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Ir- and Ru-Catalyzed Sequential Reactions Asymmetric -Alkylative Reduction of Ketones with Alcohols.

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Angewandte
Chemie
Alkylation
DOI: 10.1002/anie.200600677
Ir- and Ru-Catalyzed Sequential Reactions:
Asymmetric a-Alkylative Reduction of Ketones
with Alcohols**
Gen Onodera, Yoshiaki Nishibayashi,* and
Sakae Uemura
Transition-metal-catalyzed asymmetric reduction of prochiral
ketones is one of the most intensive subjects in organic
synthesis.[1, 2] Among a variety of systems for the catalytic
reduction, ruthenium-catalyzed hydrogenation, and transfer
hydrogenation of prochiral ketones have been developed and
used as reliable synthetic methods to
obtain reduced alcohols with a highto-excellent enantioselectivity.[1, 2] We
have also reported the enantioselective redox reaction of ketones and
alcohols using ruthenium complex
[RuCl2(PPh3)(ip-foxap[3])] (1) as a
catalyst.[4]
Multiple catalysis in the same
medium to obtain the desired products from simple starting materials is one of the most current
and important topics in synthetic chemistry.[5, 6] Such catalysis
[*] Prof. Dr. Y. Nishibayashi
Institute of Engineering Innovation
The University of Tokyo
Yayoi, Bunkyo-ku, Tokyo, 113-8656 (Japan)
Fax: (+ 81) 3-5841-1175
E-mail: ynishiba@sogo.t.u-tokyo.ac.jp
G. Onodera, Prof. Dr. S. Uemura
Department of Energy and Hydrocarbon Chemistry
Graduate School of Engineering
Kyoto University
Katsura, Nishikyo-ku, Kyoto, 615-8510 (Japan)
[**] This work was supported by a Grant-in-Aid for Scientific Research
for Young Scientists (A; No. 15685006) to Y.N. from the Ministry of
Education, Culture, Sports, Science and Technology, Japan.
Supporting information for this article is available on the WWW
under http://www.angewandte.org or from the author.
Angew. Chem. Int. Ed. 2006, 45, 3819 –3822
2006 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
3819
Communications
lessens the reaction time and the loss of yield by avoiding the
isolation and purification procedure of intermediates
required in multistep reactions. The sequential reaction
looks easy and simple, but the compatibility between different
transition-metal complexes should be established to achieve
it.
During our study on the development of novel catalytic
transformation using chalcogenolate-bridged diruthenium
complexes, we discovered a new type of ruthenium- and
platinum- or gold-catalyzed sequential reaction, in which triand tetrasubstituted furans, pyrroles, oxazoles, and fused
polycyclic products were obtained in good-to-high yields with
excellent selectivities from simple and readily available
starting compounds.[7] These findings prompted us to further
develop useful sequential reactions catalyzed by two different
transition-metal complexes. Toward this end, our attention
was focused on the iridium-catalyzed a-alkylation of ketones
with alcohols[8] and the ruthenium-catalyzed transfer hydrogenation of prochiral ketones[4] because the combination of
these two catalytic reactions might realize asymmetric aalkylative reduction of prochiral ketones with alcohols to
obtain optically active alcohols directly with elongation of the
carbon skeleton.
A mixture of acetophenone (2 a) and 1-butanol (3 a) in the
presence of a catalytic amount of [{IrCl(cod)}2] (cod = 1,5cyclooctadiene; 1 mol %), PPh3 (4 mol %), and KOH
(5 mol %) was heated at 100 8C for 4 h and then kept at
room temperature for 2 h after the addition of a catalytic
amount of 1 (1 mol %) and iPrONa (4 mol %) in iPrOH. As a
result, (R)-1-phenyl-1-hexanol (4 aa) was obtained in 75 %
yield of the isolated product with 94 % ee (Scheme 1).
Scheme 1. Asymmetric a-alkylative reduction of a ketone with an
alcohol catalyzed by iridium and ruthenium.
