussion
When the Pd(OAc)2-catalyzed addition of tetraphenyldiphos-
phine (0.1 mmol) to 1-octyne (0.2 mmol) was examined in the
co-presence of hydrosilane (Et2MeSiH, 0.3 mmol) as the hydrogen
source (eq 4), the hydrophosphination product was obtained in 84%
yield with excellent regioselectivity. Interestingly, neither silylphos-
phination product of the alkynes nor hydrosilylation product of
the alkynes was obtained. The hydrophosphination product pro-
vided the corresponding phosphine oxide by air oxidation during
workup, whereas the treatment of S8 before exposing to air led to
the formation of the corresponding phosphine sulfide.
a Reaction conditions: alkyne (2 equiv), (Ph2P)2 (0.1 mmol), Et2-
MeSiH (3 equiv), C6D6 (0.8 mL). b The values in parentheses are 1H
NMR yield. c In the case of alkynes bearing a CdO group, a complex
mixture was obtained.
Table 2 represents the results of the Pd(PPh3)4-catalyzed hydro-
phosphination of several alkynes using the binary system of (Ph2P)2
and Et2MeSiH. Aliphatic alkynes such as 1-octyne and 5-methyl-
1-hexyne underwent the Pd(0)-catalyzed regioselective hydrophos-
phination, providing the corresponding vinylic phosphine oxides
in excellent yields (entries 1 and 2). Cyano and chloro substituents
were tolerant of the hydrophosphination (entries 3 and 4). In the
cases of aromatic alkynes such as phenylacetylene, p-(n-pen-
tyl)phenylacetylene, and p-trifluoromethylphenylacetylene the hy-
drophosphination proceeded regioselectively, but the yields were
Next, to optimize the reaction conditions, the hydrophosphi-
nation using divalent or zerovalent palladium catalysts and
several hydrosilanes was examined (Table 1). In the presence
of 1 equiv of alkyne and 1 equiv of hydrosilane, 64% of the
desired hydrophosphination product was obtained (entry 2).
When Pd(PPh3)4 and Et2MeSiH were used, the hydrophosphi-
nation product was obtained in almost quantitative yield (entry
3). Et3SiH was also useful (entry 4), but PhSiH3 and (TMS)3SiH
were ineffective in the reaction (entries 5 and 6).
(5) For the transition-metal-catalyzed hydrophosphinylation to carbon-carbon
unsaturated bonds, see: (a) Han, L.-B.; Tanaka, M. J. Am. Chem. Soc. 1996, 118,
1571. (b) Han, L.-B.; Choi, N.; Tanaka, M. Organometallics 1996, 15, 3259. (c) Han,
L.-B.; Hua, R.; Tanaka, M. Angew. Chem., Int. Ed. 1998, 37, 4196. (d) Zhao, C.-Q.;
Han, L.-B.; Tanaka, M. Organometallics 2000, 19, 4196. (e) Han, L.-B.; Zhao, C.-Q.;
Tanaka, M. J. Org. Chem. 2001, 66, 5929. (f) Depre`le, S.; Montchamp, J.-L. J. Am.
Chem. Soc. 2002, 124, 9386. (g) Allen, A., Jr.; Ma, L.; Lin, W. Tetrahedron Lett.
2002, 43, 3707. (h) Milton, M. D.; Onodera, G.; Nishibayashi, Y.; Uemura, S. Org.
Lett. 2004, 6, 3993. (i) Han, L.-B.; Zhang, C.; Yazawa, H.; Shimada, S. J. Am. Chem.
Soc. 2004, 126, 5080. (j) Ribie`re, P.; Bravo-Altamirano, K.; Antczak, M. I.; Hawkins,
J. D.; Montchamp, J.-L. J. Org. Chem. 2005, 70, 4064. (k) Stockland, R. A., Jr.; Lipman,
A. J.; Bawiec, J. A., III.; Morrison, P. E.; Guzei, I. A.; Findeis, P. M.; Tamblin, J. F. J.
Organomet. Chem. 2006, 691, 4042. (l) Dobashi, N.; Fuse, K.; Hoshino, T.; Kanada,
J.; Kashiwabara, T.; Kobata, C.; Nune, S. K.; Tanaka, M. Tetrahedron Lett. 2007, 48,
4669.
