Synthesis of planar chiral tricarbonylcyclopentadienylmanganese complexes using a Mn(CO)3(+) transfer reaction

Article abstract of DOI:10.1039/b102693n

Planar chiral ligand transfer reactions can be carried out by the reaction of [(naphthalene)Mn(CO)3]BF4 with planar chiral ferrocene derivatives.

Full text of DOI:10.1039/b102693n

Synthesis of planar chiral tricarbonylcyclopentadienylmanganese
+
complexes using a Mn(CO)3 transfer reaction†
Seung Uk Son,a Kang Hyun Park,a Seung Jung Lee,a Young Keun Chung*a and
Dwight A. Sweigart*b
a School of Chemistry and Center for Molecular Catalysis, Seoul National University, Seoul 151-747,
Korea. E-mail: ykchung@plaza.snu.ac
b Department of Chemistry, Brown University, Providence, RI 02912, USA
Received (in Cambridge, UK) 22nd March 2001, Accepted 30th May 2001
First published as an Advance Article on the web 27th June 2001
Planar chiral ligand transfer reactions can be carried out by
the reaction of [(naphthalene)Mn(CO)3]BF4 with planar
chiral ferrocene derivatives.
have been no known reactions on the synthesis of tricarbonylcy-
clopentadienylmanganese derivatives. Surprisingly, during the
transfer reaction, a complete inversion of the absolute config-
uration occurred [eqn. (1)]. This suggests that a bimetallic
species [Cp–Fe–Cp–Mn(CO)3]+ A, in which one of the Cp rings
Ligand transfer from one metal to another is a useful reaction
when the complex cannot be easily prepared by conventional
methods and is popular in organometallic chemistry.1 Among
these, cyclopentadienyl transfer reactions may be of synthetic
interest,2,3 in particular if cheap substrates such as commer-
cially available ferrocene derivatives can be used as starting
materials. However, there have been no reports of ligand
transfer reactions from ferrocene derivatives to a manganese
moiety to prepare cyclopentadienyl manganese complexes.
Such complexes have many notable features such as high
thermal stability, lack of substantial air or water sensitivity,
kinetic inertness toward substitution reactions, and stereochem-
ical robustness. These characteristics will be useful properties
when manganese complexes are used as auxiliaries in other
reactions.
is coordinated to both metals, occurs as an intermediate in this
reaction especially given the recent isolation and character-
ization of bimetallic complexes [Cp*–M–Cp*–Mn(CO)3]+ (M
= Fe, Ru, Os).8 In the same way, compounds 2b,c were
synthesized from the corresponding mixed ferrocenes 1b,c.
According to the study of Herberich et al.,9 the migrating Cp is
always the unsubstituted ligand. They explained this observa-
tion based upon on the electronic structural differences between
Cp2 and Cp*2. However, in our case, the substituted cyclo-
pentadienyl ligand always migrated.
Herein we report the synthesis of planar chiral cyclopentadi-
enyltricarbonylmanganese complexes from the reaction of
6
4
planar chiral ferrocenes with [(h -naphthalene)Mn(CO)3]BF4
and their application in asymmetric reactions. Planar chiral
chelates of CpMn(CO)3 derivatives are quite rare and hence
their use in asymmetric reactions has not been developed. There
has been a report5 of enantioselective allylic substitution of
cyclic substrates by catalysis with palladium complexes of P,N-
chelate ligands attached to a CpMn(CO)3 unit.
Acid hydrolysis of 2a yielded the known compound 3 [eqn.
(2)];10 according to the 1H NMR spectrum of 2a and the optical
rotation of 3, compound 3 is optically pure.
Refluxing equimolar amounts of a planar chiral ferrocene
6
derivative 1a and [(h -naphthalene)Mn(CO)3]BF4 in the pres-
(2)
ence of 4 Å molecular sieves in CH2Cl2, followed by standard
work-up procedures, led to a 46% yield of the air-stable, planar
chiral tricarbonylcyclopentadienylmanganese complex 2a [eqn.
(1)].‡
We investigated whether the triol group in 2 could be used as
a directing group in the functionalization of the cyclopentadie-
nyl ring. Deprotonation of 2a by ButLi followed by the addition
of PPh2Cl yielded 4 in 67% yield [eqn. (3)].
(1)
(3)
As far as we are aware, this is the first use of a ligand transfer
reaction in the synthesis of a planar chiral tricarbonylcyclo-
pentadienylmanganese complex. Interestingly, formation of
CpMn(CO)3 was not observed in the reaction products. Birch
et al.6 first tested the idea of chirality transfer in the reaction
between a chiral donor complex and an unsymmetrical diene
ligand. Since then, there have been many reports on the
synthesis of chiral organometallic compounds.7 However, there
The structure of 4 was confirmed by an X-ray crystal
structure determination (Fig. 1).11 Thus, the diphenylphosphino
group was successfully introduced with the aid of the triol
group.
We next investigated the use of the ligand transfer reaction in
the synthesis of P,N-ligands and studied palladium-catalyzed
asymmetric allylic alkylation. The use of ligands derived from
(arene)Cr(CO)3 as a chiral chelating ligand is quite popular.12
However, the use of CpMn(CO)3 as a chiral chelating ligand is
quite rare.5
† Electronic supplementary information (ESI) available: characterization of
2b, 2c, 4, 6, 7, 8 and 9, and a typical procedure for Pd-catalyzed allylic
alkylation. See http://www.rsc.org/suppdata/cc/b1/b102693n/
1290
Chem. Commun., 2001, 1290–1291
This journal is © The Royal Society of Chemistry 2001
DOI: 10.1039/b102693n

