Copper-catalyzed anti-hydrophosphination reaction of 1-alkynylphosphines with diphenylphosphine providing (Z)-1,2-diphosphino-1-alkenes

Article abstract of DOI:10.1021/ja070048d

Hydrophosphination of 1-alkynylphosphines with diphenylphosphine proceeds in an anti fashion under copper catalysis, providing an easy and efficient access to a variety of (Z)-1,2-diphosphino-1-alkenes and their sulfides. The reaction is highly chemoselec

Full text of DOI:10.1021/ja070048d

Published on Web 03/14/2007
Copper-Catalyzed anti-Hydrophosphination Reaction of
1-Alkynylphosphines with Diphenylphosphine Providing
(Z)-1,2-Diphosphino-1-alkenes
Azusa Kondoh, Hideki Yorimitsu,* and Koichiro Oshima*
Contribution from the Department of Material Chemistry, Graduate School of Engineering,
Kyoto UniVersity, Kyoto-daigaku Katsura, Nishikyo-ku, Kyoto 615-8510, Japan
Received January 9, 2007; E-mail: yori@orgrxn.mbox.media.kyoto-u.ac.jp; oshima@orgrxn.mbox.media.kyoto-u.ac.jp
Abstract: Hydrophosphination of 1-alkynylphosphines with diphenylphosphine proceeds in an anti fashion
under copper catalysis, providing an easy and efficient access to a variety of (Z)-1,2-diphosphino-1-alkenes
and their sulfides. The reaction is highly chemoselective and can be performed even in an aqueous medium.
The reaction is reliable enough to realize a gram-scale synthesis of (Z)-1,2-diphosphino-1-alkene. Radical
reduction of the diphosphine disulfides with tris(trimethylsilyl)silane yields the parent trivalent diphosphines
without suffering from the isomerization of the olefinic geometry. Enantioselective hydrogenation of (Z)-
3,3-dimethyl-1,2-bis(diphenylthiophosphinyl)-1-butene followed by desulfidation leads to a new chiral
bidentate phosphine ligand.
Introduction
Ethynyldiphenylphosphine and bis(diphenylphosphino)ethyne
undergo syn-hydrophosphination in the presence of strong bases
Organophosphines have been gaining in importance as ligands
for transition metal catalysts, as clearly demonstrated in cross-
coupling reactions1 and asymmetric transformations.2 Creation
of new organophosphines and, naturally, of new phosphination
reactions can thus have great impact on various fields of
chemical science.
Metal-catalyzed hydrophosphination reactions of C-C mul-
tiple bonds represent a straightforward method for the synthesis
of organophosphines.3 In particular, catalytic hydrophosphina-
tions of phosphorus-substituted unsaturated C-C bonds seem
to be quite useful since the reactions provide bidentate diphos-
phines. In spite of their potential utility, the hydrophosphinations
providing bidentate phosphines are rather limited. Although the
hydrophosphinations of vinylphosphines proceed smoothly in
the presence of a base to afford useful 1,2-diphosphinoethanes,
such as phenyllithium.4b,6 Upon complexation with platinum or
palladium, 1-alkynylphosphines of some generality participate
in anti-hydrophosphination.7 The use of stoichiometric amounts
of expensive transition metals is a definite and significant
drawback. Here we report that hydrophosphinations of various
1-alkynylphosphines with diphenylphosphine proceed in an anti
fashion under copper catalysis with perfect stereo- and regio-
selectivity. The diphosphines obtained, (Z)-1,2-diphosphino-1-
alkenes, are not only structurally intriguing entities but also
potentially useful bidentate ligands for transition metals. Fur-
thermore, the carbon-carbon double bonds of the diphosphines
can enjoy further functionalizations. Despite their latent rich
chemistry, efficient and general methods for the synthesis of
(Z)-1,2-diphosphino-1-alkenes have scarcely been reported so
far.8,9
the hydrophosphinations require the native vinyl group, i.e.,
(CH2dCH)nPR3-n
4,5
.
In this paper, we focus on 1-alkynylphosphines as the
substrates. The precedent hydrophosphinations of 1-alkynylphos-
phines highlight the difficulty in achieving the transformation.
(4) (a) King, R. B. Acc. Chem. Res. 1972, 5, 177-185. (b) Schmidbaur, H.;
Paschalidis, C.; Reber, G.; Mu¨ller, G. Chem. Ber. 1988, 121, 1241-1245.
(c) Bookham, J. L.; McFarlane, W.; Colquhoun, I. J. J. Chem. Soc., Chem.
Commun. 1986, 1041-1042. (d) Casey, C. P.; Paulsen, E. L.; Beutten-
mueller, E. W.; Proft, B. R.; Petrovich, L. M.; Matter, B. A.; Powell, D.