(6) For the rhodium-catalyzed synthesis of 1-alkynylphosphine oxides from
1-alkynes and tetraphenyldiphosphine, see: Arisawa, M.; Onoda, M.; Hori, C.;
Yamaguchi, M. Tetrahedron Lett. 2006, 47, 5211.
(7) For the Lewis acid mediated silylphosphination to substituted propiolates,
see: Hayashi, M.; Matsuura, Y.; Kurihara, K.; Maeda, D.; Nishimura, Y.; Morita,
E.; Okasaka, M.; Watanabe, Y. Chem. Lett. 2007, 36, 634.
(4) For the metal-catalyzed hydrophosphination to carbon-carbon unsaturated
bonds, see: (a) Pringle, P. G.; Smith, M. B. J. Chem. Soc., Chem. Commun.
1990, 1701. (b) Kazankova, M. A.; Efimova, I. V.; Kochetkov, A. N.; Afanas’ev,
V. V.; Beletskaya, I. P.; Dixneuf, P. H. Synlett 2001, 497. (c) Shulyupin, M. O.;
Kazankova, M. A.; Beletskaya, I. P. Org. Lett. 2002, 4, 761. (d) Takaki, K.;
Koshoji, G.; Komeyama, K.; Takeda, M.; Shishido, T.; Kitani, A.; Takehira, K.
J. Org. Chem. 2003, 68, 6554. (e) Komeyama, K.; Kawabata, T.; Takehira, K.;
Takaki, K. J. Org. Chem. 2005, 70, 7260. (f) Ohmiya, H.; Yorimitsu, H.; Oshima,
K. Angew. Chem., Int. Ed. 2005, 44, 2368. (g) Scriban, C.; Kovacik, I.; Glueck,
D. S. Organometallics 2005, 24, 4871. (h) Takaki, K.; Komeyama, K.; Kobayashi,
D.; Kawabata, T.; Takehira, K. J. Alloys Compd. 2006, 408, 432. (i) Hayashi,
M.; Matsuura, Y.; Watanabe, Y. J. Org. Chem. 2006, 71, 9248. (j) Komeyama,
K.; Kobayashi, D.; Yamamoto, Y.; Takehira, K.; Takaki, K. Tetrahedron 2006,
62, 2511. (k) Join, B.; Mimeau, D.; Delacroix, O.; Gaumont, A.-C. Chem.
Commun. 2006, 3249. (l) Crimmin, M. R.; Barrett, A. G. M.; Hill, M. S.;
Hitchcock, P. B.; Procopiou, P. A. Organometallics 2007, 26, 2953.
(8) Nagata, S.; Kawaguchi, S.-i.; Matsumoto, M.; Kamiya, I.; Nomoto, A.;
Sonoda, M.; Ogawa, A. Tetrahedron Lett. 2007, 48, 6637.
J. Org. Chem. Vol. 73, No. 20, 2008 7929

Kawaguchi et al.
TABLE 3. Hydrophosphination to 1-Octyne with Phosphine Oxide
phosphination product was obtained). This fact indicates the
presence of a small amount of oxygen is essential to attain this
hydrophosphination with high efficiency.10 Although tetraphe-
nyldiphosphine (1) is fairly stable in the solid state, it is
extremely air-sensitive in solvent, generating immediately
several oxidation products, which can be assigned unambigu-
ously by measurement of their 31P NMR spectra11 (in C6D6)
(Ph2PP(O)Ph2 (5): δ -23.1 (d, J ) 218.0 Hz), 34.6 (d, J )
218.0 Hz);12 Ph2P(O)H (6): δ 18.0 ppm13) (eq 7).
To gain insight into the role of these oxidation products (5 and
6) in the present hydrophosphination, we examined the hydro-
phosphination in the presence/absence of 5 or 6, and the results
are summarized in Table 3. When 5 was used instead of 1, both
hydrophosphination product 2 and hydrophosphinylation product
3 were obtained in low yields (entry 1). On the other hand, use of
only 6 resulted in no formation of the hydrophosphinylation product
(entry 2). When equimolar amounts of 1 and 5 were employed,
the corresponding vinylic phosphines 2 and 3 were obtained in
53% and 36% yields, respectively (entry 3). In addition, when the
proportion of 1 to 5 was altered, the yields were diminished (entries
4 and 5). These results suggest tetraphenyldiphosphine oxide (5)
played an important role in this hydrophosphination.