Previously, the ruthenium-catalyzed direct synthesis of elongated secondary alcohols through the a-alkylation of ketones
with primary alcohols had been reported.[9–11] We tried to
develop the enantioselective version of this reaction catalyzed
by using only 1, but a low-to-moderate enantioselectivity was
achieved. When the Noyori complexes,[1, 2] such as [RuCl(tsdpen)(mesitylene)] (tsdpen = N-(p-toluenesulfonyl)-1,2diphenylethanediamine), were used as catalysts in place of
1, the sequential reaction did not proceed effectively. These
results indicate that the compatibility between [{IrCl(cod)}2]
and 1 is an essential factor in directly obtaining optically
active alcohols with elongation of the carbon skeleton.
Next, reactions of other acetophenones with 1-butanol
were investigated by using catalytic amounts of [{IrCl(cod)}2]
(1 mol %) and 1 (1 mol %). Typical results are shown in
Table 1. The introduction of a methyl group at the para or
meta position of acetophenone did not affect the reactivity
and enantioselectivity (entries 2 and 3). Slightly lower yields
3820
www.angewandte.org
Table 1: Reactions of acetophenones 2 with alcohols 3 in the presence of
an iridium complex and ruthenium complex 1.[a]
Entry 2, Ar
3, R
Product Yield [%][b] ee [%][c]
1
2
3
4
5
6
7
8
9
10
11
3 a, nPr
3 a, nPr
3 a, nPr
3 a, nPr
3 a, nPr
3 a, nPr
3 a, nPr
3 b, iPr
3 c, nBu
3 d, CH2CHMe2
3 e, Ph
4 aa
4 ba
4 ca
4 da
4 ea
4 fa
4 ga
4 ab
4 ac
4 ad
4 ae
2 a, Ph
2 b, 4-MeC6H4
2 c, 3-MeC6H4
2 d, 2-MeC6H4
2 e, 4-MeOC6H4
2 f, 4-ClC6H4
2 g, 4-FC6H4
2 a, Ph
2 a, Ph
2 a, Ph
2 a, Ph
75
72
77
52
57
58
15
51
77
79
0
94 (R)[d]
98
96
97
97 (R)[d]
88
95
96 (R)[d]
93 (R)[d]
96
–
[a] All reactions of 2 (2.0 mmol) with 3 (6.0 mmol) were carried out in the
presence of [{IrCl(cod)}2] (1 mol %), PPh3 (4 mol %), and KOH (5 mol %)
at 100 8C for 4 h, and the reaction mixture was kept at room temperature
for 2 h by the addition of 1 (1 mol %), iPrONa (4 mol %), and iPrOH
(160 mL). [b] Yield of the isolated product. [c] Determined by HPLC with
a chiral column. [d] The absolute configuration was determined by
comparison of the value of the optical rotation with that reported in the
literature.
of products were observed without loss of optical purity when
2’-methyl- and 4’-methoxyacetophenones were used as substrates (entries 4 and 5). The presence of an electron-withdrawing group, such as a chloro moiety, at the para position of
acetophenone slightly decreased both the reactivity and the
enantioselectivity (entry 6). When 4’-fluoroacetophenone was
used as a substrate, only a low yield of product was observed,
even for a prolonged reaction time (entry 7).
Various primary alcohols are available as alkylating
reagents for ketones. Reactions of acetophenone (2 a) with
2-methyl-1-propanol, 1-pentanol, and 3-methyl-1-butanol
were carried out in the presence of catalytic amounts of
[{IrCl(cod)}2] (1 mol %) and 1 (1 mol %) to afford the
corresponding a-alkylated alcohols in good yields with a
high enantioselectivity (entries 8–10). However, benzyl alcohol could not be employed for this reaction (entry 11).
Although the detailed reaction mechanism is not yet
known, it is considered that a primary alcohol is catalytically
dehydrogenated by the iridium complex to form the corresponding aldehyde, followed by its base-catalyzed aldol
condensation with ketone to afford an a,b-unsaturated
ketone, and then iridium-catalyzed hydrogenation to give an
a-alkylated ketone. Finally, ruthenium-catalyzed enantioselective transfer hydrogenation of the a-alkylated ketone
results in formation of the optically active alcohol with
elongation of the carbon skeleton (Scheme 2).