R. J. Am. Chem. Soc. 1997, 119, 11817-11825. (e) Imamoto, T.; Oshiki,
T.; Onozawa, T.; Kusumoto, T.; Sato, K. J. Am. Chem. Soc. 1990, 112,
5244-5252. (f) Bunlaksananusorn, T.; Knochel, P. Tetrahedron Lett. 2002,
43, 5817-5819. (g) King, R. B.; Bakos, J.; Hoff, C. D.; Marko, L. J. Org.
Chem. 1979, 44, 3095-3100. (h) Brunner, H.; Limmer, S. J. Organomet.
Chem. 1990, 403, 55-63.
(1) (a) Tamao, K.; Sumitani, K.; Kumada, M. Bull. Chem. Soc. Jpn. 1976, 49,
1958-1969. (b) Valentine, D. H., Jr.; Hillhouse, J. H. Synthesis 2003,
2437-2460. (c) Tsuji, J. Palladium Reagents and Catalysts; Wiley,
Chichester, U.K., 2004. (d) Metal-Catalyzed Cross-Coupling Reactions;
Diederich, F., Stang, P. J., Eds.; Wiley-VCH, 1998. (e) Metal-Catalyzed
Cross-Coupling Reactions; de Meijere, A., Diederich, F., Eds.; Wiley-VCH,
2004.
(2) (a) Knowles, W. S. Angew. Chem., Int. Ed. 2002, 41, 1998-2007. (b)
Noyori, R. Angew. Chem., Int. Ed. 2002, 41, 2008-2022. (c) Hayashi, T.;
Kumada, M. Acc. Chem. Res. 1982, 15, 395-401. (d) Noyori, R.
Asymmetric Catalysis in Organic Synthesis; Wiley, New York, 1994.
(3) (a) Wicht, D. K.; Glueck, D. S. In Catalytic Heterofunctionalization; Togni,
A., Gru¨tzmacher, H., Eds.; Wiley-VCH: Weinheim, Germany, 2001;
Chapter 5. (b) Alonso, F.; Beletskaya, I. P.; Yus, M. Chem. ReV. 2004,
104, 3079-3159. (c) Delacroix, O.; Gaumont, A. C. Curr. Org. Chem.
2005, 9, 1851-1882. (d) Baillie, C.; Xiao, J. L. Curr. Org. Chem. 2003,
7, 477-514.
(5) The only exception: Bookham, J. L.; Smithies, D. M. J. Organomet. Chem.
1999, 577, 305-315.
(6) King, R. B.; Kapoor, P. N. J. Am. Chem. Soc. 1971, 93, 4158-4166.
(7) Carty, A. J.; Johnson, D. K.; Jacobson, S. E. J. Am. Chem. Soc. 1979, 101,
5612-5619.
(8) Examples of the methods for the synthesis of (Z)-1,2-diphosphino-1-alkenes,
which lack generality: (a) Banert, K.; Fendel, W.; Schlott, J. Angew. Chem.,
Int. Ed. 1998, 37, 3289-3292. (b) Tzschach, V. A.; Baensch, S. J. Prakt.
Chem. 1971, 313, 254-258. (c) Cullen, W. R.; Dawson, D. S. Can. J.
Chem. 1967, 45, 2887-2894. (d) Dodds, D. L.; Haddow, M. F.; Orpen, A.
G.; Pringle, P. G.; Woodward, G. Organometallics 2006, 25, 5937-5945.
9
10.1021/ja070048d CCC: $37.00 © 2007 American Chemical Society
J. AM. CHEM. SOC. 2007, 129, 4099-4104
4099

A R T I C L E S
Scheme 1
Kondoh et al.
Table 1. Copper-Catalyzed Hydrophosphination of
1-Alkynylphosphines with Diphenylphosphinea
CuI
Cs2CO3
yield of 3
/%b
entry
R
/mol %
/mol %
1
2c
3d
4c
5
nC6H13 (a)
1
10
2
10
1
10
2
2
10
20
10
20
10
20
10
10
40
20
99 (88)
98 (84)
99 (87)
90 (84)
98 (72)
98 (87)
88 (62)
85 (79)
94 (75)
87 (84)
iPr (b)
tBu (c)
tBu (c)
Ph (d)
6
7
8
4-Ac-C6H4 (e)
3-pyridyl (f)
EtOC(dO)(CH2)6 (g)
AcS(CH2)9 (h)
PhCH(OH) (i)
9e
10
20
10
a Hydrophosphination conditions: 1 (0.50 mmol), Ph2PH (0.60 mmol),
DMF (3 mL), 25 °C, 4 h. Sulfidation conditions: sulfur (2 mmol), 25 °C,
1 h. b Based on 31P NMR with a sufficient first decay period. Isolated yields
are in parentheses. c The reaction was performed for 6 h. d The reaction
was performed at 90 °C. e The reaction was performed for 20 h.
