3,3′-Br2-BINOL-Zn complex: A highly efficient catalyst for the enantioselective hetero-Diels-Alder reaction

Article abstract of DOI:10.1021/ol027034r

(equation presented) A BINOLate-zinc complex prepared in situ from Et₂Zn and 3,3′-dibromo-1,1′-bi-2-naphthol (3,3′-Br₂-BINOL) was found to be a highly efficient catalyst for the enantioselective hetero-Diels-Alder reaction of Danishe

Full text of DOI:10.1021/ol027034r

ORGANIC
LETTERS
2
002
Vol. 4, No. 24
349-4352
3
,3′-Br -BINOL-Zn Complex: A Highly
2
4
Efficient Catalyst for the
Enantioselective Hetero-Diels−Alder
Reaction
Haifeng Du, Jiang Long, Jieyu Hu, Xin Li, and Kuiling Ding*
State Key Laboratory of Organometallic Chemistry, Shanghai Institute of Organic
Chemistry, Chinese Academy of Sciences, 354 Fenglin Road,
Shanghai 200032, The People’s Republic of China
kding@pub.sioc.ac.cn
Received October 5, 2002
ABSTRACT
A BINOLate-zinc complex prepared in situ from Et
catalyst for the enantioselective hetero-Diels−Alder reaction of Danishefsky’s diene and aldehydes to give 2-substituted 2,3-dihydro-4H-pyran-
-one in up to quantitative yield and 98% ee.
2 2
Zn and 3,3′-dibromo-1,1′-bi-2-naphthol (3,3′-Br -BINOL) was found to be a highly efficient
4
A catalytic asymmetric hetero-Diels-Alder (HDA) reaction
between Danishefsky’s diene and aldehydes provides a
powerful approach for achieving optically active 2-substituted
ZnCl
transition and lanthanide metal complexes, and so on, have
,4 various chiral Lewis acids, such as aluminum, boron,
2
5
-12
been employed for this type of reaction.
However, the
2
,3-dihydro-4H-pyran-4-one, a type of heterocycle with
use of chiral zinc catalysts for this reaction has been less
successful although the chiral zinc alkoxide 1 and phenoxide
2 have been recently reported to be efficient catalysts for
extensive synthetic applications in natural or unnatural
products. Since the first HDA reaction of Danishefsky’s
diene and aldehydes was achieved with the catalysis of
1
-3
1
3,14
direct asymmetric aldol-type reactions.
The Lewis acid
3
obtained from diethylzinc and 1,1′-bi-2-naphthol (BINOL)
(1) (a) Noyori, R. Asymmetric Catalysis in Organic Synthesis; Wiley-
Interscience: New York, 1994. (b) Catalysis Asymmetric Synthesis, 2nd
ed.; Ojima, I., Ed.; Wiley-VCH: New York, 2000. (c) Kagan, H. B.
ComprehensiVe Organic Chemistry; Pergamon: Oxford, UK, 1992; Vol.
(3) (a) Boger, D. L.; Weinreb, S. N. In Hetero Diels-Alder Methodology
in Organic Synthesis; Wasserman, H. H., Ed.; Academic Press: San Diego,
CA, 1987. (b) Tietze, L. F.; Kettschau, G. In StereoselectiVe Heterocyclic
Synthesis I; Metz, P., Ed.; Springer: Berlin, Germany, 1997.
(4) Danishefsky, S.; Kerwin, J. F.; Kobayashi, S. J. Am. Chem. Soc. 1982,
104, 358-360.
8
. (d) ComprehensiVe Asymmetric Catalysis; Jacobsen, E. N., Pfaltz, A.,
Yamamoto, H., Eds.; Springer: Berlin, Germany, 1999; Vols. I-III. (e)
Lewis Acids in Organic Synthesis; Yamamoto, H., Ed.; Wiley-VCH: New
York, 2001.
(2) For reviews see: (a) Danishefsky, S. J.; De Ninno, M. P. Angew.
(5) (a) Maruoka, K.; Itoh, T.; Shirasaka, T.; Yamamoto, H. J. Am. Chem.
Soc. 1988, 110, 310-312. (b) Simonsen, K. B.; Svenstrup, N.; Roberson,
M.; Jorgensen, K. A. Chem. Eur. J. 2000, 6, 123-128.
(6) Corey, E. J.; Cywin, C. L.; Roper, T. D. Tetrahedron Lett. 1992, 33,
6907-6910.
Chem., Int. Ed. Engl. 1987, 26, 15-23. (b) Jorgensen, K. A. Angew. Chem.,
Int. Ed. 2000, 39, 3558-3588. (c) Maruoka, K. In Catalysis Asymmetric
Synthesis, 2nd ed.; Ojima, I., Ed.; Wiley-VCH: New York, 2000; Chapter
8
A.
1
0.1021/ol027034r CCC: $22.00 © 2002 American Chemical Society
Published on Web 11/08/2002

