Synthesis of planar chiral (1,3-disubstituted arene)Mn(CO)3(+) cations via addition of nucleophiles to (oxocyclohexadienyl)Mn(CO)3 in the presence of chiral ligands

Article abstract of DOI:10.1039/b201341j

The first example of the synthesis of planar chiral (1,3-disubstituted arene)Mn(CO)3(+) cations (3) has been demonstrated by a reaction of (p-cresol)Mn(CO)3(+) with KOBu-t followed by adition of nucleophiles and subsequent quenching with electrophiles in the presence of (S)-binaphthol in CH2Cl2.

Full text of DOI:10.1039/b201341j

+
Synthesis of planar chiral (1,3-disubstituted arene)Mn(CO)3 cations via
addition of nucleophiles to (oxocyclohexadienyl)Mn(CO)3 in the presence
of chiral ligands†
Seung Uk Son, Kang Hyun Park, Seung Jung Lee, Hwimin Seo and Young Keun Chung*
School of Chemistry and Center for Molecular Catalysis, Seoul National University, Seoul 151-747, Korea.
E-mail: ykchung@plaza.snu.ac.kr
Received (in Cambridge, UK) 8th February 2002, Accepted 24th April 2002
First published as an Advance Article on the web 7th May 2002
The first example of the synthesis of planar chiral (1,3-dis-
the sequential nucleophile/electrophile addition to 1 [eqn.
(2)].
+
ubstituted arene)Mn(CO)3 cations (3) has been demon-
strated by a reaction of (p-cresol)Mn(CO)3 with KOBut
+
followed by addition of nucleophiles and subsequent quench-
ing with electrophiles in the presence of (S)-binaphthol in
CH2Cl2.
(2)
Planar chiral transition-metal p-complexes of ortho- and meta-
disubstituted arenes have emerged as useful starting materials in
organic synthesis and as potential ligands for asymmetric
catalysis. The planar chirality enables new stereogenic centers
to be formed with high stereoselectivity.1 In this regard,
tricarbonylchromium(0) complexes of aromatic compounds
have received much attention.2 Optically active arene chro-
mium complexes have been obtained through resolution via
diastereoselective synthesis and by enantioselective meth-
ods.3–7
Thus, we screened several chiral ligands in the nucleophile
addition reaction to 1 (Table 1). As we expected, planar chiral
(h -cyclohexadienyl)Mn(CO)3 complexes 2 were obtained in
5
reasonable to high yields. The yields were sensitive to the chiral
ligand and reaction medium, the ee values were highly
dependent upon them, and the S or R configuration was also
dependent upon the chiral ligand. Generally, chiral diol ligands
were superior to chiral N,O- and N,N-chelating ligands. The
best result was obtained when the reaction was conducted in the
presence of (S)-binaphthol in CH2Cl2.
The reaction of organotransition metal complexes with
nucleophiles offers a powerful method in the formation of
carbon–carbon bonds. When an arene is bound to the cationic
+
Mn(CO)3 fragment, it becomes substantially more electro-
philic than in the neutral (arene)Cr(CO)3 complexes.8 However,
in spite of their potential usefulness, there have been no reports
Next we investigated the reaction with various nucleophiles
(Table 2). When an electron-withdrawing group such as p-CF3
was introduced to a phenyl ring, no reaction was observed,
presumably due to the low nucleophilicity of the resulting
+
on the synthetic methods of planar chiral (arene)Mn(CO)3
complexes from achiral arenes, even though the respective
5
groups of Pearson and Miles9 reported the synthesis of chiral h -
dienyl manganese complexes by a chiral auxiliary-directed
asymmetric additions to arene–manganese tricarbonyl com-
plexes. Herein we describe our initial study of the synthesis of
planar chiral manganese complexes of 1,3-disubstitued arenes
from a readily available p-cresol manganese complex. To the
best of our knowledge, this is the first synthesis of planar chiral
1,3-disubstituted arene manganesetricarbonyl complexes.
Table 1 The results of chiral induction with various ligandsa
Treatment of (p-cresol)Mn(CO)3 with KOBut in THF
+
afforded oxocyclohexadienyl manganese complex 1 [eqn.
(1)].
(1)
Entry
Ligand
Solvent
Yieldb (%)
Eec (%) Config.d
1e
2
3
4
5
6
7
8
9
la
lb
lc
lg
lc
ld
le
lf
THF
THF
THF
THF
CH2Cl2
CH2Cl2
CH2Cl2
CH2Cl2
CH2Cl2
85
61
95
82
51
67
65
70
78
7
24
35
54
50
35
13
9
R
R
S
S
R
S
R
R
S
Complex 1 was easily attacked by nucleophiles such as
Grignard reagents and alkyllithium.10 Nucleophiles exclusively
attacked the terminal positions of the cyclohexadienyl ring.
The external ligand-controlled enantioselective addition of
organometallic reagents to prochiral molecules is a powerful
tool in asymmetric methodology. Thus, it was expected that the
nucleophile addition to a prochiral manganese complex 1 in the
presence of external chiral ligand would induce asymmetry in
lg
95
a Reaction conditions: 1.5 equiv. ligand and 4.5 equiv. PhMgBr, 278 °C, 18
h. b Isolated yields. c Determined by HPLC using a Chiralcel OD column.
d The absolute configuration was determined by X-ray analyses of 3a and
3b. e 1.5 equiv. ligand and 1.5 equiv. PhMgBr used.
† Electronic supplementary information (ESI) available: experimental
section. See http://www.rsc.org/suppdata/cc/b2/b201341j/
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CHEM. COMMUN., 2002, 1230–1231
This journal is © The Royal Society of Chemistry 2002