exclusively (Table 1, entry 1). Handling of 2a under air for
purification led to gradual oxidation. To evaluate the efficiency
of the reaction accurately, we isolated the product as phosphine
sulfide 3a after treatment with crystalline sulfur. Isolation of
the parent phosphine 2a and its analogues is discussed in the
following section. The yield of 3a based on 31P NMR was 99%,
and the isolated yield was 88%. The formation of the (Z) isomer
was determined by the coupling constant of J(31P-31P) of 3a
(16 Hz), whereas (E)-1,2-bis(diphenylthiophosphinyl)-1-alkenes
and 1,1-bis(diphenylthiophosphinyl)-1-alkenes exhibit ca. 50 and
30 Hz of J(31P-31P), respectively.11
Results and Discussion
Aprotic polar solvents are the choice of solvents. The
reactions in dimethyl sulfoxide, THF, and ether afforded 3a in
94%, 62%, and 0% NMR yields, respectively, under the
otherwise same reaction conditions. Surprisingly, the reaction
in aqueous DMF (1:1) also provided 3a in 82% yield.
Copper(I) iodide is the best among transition metal catalysts
we tested. Copper(I) chloride was as effective as CuI (98%
yield). Other copper salts such as CuCN, CuBr, CuBr‚Me2S,
and CuCl2 also effected the hydrophosphination albeit the yields
were lower (10%, 57%, 87%, and 84%, respectively). Neither
metallic copper, CuO, nor Cu2O are inactive. Silver(I) iodide
(5 mol % in DMSO) also served to afford 3a in 88% yield.
None of gold(I) chloride, nickel(II) chloride, or cobalt(II)
chloride exhibited any catalytic activity. The use of 5 mol %
of palladium(II) chloride or platinum(II) chloride yielded 3a in
5% yield, which invokes the formation of a stable and
catalytically inactive palladium or platinum complex in the
reaction mixture.7 It is worth noting that a diphenylphosphide
anion has been regarded as an untransferable dummy ligand in
cuprate chemistry.12
Preparation of 1-Alkynylphosphines. Starting alkynes 1
were prepared by nucleophilic substitution reactions of chlo-
rophosphines with 1-lithio-1-alkynes (Scheme 1, method A) or
nickel-catalyzed coupling reactions of chlorodiphenyl phosphine
and terminal alkynes in the presence of triethylamine (method
B).10 Whereas method A was high-yielding, method B was
suitable for the synthesis of 1 having labile functional groups.
The nickel-catalyzed reactions of aliphatic alkynes did not go
to completion (1g, 1h). Alkynylphosphine 1i, having a hydroxy
group, was available in three steps, i.e., preparation of diphenyl-
(trimethylsilylethynyl)phosphine by method A, protodesilylation,
and nucleophilic addition of diphenylphosphinoethynyllithium
to benzaldehyde. Diphosphine 1j was prepared by the dilithiation
of 4,4′-diethynylbiphenyl followed by the reaction with chlo-
rodiphenylphosphine (method A′). Aliphatic phosphine 1k was
prepared in fashions similar to method A by using chlorodicy-
clohexylphosphine (method A′′).
Hydrophosphination Reactions of 1-Alkynylphosphines.
Treatment of 1-octynyldiphenylphosphine (1a) with diphen-
ylphosphine in the presence of catalytic amounts of copper(I)
iodide and cesium carbonate in N,N-dimethylformamide (DMF)
at 20 °C yielded (Z)-1,2-bis(diphenylphosphino)-1-octene (2a)
(11) (a) Bookham, J. L.; Conti, F.; McFarlane, H. C. E.; McFarlane, W.;
Thornton-Pett, M. J. Chem. Soc., Dalton Trans. 1994, 1791-1797. (b) Sato,
A.; Yorimitsu, H.; Oshima, K. Angew. Chem., Int. Ed. 2005, 44, 1694-
1696.
(9) A number of hydrophosphonylations, the additions of pentavalent hydro-
phosphorous compounds, aiming at the synthesis of bidentate ligands, were
reported: (a) Stockland, R. A., Jr.; Taylor, R. I.; Thompson, L. E.; Patel,
P. B. Org. Lett. 2005, 7, 851-853 and references therein. (b) Allen, A.,
Jr.; Ma, L.; Lin, W. Tetrahedron Lett. 2002, 43, 3707-3710. (c) Ref 4f.
(10) Beletskaya, I. P.; Afanasiev, V. V.; Kazankova, M. A.; Efimova, I. V. Org.
Lett. 2003, 5, 4309-4311.
(12) (a) Bertz, S. H.; Dabbagh, G.; Villacorta, G. M. J. Am. Chem. Soc. 1982,
104, 5824-5826. (b) Martin, S. F.; Fishpaugh, J. R.; Power, J. M.;
Giolando, D. M.; Jones, R. A.; Nunn, C. M.; Cowley, A. H. J. Am. Chem.
