Ruthenium-catalyzed formation of aryl(diphenyl)phosphine oxides by reactions of propargylic alcohols with diphenylphosphine oxide

Article abstract of DOI:10.1021/ol0515311

(Chemical Equation Presented) 1,1-Diaryl-1-penten-4-yn-3-ols react with diphenylphosphine oxide in the presence of a thiolate-bridged diruthenium complex as a catalyst and give high yields of aryl(diphenyl)phosphine oxide products via an initial substitut

Full text of DOI:10.1021/ol0515311

ORGANIC
LETTERS
2005
Vol. 7, No. 18
4029-4032
Ruthenium-Catalyzed Formation of
Aryl(diphenyl)phosphine Oxides by
Reactions of Propargylic Alcohols with
Diphenylphosphine Oxide
Gen Onodera,† Hideyuki Matsumoto,† Marilyn Daisy Milton,†
Yoshiaki Nishibayashi,*,‡ and Sakae Uemura†
Department of Energy and Hydrocarbon Chemistry, Graduate School of Engineering,
Kyoto UniVersity, Katsura, Nishikyo-ku, Kyoto 615-8510, Japan, and Institute of
Engineering InnoVation, The UniVersity of Tokyo, Yayoi, Bunkyo-ku,
Tokyo 113-8656, Japan
ynishiba@sogo.t.u-tokyo.ac.jp
Received June 30, 2005
ABSTRACT
1,1-Diaryl-1-penten-4-yn-3-ols react with diphenylphosphine oxide in the presence of a thiolate-bridged diruthenium complex as a catalyst and
give high yields of aryl(diphenyl)phosphine oxide products via an initial substitution followed by a cyclization at the produced allene intermediate.
i
We have been currently interested in the ruthenium-catalyzed
propargylic substitution reaction of propargylic alcohols with
a variety of heteroatom- and carbon-centered nucleophiles,
giving the corresponding propargylated products.1 These
reactions are catalyzed only by thiolate-bridged diruthenium
complexes such as [Cp*RuCl(µ2-SR)]2 (Cp* ) η5-C5Me5;
R ) Me (1a), Et (1b), nPr (1c), iPr (1d)) and [Cp*RuCl(µ2-
SR)2RuCp*(OH2)]OTf (OTf ) OSO2CF3; R ) Me (1e),
nPr, Pr) and not by various monoruthenium complexes
(Scheme 1).2 Quite recently, we have disclosed that catalytic
phosphinylation of propargylic alcohols with diphenylphos-
phine oxide (2) proceeded smoothly even at room temper-
ature to afford the corresponding propargylic substitution
products in high yields1g and also that with an excess amount
of 2 at higher temperature the corresponding double phos-
phinylated compounds were obtained in high yields (Scheme
2).3 As an extension of our study on catalytic phosphinylation
†
Kyoto University.
‡
The University of Tokyo.
(1) (a) Nishibayashi, Y.; Wakiji, I.; Hidai, M. J. Am. Chem. Soc. 2000,
122, 11019. (b) Nishibayashi, Y.; Wakiji, I.; Ishii, Y.; Uemura, S.; Hidai,
M. J. Am. Chem. Soc. 2001, 123, 3393. (c) Nishibayashi, Y.; Yoshikawa,
M.; Inada, Y.; Hidai, M.; Uemura, S. J. Am. Chem. Soc. 2002, 124, 11846.
(d) Inada, Y.; Nishibayashi, Y.; Hidai, M.; Uemura, S. J. Am. Chem. Soc.
2002, 124, 15172. (e) Nishibayashi, Y.; Onodera, G.; Inada, Y.; Hidai, M.;
Uemura, S. Organometallics 2003, 22, 873. (f) Nishibayashi, Y.; Inada,
Y.; Yoshikawa, M.; Hidai, M.; Uemura, S. Angew. Chem., Int. Ed. 2003,
42, 1495. (g) Nishibayashi, Y.; Milton, M. D.; Inada, Y.; Yoshikawa, M.;
Wakiji, I.; Hidai, M.; Uemura, S. Chem. Eur. J. 2005, 11, 1433. (h) Ammal,
S. C.; Yoshikai, N.; Inada, Y.; Nishibayashi, Y.; Nakamura, E. J. Am. Chem.
Soc.2005, 127, 9428.
Scheme 1
10.1021/ol0515311 CCC: $30.25
© 2005 American Chemical Society
Published on Web 08/09/2005