has been reported by Yamamoto to catalyze the enantiose-
15
lective cyclization of unsaturated aldehydes. Very recently,
Renaud reported that Yamamoto’s Zn-BINOL complex was
an efficient catalyst for enantioselective Diels-Alder reaction
of N-alkoxyacrylamides with cyclopentadiene.16 However,
Table 1. Screening of BINOLate-zinc Catalysts for
Enantioselective hetero-Diels-Alder Reaction of Danishefsky’s
Diene 4 and Benzaldehyde 5aa
the employment of a stoichiometric amount of Zn-BINOL
catalyst is required to obtain acceptable enantioselectivity
and reactivity of the reaction. In the present letter, we report
our preliminary results on the highly enantioselective HDA
reaction of Danishefsky’s diene 4 with aldehydes 5 using a
catalytic amount of chiral diol ligand-based zinc Lewis acids.
The first trial by using L1/zinc complex as the catalyst
for the reaction of Danishefsky’s diene 4 and benzaldehyde
5a showed that the reaction proceeded smoothly to give
2-phenyl-2,3-dihydro-4H-pyran-4-one (6a) in good yield and
moderate enantioselectivity (entry 1 in Table 1). This result
prompted us to further improve the enantioselectivity of the
reaction by tuning the steric and electronic modifications on
the diol ligands. Therefore, a series of chiral diol ligands
including commercially available or easily prepared BINOL
derivatives (L2-L12) shown in Scheme 1 were submitted
(7) For BINOL-, H4-BINOL-, and H8-BINOL-Ti catalyzed asymmetric
HDA of Danishefsky’s diene with aldehydes in the presence or absence of
molecular sieves (MS), see: (a) Mikami, K.; Motoyama, Y.; Terada, M. J.
Am. Chem. Soc. 1994, 116, 2812-2820. (b) Keck, G. E.; Li, X. Y.;
Krishnamurthy, D. J. Org. Chem. 1995, 60, 5998-5999. (c) Wang, B.;
Feng, X.; Cui, X.; Liu, H.; Jiang, Y. Chem. Commun. 2000, 1605-1606.
(
1
d) Long, J.; Hu, J.; Shen, X.; Ji, B.; Ding, K. J. Am. Chem. Soc. 2002,
24, 10-11. (e) Yuan, Y.; Long, J.; Li, X.; Sun, J.; Ding, K. Chem. Eur.
J. 2002, 8, 5033-5042. (f) For BINOL-Zr catalyzed asymmetric HDA of
Danishefsky’s diene with aldehydes, see: Yamashita, Y.; Saito, S.; Ishitani,
H.; Kobayashi, S. Org. Lett. 2002, 4, 1221-1223.
to asymmetric catalysis. The details of the results were
summarized in Table 1, which clearly demonstrated that the
enantioselectivity and reactivity of the reaction were sig-
nificantly influenced by both the electronic effect and steric
hindrance of the substituents at 3,3′-positions of BINOL. The
serious steric hindrance of phenyl groups at 3,3′-positions
of BINOL was proved to be disadvantageous for the reaction
(8) (a) Schaus, S. E.; Branalt, J.; Jacobsen, E. N. J. Org. Chem. 1998,
6
3, 403-405. (b) Dossetter, A. G.; Jamison, T. F.; Jacobsen, E. N. Angew.
Chem., Int. Ed. 1999, 38, 2398-2400. (c) Li, L.-S.; Wu, Y.; Hu, Y.-J.;
Xia, L.-J.; Wu, Y.-L. Tetrahedron: Asymmetry 1998, 9, 2271-2277.
(9) Doyle, M. P.; Phillips, I. M.; Hu, W. J. Am. Chem. Soc. 2001, 123,
5
366-5367.
(10) (a) Yao, S.; Johennsen, M.; Audrain, H.; Hazell, R. G.; Jorgensen,
K. A. J. Am. Chem. Soc. 1998, 120, 8599-8605. (b) Jorgensen, K. A.;
Johennsen, M.; Yao, S.; Audrain, H.; Thorhauge, J. Acc. Chem. Res. 1999,
(entries 1 and 2 vs 11 and 12, respectively). Moreover, the
3
2, 605-613. (c) Dalko, P. I.; Moisan, L.; Cossy, J. Angew. Chem., Int.
Ed. 2002, 41, 625-628.
11) (a) Danishefsky, S. J.; Maring, C.; Bednarski, M. Tetrahedron Lett.
983, 24, 3451-3454. (b) Danishefsky, S. J.; Bednarski, M. J. Am. Chem.
Soc. 1983, 105, 6968-6969.
12) (a) Hanamoto, T.; Furuno, H.; Sugimoto, Y.; Inanaga, J. Synlett
absolute configuration of product was significantly influenced
by the substituents in the binaphthyl unit. The steric
hindrance of substituents could switch the asymmetric
induction from the formation of S product to R product
(
1
(
1
997, 79-80. (b) Qian, C.; Wang, L. Tetrahedron Lett. 2000, 41, 2203-
(entries 1-3 vs 4-12). The backbone effect of the binaphthyl
2
206.
moiety was not evident in the cases of L1 and L2 (entry 1
vs 2). Nevertheless, in the asymmetric induction of 3,3′-
substituted BINOL derivatives, partially reduced ligands L8
and L12 are inferior to their parent ligands L6 and L11 in
terms of both enantioselectivity and reactivity (entries 6 and
(
13) (a) Trost, B. M.; Ito, H. J. Am. Chem. Soc. 2000, 122, 12003-
1
2
8
1
2004. (b) Trost, B. M.; Silcoff, E. R.; Ito, H. Org. Lett. 2001, 3, 2497-
500. (c) Trost, B. M.; Yeh, V. S. C. Angew. Chem., Int. Ed. 2002, 41,
61-863. (d) Trost, B. M.; Ito, H.; Silcoff, E. R. J. Am. Chem. Soc. 2001,
23, 3367-3368.
(14) (a) Yoshikawa, N.; Kumagai, N.; Matsunaga, S.; Moll, G.; Ohshima,
T.; Suzuki, T.; Shibasaki, M. J. Am. Chem. Soc. 2001, 123, 2466-2467.
1
1 vs 8 and 12, respectively). We were pleased to find that
(
4
b) Kumagai, N.; Matsunaga, S.; Shibasaki, M. Org. Lett. 2001, 3, 4251-
254.
L6, (R)-3,3′-dibromo-1,1′-bi-2-naphthol (3,3′-Br -BINOL),
2
(15) Sakane, S.; Maruoka, K.; Yamamoto, H. Tetrahedron Lett. 1985,
was particularly efficient for the reaction, affording the
product in up to quantitative yield and 93% ee. Therefore,
2
6, 5536-5538.
(16) Corminboeuf, O.; Renaud, P. Org. Lett. 2002, 4, 1735-1738.
4350
Org. Lett., Vol. 4, No. 24, 2002

