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Diastereoselective Complexation of Temporarily Chirally Modified Ligands Enantioselective Preparation and Configurational Assignment of Synthetically Valuable 6-Tricarbonylchromium-1-tetralone Derivatives.

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[12] a ) J. L. Kerschner, P. E. Fanwick, I. P. Rothwell, L Am. Chem. Soe. 1987,
109, 5840-5842; b) J. L. Kerschner, I. P. Rothwell, J. C. Huffman, W. E.
Streib. Organornetallies 1988, 7,1871 -1873; c) J. L. Kerschner, P. E. Fanwick, I . P. Rothwell, J. C. Huffman, ibid. 1989, 8, 1431-1438.
[13] M. E. Thompson, S . M. Baxter, A. R. Bulls, B. J. Burger, M. C. Nolan,
B. D. Santarsiero, W. P. Schaefer, J. E. Bercaw, L. Am. Chem. Sor. 1987,
109, 203 -219.
[14] For the metathesis of cis-2-pentene, the stereoselectivity at 0 % conversion
is accurately determined by plotting the tronslcis ratio of 2-butene vs. the
trans/cis ratio of 2-pentene and by extrapolating at truns/cis-2-pentene = 0
(in the case of trans-2-pentene, cisltrans C, is plotted vs. cisjtrans Cs)."51
1151 M. Leconte, J.-M. Basset, J. Am. Chem. Soc. 1979, 101, 7296-7302.
[I61 The catalyst is deactivated by addition of benzaldehyde; palynorbornene
is recovered after addition of THF to the reaction mixture, precipitation
with methanol, filtration, and drying.
[17] Dj. Boutarfa, F. Quignard, M. Leconte, J.-M. Basset, J. G. Hamilton, K. J.
Ivin, J. J. Rooney in Transilion Metal Catalyzed Polymerizations: ZieglerNatta and Metathesis Polymerizations (Ed.: R. P. Quirk), Cambridge University Press, Cambridge, 1988, p. 695.
[18] The 100% head-tail, 100% cis structure of the poly-1-methylnorbornene
obtainedwith IaorIbwasdeducedfrom'Hand "CNMRspectraofthe
13C{1H)NMR (62.8 MHz, CDCI,): 6 = 29.29 (C-X), 33.02
(C-5), 38.14 (C-4), 41.82 (C-6), 44.13 (C-I), 50.02 (C-7), 135.08 (C-3),
139.47 (C-2) (see Scheme 3 for the numbering of the carbon atoms). The
predominantly syndiotactic structure was deduced from the I3C NMR
spectrum of the hydrogenated polymer [19].
[19] J. G. Hamilton, K. J. Ivin, J. J. Rooney, Br. Polym. L 1984, 16, 21-33.
[20] J.-M. Basset. Dj. Boutarfa, E. Custodero, M. Leconte, C. Paillet in Olefin
Metathesis and Polymerization Catalysts (Eds.: Y Imamoglu, B. Zumreoglu-Karan, A. J. Amass), Kluwer Academic Publishers, Dordrecht,
1990, p. 45.
121) Ethyl oleate (Sigma, 99%) was used immediately after the ampules were
opened and the contents purified by passage through a column of activated
alumina.
[22] J. C. Mol, J. Mol. Catal. 1991,65, 145-162.
Me?
'c~(co),
Me
Me
2
1
Scheme 1.
we describe an eficient enantioselective method for the
preparation of 2 and other @-tricarbonylchromium-Itetralone derivatives in defined and selectable absolute configuration.