In the presence of the catalyst (prepared by the reaction of
Pd(PPh3)4 (0.01 mmol) with 1 (0.005 mmol) and 5 (0.005
mmol)), 1 successfully added to 1-octyne, providing the
corresponding vinylic phosphine in good yield (eq 8). In
contrast, when 5 was employed as the substrate in place of 1,
the hydrophosphination product was obtained in only very poor
yield. These results clearly indicate that, in this hydrophosphi-
nation, tetraphenyldiphosphine (1), not tetraphenyldiphosphine
oxide (5), acts as the phosphination reagent.
a
1H NMR yield.
somewhat lower compared with aliphatic ones (entries 5-7). In
the case of a conjugate enyne, the hydrophosphination proceeded
in moderate yield (entry 8). Unfortunately, the internal alkynes such
as 4-octyne and 1-phenyl-1-butyne did not afford the desired
hydrophosphination product.
To clarify the hydrogen source of the present catalytic
hydrophosphination using the diphosphine-hydrosilane binary
system, we examined the hydrophosphination of phenylacetylene
deuterized at the terminal acetylenic hydrogen (98 atom% D),
which afforded the corresponding (E)-vinylphosphine and (E)-
vinylphosphine oxide stereoselectively (eq 5). This result
strongly suggests that the hydrophosphination proceeds via a
syn-addition process using the hydrosilane as a hydrogen source.
Furthermore, the formation of silylphosphine oxide as a by-
product was confirmed by 31P NMR (eq 6) (Et2MeSiP(O)Ph2:
31P NMR (C6D6) δ ) 21.8 ppm, 29Si NMR δ ) 24.6 ppm (d,
J ) 8.7 Hz)).9
(9) Literature value of 31P NMR of Ph3SiP(O)Ph2, which is similar compound
to Et2MeSiP(O)Ph2, is δ ) 28.6 ppm (CDCl3). See: Ferguson, I. G. T.; Glidewell,
C. J. Chem. Soc., Dalton Trans. 1977, 2071.
(10) To clarify the effect of oxygen on the reaction, we examined the
hydrophosphination of 1-octyne (0.1 mmol) in the presence of air: (mol % of
O2, yield of 2, yield of 3) ) (25 mol %, 30%, 6%); (50 mol %, 30%, 13 %).
(11) (a) Postigo, A.; Barata, S.; Ogawa, A.; Sonoda, M. Tetraphenyldiphos-
phine. In Encycopedia of Reagent for Organic Synthesis; John Wiley Sons, Ltd.:
New York, March 14, 2008, online. (b) Kawaguchi, S.; Nagata, S.; Tsuchii, K.;
Nomoto, A.; Ogawa, A. Tetrahedron Lett. 2006, 47, 3919.
(12) Irvine, D. J.; Glidewell, C.; Cole.Hamilton, D. J.; Barnes, J. C.; Howie,
A. J. Chem. Soc., Dalton Trans. 1991, 1765.
(13) (a) Dabkowski, W.; Michalski, J.; Skrzypczynski, Z. J. Chem. Soc., Chem.
Commun. 1982, 1260. (b) Ko¨ster, R.; Schu¨ꢀler, W.; Synoradzki, L. Chem. Ber. 1987,
120, 1105.