Soc. 1988, 110, 7226-7228. We have observed a copper-mediated
phosphination reaction of trialkyl(dibromomethyl)silanes: (c) Kondo, J.;
Someya, H.; Kinoshita, H.; Shinokubo, H.; Yorimitsu, H.; Oshima, K. Org.
Lett. 2005, 7, 5713-5715.
9
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Catalytic Hydrophosphination of 1-Alkynylphosphines
A R T I C L E S
Table 2. Isolation of 1,2-Bis(diphenylphosphino)-1-alkenesa
Scheme 2. Plausible Reaction Mechanism
CuI
Cs2CO3
/mol %
yield of 2
/%b
entry
R
/mol %
1c
2
3
4
5
tBu (c)
2
1
1
10
2
10
10
10
10
10
20
10
20
20
69 (99)
71
70
60
65
nC6H13 (a)
Ph (d)
4-Ac-C6H4 (e)
3-pyridyl (f)
PhCH(OH) (i)
tBu (c)
6
51
87
7c,d
a Hydrophosphination conditions: 1 (0.50 mmol), Ph2PH (0.52 mmol),
DMF (3.0 mL), 25 °C, 4 h. b Isolated yields. NMR yield is in parenthesis.
c The reaction was performed at 90 °C. d The reaction was performed with
1.0 g of 1c (3.8 mmol) and 0.71 g of diphenylphosphine (3.8 mmol).
(Table 1, entry 9) can be useful for constructing supramolecular
architectures.
The reaction was efficient enough to provide tetraphosphine
sulfide 3j in excellent yield (eq 1). Although hydrophosphination
Table 3. Radical Reduction of 3 to 2 by TTMSSa
isolated yield of 2
entry
R
/%
1
2
3
4
tBu (c)
89
nC6H13 (a)
Ph (d)
87 (97)b
78 (94)b
63
4-Ac-C6H4 (e)
3-pyridyl (f)
3-pyridyl (f)
5
44
58
6c
across 1k having a dicyclohexylphosphino group at 25 °C led
to complete recovery of 1k, the anticipated 3k could be prepared
at 90 °C (eq 2). Attempts to perform the addition of dicyclo-
a Conditions: 3 (0.25 mmol), TTMSS (0.30 mmol), AIBN (0.025 mmol),
benzene (3.0 mL), reflux, 4 h. b NMR yields are in parentheses. c The
reaction was performed with TTMSS (0.60 mmol) for 12 h.
The use of Cs2CO3 is crucial. Potassium carbonate, sodium
carbonate, and triethylamine promoted the hydrophosphination
reaction much less effectively (18%, 3%, and 2% yields,
respectively). Neutral CsCl did not induce the reaction. Instead
of the CuI/Cs2CO3/DMF system, a CuI (10 mol %)/nBuLi (20
mol %)/THF system was effective yet led to slower conversion
(4 h, 49%; 8 h, 76%; 20 h, 86%). Without copper salts, Cs2-
CO3 by itself could not promote the reaction. Although
butyllithium alone could effect the hydrophosphination in THF
at ambient temperature, the reaction afforded a mixture of the
(Z) and (E) isomers in 27% and 70% yields, respectively.
A wide range of 1-alkynylphosphines 1 were subjected to
the phosphination reaction (Table 1). Sterically demanding
1-alkynylphosphines including 1b and 1c underwent the hy-
drophosphination smoothly, although higher catalyst loadings
were required to complete the reaction (Table 1, entries 2 and
4). An elevated temperature also facilitated the reaction of 1c
(Table 1, entry 3). A variety of functional groups such as keto
and hydroxy groups were compatible under the reaction
conditions (Table 1, entries 6-10), whereas known hydrophos-
phination reactions of alkynes were generally unsatisfactory with
regard to the functional group compatibility.13 Pyridine-contain-
ing 2f or 3f (Table 1, entry 7) and sulfur-containing 2h or 3h
hexylphosphine to 1a or 1d resulted in failure.
Reaction Mechanism. The mechanism of the phosphination
reaction is not clear. Radical inhibitors such as 2,2,6,6-
tetramethylpiperidine-N-oxyl had little influence on the reaction,
which is suggestive of an ionic reaction process. With several
experiments, we are tempted to propose the mechanism outlined
in Scheme 2. Deprotonation by Cs2CO3 with the aid of copper
iodide would provide copper phosphide14 (step A). As mentioned
above, highly basic Cs2CO3 is thus essential to abstract the
hydrogen of the CuI‚HPPh2 complex.15 The phosphide would
then attack 1-alkynylphosphine to form 7 (steps B and D). The
alkynylphosphine probably coordinates to copper to be activated
(14) (a) Eichho¨fer, A.; Fenske, D.; Holstein, W. Angew. Chem., Int. Ed. Engl.
1993, 32, 242-245. (b) Cowley, A. H.; Giolando, D. M.; Jones, R. A.;
Nunn, C. M.; Power, J. M. J. Chem. Soc., Chem. Commun. 1988, 208-
209.