Table 2 The results of chiral induction with various nucleophilesa
occurred at one of the two ortho positions of the ketone group
of (oxocyclohexadienyl)Mn(CO)3 to yield 2 and the acid
treatment of 2 generated the planar chiral 1,3-disubstituted
arene manganese tricarbonyl cations which could not be
obtained by the other methods.
Entry
RMgX
Product
Yieldb (%) Eec (%)
Config.
1
2
3
4
5
6
7
4-CF3C6H4
2-Thienyl
Ph
4-MeC6H4
4-MeOC6H4
1-Naphthyl
Bun
2a
2b
2c
2d
2e
2f
n.r.
68
78
75
65
70
75
—
98
95
90
76
66
67
—
S
S
S
S
In conclusion, we have demonstrated the first synthesis of
planar chiral manganesetricarbonyl complexes of 1,3-dis-
ubstituted arenes starting from a readily available achiral (p-
+
S
S
cresol)Mn(CO)3 cation. Future work will be directed at
2g
applying this chemistry to other transition metal complexes of
p-substituted phenols as well as studying the synthetic applica-
tion of this method.
This work was supported by Korea Research Foundation
Grant (KRF-2001-015-DS0025). The authors thank Prof. Lah
(Han Yang University) for refining the X-ray crystal structure.
S. U. S., K. H. P., S. J. L., and H. S. acknowledge receipt of the
Brain Korea 21 fellowship.
a Reaction conditions: 1.5 equiv. (S)-binaphthol, 4.5 equiv. nucleophile,
278 °C, 18 h in CH2Cl2 b Isolated yields. c Ee was determined by HPLC
using a Chiralcel OD column.
Grignard reagent. Introduction of an electron-donating group
such as p-methyl and p-methoxy groups to a phenyl ring led to
a decrease of the ee value to 90 and 76%, respectively. When a
bulky nucleophile such as 2-naphthyl Grignard reagent was
used, the ee value fell to 66%. Interestingly, treatment of 1 with
2-thienyl magnesium bromide gave 2b in 68% yield with a high
enantioselectivity 98%.
Other nucleophiles such as PhMgBr/CuI, PhLi and PhLi/CuI
were also screened. When PhMgBr/CuI was used as a
nucleophile, the ee value was 48%. In the case of phenyllithium,
the ee value (14%) was quite poor. When phenyllithium cuprate
was used, almost no asymmetric induction occurred. When
Et2Zn was used as a nucleophile, no reaction was observed.
Notes and references
1 (a) S. G. Davies and T. D. McCarthy, Transition Metal Arene
Complexes: Side-chain Activation and Control of Stereochemistry in
Comprehensive Organometallic Chemistry II, ed. E. W. Abel, F. G. A.
Stone and G. Wilkinson, Pergamon, 1995, vol. 12, pp. 1039–1070; (b)
A. R. Pape, K. P. Kaliappan and E. P. Kündig, Chem. Rev., 2000, 100,
2917.
2 (a) S. E. Gibson and E. G. Reddington, Chem. Commun., 2000, 989; (b)
C. Bolm and K. Muñiz, Chem. Soc. Rev., 1999, 28, 51.
3 For examples, see:(a) A. Alexakis, P. Mangeney, I. Marek, F. Rose-
Munch, A. Semra and F. Robert, J. Am. Chem. Soc., 1992, 114, 8288; (b)
J. F. Carpentier, L. Pamart, L. Maciewjeski, Y. Castanet, J. Brocard and
A. Mortreux, Tetrahedron Lett., 1996, 37, 167.
+
To generate planar chiral (1,3-disubstituted arene)Mn(CO)3
cations (3) while retaining optical purity (see ESI†), complexes
2 were treated with HBF4 [eqn. (3)].
4 (a) M. Uemura, R. Miyake, K. Nakayama, M. Shiro and Y. Hayashi, J.
Org. Chem., 1993, 58, 1238; (b) H.-G. Schmalz, B. Millies, J. W. Bats
and G. Dürner, Angew. Chem., Int. Ed. Engl., 1992, 31, 631.
5 (a) D. A. Price, N. S. Simpkins, A. M. McLeod and A. P. Watt, J. Org.
Chem., 1994, 59, 1961; (b) H.-G. Schmalz and K. Schellhaas,