Scheme 2
Table 1. Reactions of Propargylic Alcohol (3a) with
Diphenylphosphine Oxide (2) Catalyzed by Diruthenium
Complexes (1)a
of propargylic alcohols, we now report the unexpected and
high yield formation of aryl(diphenyl)phosphine oxide from
1,1-diaryl-1-pentene-4-yn-3-ol (3) (Figure 1) and 2 in the
presence of 1 as a catalyst.
run
catalyst
yield (%)b
1
2
3
4
5
6
7
[Cp*RuCl(SMe)]2 (1a)
92
98
99
98
91
89
86
[Cp*RuCl(SEt)]2 (1b)
[Cp*RuCl(SnPr)]2 (1c)
[Cp*RuCl(SiPr)]2 (1d)
[Cp*RuCl(SMe)2RuCp*(OH2)]OTf (1e)c
[Cp*RuCl(SeMe)]2 (1f)
[Cp*RuCl(TeMe)]2 (1g)
a All reactions of propargylic alcohol (3a) (0.30 mmol) with diphe-
nylphosphine oxide (2) (0.45 mmol) were carried out in the presence of 1
(0.015 mmol) and NH4BF4 (0.03 mmol) in ClCH2CH2Cl (5 mL) at 80 °C
for 48 h. b Isolated yield. c In the absence of NH4BF4.
Figure 1.
Next, the reactions of various propargylic alcohols 3 with
2 catalyzed by 1a were investigated. Typical results are
shown in Table 2. In all cases, the corresponding aryl-
(diphenyl)phosphine oxides were produced in high yields
(Table 2, runs 1-5). By use of the propargylic alcohol 3f
bearing a fluorene moiety, the corresponding arylphosphine
oxide 4f was obtained in only a low yield (Scheme 4).
Treatment of 3a (3; Ar ) Ph)4 with 2 in the presence of
a catalytic amount of 1a (5 mol %) and NH4BF4 (10 mol
%) in 1,2-dichloroethane (ClCH2CH2Cl) at 80 °C for 48 h
gave aryl(diphenyl)phosphine oxide 4a in 92% isolated yield
(Scheme 3).5 The structure of 4a was unambiguously clarified
Scheme 3
Scheme 4
by X-ray analysis.6 When 1b-1e or [Cp*RuCl(µ2-YMe)]2
(Cp* ) η5-C5Me5; Y ) Se (1f), Te (1g)) were used as
catalysts in place of 1a, 4a was obtained in high yields in
all cases (Table 1).
It is noteworthy that from (E)-1-phenyl-1-penten-4-yn-3-
ol (5), the corresponding aryl(diphenyl)phosphine oxide was
not obtained (Scheme 5). This result indicates that this
(2) (a) The thiolate-bridged diruthenium complexes were found to provide
a unique bimetallic reaction site for activation and transformation of various
terminal alkynes; see: Nishibayashi, Y.; Yamanashi, M.; Wakiji, I.; Hidai,
M. Angew. Chem., Int. Ed. 2000, 39, 2909 and references therein. (b)
Nishibayashi, Y.; Imajima, H.; Onodera, G.; Hidai, M.; Uemura, S.
Organometallics 2004, 23, 26. (c) Nishibayashi, Y.; Imajima, H.; Onodera,
G.; Inada, Y.; Hidai, M.; Uemura, S. Organometallics 2004, 23, 5100. (d)
The methanethiolate-bridged diruthenium complexes are commercially
available from Wako Pure Chemical Industries (Japan) as met-DIRUX
(methanethiolate-bridged diruthenium complex) (1a) (130-14581) and met-
DIRUX-OTf (1e) (132-14781).
Scheme 5
(3) Milton, M. D.; Onodera, G.; Nishibayashi, Y.; Uemura, S. Org. Lett.
2004, 6, 3993.
(4) The propargylic alcohol 3a can react with various nucleophiles to
afford the corresponding propargylic substituted products; see refs 1b-
d,f,g.
(5) Typical results are shown in Supporting Information as Table S1.
(6) An ORTEP drawing of 4a is shown in Supporting Information as
Figure S1.
cyclization reaction requires an aryl group at the C1 position
of the propargylic alcohol in the cis-position. The introduc-
tion of an aromatic double bond (the use of 6) only resulted
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Org. Lett., Vol. 7, No. 18, 2005

