Catalytic enantioselective oxidation of alkanes and alkenes using (salen)manganese complexes bearing a chiral binaphthyl strapping unit

Article abstract of DOI:10.1002/adsc.200303190

A (salen)manganese(III) complex bearing a chiral binaphthyl strapping unit catalyzes the enantioselective hydroxylation of indane (up to 34percent ee) and the epoxidation of alkenes (up to 93percent ee) with iodosylbenzene.

Full text of DOI:10.1002/adsc.200303190

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Catalytic Enantioselective Oxidation of Alkanes and Alkenes
Using (Salen)Manganese Complexes Bearing a Chiral Binaphthyl
Strapping Unit
a, b,
b
b
Shun-Ichi Murahashi, * Satoru Noji, Naruyoshi Komiya
a
Department of Applied Chemistry, Okayama University of Science, 1 ± 1, Ridaicho, Okayama, Okayama 700 ± 0005,
Japan,
Fax: ( ‡ 81)-86-256-4292, e-mail: murahashi@high.ous.ac.jp
b
Department of Chemistry, Graduate School of Engineering Science, Osaka University, 1 ± 3, Machikaneyama , Toyonaka,
Osaka 560 ± 8531, Japan,
Received: October 27, 2003; Accepted: January 10, 2004
Supporting Information for this article is available on the WWW under http://asc.wiley-vch.de.
porphyrins[3] and a concave type (salen)manganese
[
4]
complex 4 bearing a chiral environment were designed
Abstract: A (salen)manganese(III) complex bearing
a chiral binaphthyl strapping unit catalyzes the
enantioselective hydroxylation of indane (up to
and used for asymmetric hydroxylation of hydrocar-
[
5]
[6]
bons. The (salen)manganese complexes 3 and 4 are
also known to be effective for the asymmetric epoxida-
tion of alkenes (Figure 1).
3
9
4% ee) and the epoxidation of alkenes (up to
3% ee) with iodosylbenzene.
During the course of our study on the biomimetic
[
7,8]
oxidation of alkanes, we found that enantioselective
oxidation of symmetrical alkanes using the catalyst 3
proceeds to give the corresponding optically active
ketones in up to 70% ee. In order to aim at asymmetric
hydroxylation of alkanes, we synthesized new bridged
Mn(salen) complexes bearing a strapping unit (1 and
Keywords: asymmetric epoxidation; asymmetric hy-
droxylation; CÀH activation; hydrocarbons; iodosyl-
benzene; salen-manganese complex
[
9]
[
10]
2
). The strategy is the generation of oxo-manganese
Catalytic asymmetric oxidation of hydrocarbons is an species in a cage. Herein, we wish toreport that the novel
important and rapidly growing area in organic synthesis, manganese salen complex (1) bearing a chiral strapping
and much effort has been devoted to create a new chiral unit is an effective catalyst for the enantioselective
metal complex directed towards asymmetric oxida- hydroxylation of alkanes and epoxidation of alkenes.
tions.[
1]
The strapped Mn(salen) complexes were synthesized
For asymmetric hydroxylation of CÀH bonds of as shown in Scheme 1. (S)-2,2'-Binaphthol was allowed
alkanes, it is important to control the direction of to react with p-bromobenzaldehyde in the presence of
substrate×s approach to the active metal-oxo center. For copper. The dialdehyde was converted to the corre-
this purpose, chiral metalloporphyrin complexes such as sponding diol 5 by reduction with LiAlH . 3-tert-Butyl-
4
[
11]
bridged iron-porphyrins bearing a chiral binaphthyl 5-formyl-4-methoxymethoxyphenylacetic acid
was
vaulted unit[ and D -symmetric chiral ruthenium prepared in four steps; that is, Friedel±Crafts alkylation
2]
4
Figure 1. (Salen)manganese(III) complexes.
Adv. Synth. Catal. 2004, 346, 195 ± 198
DOI:10.1002/adsc.200303190
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195

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Shun-Ichi Murahashi et al.
Scheme 1. For (S,S,aS)-1: (a) p-bromobenzaldehyde, Cu, CuO, K CO , pyridine, reflux, 100%; (b) LiAlH , THF, reflux, 97%;
2
3
4
(
c) 3-formyl-4-methoxymethoxy-5-tert-butylphenylacetic acid, DCC, DMAP, CH Cl , 50%; (d) TMSBr, CH Cl , 85%; (e)
2
2
2
2
(
S,S)-cyclohexanediamine, EtOH, 71%; (f) Mn(OAc) ¥ H O, LiCl, EtOH, reflux, 93%. For (R,R,aS)-2: (g) (R,R)-cyclo-
2
2
hexanediamine, EtOH, 53%; (h) Mn(OAc) ¥ H O, LiCl, EtOH, reflux, 66%.