(15) One singlet signal appeared at δ ) -41.6 ppm in the 31P NMR spectrum
of diphenylphosphine in DMF. The addition of a stoichiometric amount of
CuI to the DMF solution resulted in the formation of a clear solution and
in broadening the signal with unambiguous splitting. Upon further addition
of a stoichiometric amount of cesium carbonate, the signal disappeared
and no new discrete signals were observed. These facts indicate that the
copper-phosphorus bond of the complex [CuI‚HPPh2] would be labile and
that many sorts of copper-phosphide species might be formed upon the
addition of cesium carbonate.
(13) (a) Douglass, M. R.; Stern, C. L.; Marks, T. J. J. Am. Chem. Soc. 2001,
123, 10221-10238. (b) Takaki, K.; Koshoji, G.; Komeyama, K.; Takeda,
M.; Shishido, T.; Kitani, A.; Takehira, K. J. Org. Chem. 2003, 68, 6554-
6565. (c) Kazankova, M. A.; Efimova, I. V.; Kochetkov, A. N.; Afanas’ev,
V. V.; Beletskaya, I. P.; Dixneuf, P. H. Synlett 2001, 497-500.
9
J. AM. CHEM. SOC. VOL. 129, NO. 13, 2007 4101

A R T I C L E S
Kondoh et al.
Scheme 3. Mechanism for Desulfidation of 3 with a Substoichiometric Amount of TTMSS
Scheme 4. Synthesis of a New Bidentate Chiral Diphosphine
in the form of 516 (step C).17 The activation by copper is
indispensable, due to the experimental fact that both 1-octy-
nyldiphenylphosphine sulfide and oxide resisted the hydrophos-
phination reaction under the otherwise same reaction conditions.
Unlike the insertion of an alkyne to a transition metal-
phosphorus bond which proceeds in a syn manner, nucleophilic
addition to alkyne usually proceeds in an anti manner. The latter
is the case for the present reaction (step D). Immediate formation
of chelating diphosphine skeleton 7 controls the complete
stereoselectivity. During the reaction, no (E) isomer was
detected, which suggests that it is improbable that initially
formed (E)-diphosphine isomerizes into its (Z) form in the
reaction flask. Protonation of the vinylcopper 7 by HPPh2 affords
the product and regenerates the copper phosphide (step E).
Isolation of Trivalent Phosphines 2. The diphosphines 2
could be handled under air, although gradual oxidation occurred.
The isolations of trivalent phosphines 2 are summarized in Table
2. The oxidation led to lower yields of 2, compared to the yields
of sulfides 3 (Table 2 vs Table 1). When the hydrophosphination
reaction of 1c was conducted on a 0.5 mmol scale, 2c was
obtained in 99% NMR yield and 69% isolated yield (Table 2,
entry 1). Without special care to avoid oxidation, other
phosphines, 2a, 2d-2f, and 2i, were isolated in good yields
(Table 2, entries 2-6).
phosphines 2. Radical desulfidation with tris(trimethylsilyl)silane
(TTMSS) proved to be a reliable procedure (Table 3). Although
the original report employed 1-3 equimolar amounts of
TTMSS,18 we found that a substoichiometric amount of TTMSS
to PdS bond is sufficient. A plausible radical chain mechanism
is depicted in Scheme 3. The first equimolar amount of 3 would
undergo desulfidation in the reported manner18 (steps F and G).
The silicon-centered radical 10, which is to be generated by a
1,2-Si shift19 (step H), would be reactive enough to reduce a
PdS moiety. [Bis(trimethylsilylthio)trimethylsilyl]silyl radical
(13), formed through the second 1,2-Si shift (step K), seemed
unreactive, based on the fact that a smaller amount of TTMSS
for the reduction of 3 led to unsatisfactory conversion of 3. The
radical 13 would abstract the hydrogen of TTMSS (step L) to
form tris(trimethylsilyl)silyl radical, which completes the radical
chain. Purification on silica gel was quite easy, simply removing
less polar silicon residues through a short-path column.
Complexation of NiCl2 with 2c. The Z stereochemistry of
2 was also confirmed by X-ray crystallographic analysis of
[NiCl2(2c)] (Figure 1). Due to the bulky tert-butyl group, the
atoms, P1, P2, Cl1, and Cl2, coordinating to the nickel are not
in one plane (Figure 1b).
Enantioselective Hydrogenation Leading to Chiral Biden-
tate Phosphine Ligand. Compounds 2 and 3 have carbon-
carbon double bonds, which can enjoy further transformations.
In light of the importance of chiral bidentate ligands in transition
metal-catalyzed asymmetric synthesis, we examined enantiose-
lective hydrogenation of 3c to obtain a new chiral ligand.