The planar chiral P,N-ligands 9 were synthesized from 5
[eqn. (4)].
Notes and references
6
‡ Compounds (h -C10H8)Mn(CO)3]BF4, 1 and 5 were synthesized as
previously described.4a,13,14
Synthesis of 2a: a Schlenk flask containing 0.50 g of molecular sieves was
6
flame-dried. After the flask was cooled to r.t., 1a (0.35 g, 1.06 mmol), [(h -
C10H8)Mn(CO)3]BF4 (0.40 g, 1.13 mmol), and 15 mL of CH2Cl2 were
added to the flask. The resulting solution was heated at reflux for 18 h. After
the solution was cooled to r.t., the solution was filtered over a pad of Celite.
The filtrate was evaporated to dryness and chromatographed on a silica gel
column eluting with hexane and diethyl ether (10+1 v/v). Removal of the
solvent gave 2a (oil, 46%, 0.17 g). IR n(CO) 2012, 1920 cm21; dH(300
MHz, d6-benzene, TMS) 5.21 (br s, 1 H), 5.03 (br s, 1 H), 4.15 (br s, 1 H),
4.07 (dd, 3.7, 11.0 Hz, 1 H), 3.85 (m, 1 H), 3.60 (m, 2 H), 3.56 (m, 1 H), 3.55
(s, 3 H), 2.05 (s. 3 H), 1.87 (m, 1 H), 1.26 (d, 13.0 Hz, 1 H); dC(75 MHz,
d6-benzene) 225.7, 102.8, 99.5, 96.4, 82.6, 81.1, 79.8, 76.1, 75.3, 66.6, 59.1,
28.0, 12.1; HRMS calc. for C15H16MnO6: m/z 349.0484; obs: 349.0483.
[a]2D1 = 236 (c 0.42 in CH2Cl2).
(4)
Ligand transfer reaction of 5 afforded 6 in 74% yield.
Deprotonation of 6 followed by the addition of PPh2Cl and
subsequent reaction with acid gave 8 in 75% yield. The
condensation reaction of 8 with tert-butyl amine gave a P,N-
ligand 9a in 96% yield. The de of 7 prepared from 6 was 75%.
However, after recrystallization, the de of 7 was > 99.5%.
The palladium-catalyzed asymmetric allylic alkylation of
rac-1,3-diphenylprop-2-en-1-yl acetate with dimethyl malonate
was successfully carried out [eqn. (5)].
1 A. Z. Rubezhov and S. P. Gubin, Adv. Organomet. Chem., 1972, 10,
347; A. Efraty, J. Organomet. Chem., 1973, 57, 1; P. E. Garrou, Adv.
Organomet. Chem., 1984, 23, 95.
2 S. Top, C. Lescop, J.-S. Lehm and G. Jaouen, J. Organomet. Chem.,
2000, 593–594, 167; R. L. Halterman, Chem. Rev., 1992, 92, 965.
3 T. W. Spradau and J. A. Katzenellenbogen, Organometallics, 1998, 17,
2009; M. Wenzel, J. Labelled Compd. Radiopharm., 1992, 31, 641.
4 (a) S. Sun, L. K. Yeung, D. A. Sweigart, T.-Y. Lee, S. S. Lee, Y. K.
Chung, S. R. Switzer and R. D. Pike, Organometallics, 1995, 14, 2613;
(b) J. E. Kim, J. S. U. Son, S. S. Lee and Y. K. Chung, Inorg. Chim. Acta,
1998, 281, 229; (c) I. S. Lee, H. M. Seo and Y. K. Chung,
Organometallics, 1999, 18, 1091.
(5)
5 S. Kudis and G. Helmchen, Angew. Chem., Int. Ed., 1998, 37, 3047.
6 A. J. Birch, W. D. Raverty and G. R. Stephenson, Tetraheron Lett.,