Table 2. Reactions of Propargylic Alcohols (3) with Diphenylphosphine Oxide (2) Catalyzed by Diruthenium Complex (1a)a
a All reactions of propargylic alcohol 3 (0.30 mmol) with diphenylphosphine oxide 2 (0.45 mmol) were carried out in the presence of 1a (0.015 mmol)
and NH4BF4 (0.03 mmol) in ClCH2CH2Cl (5 mL) at 80 °C for 48 h. b Isolated yield.
in the expected formation of the propargylic phosphinylated
product (7) (Scheme 6).
as a result of the electron-withdrawing group of diphenyl
phosphine oxide, and so a neighboring phenyl group readily
attacks this carbon to give the cyclized product B. We
consider that this transformation is a Michael-type endo-
mode cyclization.9 Finally, aromatization of B affords 4a.
The cyclization step may also be considered as a typical 6π-
electrocyclization of allene-diene species.
Scheme 6
Scheme 8
Treatment of the propargylic phosphinylated compound
(8) in the presence of catalytic amounts of both 1a and NH4-
BF4 in ClCH2CH2Cl at 80 °C for 48 h gave 4a in 55%
isolated yield. However, even in the reaction without
catalysts, 4a was produced in 59% isolated yield. These
results indicate that this catalytic cyclization proceeds via
the initial formation of 8 and also that the ruthenium complex
is not indispensable for the cyclization step of 8 into 4a
(Scheme 7).
Scheme 7
Next, we investigated the transformation of 4a into some
other organic compounds. Unfortunately, the reduction of a
phosphine oxide moiety did not proceed smoothly when the
usual combination of trichlorosilane and triethylamine was
employed as a reducing reagent, but it has been achieved
smoothly by use of triethoxysilane.10 Thus, treatment of 4a
On the basis of these findings, a plausible reaction pathway
of this catalytic reaction is shown in Scheme 8. At first,
propargylic substitution reaction catalyzed by diruthenium
complex occurs to produce 8 followed by isomerization to
allene A,7 which is more stable than 7 by 8.50 kcal/mol.8
The central carbon of an allene moiety is electron-deficient
(9) (a) Mukai and co-workers reported an endo-mode ring-closing
reaction of allenyl phosphine oxides: Mukai, C.; Ohta, M.; Yamashita, H.;
Kitagaki, S. J. Org. Chem. 2004, 69, 6867. (b) Maynard and co-workers
reported a similar endo-mode ring-closing reaction: Pravia, K.; White, R.;
Fodda, R.; Maynard, D. F. J. Org. Chem. 1996, 61, 6031. (c) Michael-type
exo-mode ring-closing reactions have also been reported: Brel, V. K.
Synthesis 2001, 1539.
(7) The isomerization of propargylic phosphine oxide to allenyl phosphine
oxide was observed, and allenyl phosphine oxide can be isolated; see ref 3.
(8) Ab initio molecular orbital calculations of A and 8 were carried out.
(10) (a) Coumbe, T.; Lawrence, N. J.; Muhammad, F. Tetrahedron Lett.
1994, 35, 625. (b) Allen, A., Jr.; Ma, L.; Lin, W. Tetrahedron Lett. 2002,
43, 3707.
Org. Lett., Vol. 7, No. 18, 2005
4031

with triethoxysilane in the presence of titanium tetraisopro-
poxide in benzene at 80 °C for 30 min gave the correspond-
ing aryl(diphenyl)phosphine 9 in 90% isolated yield (Scheme
9).
Scheme 10
Scheme 9
The methyl group at the C1 position of the naphthalene
ring of 4a was easily brominated by use of NBS (N-
bromosuccinimide) with BPO (benzoyl peroxide) to afford
the corresponding brominated product 10 (Scheme 10),11 and
the introduced bromine was replaced easily by an ethoxide
group by the usual SN2 reaction to give 11 (Scheme 10).
These phosphine compounds may be used as the precursors
of a new type of monodentate or bidentate ligands.12
In summary, we have explored the scope and limitations
of a novel, one-pot ruthenium-catalyzed synthesis of aryl-
(diphenyl)phosphine oxides (4) from propargylic alcohols
(3) and diphenylphosphine oxide (2). A mechanism is
proposed that involves the isomerization of an initial prop-
argylic substituted product to an allenyl intermediate, fol-
lowed by a cyclization and rearomatization to afford the final
product.
Acknowledgment. This work was supported by a Grant-
in-Aid for Scientific Reserch for Young Scientists (A) (no.
15685006) from the Ministry of Education, Culture, Sports,
Science and Technology, Japan. We thank Mr. Youichi Inada
of our group for assistance with ab initio molecular orbital
calculations of A and 8.
Supporting Information Available: Experimental pro-
cedures and spectral data for all new compounds, and
crystallographic data in CIF format. This material is available
free of charge via the Internet at http://pubs.acs.org.
(11) For a recent example, see: Oestreich, M.; Schmid, U. K.; Auer,
G.; Keller, M. Synthesis 2003, 2725.
(12) For an example, the complex prepared from (o-Tol)3P and Pd(OAc)2
is found to work as a highly efficient catalyst for the Heck vinylation of
aryl halides: Herrmann, W. A.; Brossmer, C.; Reisinger, C.-P.; Riermeier,
T. H.; O¨ fele, K.; Beller, M. Chem. Eur. J. 1997, 3, 1357.
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