Enantioselective hydrogenation of 3c under the catalysis of
[RuCl2(PPh3)3]/(R)-(+)-BINAP provided a tert-butyl-substituted
chiral diphosphine disulfide 15 in 91% isolated yield with 83%
ee (Scheme 4).20 Recrystallization of the product yielded an
enantiomerically pure form of 15 in the supernatant, whereas
the crystals were a mixture of the enantiomers. The desulfidation
The catalytic hydrophosphination reaction was reliable enough
to permit a gram-scale synthesis (Table 2, entry 7). The reaction
of 1.0 g of 1c (3.8 mmol) and 0.71 g of diphenylphosphine
(3.8 mmol) provided 1.5 g of 2c (3.3 mmol) in 87% isolated
yield after purification on silica gel under ambient atmosphere.
The lower isolated yield in the smaller-scale synthesis (Table
2, entry 1) would originate from the formation of a larger
proportion of phosphine oxide of 2c.
Radical Reduction of 3 to 2. We surveyed an efficient
method for the reduction of phosphine sulfides 3 to the parent
(16) There can be an interaction between the copper and the acetylenic part of
5.
(18) Romeo, R.; Wozniak, L. A.; Chatgilialoglu, C. Tetrahedron Lett. 2000,
41, 9899-9902.
(19) (a) Daroszewski, J.; Lusztyk, J.; Degueil, M.; Navarro, C.; Maillard, B. J.
Chem. Soc., Chem. Commun. 1991, 586-587. (b) Ballestri, M.; Chatgil-
ialoglu, C.; Seconi, G. J. Organomet. Chem. 1991, 408, C1-C4.
(20) (a) Cui, X.; Burgess, K. Chem. ReV. 2005, 105, 3272-3296. (b) Noyori,
R. Angew. Chem., Int. Ed. 2002, 41, 2008-2022.
(17) One singlet signal appeared at δ ) -34.7 ppm in the 31P NMR spectrum
of 1a in DMF. The addition of a stoichiometric amount of CuI to the DMF
solution furnished a clear homogeneous solution, which exhibited a broad
and highly splitting signal at the same chemical shift. The dissolution of
CuI indicates the formation of the complex [CuI‚1a]. The NMR experiments
suggest that the complex would not be robust.
9
4102 J. AM. CHEM. SOC. VOL. 129, NO. 13, 2007

Catalytic Hydrophosphination of 1-Alkynylphosphines
A R T I C L E S
filtrate was concentrated. The crude oil obtained was chromatographed
on silica gel to yield 1e in 70% yield (1.1 g, 3.5 mmol).
Preparation of 1i. Crude diphenyl(trimethylsilylethynyl)phosphine
was prepared from trimethylsilylacetylene (0.99 mL, 7.0 mmol) by
method A. The crude product was dissolved in methanol (10 mL).
Potassium carbonate (2.0 g, 14 mmol) was then added. The whole
mixture was stirred for 1 h. The product was extracted with a hexane/
ethyl acetate mixture. Concentration followed by purification on silica
gel provided 1.3 g of ethynyldiphenylphosphine (6.0 mmol, 86%). A
part of the ethynylphosphine (0.44 g, 2.1 mmol) was dissolved in 4
mL of THF under argon. At 0 °C, butyllithium (1.3 mL, 1.6 M in
hexane, 2.0 mmol) was added dropwise. The mixture was stirred for
30 min. After benzaldehyde (0.20 g, 1.9 mmol) was charged, the
mixture was stirred for an additional 1 h at 25 °C. The reaction was
quenched with 10 mL of water. Extraction, concentration, and purifica-
tion furnished 1i in 95% yield (0.57 g, 1.8 mmol).
Typical Procedure for Copper-Catalyzed anti-Hydrophosphi-
nation of 1-Alkynylphosphines with Diphenylphosphine to Obtain
1,2-Bis(diphenylthiophosphinyl)-1-alkene 3 (Table 1). Copper(I)
iodide (1 mg, 0.005 mmol) and cesium carbonate (16 mg, 0.050 mmol)
were placed in a 20-mL reaction flask under argon. DMF (3.0 mL), 1a
(0.15 g, 0.50 mmol), and diphenylphosphine (0.11 g, 0.60 mmol) were
sequentially added. The resulting mixture was stirred for 4 h at 25 °C.
Elemental sulfur (64 mg, 2.0 mmol) was then added, and the mixture
was stirred for 1 h. Water (10 mL) was added, and the product was
extracted with ethyl acetate (10 mL × 3). The combined organic layer
was dried over sodium sulfate and concentrated under reduced pressure.
Chromatographic purification on silica gel yielded (Z)-1,2-bis(diphen-
ylthiophosphinyl)-1-octene (3a, 0.24 g, 0.44 mmol, 88%) as a white
solid.