2
2
of methyl p-hydroxyphenylacetate with t-butanol, for-
mylation, protection of the hydroxy group with methox-
ymethyl group (MOM), and hydrolysis of the methyl
ester under basic conditions, and then was allowed to
condense with the diol 5. Subsequent deprotection of
the methoxymethyl group with trimethylsilyl bromide
gave the corresponding disalicylaldehyde 6. Diastereo-
meric pairs of the strapped salen ligands 7 and 8 were
Scheme 2. Enantioselective oxidation of indane with Mn
salen) catalyst 1.
(
prepared by the condensation of 6 with optically active fifth ligand was observed (Table 1). The Mn(salen) 1-
(
S,S)- and (R,R)-cyclohexanediamine, respectively. catalyzed oxidation of indane without an axial ligand
Metalation of the salen ligands 7 and 8 with gave 1-indanol with only 5% ee (entry 1). Whenthe non-
Mn(OAc) ¥4 H O gave the corresponding diastereomer- substituted imidazole was used, the enantioselectivity
4
2
ic isomers of the strapped Mn(salen) complexes 1 and 2, was not influenced (8% ee) (entry 2). In contrast, when
respectively. bulky 4-phenylpyridine N-oxide and 1,5-dicyclohexyl-
Asymmetric hydroxylation of an alkane with iodosyl- imidazole were used as the fifth ligand, the enantiose-
benzene in the presence of the chiral strapped Mn(sa- lectivity was improved to 14% ee and 25% ee, respec-
len) complex catalyst 1 can be carried out. Typically, tively (entries 3 and 4). Furthermore, the enantioselec-
treatment of indane with PhIO in the presence of tivity was improved, when the reaction temperature was
0
.2 mol % of Mn(salen) catalyst 1 in CH Cl at À 308C low (at À 308C, 34% ee) (entry 5). A substrate seems to
2
2
under argon gave (S)-1-indanol (20% yield) with 34% approach to the cage with recognition of the slope of the
ee along with a small amount of 1-indanone (Scheme 2). bridging naphthyl group [(A) in 9 in Figure 2]. Actually,
In the present reaction, coordination of a fifth ligand the Mn(salen) 2 which is a diastereomer of 1 and an
[
12]
to the Mn(salen) complex as an axial ligand
is unmatched pair gave the (R)-alcohol with only 15% ee
important to control the reaction site; that is, either (entry 6). The non-bridging complex 3 gave the (S)-
inside or outside the cavity (Figure 2). A sterically alcohol with 15% ee (entry 7).
hindered ligand favors coordination to the opposite side
Enantioselective epoxidation of alkenes can be also
of the strapped unit, resulting in formation of the active carried out using the chiral strapped Mn(salen) complex
oxo-manganese species in the chiral cavity. In contrast, a 1 (Scheme 3). Typically, treatment of 2,2-dimethylchro-
small ligand coordinates to the Mn from both non- mene with PhIO in the presence of the catalyst 1 and 4-
strapped and strapped sides. An interesting effect of the phenylpyridine N-oxide in CH Cl under argon gave the
2
2
196
¹ 2004 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim
asc.wiley-vch.de
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Oxidation of Alkanes and Alkenes Using (Salen)Manganese Complexes
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Figure 2. (a) L ˆ bulky ligand (1,5-dicyclohexylimidazole). (b) L ˆ small ligand (imidazole).
Table 1. Asymmetric hydroxylation of indane using various Mn(salen) complexes.[a]
Entry
Catalyst
Temperature [8C]
Additive
Conversion [%][b]
Alcohol/Ketone
ee [%][c]
1
2
3
4
5
6
7
1
1
1
1
1
2
3
0
0
0
none
imidazole
20
35
18
41
25
24
24
1.3
4.2
5.0
4.9
4.1
9.0
3.5
5 (S)
8 (S)
4-phenylpyridine N-oxide
1,5-dicyclohexylimidazole
1,5-dicyclohexylimidazole
1,5-dicyclohexylimidazole
1,5-dicyclohexylimidazole
14 (S)
25 (S)
34 (S)
15 (R)
15 (S)
0
À 30
À 30
À 30
[
a]
To a mixture of indane (1 mmol), additive (0.25 mmol), and Mn(salen) complex (0.002 mmol) in CH Cl was added PhIO
2
2
(
0.1 mmol). The mixture was stirred for 7 h.