The heart of our process (Scheme 2) is the diastereoselective c~mplexation[~]
of the tetralol derivatives 4, which are
obtained by enantioselective catalytic reduction of the tetralones 3 according to the method of Corey, Bakshi, and
initially carried out with
Shibata (CBS r e d ~ c t i o n ) .A~ ~study
]
0
_____&
R3
3
7 (7c
t
I
a)
=
2)
c,
a;:
OH
Diastereoselective Complexation of Temporarily
Chirally Modified Ligands: Enantioselective
Preparation and Configurational Assignment of
Synthetically Valuable q6-Tricarbonylchromium1-tetralone Derivatives**
5
R3 Cr(C0)3
OH
By Hans-Giinther Schmalz,* Birgitta Millies, Jan U.: Bats,
and Gerd Diirner
Dedicated to Professor Gerhard Quinkert
on the occasion of his 65th birthday
Chiral transition-metal complexes of achiral x-ligands
offer as synthetic building blocks new strategies for the total
synthesis of biologically active compounds. If under the influence of the chiral metal-complex substructure, new, permanent chirality centers are generated (diastereoselectively),
the competitiveness of such syntheses depends to a large
extent on the accessibility of the starting materials in optically active form. In the course of a project in which we want to
take advantage of the specific reactivity of q6-arenetricarbonylchromium complexes['] for the total synthesis of the
antiinflammatory pseudopterosines['I such as 1, we required
complex 2 (Scheme 1).
The reported techniquesr3] for the preparation of nonracemic q6-tricarbonylchromium complexes of achiral arene
ligands are all based on the resolution of racemic mixtures
(involving high losses) and did not satisfy our criteria. Here
["I
[**I
Dr. H.-G. Schmalz, Dip1.-Chem. B. Millies, Dr. J. W. Bats, Dr. G. Diirner
Institut fur Organische Chemie der Universitat
Niederurseler Hang, D-W-6000 Frankfurt/Main 50 (FRG)
This work was supported by the Fonds der Chemischen Industrie and the
Bundesministerium fur Forschung und Technologie (project 0318801B,
"gezielte Synthese biologisch aktiver Molekiile"). We thank Prof. Dr. G.
Quinkert. Frankfurt, for support.
Anxew. Chem. l n t . Ed. Engl. 31 (1992) No. 5
0 VCH
Scheme 2. Preparation of nonracemic tf'-tricarbonylchromium-l-tetralone
derivatives by a) enantioselective reduction, b) diastereoselective complexation,
and c) reoxidation (for reaction conditions and yields see text and Table 2).
Table 1. Diastereoselective complexation of the alcohols rac-4.
Alcohol
rac-4a
rac4b
racilc
rac-4d
rac-4a
roc-4b
rac-4c
rue-4a
rac-4b
roc-t
rue-4d
Complexation
Method [a]
A
A
A
A
B
B
B
C
C
C
C
Reaction
Time p]
5
5
5
5
30
39
41
50
45
30
21
Ratio [b]
racd: rac-6
>99: 1
>99:1
>99:1
>99:1
90:lO
70: 30
52:48
98:2
99: 1
96:4
93:7
Yield [c]
["/I
91
94
92
94
65
62
28
70
70
86
74
[a] A: [Cr(CO),(naphthalene)] (1.2 equiv), TH F (1.5 equiv), Et,O, 70°C (pressure); B: [Cr(CO),] (1.1 equiv), nBu,O/THF ( l O : l ) , reflux; C: [Cr(CO),]
(1.1 equiv), cat. THF, nBu,O/heptane (1 :l), reflux. [b] Determined by HPLC
analysis of the crude product mixture. [c] Yield of isolated diastereomerically
pure rac-5.
Verlagsgesellschaft mbH, W-6940 Weinheim, 1992
0S70-0833/92j0505-0631$3.50+ .25/0
631
racemic compounds (Table
revealed that the complexation that employ Kiindig's reagent, tricarbonyl(naphtha1ene)chromium (method A),[71always afforded (as antici~ a t e d ) [ ~the
I syn-tetralol complexes rac-5 with excellent
yields and diastereoselectivities. The substantially better accessible reagent [Cr(CO),] gave completely unsatisfactory
results under standard conditions (method B),[4b, in particular in the synthetically relevant case of r a c - 4 ~ . However,
[~]
by changing the solvent mixture (from nBu,O/THF = 10: I
to nBu,O/heptane = 1 :1 ; method C) good yields and selectivities were obtained with [Cr(CO),] as well.