Tetrahedron Lett., 1995, 36, 5515; (c) R. A. Ewin, A. M. McLeod, D. A.
Price, N. S. Simpkins and A. P. Watt, J. Chem. Soc., Perkin Trans. 1,
1997, 401; (d) E. P. Kündig and A. Quattropani, Tetrahedron Lett.,
1994, 35, 3497; (e) E. L. M. Cowton, S. E. Gibson, M. J. Schneider and
M. H. Smith, Chem. Commun., 1996, 839.
(3)
High yields of 3 were obtained with high enantioselectivities.
Careful crystallization of 3a and 3b from diethyl ether/
nitromethane gave single crystals. The molecular structures of
3a and 3b were determined by X-ray diffraction. They have
very similar unit cell dimensions and the X-Ray crystal
structures are quite similar to each other. Thus only the X-ray
crystal structure of 3b is presented in Fig. 1,11 which clearly
shows that nucleophile addition occurs preferentially at the
meta position of the methyl group and the absolute configura-
tion is S.
In general, ortho positions are more easily influenced by a
nearby chiral auxiliary than meta positions. Therefore, most
auxilliary-controlled asymmetric reactions provide planar chiral
1,2-disubstituted arene transition-metal complexes, sometimes,
with excellent results. In our reactions, chiral induction
6 A. Amurrio, K. Khan and E. P. Kündig, J. Org. Chem., 1996, 61,
2258.
7 See for examples: (a) M. Uemura, H. Nishimura and T. Hayashi,
Tetrahedron, 1993, 34, 107; (b) M. Uemura, H. Nishimura and T.
Hayashi, J. Organomet. Chem., 1994, 473, 129; (c) S. L. Griffiths, S.
Perrio and S. E. Thomas, Tetrahedron: Asymmetry, 1994, 5, 1847; (d) J.
A. S. Howell, M. G. Palin, G. Jaouen, B. Maleziux, S. Top, J. M. Cense,
J. Saläun, P. McArdie, D. Cunnigham and M. O’Gara, Tetrahedron:
Asymmetry, 1996, 7, 95; (e) K. Kamikawa, T. Watanabe and M.
Uemura, J. Org. Chem., 1996, 61, 1375; (f) E. P. Kündig, R. Liu and A.
Ripa, Helv. Chim. Acta, 1992, 75, 2657.
8 R. D. Pike and D. A. Sweigart, Synlett, 1990, 565.
9 (a) A. J. Pearson, P. Y. Zhu, W. J. Youngs, J. D. Bradshaw and D. B.
McConville, J. Am. Chem. Soc., 1993, 115, 10376; (b) A. J. Pearson, P.
R. Bruhn, F. Gouzoules and S. Lee, J. Chem. Soc., Chem. Commun.,
1989, 659; (c) W. H. Miles, P. M. Smiley and H. R. Brinkman, J. Chem.
Soc., Chem. Commun., 1989, 1897; (d) W. H. Miles and H. R.
Brinkman, Tetrahedron Lett., 1992, 33, 589; (e) A. J. Pearson and H.
Shin, Tetrahedron, 1992, 48, 7527; (f) A. J. Pearson, A. V. Gontcharov
and P. Y. Zhu, Tetrahedron, 1997, 53, 3849.
10 (a) S.-G. Lee, J.-a. Lim, Y. K. Chung, T.-S. Yoon, N.-J. Kim, W. Shin,
J. Kim and K. Kim, Organometallics, 1995, 14, 1023; (b) H. Seo, S. G.
Lee, D. M. Shin and Y. K. Chung, manuscript submitted.
11 Crystal data for 3a: monoclinic, P21, a = 14.614(1), b = 10.729(1), c
= 17.076(1) Å, b = 114.487(1)°, limiting indices 217 @ h @ 17, 212
@ k @ 11, 220 @ l @ 17, reflections collected/unique 11697/7033 (Rint
= 0.0500), final R indices [I > 2s(I)] R1 = 0.0458, wR2 = 0.0885. For
3b: monoclinic, P21, a = 15.1163(4), b = 10.6658(3), c = 17.0086(6)
Å, b = 114.0125(13)°, limiting indices 218 @ h @ 18, 213 @ k @ 10,
221 @ l @ 21, reflections collected/unique 8896/8896 (Rint = 0.0000),
final R indices [I > 2s(I)] R1
= 0.0654, wR2 = 0.1560. CCDC
reference number 182208. See http://www.rsc.org/suppdata/cc/b2/
b201341j/ for crystallographic data in CIF or other electronic format.
Fig. 1 Crystal structure of 3b.
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