4190
Organometallics 2003, 22, 4190-4192
High ly Efficien t Ch em oselective Hyd r ogen olysis of
Ep oxid es Ca ta lyzed by a (η5-C5(CH3)5)Ru Com p lex
Bea r in g a 2-(Dip h en ylp h osp h in o)eth yla m in e Liga n d
Masato Ito, Makoto Hirakawa, Akihide Osaku, and Takao Ikariya*
Department of Applied Chemistry, Graduate School of Science and Engineering and Frontier
Collaborative Research Center, Tokyo Institute of Technology, 2-12-1 O-okayama, Meguro-ku,
Tokyo 152-8552, J apan
Received J une 24, 2003
Summary: Terminal epoxides are hydrogenolyzed to give
secondary alcohols with high regioselectivity using the
ternary catalyst system of Cp*RuCl(cod)-2-(diphenyl-
phosphino)ethylamine (1a )-KOH (Cp* ) η5-C5(CH3)5,
cod ) 1,5-cyclooctadiene) in 2-propanol under mild
conditions.
furtherextend this unique Brønsted acid-base catalyst
system to the reductive opening reaction of epoxides
with H2, giving alcohols. Although hydrogenolysis of
epoxides with heterogeneous catalysts such as modified
Raney Ni or Pd/C has been extensively investigated as
an industrial process,7 there have been few reports on
the selective hydrogenolysis of epoxides promoted by
homogeneous catalysts.8,9 We describe here that the
Cp*RuII-based catalyst system including 2-(diphenylphos-
phino)ethylamine (1a ) in place of 1b as a primary amine
ligand effects the selective hydrogenolysis of epoxides,
leading to secondary alcohols.
Screening experiments using several amine ligands
in the reaction of styrene oxide with H2 revealed that
the hydrogenolysis proceeds smoothly under 10 atm of
H2 at 30 °C in 2-propanol which contains a ternary
catalyst system of Cp*RuCl(cod), 1a , and KOH (epoxide:
Ru:amine:KOH ) 100:1:1.5:1) to give a mixture of
branch and linear alcohols with an 89:11 molar ratio in
63% yield after 2 h (Scheme 1, entry 1 in Table 1). The
reaction is delicately influenced by the ligand structures
and the reaction conditions. When the primary amino
group in 1a was changed to a secondary (1c) or tertiary
amino group (1d ), a significant drop in the catalytic
activity, but with a slight improvement in the regiose-
lectivity, was observed (entries 3 and 4). 1,2-Bis(diphen-
ylphosphino)ethane, in which the primary amino group
in 1a is replaced with a diphenylphosphino group,
completely suppressed the reaction under the conditions
described above. Furthermore, the use of an equimolar
mixture of benzylamine and triphenylphosphine in place
Recently much attention has been given to the design
of transition-metal-based molecular catalysts with a
“metal/NH bifunctionality”,1,2 in which an amino proton
and a metal hydride are concertedly transferred to
CdO or CdN double bonds via pericyclic transition
states.3-5 The most striking aspect in these catalyses
is that the Brønsted acidic amino proton and the
Brønsted basic metal hydride are cooperatively activat-
ing the substrate, which is not necessarily bonded
directly to the central metal. We have recently reported
that a ternary catalyst system with a unique Brønsted
acid-base function, Cp*RuCl(cod)-2-(dimethylamino)eth-
ylamine (1b)-KOH, effects the hydrogenation of ke-
tones in 2-propanol, in which 2-propanol participates
in the heterolytic cleavage of H2 possibly through the
formation of a hydrogen-bonding network.6 We now
* To whom correspondence should be addressed.
(1) For the term “metal-ligand bifunctional catalysis,” see: Noyori,
R.; Yamakawa, M.; Hashiguchi, S. J . Org. Chem. 2001, 66, 7931-7944
and references therein.
(2) Theoretical calculations and experimental considerations for
metal-ligand bifunctional catalysis: (a) Alonso, D. A.; Brandt, P.;
Nordin, S. J . M.; Andersson, P. G. J . Am. Chem. Soc. 1999, 121, 9580-
9588. (b) Yamakawa, M.; Ito, H.; Noyori, R. J . Am. Chem. Soc. 2000,
122, 1466-1478. (c) Adbur-Rashid, K.; Lough, A. J .; Morris, R. H.
Organometallics 2000, 19, 2655-2657. (d) Adbur-Rashid, K.; Faatz,
M.; Lough, A. J .; Morris, R. H. J . Am. Chem. Soc. 2001, 123, 7473-
7474. (e) Adbur-Rashid, K.; Clapham, S. E.; Hadzovic, A.; Harvey, J .