We next investigated in detail the influence of oxygen on
the present hydrophosphination. When oxygen was strictly
removed from this reaction system, the present hydrophosphi-
nation was dramatically suppressed (only 20% of the hydro-
7930 J. Org. Chem. Vol. 73, No. 20, 2008

Palladium-Catalyzed Hydrophosphination of Alkynes
SCHEME 1. A Plausible Pathway for Hydrophosphination of Alkynes with (Ph2P)2 and R′3SiH
A plausible catalytic pathway is shown in Scheme 1: (1)
generation of the active Pd species 7;14 (2) the phosphinopal-
ladation of an alkyne with this active Pd species 7, affording a
vinylpalladium intermediate 8; (3) the exchange reaction of a
vinylphosphine with the hydrosilane to afford a vinylphosphine
product 2; (4) regeneration of the active Pd species 7 by the
reaction of Pd species with tetraphenyldiphosphine along with
generation of silylphosphine15 as byproduct.
photoinduced addition of tetraphenyldiphosphine to 1-octyne
afforded (Z)-1,2-bis(diphenylphosphino)-1-octene,11b which was
then treated with Pd(PPh3)4 (Scheme 2). Immediately, the signals
(δ -24.5 (d, JP-P ) 157.0 Hz), δ -5.8 (d, JP-P ) 157.0 Hz),
in C6D6) of (Z)-1,2-bis(diphenylphosphino)-1-octene disappeared
completely, and new signals were observed at δ 26.7-27.1 and
46.4-47.0 ppm (C6D6) as a characteristic multiplet, which can
be assigned as the signal of the Pd complex 9.
Furthermore, to get some information about the mechanism for
this hydrophosphination, the hydrophosphination of 1-octyne in
the absence of oxygen was monitored by 31P NMR. Surprisingly,
31P NMR indicated the formation of the Pd complex 9: δ 26.7-27.1
and 46.4-47.0 ppm in C6D616 (ca. 5%) (Figure 1).
Furthermore, when the crude solution including the Pd
complex 9 was treated with S8, (Z)-1,2-bis(diphenylthiophos-
phinyl)-1-octene (10) was obtained (eq 9).
Most probably, (Z)-1,2-bis(diphenylophosphino)-1-alkenes
may work as a catalyst poison and inhibit the desired hydro-
phosphination reaction of alkynes and/or the bisphosphination
reaction.17 Accordingly, the existence of small amounts of
oxygen in this hydrophosphination presumably leads to the
formation of tetraphenyldiphosphine oxide, which may depress
the formation of the Pd complex 9.18
(15) When the hydrophosphination of 1-octyne was monitored by 31P NMR,
three major peaks were observed at δ-2.4, 21.8, and 28.9 ppm. The two peaks
(δ-2.4, 28.9 ppm) can be assigned to 2 and 3, respectively. The other peak at
FIGURE 1. 31P NMR spectrum of complex 9.
δ
21.8 ppm is assumed to be Et2MeSiP(O)Ph2. However, the peak of
Et2MeSiPPh2 was not observed, probably because oxygen atom exchange reaction
between Et2MeSiPPh2 and other phosphine oxide products in situ may proceed
immediately.
(16) (a) Carty, A. J.; Johnson, D. K. J. Chem. Soc., Chem. Commun. 1977,
903. (b) Carty, A. J.; Johnson, D. K.; Jacobson, S. E. J. Am. Chem. Soc. 1979,
101, 5612. (c) Dodds, D. L.; Haddow, M. F.; Orpen, A. G.; Pringle, P. G.;
Woodward, G. Organometallics 2006, 25, 5937. (d) Kondoh, A.; Yorimitsu,
H.; Oshima, K. J. Am. Chem. Soc. 2007, 129, 4099.
(17) When 15 mol % of (Z)-1,2-bis(diphenylphosphino)-1-octene was added
to the reaction system, no hydrophosphination product was obtained. Furthermore,
when 15 mol % of cis-bis(diphenylphosphino)ethene was added to the reaction
system, no hydrophosphination product was also obtained.