Figure 1. ORTEP drawing of [NiCl2(2c)]. (a) Top view. (b) Side view.
of 15 with a large excess of Cp2Zr(H)Cl21,22 afforded enantio-
merically pure bidentate phosphine 16. The typical SN2 phos-
phination reactions of the ditosylates of chiral diols23 may suffer
in the synthesis of phosphines with a sterically congested chiral
center. The sequential phosphination/hydrogenation protocol
offers an alternative to the conventional approach.
Conclusion
We have devised a highly efficient method for the synthesis
of (Z)-1,2-diphosphino-1-alkenes. The method will create a
variety of functionalized bidentate phosphines, which can be
applicable to various fields of chemical science. As exemplified
by the synthesis of a new chiral bidentate ligand 16, the (Z)-
1,2-diphosphino-1-alkene derivatives can be precursors of new
phosphorus compounds.
Experimental Section
Hydrophosphination to Isolate 1,2-Bis(diphenylphosphino)-1-
alkene (Table 2, Entries 1-6). Isolation of 2c is representative.
Copper(I) iodide (1.9 mg, 0.010 mmol) and cesium carbonate (0.016
g, 0.050 mmol) were placed in a 20-mL reaction flask under an
atmosphere of argon. DMF (3.0 mL), 1c (0.13 g, 0.50 mmol), and
diphenylphosphine (0.097 g, 0.52 mmol) were sequentially added. The
mixture was heated at 90 °C for 4 h. After being cooled to room
temperature, the mixture was passed through a pad of florisil. The
filtrate obtained was evaporated to leave solid. Purification on silica
gel provided 2c (0.16 g, 0.35 mmol) in 69% yield as a white solid.
During the process, no deaerated solvents were employed.
Gram-Scale Hydrophosphination to Isolate 2c (Table 2, Entry
7). The procedure is similar to the smaller-scale reaction. Copper(I)
iodide (0.014 g, 0.075 mmol), cesium carbonate (0.12 g, 0.38 mmol),
1c (1.0 g, 3.8 mmol), and diphenylphosphine (0.71 g, 3.8 mmol) were
mixed in DMF (7.5 mL). The whole mixture was heated at 90 °C for
4 h. Filtration through a pad of florisil, concentration, and purification
afforded 1.5 g of 2c (3.3 mmol) in 87% yield.
Representative Procedure for TTMSS-Mediated Radical Reduc-
tion of 3 to 2 (Table 3). In a 20-mL reaction flask, 3c (0.13 g, 0.25
mmol) and AIBN (4.1 mg, 0.025 mmol) were placed under argon.
Benzene (3.0 mL) and TTMSS (0.075 g, 0.30 mmol) were added, and
the resulting mixture was boiled for 4 h. After cooling, evaporation
followed by purification on silica gel furnished 0.10 g of 2c (0.22 mmol)
in 89% yield.
Preparation of [NiCl2(2c)] for X-ray Crystallographic Analysis.
Nickel(II) chloride (52 mg, 0.40 mmol) was placed in a 20-mL reaction
flask under argon. Ethanol (2.0 mL) was charged to dissolve the nickel
salt. Diphosphine 2c (0.20 g, 0.44 mmol) in ethanol (20 mL) was added.
Immediately, orange precipitate appeared. The precipitate was washed
with ether and dried in vacuo. The complex weighed 0.093 g (0.16
mmol, 40%, unoptimized). X-ray quality crystals were grown from
acetonitrile. Crystallographic data for the structure has been deposited
with the Cambridge Crystallographic Data Center (CCDC 601317).
Ruthenium-Catalyzed Enantioselective Hydrogenation of (Z)-3,3-
Dimethyl-1,2-bis(diphenylthiophosphinyl)-1-butene. Tris(triphen-
Preparation of 1-Alkynylphosphines 1a-1d, 1f, 1j, and 1k
(Method A). Preparation of 1a is representative. Under an atmosphere
of argon, a solution of 1-octyne (1.2 g, 11 mmol) in THF (15 mL) was
placed in a 50-mL reaction flask. Butyllithium (6.6 mL, 1.6 M in
hexane, 11 mmol) was added to the flask at 0 °C. The resulting mixture
was stirred for 30 min at the same temperature. Chlorodiphenylphos-
phine (2.2 g, 10 mmol) was then added at 0 °C. After the addition, the
reaction mixture was stirred for 1 h at ambient temperature. After water
(20 mL) was added, the product was extracted with a hexane/ethyl
acetate mixture. Concentration followed by silica gel column purifica-
tion provided 2.5 g of 1a (8.5 mmol, 85%) as a yellow oil. It is worth
noting that 1-alkynylphosphines are so stable under air that no
observable oxidation occurred during the conventional handling. The
alkynylphosphines could be stored at least for 6 months in a capped
vial.
Preparation of 1-Alkynylphosphines 1e, 1g, and 1h (Method B).