[
[
b]
c]
Conversion of indane (total yield of 1-indanol and 1-indanone).
Determined by HPLC analysis using CHIRALCEL OB-H (hexane:2-propanol ˆ 10: 1).
corresponding (3S,4S)-epoxide with 93% ee (50%
yield).[ cis-b-Methylstyrene was also oxidized to give
13]
[
14]
the corresponding epoxide with 82% ee. The absolute
configuration of the epoxide is the same as that obtained
using (S,S)-3 and is opposite to that obtained with 4.
In conclusion, we have synthesized novel manganese
complexes (1 and 2) bearing a chiral strapping unit, and
found that these complexes are effective for the
Scheme 3. Enantioselective oxidation of 2,2-dimethylchro-
mene with Mn(salen) catalyst 1.
asymmetric hydroxylation of alkanes and asymmetric Experimental Section
epoxidation of alkenes. Work is in progress to obtain
mechanistic information and design further highly
enantioselective procedures for the catalytic oxidation
of hydrocarbons.
Mn(salen) (1)-Catalyzed Enantioselective
Hydroxylation of Indane with Iodosylbenzene
Toa mixture of indane (118 mg, 1.0 mmol), Mn(salen) complex
(
0
1) (2.2 mg, 0.0020 mmol), 1,5-dicyclohexylimidazole (12 mg,
.050 mmol), and CH Cl (0.5 mL) was added iodosylbenzene
2
2
(
22 mg, 0.10 mmol) at 08C under an argon atmosphere. The
mixture was stirred at À 308C for 7 h. After removal of the
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COMMUNICATIONS
Shun-Ichi Murahashi et al.
solvent, the residue was subject to column chromatography
[2] a) J. T. Groves, P. Viski, J. Am. Chem. Soc. 1989, 111,
8537 ± 8538; b) J. T. Groves, P. Viski, J. Org. Chem. 1990,
55, 3628 ± 3634.
[3] R. Zhang, W.-Y. Yu, T.-S. Lai, C.-M. Che, Chem.
Commun. 1999, 1791 ± 1792.
(
SiO , hexane:ethyl acetate ˆ 10:1) to give 1-indanol as a
2
1
colorless oil; yield: 27 mg (20%). H NMR (CDCl , 500 MHz):
3
d ˆ 1.84 ± 1.91 (m, 1H, CH ), 2.38 ± 2.45 (m, 1H, CH ), 2.47 (br,
2
2
1H, OH), 2.74 ± 2.81 (m, 1H, CH ), 2.97 ± 3.03 (m, 1H, CH ),
2 2
5
.15 (d, J ˆ 4.6 Hz, 1H, CH), 7.18 ± 7.25 (m, 3H, ArH), 7.36 (d,
[
4] a) T. Hamada, R. Irie, J. Mihara, K. Hamachi, T. Katsuki,
Tetrahedron. 1998, 54, 10017 ± 10028; b) K. Hamachi, R.
Irie, T. Katsuki, Tetrahedron Lett. 1996, 37, 4979 ± 4982.
5] a) W. Zhang, J. L. Loebach,S. R. Wilson,E. N. Jacobsen,
J. Am. Chem. Soc. 1990, 112, 2801 ± 2803; For review, see:
b) E. N. Jacobsen, in: Catalytic Asymmetric Synthesis,
J ˆ 6.9 Hz, 1H, ArH). The enantiomeric excess was deter-
mined to be 34% ee by HPLC analysis using a chiral column
(
CHIRALCEL OBÀH, hexane:2-propanol ˆ 10:1, 0.5 mL/
[
min).
(
Ed.: I. Ojima), VCH, Weinheim, 1993, pp. 159 ± 202.
Mn(salen) (1)-Catalyzed Enantioselective Epoxidation
of 2,2-Dimethylchromene with Iodosylbenzene
[
6] For reviews, see: a) T. Katsuki, Synlett 2003, 281 ± 297;
b) Y. N. Ito, T. Katsuki, Bull. Chem. Soc. Jpn. 1999, 72,
603 ± 619; c) T. Katsuki, J. Mol. Catal. A: Chem. 1996,
113, 87 ± 107; d) T. Katsuki, Coord. Chem. Rev. 1995, 140,
189 ± 214.