The transformations carried out in the optically active
series are summarized in Table 2.[61Borane reduction of ke-
Table 2. Preparation of the nonracemic complexes 7 (and 2) from the ketones
3 according to Scheme 2.
Ketone
3a
3b
3c
3c
3d
Complexation
Method [a]
Product
A
A
A
C
A
7a
7b
2
2
7d
[MI;'
Yield [b]
["/.I
71
71
70
66
85
ee [CI
(in CHCI,)
[YO]
- 802
92
86
85
85
94
-712
- 805
-818
-400
Fig. I ' Structure Of lo in the "lid
State ["I'
ther the enantioselection of the CBS reduction nor the characteristics of the CD spectra of the ketone complexes are
(significantly) affected by the synthetically valuable methoxy
substituents.
[a]A: [Cr(CO),(naphtbalene)](1.2 equiv), THF (1.5 equiv), Et,O, 70°C (sealed
ampule); C: [Cr(CO),] (1.1 equiv), cat. T HE nBu,O/heptane (l:l), reflux. [b]
Total yield calculated on amount of ketone 3 used. [c] The enantiomeric purity
of the reduction products 4, determined by 'H NMR spectroscopy of the acetates in the presence of d-Eu(hfc), (4a, 4c, and 4d) or d-Pr(hfc), (4b), or by gas
chromatography on a chiral phase (4a and 4b), agreed well (*2%) with the
enantiomeric purities of the ketone complexes determined by 'H NMR spectroscopy in the presence of d-Eu(hfc), (2) or d-Pr(hfc), (7 b and 7d) and/or by
comparison of the chiroptical data with reference values (7a and 2).
tones 3.in the presence of catalyst 9,1s1which is readily accessible from D-proline via the intermediate 8, always lead to
high chemical (97-99%) and optical yields (Table 2) of the
alcohols 4, from which the pure syn-complexes 5 were prepared by complexation and chromatographic separation of
the diastereomers. Finally, oxidation with Ac,O/dimethyl
sulfoxide (DMSO)["] afforded the optically active ketone
complexes 7 (and 2).
Qfi.
OH
H
Ph
Ph
M
Q
P
$
h
O
~
O
M
~
Ph
,B-0
feu
8
E
:::&O
9
cr(Co),
10
Fig. 2. CD spectra (in MeOH) of ketone complexes; left: 2 (85 % ee; -),
ent-2 ( >9 9 % ee; ----); right: 2 (85% ee; J-), 7a (92% ee; -);
(85% ee; ----), and 7d (94% e e ; ....).
and
7b
The complexes 7 and their enantiomers, which are also
accessible through application of the catalyst ent-9 prepared
from L-proline, are expected to serve as valuable building
blocks in synthesis. One might anticipate that further enantiomeric enrichment can be achieved through the crystallization of suitable intermediates.
Experimental Procedure
An X-ray crystal structure analysis[111of the chiral ketal
(Fig. 1) revealed its relative and absolute configuration. Hydrolysis of the ketal function of 10 furnished enantiomerically pure ent-2 (m.p. (decomp.) 176 "C; [a];' 974,
c = 0.097 in CHCI,).
The absolute configuration of 2 and thus also those of the
precursors 4 c and 5 c were thereby established. Circular
dichroism (CD) spectra of the tetralone complexes (Fig. 2)
indicated the configurational uniformity of compounds 2,
7a, 7b, and 7d, which confirmed the earlier assignment for
7 a derived by indirect
Furthermore, the absolute
configuration of the CBS reduction products obtained by
using 9 as catalyst corresponds to expectation.[51Thus, nei-
+
632
0 VCH
Verlagsgesellschufi mbH, W-6940 Weinheim, f992
All reactions were performed in the absence of light under argon in degassed,
dry solvents.