Preparation of 1e is representative. Nickel acetylacetonate (39 mg, 0.15
mmol) was placed in a 50-mL reaction flask under argon. Toluene (10
mL), p-ethynylacetophenone (0.79 g, 5.5 mmol), chlorodiphenylphos-
phine (1.1 g, 5.0 mmol), and triethylamine (1.5 g, 15 mmol) were
sequentially added. The mixture was heated at 80 °C for 4 h. After
being cooled to room temperature, the mixture was filtered and the
(21) (a) Zablocka, M.; Delest, B.; Igau, A.; Skowronska, A.; Majoral, J.-P.
Tetrahedron Lett. 1997, 38, 5997-6000. (b) Saito, M.; Nishibayashi, Y.;
Uemura, S. Organometallics 2004, 23, 4012-4017.
(22) The radical desulfidation of 15 with TTMSS (1.2 equiv to 15) was also
successful. However, after several attempts, separation of 15 and silicon-
containing residue proved to be problematic in our hands. Small amounts
of the corresponding monooxides of 15 were generated during careful
chromatographic purification on silica gel for isolation of 15. Purification
using a solid phase technique (see the Supporting Information) resulted in
unsatisfactory separation of 15 and the silicon-containing residue. We expect
that, if the TTMSS-mediated reduction and purification of 15 were
performed in a glovebox filled with inert gas, one could isolate 15 in
excellent yield.
(23) (a) Kagan, H. B.; Dang, T.-P. J. Am. Chem. Soc. 1972, 94, 6429-6433.
(b) Fryzuk, M. O.; Bosnich, B. J. Am. Chem. Soc. 1977, 99, 6262-6267.
(c) Fryzuk, M. O.; Bosnich, B. J. Am. Chem. Soc. 1978, 100, 5491-5494.
(d) Riley, D. P.; Shumate, R. E. J. Org. Chem. 1980, 45, 5187-5193.
9
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A R T I C L E S
Kondoh et al.
ylphosphine)ruthenium(II) dichloride (9.6 mg, 0.010 mmol) and (R)-
(+)-2,2′-bis(diphenylphosphino)-1,1′-biphenyl ((R)-BINAP, 12 mg,
0.020 mmol) were placed in a 20-mL reaction flask under hydrogen.
Ethanol (0.50 mL) and benzene (0.50 mL) were added at 25 °C. After
the mixture was stirred for 10 min, (Z)-3,3-dimethyl-1,2-bis(diphen-
ylthiophosphinyl)-1-butene (3c, 65 mg, 0.13 mmol) was added. The
resulting mixture was heated at reflux for 24 h. After the mixture was
cooled to room temperature, water (10 mL) was added and the product
was extracted with ethyl acetate (10 mL × 3). The organic layer was
dried over sodium sulfate and evaporated in vacuo. Purification of the
crude solid by gel permeation chromatography provided 3,3-dimethyl-
1,2-bis(diphenylthiophosphinyl)butane (15, 59 mg, 0.11 mmol) in 91%
yield and with 83% ee. Recrystallization from ethanol/benzene yielded
crystals. The crystals were a mixture of the enantiomers. Concentration
of the supernatant provided an optically pure form of 15 (37 mg, 0.071
mmol, 57%, > 99% ee). HPLC conditions: CHIRALCEL AD-H,
hexane/2-propanol ) 90:10, 1.3 mL/min, retention time ) 4.0 min for
the major enantiomer; retention time ) 5.7 min for the minor
enantiomer.
reflux. The reaction mixture was directly subjected to evaporation. A
mixture of hexane and ethyl acetate (5:1, 10 mL, degassed) was added
to dissolve 16. The supernatant was passed through a silica, long-body
Sep-Pak cartridge. The filtrate was concentrated to afford 0.045 g of
pure 16 (0.10 mmol, 100%). The absolute configuration of 16 was
assigned as R by comparing the specific rotations of 16 and of analogous
chiral diphosphines.23c,d
Acknowledgment. This work was supported by Grants-in-
Aid for Scientific Research, Young Scientists, and COE
Research from the Ministry of Education, Culture, Sports,
Science, and Technology, Japan. Professor Masaki Shimizu is
acknowledged for allowing us to use the X-ray diffractometer.
We thank Hokko Chemical Industry Co., Ltd. For providing
chlorodicyclohexylphosphine.
Supporting Information Available: Experimental details and
characterization data for new compounds, and crystallographic
data of [NiCl2(2c)] (CIF). This material is available free of
charge via the Internet at http://pubs.acs.org.
Desulfidation of 15 for Synthesis of New Bidentate Ligand 16.
Zirconocene chloride hydride (0.19 g, 0.75 mmol) and 15 (0.052 g,
0.10 mmol) were placed in a 20-mL reaction flask under argon. After
1,4-dioxane (3.0 mL) was added, the mixture was stirred for 12 h at
JA070048D
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4104 J. AM. CHEM. SOC. VOL. 129, NO. 13, 2007