To a mixture of 2,2-dimethylchromene (16.0 mg, 0.100 mmol),
Mn(salen) catalyst (1) (1.1 mg, 0.00100 mmol), 4-phenylpyr-
idine N-oxide (17.1 mg, 0.100 mmol), and CH Cl (1.0 mL) was
2
2
added iodosylbenzene (22 mg, 0.10 mmol) at À 308C. The
mixture was stirred for 4 h at this temperature. After removal
of the solvent, the residue was subject to column chromatog-
[7] For reviews, see: a) S.-I. Murahashi, Angew. Chem. Int.
Ed. Engl. 1995, 34, 2443 ± 2465; b) S.-I. Murahashi, N.
Komiya, In: Biomimetic Oxidations Catalyzed by Tran-
sition Metal Complexes, (Ed.: B. Meunier), Imperial
College Press: London, 2000, pp. 563 ± 611.
[8] a) S.-I. Murahashi, Y. Oda, T. Naota, J. Am. Chem. Soc.
1992, 114, 7913 ± 7914; b) N. Komiya, T. Naota, Y. Oda,
S.-I. Murahashi, J. Mol. Catal. A: Chem. 1997, 117, 21 ±
raphy (SiO , hexane:ethyl acetate ˆ 30:1) to give 3,4-epoxy-
2
2
,2-dimethylchromene as a colorless oil; yield: 8.8 mg (50%).
1
H NMR (CDCl , 500 MHz): d ˆ 1.26 (s, 3H, CH ), 1.58 (s, 3H,
3
3
CH ), 3.50 (d, J ˆ 4.4 Hz, 1H, CH), 4.58 (d, J ˆ 4.6 Hz, 1H,
3
CH), 6.81 (d, J ˆ 8.0 Hz, 1H, ArH), 6.93 (dt, J ˆ 7.5 and 1.1 Hz,
1
1
H, ArH), 7.20 ± 7.26 (m, 1H, ArH), 7.34 (dd, J ˆ 7.3 and
3
7; c) S.-I. Murahashi, N. Komiya, Y. Oda, T. Kuwabara,
.6 Hz, 1H, ArH). The enantiomeric excess was determined to
T. Naota, J. Org, Chem. 2000, 65, 9186 ± 9193.
be 93% ee by HPLC analysis using a chiral column (CHIR-
ALCEL OB-H, hexane:2-propanol ˆ 10:1, 0.5 mL/min). The
absolute configuration was determined by comparison of the
retention time of HPLC analysis with literature data.[
[
9] N. Komiya, S. Noji, S.-I. Murahashi, Tetrahedron Lett.
1
998, 39, 7921 ± 7924.
th
[
[
[
10] Presented at 78 Annual Meeting of Chemical Society of
15]
Japan (Chiba) 2000, Abstr. 4F402.
11] M. D. Kaufman, P. A. Grieco, D. W. Bougie, J. Am.
Chem. Soc. 1993, 115, 11648 ± 11649.
12] N. S. Finney, P. J. Pospisil, S. Chang, M. Palucki, R. G.
Konsler, K. B. Hansen, E. N. Jacobsen, Angew. Chem.
Int. Ed. Engl. 1997, 36, 1720 ± 1723.
Acknowledgements
This work was supported by the Research for the Future
program, the Japan Society for the Promotion of Science, and a
Grant-in-Aid for Scientific Research, the Ministry of Education,
Culture, Sports, Science, and Technology, Japan.
[
[
13] Enantiomeric excess was determined by HPLC analysis
using CHIRALPAK AD (hexane:2-propanol ˆ 10:1).
1
14] Enantiomeric excess was determined by H NMR
(
500 MHz) using Eu(hfc) . cis/trans epoxide ratio was
3
3
.5:1.
References and Notes
[
15] T. Hashihayata, Y. Ito, T. Katsuki, Tetrahedron 1997, 53,
9
541 ± 9552.
[1] Comprehensive Asymmetric Catalysts, (Eds.: E. N. Jacob-
sen, A. Pfaltz, H. Yamamoto), Springer, Berlin, 1999.
198
¹ 2004 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim
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Adv. Synth. Catal. 2004, 346, 195 ± 198