1980, 197.
7 V. I. Sokolov, Chirality and Optical Activity of Organometallics
Compounds, Gordon and Breach, New York, 1990; A. Togni,
Metallocenes, ed. A. Togni and R. L. Halterman, Wiley-VCH:
Weinheim, Germany, 1998, vol. 2.
8 E. J. Watson, K. L. Virkaitis, H. Li, A. J. Nowak, J. S. D’Acchioli, K.
Yu, G. B. Carpenter, Y. K. Chung and D. A. Sweigart, Chem. Commun.,
2001, 457.
9 G. E. Herberich, U. Englert, F. Marken and P. Hofmann, Organome-
tallics, 1993, 12, 4039.
10 N. M. Loim, M. A. Kondratenkp and V. I. Sokolov, J. Org. Chem., 1994,
59, 7485; Y. Yamazaki, J. Chromatogr., 1991, 542, 129.
11 Crystal data: for 4: monoclinic, space group P21; a = 8.0816(7), b =
15.0390(4), c = 10.9049(9) Å, b = 90.422(3)°, V = 1325.34(16) Å3,
Z = 2, Dc = 1.334 Mg m23; 210 < h < 10, 217 < k < 17, 214 < l < 13,
R1 = 0.0379, wR2 = 0.10791. For 7: orthorhombic, space group
P212121; a = 7.6659(2), b = 17.7774(8), c = 18.6479(10) Å; V =
2541.33(19) Å3, Z = 4; Dc = 1.355 Mg m23; 29 < h < 9, 223 < k < 22,
224 < l < 24; R1 = 0.0526, wR2 = 0.1398. CCDC reference numbers
157495 and 157496. See http://www.rsc.org/suppdata/cc/b1/b102693n/
for crystallographic data in CIF or other electronic format.
12 M. Uemura, R. Miyake and Y. Hayashi, J. Chem. Soc., Chem. Commun.,
1991, 1696; S. B. Heaton and G. B. Jones, Tetrahedron Lett., 1993, 33,
1693; Y. Hayashi, H. Sakai, N. Kaneta and M. Uemura, J. Organomet.
Chem., 1995, 503, 143; H.-Y. Jang, H. Seo, J. W. Han and Y. K. Chung,
Tetrahedron Lett., 2000, 41, 5083; C. Bolm and K. Muniz, Chem. Soc.
Rev., 1999, 28, 51.
Reaction of rac-1,3-diphenylprop-2-en-1-yl acetate with
dimethyl malonate in the presence of 1 mol% Pd catalyst at 15
°C for 4 h gave the allylic alkylation product methyl-
2-carbomethoxy-3,5-diphenylpent-4-enolate in high yields and
high ee values (95% yield and 89% ee in CH2Cl2; 96% yield and
92% ee in DMSO). Lowering the reaction temperature to
220 °C in CH2Cl2 led to an increase of the ee value to 94% with
a 74% yield.
In conclusion, we have conducted the first demonstration that
a planar chiral ligand transfer reaction can be carried out by the
reaction of [(naphthalene)Mn(CO)3]BF4 with planar chiral
ferrocene derivatives and we have shown that the P,N-ligand
prepared in this study can be employed in palladium-catalyzed
asymmetric allylic alkylation.
13 O. Riant, O. Samuel, T. Flessner, S. Tandien and H. Kagan, J. Org.
Chem., 1997, 62, 6733.
14 G. Hftime, J.-C. Daran, E. Manoury and G. G. A. Balavoine,
J. Organomet. Chem., 1998, 565, 115.
Fig. 1 X-Ray structure of 4.
Chem. Commun., 2001, 1290–1291
1291