Identification of the Pd complex 9 was performed by
comparison with the authentic sample synthesized alternatively:
(14) We attempted the observation of Pd species 7 by 31P NMR. In the
literature, the chemical shift of the Pd-P(O)Ph2 unit appears at δ 86 ppm (in
benzene). When the stoichiometric reaction of Pd(PPh3)4 with (Ph2P)2 and
Ph2PP(O)Ph2 (in C6D6, 298 K, 3 h) was conducted, we observed two signals at
δ 85.8 and 86.3 ppm, which indicate the possibility of Pd-P(O)Ph2 bond
formation. See: Belntykh, L. B.; Goremyka, T. V.; Zinchenko, S. V.; Rokhin,
A. V.; Ratovskii, G. V.; Shmidt, F. K. Russ. J. Coord. Chem. 2002, 28, 664.
J. Org. Chem. Vol. 73, No. 20, 2008 7931

Kawaguchi et al.
SCHEME 2. 31P NMR Data Concerning the Reaction of (Z)-1,2-Bis(diphenylphosphino)-1-octene with Pd(PPh3)4
725, 696, 540 cm-1; 1H NMR (CDCl3) δ 0.75 (t, J ) 6.3 Hz, 3H),
1.13-1.17 (m, 6H), 1.37-1.42 (m, 2H), 2.19-2.25 (m, 2H), 5.53
(d, J ) 21.4 Hz, 1H), 5.85 (d, J ) 42.9 Hz, 1H), 7.36-7.47 (m,
6H), 7.60-7.64 (m, 4H); 13C NMR (CDCl3) δ 14.0, 22.5, 28.0 (d,
Conclusion
We have discovered that a novel transition-metal-catalyzed
hydrophosphination of terminal alkynes using diphosphine-
hydrosilane binary system, which takes place regioselectively
and efficiently, provides vinylic phosphines. The present hy-
drophosphination of alkynes smoothly takes place in the
presence of small amounts of oxygen, which leads to the
tetraphenyldiphosphine oxide in situ from tetraphenyldiphos-
phine. It has been suggested that the presence of tetraphenyl-
diphosphine oxide is useful for keeping the catalytic activity
forward in the hydrophosphination of alkynes. We believe this
reaction opens up a new field of transition-metal-catalyzed
reactions using heteroatom binary systems.
JC-P ) 5.0 Hz), 29.2 (d, JC-P ) 85.3 Hz), 31.49, 31.50 (d, JC-P
)
11.0 Hz), 128.4 (d, JC-P ) 12.0 Hz), 128.6, 131.4 (d, JC-P ) 94.4
Hz), 131.8, 131.9 (d, JC-P ) 10.0 Hz), 144.1 (d, JC-P ) 92.4 Hz);
31P NMR (CDCl3) δ 32.3; HRMS (EI) calcd for C20H25OP
312.1643, found 312.1649.
2-(Diphenylphosphinyl)-5-methyl-1-hexene (3b):8 yellow oil;
IR (NaCl) 2954, 2868, 1436, 1193, 1116, 939, 725, 696, 538 cm-1
;
1H NMR (CDCl3) δ 0.81 (d, J ) 6.4 Hz, 6H), 1.34-1.39 (m, 2H),
1.47-1.53 (m, 1H), 2.27-2.34 (m, 2H), 5.62 (d, J ) 21.0 Hz,
1H), 5.94 (d, J ) 42.9 Hz, 1H), 7.46-7.49 (m, 4H), 7.52-7.56
(m, 2H), 7.68-7.73 (m, 4H); 13C NMR (CDCl3) δ 22.4, 27.7, 29.3
(d, JC-P ) 11.3 Hz), 37.1 (d, JC-P ) 4.5 Hz), 128.39, 128.42 (d,
JC-P ) 11.3 Hz), 131.4 (d, JC-P ) 101.9 Hz), 131.78, 131.84 (d,
JC-P ) 9.8 Hz), 144.3 (d, JC-P ) 90.5 Hz); 31P NMR (CDCl3) δ
32.3; HRMS (EI) calcd for C19H23OP 298.1487, found 298.1491.