As described above, it is known that the iridium complex
[{IrCl(cod)}2] catalytically promotes the a-alkylation of
ketones with alcohols.[8] This result indicates that the presence
of the iridium complex, PPh3, and KOH did not interfere with
the final reduction step of the ketone intermediate. It is
noteworthy that the iridium and ruthenium complexes play
their roles independently in each step. The method presented
herein provides a useful synthetic route to obtaining optically
2006 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Angew. Chem. Int. Ed. 2006, 45, 3819 –3822
Angewandte
Chemie
35.0 (c = 0.88, CHCl3),
with that reported in literature ([a]24
D =
92 % ee (S)).[12]
Received: February 21, 2006
Published online: May 3, 2006
.
Keywords: alkylation · homogeneous catalysis · iridium ·
reduction · ruthenium
Scheme 2. Plausible reaction pathway.
active alcohols with elongation of the carbon skeleton directly
from prochiral ketones and alcohols, in contrast to the
conventional asymmetric reduction of prochiral ketones
which only gives the simple reduced alcohols.
In summary, we have disclosed that asymmetric aalkylative reduction of prochiral ketones with primary
alcohols catalyzed by both iridium and ruthenium complexes
gave the corresponding optically active alcohols with the
elongation of the carbon skeleton and with a high enantioselectivity (up to 98 % ee). The compatibility between iridium
and ruthenium complexes is an essential factor in directly
obtaining optically active alcohols with elongation of the
carbon skeleton. Further investigations involving the broadening of the scope of this sequential reaction system are
currently in progress.
Experimental Section
A typical experimental procedure for the reaction of acetophenone
(2 a) with 1-butanol (3 a) catalyzed by [{IrCl(cod)}2] and [RuCl2(PPh3)(ip-foxap)] (1): KOH (5.8 mg, 0.10 mmol), [{IrCl(cod)}2]
(13.1 mg, 0.020 mmol), and PPh3 (21.4 mg, 0.082 mmol) under N2
were place in a 20-mL flask. After the addition of 2 a (240.1 mg,
2.0 mmol) and 3 a (445.8 mg, 6.0 mmol), the reaction mixture was
kept at 100 8C for 4 h. A solution of iPrOH containing iPrONa
(0.080 mmol) and 1 (18.4 mg, 0.020 mmol) was added to the reaction
mixture, and then the reaction mixture was kept at room temperature
for 2 h. For the workup, aqueous HCl (1n, 0.5 mL) was added to the
reaction mixture. The solvent was concentrated under reduced
pressure, and the residue was extracted with water (50 mL) and
diethyl ether (3 C 50 mL). The organic solution was dried over
anhydrous MgSO4. For isolation, the extract was concentrated
under reduced pressure by an aspirator, and the residue was purified
by column chromatography on silica gel (EtOAc/n-hexane, 10:90) to
yield 267.7 mg (1.50 mmol, 75 %, 94 % ee) of (R)-1-phenyl-1-hexanol
(4 aa) as a white solid, which was identified by comparison of its
spectroscopic data with that in the literature.[9] [a]28
D = + 35.3 (c = 1.04,
CHCl3); 1H NMR (CDCl3, 270 MHz) d = 0.85–0.90 (m, 3 H), 1.29–1.43
(m, 6 H), 1.71–1.79 (m, 2 H), 1.82 (d, 1 H, J = 3.3 Hz), 4.64–4.70 (m,
1 H), 7.24–7.36 ppm (m, 5 H); the ee value was determined by HPLC
analysis with a Chiralcel OD column (eluent: n-hexane/2-propanol,
98:2, flow rate: 0.5 mL min 1, column temperature: 30 8C, retention
time: 34.72 min (R) and 46.60 min (S)); the absolute configuration
was determined by comparison of the value of the optical rotation
Angew. Chem. Int. Ed. 2006, 45, 3819 –3822
[1] For recent reviews, see: a) R. Noyori, S. Hashiguchi, Acc. Chem.