4c: A solution of BH, . Me,S in THF (0.48 M, 13.2 mL) was added dropwise
over 8 h at about 20 "C to 25 mL of a THF solution containing both 2.15 mmol
of 9 (prepared from 546 mg of 8 and 241 mg of nBuB(OH), by heating for 16 h
in 25 mL of toluene in the presence of 4 A molecular sieves and subsequent
removal of the toluene in vacuum) and 2.21 g (10.7 mmol) of 3c. After the
addition of 5 mL of 95% MeOH, all volatile components were removed in
vacuum and the residue was flash-chromatographed with hexane/EtOAc (1 : 1).
Yield: 2.18 g (98%, m.p. 72-74°C).
5c: 4c (1.0 g, 4.8 mmol), [Cr(CO),] (1.28 g, 1.2equiv), nBu,O and n-heptane
(30 mL each), and THF (1 mL) was heated at 150 "C (weak reflux) in an oil bath
for 30 h. Removal of the solvent in vacuum and flash chromatography of the
residue with CH,CI,/EtOAc (15:l) yielded 1.42g (86%) of 5c (m.p. 143145"C, decomp.) and about 0.1 g of a mixture of 6 c and unchanged 4c.
OS70-0833/92/0SOS-O632S
3.50+.28/0
Angew. Chem. Int. Ed. Engl. 31 (1992) No. 5
2:ArnixtureofSc(1.31 g,3.8 mmol)inDMSO(30mL)andAc,O(20mL)was
stirred for 3.5 h at room temperature. The mixture was partitioned between
200 mL of cold 20% NaOH and 300 mL of Et,O under ice cooling, and the
aqueous phase was extracted several times with Et,O. The combined organic
solutions were washed with brine and dried over Na,SO,. Flash chromatography with hexane/CH,Cl,/EtOAc (10: 10: 1 to 5:5:1) afforded 2 (1.01 g, 78 %)as
an orange solid. M.p. 176-178"C, decomp.; [a]EO -818, c = 0.111 in CHCI,;
IR(KBr): i. [cm-'1 = 1959(s), 1896(s), 1869(s), 1682(s), 1437(m), 1287(s);
N-Lithiomethyl-N,N"",N"-tetramethy ldiethylenetriamine: The First Alkyllithium Compound which
is Monomeric in Hydrocarbons
By Gerhard u! Klumpp,* Hendrikus Luitjes, Marius Schakel,
Franciscus J. J de Kanter, Robert R Schmitz
and Nicolaas J. R . van Eikema Hommes
'HNMR(270MHz,CDC1,):6=6.00(s,1H),5.11(s,1H),3.85(s,3H),3.80
(s, 3H), 2.91 (m, l H ) , 2.69 (m, 2H), 2.36 (m, IH), 2.11 (m, 2H); '-'CNMR
(62.9 MHz, CDCI,, additional DEPT): 6 = 21.9(CH2),28.0(CH2), 37.3(CHz),
56.7(CH3), 57.3(CH3), 74.3(CH), 75.5(CH), 87.8, 109.9, 130.5, 135.5, 196.0,
231.3.
Received: December 4, 1991 [Z 5055 IE]
German version: Angew. Chem. 1992, 104, 640
[I] a) J, P. Collman, L. S. Hegedus, J. R. Norton, R. G. Finke, Principles and
Applications of Organotransition Metal Chemistry, University Science
Books, Mill Valley, CA, USA, 1987, Chap. 20; b) V. N. Kalinin, Russ.
Chem. Rev. 1987,56,682-700; c) M. Uemura, H. Nishimura, T. Minami,
Y Hayashi, J. Am. Chem. Soc. 1991, 113, 5402-5410.
[2] a ) S. A. Look, W. Fenical, R. S. Jacobs, J. Clardy, Proc. Natl. Acad. Sci.
USA 1986,83,6238-6240; b) S. A. Look, W. Fenical, G. K. Matsumoto,
J. Clardy, J. Org. Chem. 1986, 51, 5140-5145; c) V. Roussis, 2. Wu, W.
Fenical, S. A. Strobel, G. D. Van Duyne, J. Clardy, ibid. 1990, 55,49164922.