5-Cyano-2-(diphenylphosphinyl)-1-pentene (3c):5c yellow oil;
IR (NaCl) 2358, 2341, 1437, 1182, 1119, 723, 696, 540 cm-1; 1H
NMR (CDCl3) δ 1.83-1.99 (m, 2H), 2.25-2.37 (m, 2H), 2.46-2.53
(m, 2H), 5.58 (d, J ) 19.8 Hz, 1H), 5.98 (d, J ) 42.3 Hz, 1H),
7.50-7.62 (m, 6H), 7.62-7.83 (m, 4H); 13C NMR (CDCl3) δ 16.6,
24.5 (d, JC-P ) 4.0 Hz), 31.4 (d, JC-P ) 10.0 Hz), 119.2, 128.7 (d,
Experimental Section
General Procedure for Palladium-Catalyzed Hydrophosphi-
nation to Alkynes Using Diphosphine-Hydrosilane Binary
System. (Ph2P)2 (37.6 mg, 0.1 mmol), Pd(PPh3)4 (5.8 mg, 0.005
mmol), alkyne (0.3 mmol), Et2MeSiH (43.4 µL, 0.3 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 s, and the
tube was covered by aluminum foil. The mixture was heated at
reflux for 18 h. The reaction mixture was left under air overnight.
Purification of the crude was performed by preparative TLC (silica
gel, 3a: hexane/AcOEt ) 9/1, Rf ) 0.04; 3b: hexane, Rf ) 0.03;
3c: hexane/AcOEt ) 3/1, Rf ) 0.07; 3d: hexane/AcOEt ) 3/1, Rf
) 0.09; 3e: hexane, Rf ) 0.03; 3f: hexane/AcOEt )10/1, Rf )
0.04; 3g: Et2O, Rf ) 0.30; 3h: Et2O, Rf ) 0.38).
JC-P ) 11.0 Hz), 130.6 (d, JC-P ) 10.0 Hz), 130.8 (d, JC-P
102.4 Hz), 131.8 (d, JC-P ) 11.0 Hz), 132.2, 142.3 (d, JC-P
)
)
89.4 Hz); 31P NMR (C6D6) δ 28.7; HRMS (EI) calcd for
C18H18NOP 295.1126, found 295.1129. Anal. Calcd for C18H18NOP:
C, 73.21; H, 6.14; N, 4.74%. Found: C, 72.92; H, 6.05; N, 4.58%.
5-Chloro-2-(diphenylphosphinyl)-1-pentene (3d):8 yellow oil;
IR (NaCl) 3431, 3055, 2923, 2854, 1436, 1184, 1118, 1099, 721,
694, 540 cm-1; 1H NMR (CDCl3) δ 1.94-2.03 (m, 2H), 2.46-2.55
(m, 2H), 2.46-2.55 (m, 2H), 5.62 (dd, J ) 20.1, 0.9 Hz, 1H), 5.98
(dd, J ) 42.3, 0.9 Hz, 1H), 7.43-7.59 (m, 6H), 7.64-7.75 (m,
4H); 13C NMR (CDCl3) δ 29.4 (d, JC-P ) 11.3 Hz), 31.2 (d, JC-P
) 4.5 Hz), 44.1, 128.5 (d, JC-P ) 12.8 Hz), 128.6 (d, JC-P ) 11.3
Hz), 129.8 (d, JC-P ) 10.6 Hz), 131.8 (d, JC-P ) 9.1 Hz), 132.0
The Spectral and Analytical Data. 2-(Diphenylphosphinyl)-
1-octene (3a):5c yellow oil; IR (NaCl) 2927, 1437, 1190, 1118,
(18) When the equimolar reaction of Pd(PPh3)4 (0.1 mmol) with (Ph2P)2 (0.1
mmol) was conducted in C6D6 at 298 K for 3 h, only 25% of (Ph2P)2 was
consumed for the construction of the Pd complex by monitoring the reaction
with 31P NMR (75% of (Ph2P)2 was recovered). On the other hand, the equimolar
reaction of Pd(PPh3)4 with (Ph2P)2 and Ph2PP(O)Ph2 at room temperature for
3 h led to a consumption of Ph2PP(O)Ph2 completely. These results suggest that
Ph2PP(O)Ph2 is readily added to Pd(PPh3)4 than (Ph2P)2.