Res. 1997, 30, 97; b) R. Noyori, T. Ohkuma, Angew. Chem. 2001,
113, 40; Angew. Chem. Int. Ed. 2001, 40, 40; c) R. Noyori,
Angew. Chem. 2002, 114, 2108; Angew. Chem. Int. Ed. 2002, 41,
2008; d) S. E. Clapham, A. Hadzovic, R. H. Morris, Coord.
Chem. Rev. 2004, 248, 2201.
[2] For recent examples, see: a) T. Ohkuma, H. Ooka, S. Hashiguchi,
T. Ikariya, R. Noyori, J. Am. Chem. Soc. 1995, 117, 2675; b) S.
Hashiguchi, A. Fujii, J. Takehara, T. Ikariya, R. Noyori, J. Am.
Chem. Soc. 1995, 117, 7562; c) T. Ohkuma, H. Doucet, T. Pham,
K. Mikami, T. Korenaga, M. Terada, R. Noyori, J. Am. Chem.
Soc. 1998, 120, 1086; d) Q. Jiang, Y. Jiang, D. Xiao, P. Cao, X.
Zhang, Angew. Chem. 1998, 110, 1203; Angew. Chem. Int. Ed.
1998, 37, 1100; e) H. Doucet, T. Ohkuma, K. Murata, T.
Yokozawa, M. Kozawa, E. Katayama, A. F. England, T. Ikariya,
R. Noyori, Angew. Chem. 1998, 110, 1792; Angew. Chem. Int. Ed.
1998, 37, 1703; f) M. Bernard, V. Guiral, F. Delbecq, F. Fache, P.
Sautet, M. Lemaire, J. Am. Chem. Soc. 1998, 120, 1441; g) Y.
Jiang, Q. Jiang, X. Zhang, J. Am. Chem. Soc. 1998, 120, 3817;
h) D. A. Alonso, P. Brandt, S. J. M. Nordin, P. G. Andersson, J.
Am. Chem. Soc. 1999, 121, 9580; i) C. J. A. Daley, S. H. Bergens,
J. Am. Chem. Soc. 2002, 124, 3680; j) K. Abdur-Rashid, S. E.
Clapham, A. Hadzovic, J. N. Harvey, A. J. Lough, R. H. Morris,
J. Am. Chem. Soc. 2002, 124, 15 104; k) R. J. Hamilton, C. G.
Leong, G. Bigam, M. Miskolzie, S. H. Bergens, J. Am. Chem. Soc.
2005, 127, 4152.
[3] a) Since the first preparation of optically active ferrocenyloxazolinylphosphines (FOXAPs) by us in 1995,[3b] we have
developed many enantioselective reactions catalyzed by various
transition-metal complexes bearing FOXAP as a chiral ligand;
b) Y. Nishibayashi, S. Uemura, Synlett 1995, 79; c) Y. Nishibayashi, K. Segawa, K. Ohe, S. Uemura, Organometallics 1995, 14,
5486; d) Y. Nishibayashi, K. Segawa, H. Takada, K. Ohe, S.
Uemura, Chem. Commun. 1996, 847; e) Y. Nishibayashi, I.
Takei, S. Uemura, M. Hidai, Organometallics 1998, 17, 3420; f) I.
Takei, Y. Nishibayashi, Y. Arikawa, S. Uemura, M. Hidai,
Organometallics 1999, 18, 2271; g) I. Takei, Y. Nishibayashi, Y.
Ishii, Y. Mizobe, S. Uemura, M. Hidai, Chem. Commun. 2001,
2360; h) T. Iwata, Y. Miyake, Y. Nishibayashi, S. Uemura, J.
Chem. Soc. Perkin Trans. 1 2002, 1548; i) the optically active
FOXAP ligand is commercially available from Wako Pure
Chemical Industries (Japan) as ip-FOXAP (065-04331).
[4] a) Y. Nishibayashi, I. Takei, S. Uemura, M. Hidai, Organometallics 1999, 18, 2291; b) Y. Nishibayashi, A. Yamauchi, G.