[3] a) A. Solladie-Cavallo in Advances in M e l d o r g a n i c Chemistry, Vol. 1
(Ed.: L. S. Liebeskind), JAI Press, Greenwich, CT, USA, 1989, p. 99133 and references cited therein.; b) K. Schlogel in OrganomelaNics in
Organic Synthesis 2 (Eds.: H. Werner, G. Erker), Springer, Berlin, 1989,
p. 63; c) S. G. Davies, C. L. Goodfellow, Synlett 1989, 59-61; J. Chem.
Soc. Perkin Trans. I . 1989.192-193; d) S. Top, G. Jaouen, C. Baldoli, P.
Del Buttero, S. Maiorana, J Organomet. Chem. 1991,413, 125-135, and
references cited therein.
[4] a) G. Jaouen. A. Meyer, J. Am. Chem. SOC.1975,97,4667-4672; b) S. G.
Davies, C. L. Goodfellow,J. Organornet. Chem. 1988,340,195-201; c) B.
Ohlson, C. Ullenius, S. Jagner, C. Grivet, E. Wenger, E. P. Kundig, ibid.
1989. 365, 243 -267, and references cited therein.; J. Brocard, L. Pelinski,
J. Lebibi, M. Mahmoudi, L. Maciejewski, Tetrahedron, 1989,45,709-720,
and references cited therein.
[5] a) E. J. Corey, R. K. Bakshi, S. Shibata, J. Am. Chem. SOC.1987, f09,
5551 -5553; b) E. J. Corey, R. K. Bakshi, S. Shibata, C. P. Chen., V. K.
Singh, ibid. 1987, 109, 7925-7926; c)T. K. Jones, J. J. Mohan, L. C.
Xavier, T. J. Blacklock, D. J. Mathre, P. Sohar, E. T. Turner Jones, R. A.
Reamer, F. E. Roberts, E. J. J. Grabowski, J. Org. Chem. 1991, 56, 763769. and references cited therein.
[6] All compounds were characterized by the usual spectroscopic methods and
gave correct elemental analyses.
[7] E. P. Kundig, C. Perret, S. Spichiger, G. Bernardinelli, J. Organomet.
Chem. 1985,286, 183-200.
[El C. A. L. Mahaffy, P. L. Pauson, Inorg. Synth. 1979, 19, 154.
[9] A time-resolved study of the reactions by means of HPLC showed that (in
contrast to the complexation of I-indanol [c]) the synlanti ratio (5:6)
decreases continuously during the conversions. This loss of selectivity,
which is attributable to a change of the Cr(CO), group to the opposite n
face. is more pronounced (faster), the more methoxy substituents are
present on the arene ring. In our laboratory the complete diastereoselection described by Davies et al. in [4b] for the complexation of ruc4a under
similar conditions (19 h reaction time, 36% yield) could not be observed.
[lo] S. G. Levine. B. Gopalaknshnan, Tetrahedron Lett. 1982, 23, 12391240.
[I I] X-ray crystal structure analysis of 10: Enraf-Nonius CAD4 diffractometer, Cu,, radiation, 2 0 = 120"; empirical absorption correction based on
scans; structure determination with direct methods (SHELXS 86); the
positions of the C and 0 atoms were determined by difference syntheses,
and the hydrogen atoms in calculated positions were not refined.
C,,H,,CrO, . 0.5EtOAc, trigonal, space group P 3,21, a = b =
11.5377(7). c = 32.438(2) A, V = 3739.6(8) A',
2 = 6, pCalrd
=
1.379 gcm-'; 2159 independent reflections, ofwhich 2104 with I > 0 were
used, R = 0.057, R, = 0.055. The residual density was less than
0.54 eA - 3 . The absolute configuration was deduced from anomalous scattering of the Cr atom (R = 0.095, R, = 0.092 for the enantiomorphic
structure in the space group P 3,21). Further details of the crystal structure
investigation may be obtained from the Fachinformationszentrum Karlsruhe, Gesellschaft fur wissenschaftlich-techniscbe Information mbH. DW-7514 Eggenstein-Leopoldshafen2 (FRG) on quoting the depository
number CSD-55874, the names of the authors, and the journal citation.