N.; Lough, A. J .; Morris, R. H. J . Am. Chem. Soc. 2002, 124, 15104-
15118.
(3) Hydrogenation: (a) Ohkuma, T.; Ooka, H.; Hashiguchi, S.;
Ikariya, T.; Noyori, R. J . Am. Chem. Soc. 1995, 117, 2675-2676. (b)
Doucet, H.; Ohkuma, T.; Murata, K.; Yokozawa, T.; Kozawa, M.;
Katayama, E.; England, A. F.; Ikariya, T.; Noyori, R. Angew. Chem.,
Int. Ed. 1998, 37, 1703-1707.
(4) Transfer hydrogenation: (a) Hashiguchi, S.; Fujii, A.; Takehara,
J .; Ikariya, T.; Noyori, R. J . Am. Chem. Soc. 1995, 117, 7562-7563.
(b) Uematsu, N.; Fujii, A.; Hashiguchi, S.; Ikariya, T.; Noyori, R. J .
Am. Chem. Soc. 1996, 118, 4916-4917. (c) Haack, K.-J .; Hashiguchi,
S.; Fujii, A.; Ikariya, T.; Noyori, R. Angew. Chem., Int. Ed. 1997, 36,
285-288.
(7) (a) Murai, S.; Murai, T.; Kato, S. In Comprehensive Organic
Synthesis; Trost, B. M., Fleming, I., Eds.; Pergamon Press: New York,
1991; Vol. 1, pp 871-893. (b) Sajiki, H.; Hattori, K.; Hirota, K. Chem.
Commun. 1999, 1041-1042 and references therein.
(8) Co or Rh complexes: (a) Kwiatek, J .; Mador, I. L.; Seyler, J . K.
J . Am. Chem. Soc. 1962, 84, 304-305. (b) Christopher, J . L.; McQuillin,
F. J . J . Chem. Soc., Perkin Trans. 1 1973, 21, 2509-2512. (c) Fujitsu,
H.; Shirahama, S.; Matsumura, E.; Takeshita, K.; Mochida, I. J . Org.
Chem. 1981, 46, 2287-2290. (d) Fujitsu, H.; Shirahama, S.; Mat-
sumura, E.; Takeshita, K.; Mochida, I. J . Chem. Soc., Perkin Trans. 1
1982, 855-859. (e) Chan, A. C.; Coleman, J . P. J . Chem. Soc., Chem.
Commun. 1991, 535-536. (f) Ricci, M.; Slama, A. J . Mol. Catal. 1994,
89, L1-4. (g) Bakos, J .; Orosz, AÄ .; Csere´pi, S.; To´th, I.; Sinou, D. J .
Mol. Catal. A 1997, 116, 85-97.
(5) Reviews: (a) Ohkuma, T.; Noyori, R. In Comprehensive Asym-
metric Catalysis; J acobsen, E. N., Pfaltz, A., Yamamoto, H., Eds.;
Springer: Berlin, 1999; Vol. 1, pp 199-246. (b) Noyori, R.; Hashiguchi,
S. Acc. Chem. Res. 1997, 30, 97-102. (c) Palmer, M. J .; Wills, M.
Tetrahedron: Asymmetry 1999, 10, 2045-2061. (d) Noyori, R.; Oh-
kuma, T. Angew. Chem., Int. Ed. 2001, 40, 40-73.
(9) Pd complexes: (a) Shimizu, I.; Oshima, M.; Nisar, M.; Tsuji, J .
Chem. Lett. 1986, 1775-1776. (b) Oshima, M.; Yamazaki, H.; Shimizu,
I.; Nisar, M.; Tsuji, J . J . Am. Chem. Soc. 1989, 111, 6280-6287. (c)
Shimizu, I.; Hayashi, K.; Ide, N.; Oshima, M. Tetrahedron 1991, 47,
2991-2998. (d) Shimizu, I.; Omura, T. Chem. Lett. 1993, 1759-1760.
(e) Noguchi, Y.; Yamada, T.; Uchiro, H.; Kobayashi, S. Tetrahedron
Lett. 2000, 41, 7493-7497. (f) Torii, S.; Okumoto, H.; Nakayasu, S.;
Kotani, T. Chem. Lett. 1989, 1975-1978.
(6) Ito, M.; Hirakawa, M.; Murata, K.; Ikariya, T. Organometallics
2001, 20, 379-381.
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