7932 J. Org. Chem. Vol. 73, No. 20, 2008

Palladium-Catalyzed Hydrophosphination of Alkynes
(d, JC-P ) 2.3 Hz), 142.7 (JC-P ) 92.0 Hz); 31P NMR (C6D6) δ
28.6; HRMS (EI) calcd for C17H18ClOP 304.0784, found 304.0787.
2-(Diphenylphosphinyl)-1-styrene (3e):5c yellow oil; IR (NaCl)
3060, 1436, 1180, 1116, 727, 694, 532 cm-1; 1H NMR (CDCl3) δ
5.75 (d, J ) 19.5 Hz, 1H), 6.24 (d, J ) 40.0 Hz, 1H), 7.20-7.31
(m, 3H), 7.32-7.55 (m, 8H), 7.62-7.75 (m, 4H); 13C NMR
(CDCl3) δ 128.15 (d, JC-P ) 5.0 Hz), 128.22, 128.3, 128.4, 128.5,
131.7 (d, JC-P ) 104.0 Hz), 131.9 (d, JC-P ) 9.1 Hz), 132.0, 132.1,
144.4 (d, JC-P ) 93.4 Hz); 31P NMR (CDCl3) δ 30.8; HRMS (EI)
calcd for C20H17OP 304.1017, found 304.1021.
JC-P ) 104.4 Hz), 144.3 (d, JC-P ) 91.4 Hz); 31P NMR (CDCl3)
δ 33.4; HRMS (EI) calcd for C20H17OP 308.1330, found 308.1334.
2-(Diphenylthiophosphinyl)-1-octene (4a): Tetraphenyldiphos-
phine (18.8 mg, 0.05 mmol), tetraphenyldiphosphine oxide (19.6
mg, 0.05 mmol), tetrakis(triphenylphosphine)palladium (5.8 mg,
0.005 mmol), 1-octyne (44.2 µL, 0.3 mmol), diethylmethylsilane
(43.4 µL, 0.3 mmol), and degassed C6D6 (0.6 mL) were placed in
a sealed Pyrex glass NMR tube under a nitrogen atmosphere. The
mixture was stirred for 30 s, and the tube was covered by aluminum
foil. The mixture was heated at reflux for 18 h. The reaction mixture
was added to S8 (9.6 mg, 0.3 mmol). Purification of the crude was
performed by preparative TLC (silica gel, hexane/Et2O ) 3/1, Rf
) 0.47): white yellow solid; IR (KBr) 2928, 2856, 1435, 1101,
748, 713, 692, 638 cm-1; 1H NMR (CDCl3) δ 0.83 (t, J ) 6.9 Hz,
3H), 1.18-1.25 (m, 6H), 1.44-1.50 (m, 2H), 2.33-2.38 (m, 2H),
5.49 (d, J ) 22.9 Hz, 1H), 5.89 (d, J ) 45.9 Hz, 1H), 7.41-7.53
(m, 6H), 7.77-7.80 (m, 4H); 13C NMR (CDCl3) δ 14.1, 22.6, 28.4
(d, JC-P ) 6.7 Hz), 28.9, 31.4 (d, JC-P ) 12.6 Hz), 31.6, 127.7,
128.6 (d, JC-P ) 12.6 Hz), 131.3 (d, JC-P ) 93.8 Hz), 131.6, 132.2
(d, JC-P ) 12.6 Hz), 144.1 (d, JC-P ) 72.9 Hz); 31P NMR (CDCl3)
δ 47.2; HRMS (EI) calcd for C20H25PS 328.1415, found 328.1417.