[12] Preparation of 10 (m.p. 101 "C; [a:' +160, c = 0.51 in CHCI,): H . G .
Schmalz, B. Milks, unpublished.
+
Angew. Chem. int. Ed. Engl. 3f (1992) No. 5
0 VCH
In hydrocarbon solution alkyllithium compounds usually
exist as tetramers or hexamers.['. Addition of suitable
Lewis bases B (ethers, tertiary amines) converts the hexamers
into Lewis-base complexes with a tetrameric alkyllithium
unit [R4Li4]. n B (n = 1-4)[']. Further dissociation into
dimer complexes [R,Li,] . 4 B is observed only at very low
temperatures in THF, and even trace amounts of hydrocarbons suffice to prevent it.[31By contrast, the presence of
polydentate Lewis bases such as N,N,N',N'-tetramethylethylenediamine (TMEDA), which corresponds to two
bases B,[31or N ,N,N',N",N"-pentamethyldiethylenetriamine
(PMDTA), which corresponds to three bases B,l4] is advantageous. If the organic groups contained in the aggregates
are bulky (R = tert-butyl, neopentyl), the aforementioned
favorable conditions even allow the formation of complexed
monomers [RLi] . 3 B, and dimers [R,Li,] . 4 B are formed
in ether.14].
Due to the chelate effect, intramolecular Lewis-base
groups lead to particularly stable complexes. Hence, we have
synthesized secondary alkyllithium compounds containing
two Lewis-base units. In hydrocarbon solution at room temperature, they exist exclusively as dimers.['] We have now
observed that N-lithiomethyl-N,N',N",N"-tetramethyldiethylenetriamine (l),recently prepared by usL6]and containing three Lewis-base groups, is monomeric in hydrocarbon solutions at about 5 "C. As far as we know, this is unprecedented for an alkyllithium compound. Cryoscopy of
solutions of crystals of 1['] in benzene yielded a value of 1.06
for the degree of aggregation. At 195 K, 6Li NMR spectra of
solutions of crystalline 1 (6Li-labeled) in pentane exhibit signals at 6 = 1.75 (species A) and 1.35 (species B)[**I in an
intensity ratio of 1.27: I which coalesce, regardless of the
concentration of 1, at 227.7 K (36.80 MHz) and 232.2 K
(58.88 MHz), respectively.[*I 1 :1 :I-Triplets at 6 = 51 .O and
52.9 ['J('3C,6Li) = 13.9 Hz] could be recognized in the
100.61 MHz I3C NMR spectrum at 225 K, proving that A
and B are monomers whose CI carbon atoms bind to a single
lithium atom.r9] At low temperatures, other signals in the
C,H-decoupled 13C NMR spectra['" and in the 'H NMR
spectra" 'I of pentane solutions of 1, also indicate the presence of two species in the above ratio. At higher temperatures the signal patterns attributable to (stereo)isomers and
diastereotopicity coalesced, and finally the spectra corre[*] Prof. Dr. F. W. Klumpp, Drs.-Ing. H. Luitjes, Dr. M. Schakel, Dr. F. J. J.
de Kanter, R. F. Schmitz
Scheikundig Laboratorium, Vrije Universiteit
De Boelelaan 1083, NL-1081 HV Amsterdam (The Netherlands)
Dr. N. J. R. van Eikema Hommes
Institut fur Organische Chemie der Universitit Erlangen-Nurnberg
[**I In the following text the experimentally observed species A and B are
distinguished from the calculated structures 1 a and 1b.
Verlagsgesellschaft mbH. W-6940 Weinheim, 1992
0570-0833192/050S-O633$3.50+ ,2510
633
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complexation, enantioselectivity, chirally, temporarily, synthetically, derivatives, ligand, tetralone, preparation, diastereoselective, configuration, modified, tricarbonylchromium, assignments, valuable
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