Onodera, S. Uemura, J. Org. Chem. 2003, 68, 5875.
[5] For recent reviews, see: a) J. M. Lee, Y. Na, H. Han, S. Chang,
Chem. Soc. Rev. 2004, 33, 302; b) J.-C. Wasilke, S. J. Obrey, R. T.
Baker, G. C. Bazan, Chem. Rev. 2005, 105, 1001; c) A. Ajamian,
J. L. Gleason, Angew. Chem. 2004, 116, 3842; Angew. Chem. Int.
Ed. 2004, 43, 3754; d) J.-A. Ma, D. Cahard, Angew. Chem. 2004,
116, 4666; Angew. Chem. Int. Ed. 2004, 43, 4566.
[6] For recent examples, see: a) C. J. Kressierer, T. J. J. MNller,
Angew. Chem. 2004, 116, 6123; Angew. Chem. Int. Ed. 2004, 43,
5997; b) J. Chae, J. Yun, S. L. Buchwald, Org. Lett. 2004, 6, 4809;
c) J. G. Kim, K. M. Waltz, I. F. Garcia, D. Kwiatkowski, P. J.
Walsh, J. Am. Chem. Soc. 2004, 126, 12 580; d) H. Lebel, V.
Paquet, J. Am. Chem. Soc. 2004, 126, 11 152; e) R. Guo, R. H.
2006 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.angewandte.org
3821
Communications
[7]
[8]
[9]
[10]
[11]
[12]
3822
Morris, D. Song, J. Am. Chem. Soc. 2005, 127, 516; f) L. Deng,
A. J. Giessert, O. O. Gerlitz, X. Dai, S. T. Diver, H. M. L. Davies,
J. Am. Chem. Soc. 2005, 127, 1342; g) D. M. DOSouza, F.
Rominger, T. J. J. MNller, Angew. Chem. 2005, 117, 156;
Angew. Chem. Int. Ed. 2005, 44, 153; h) Y. Yamamoto, H.
Hayashi, T. Saigoku, H. Nishiyama, J. Am. Chem. Soc. 2005, 127,
10 804; i) B. A. Seigal, C. Fajardo, M. L. Snapper, J. Am. Chem.
Soc. 2005, 127, 16 329.
a) Y. Nishibayashi, M. Yoshikawa, Y. Inada, M. D. Milton, M.
Hidai, S. Uemura, Angew. Chem. 2003, 115, 2785; Angew. Chem.
Int. Ed. 2003, 42, 2681; b) M. D. Milton, Y. Inada, Y. Nishibayashi, S. Uemura, Chem. Commun. 2004, 2712; c) Y. Nishibayashi,
M. Yoshikawa, Y. Inada, M. Hidai, S. Uemura, J. Am. Chem. Soc.
2004, 126, 16 066.
K. Taguchi, H. Nakagawa, T. Hirabayashi, S. Sakaguchi, Y. Ishii,
J. Am. Chem. Soc. 2004, 126, 72.
C. S. Cho, B. T. Kim, T.-J. Kim, S. C. Shim, J. Org. Chem. 2001,
66, 9020.
a) R. Martinez, G. J. Brand, D. J. Ramon, M. Yus, Tetrahedron
Lett. 2005, 46, 3683; b) M. S. Kwon, N. Kim, S. H. Seo, I. S. Park,
R. K. Cheedrala, J. Park, Angew. Chem. 2005, 117, 7073; Angew.
Chem. Int. Ed. 2005, 44, 6913.
A similar one-pot b-alkylation of secondary alcohols with
primary alcohols has been reported, see: a) C. S. Cho, B. T.
Kim, H.-S. Kim, T.-J. Kim, S. C. Shim, Organometallics 2003, 22,
3608; b) K. Fujita, C. Asai, T. Yamaguchi, F. Hanasaka, R.
Yamaguchi, Org. Lett. 2005, 7, 4017.
N. A. Salvi, S. Chattopadhyay, Tetrahedron 2001, 57, 2833.
www.angewandte.org
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