1-{1-(Diphenylphosphinyl)ethenyl}-4-pentylbenzene (3f): yel-
low oil; IR (NaCl) 2928, 2856, 1437, 1190, 1117, 748, 725, 696,
530 cm-1, 1H NMR (CDCl3) δ 0.86 (t, J ) 6.8 Hz 3H), 1.23-1.31
(m, 4H), 1.42-1.65 (m, 2H), 2.52 (t, J ) 8.1 Hz, 2H), 5.69 (d, J
) 19.8 Hz, 1H), 6.23 (d, J ) 40.8 Hz, 1H), 7.05 (d, J ) 8.1 Hz,
2H), 7.36-7.52 (m, 10H), 7.68-7.74 (m, 2H); 13C NMR (CDCl3)
δ 13.9 (d, J ) 12.5 Hz), 22.4, 30.8, 31.3, 35.5, 127.1 (d, JC-P
)
13.4 Hz), 127.9 (d, JC-P ) 21.1 Hz), 128.4 (d, JC-P ) 17.3 Hz),
129.4, 130.8-131.3 (m), 131.5-132.4 (m), 134.6 (d, JC-P ) 10.6
Hz), 143.0, 143.9 (d, JC-P ) 93.1 Hz), 149.4; 31P NMR (C6D6) δ
27.9; HRMS (EI) calcd for C25H27OP 374.1800, found 374.1775.
1-{1-(Diphenylphosphinyl)ethenyl}-4-(trifluoromethyl)ben-
zene (3g): white yellow solid; IR (KBr) 2359, 2343, 2179, 1437,
1325, 1182, 1119, 1067, 856, 690, 538 cm-1, 1H NMR (CDCl3) δ
5.77 (d, J ) 19.6 Hz, 1H), 6.28 (d, J ) 39.6 Hz, 1H), 7.44-7.92
(m, 14H); 13C NMR (CDCl3) δ 125.4, 127.1 (q, JC-F ) 291.2 Hz),
Acknowledgment. This work is supported by 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.
128.5 (d, JC-P ) 5.0 Hz), 128.6, 128.7, 128.9, 131.0 (d, JC-P
)
11.0 Hz), 131.1 (d, JC-P ) 103.4 Hz), 132.0 (d, JC-P ) 10.0 Hz),
132.7 (q, JC-F ) 32.1 Hz), 143.7 (d, JC-P ) 92.4 Hz); 31P NMR
(CDCl3) δ 30.8; HRMS (EI) calcd for C21H16F3OP 372.0891, found
372.0886.
Supporting Information Available: Copies of 1H NMR and
13C NMR spectra of 2-(diphenylphosphinyl)-1-octene (3a), 2-(di-
phenylphosphinyl)-5-methyl-1-hexene (3b), 5-cyano-2-(diphe-
nylphosphinyl)-1-pentene (3c), 2-(diphenylphosphinyl)-1-styrene
(3e),1-(1-diphenylphosphinylethenyl)-4-pentylbenzene(3f),1-{1-
(diphenylphosphinyl)ethenyl}-4-(trifluoromethyl)benzene (3g),
1-cyclohexen-1-yl-1-(diphenylphosphinyl)ethene (3h), and
2-(diphenylthiophosphinyl)-1-octene (4a). This material is avail-
able free of charge via the Internet at http://pubs.acs.org.
1-Cyclohexen-1-yl-1-(diphenylphosphinyl)ethene (3h):5c yel-
low oil; IR (NaCl) 2927, 1431, 1180, 1115, 1070, 751, 723, 696,
536 cm-1; 1H NMR (CDCl3) δ 1.48-1.67 (m, 4H), 1.98-2.23 (m,
4H), 5.24 (d, J ) 21.2 Hz, 1H), 5.94 (d, J ) 43.0 Hz, 1H), 6.36 (s,
1H), 7.30-7.56 (m, 6H), 7.62-7.81 (m, 4H); 13C NMR (CDCl3)
δ 21.7, 22.6, 25.8, 27.0 (d, JC-P ) 5.0 Hz), 127.0 (d, JC-P ) 10.0
Hz), 128.3 (d, JC-P ) 12.0 Hz), 130.9 (d, JC-P ) 11.0 Hz), 131.6,
131.7 (d, JC-P ) 10.0 Hz), 132.3 (d, JC-P ) 5.0 Hz), 132.6 (d,
JO801267Y
J. Org. Chem. Vol. 73, No. 20, 2008 7933