Scheme 1. The Chiral Ligands Employed for Asymmetric
Table 2. The Reaction of Danishefsky’s Diene with Aldehydes
Catalyzed by Zn/L6
Catalysis
the correct assembly of substituents and backbone of
binaphthyl is a key point in designing the chiral diol ligand
for the Zn-catalyzed HDA reaction.
The reaction promoted by L6-modified catalyst was further
optimized via decreasing the reaction temperature. The
enantioselectivity of the reaction at -10 and -25 °C could
be improved to 94% and 97%, respectively, with quantitative
yield (entries 13 and 14). When the catalyst loading was
reduced to 5 mol %, the enantioselectivity and yield of the
reaction still remain at a high level (entry 15). In our previous
on the basis of the observed unusual nonlinear effect.17 It is
obvious that the catalytic system showed both weak positive
and strong negative nonlinear effects (Figure 1). The most
interesting is that the absolute configuration of the product
was switched to S from R when the enantiomeric excesses
of partially resolved (R)- L6 were decreased to <40%, which
demonstrated the changes of active species with the decrease
of ee of the chiral ligand. The investigation of the solvent
effect showed that the reactions carried out in THF and
diethyl ether with the catalysis of (R)-L6/Zn gave the product
in the R configuration (51% and 46% ee, respectively). On
the contrary, the reactions run in dichloromethane and hexane
resulted in the product in the S configuration (28% and 7%
ee, respectively). It can be deduced that the system does not
obey Noyori’s monomer-dimer model for diethylzinc ad-
dition to aldehydes catalyzed by amino alcohols. According
4 8
work on H -BINOL- and H -BINOL-Ti complexes-catalyzed
HDA reactions, the solvent-free condition was found to be
7d
critical for reducing the catalyst loading. Therefore, 1 mol
of Zn/L6 was submitted to the reaction in the absence of
%
solvent. Unfortunately the ee (10%) of the product dropped
significantly even though the yield of product could be up
to >99%, which clearly demonstrated the importance of the
solvent effect on the reaction.
Under the optimized conditions, the reactions of a variety
of aldehydes, including aromatic, olefinic, and aliphatic
derivatives, were carried out under the catalysis of Zn/L6.
As shown in Table 2, the catalyst was highly efficient for
the reaction of aromatic aldehydes to give their corresponding
17b
to Kagan’s ML -type model, if a catalytic system processes
n
a negative nonlinear effect, the yields for the runs using a
low-ee ligand would be higher than that using an enantiopure
ligand because the heterochiral complex must necessarily
RS RR
2-substituted 2,3-dihydro-4H-pyran-4-ones in 82-99% yields
with 89-98% ee. The enantioselectivities for the reactions
of olefinic and aliphatic aldehydes could be moderate to
good, but the yields were found to be relatively lower than
those of aromatic aldehydes. The simplicity of the Zn/3,3′-
Br -BINOL experimental procedure makes it very attractive
2
from a synthetic point of view.
exhibit a higher rate (k /k > 1). In fact, the yields of the
(
17) For comprehensive reviews on NLE in asymmetric catalysis, see:
(
a) Fenwick, D. R.; Kagan H. B. In Topics in Stereochemistry; Denmark,
S. E., Ed.; John Wiley & Sons: New York, 1999; Vol. 22, pp 257-296.
(b) Girard, C.; Kagan, H. B. Angew. Chem., Int. Ed. 1998, 37, 2922-2959.
(c) Bolm, C. In AdVanced Asymmetric Catalysis; Stephenson, G. R., Ed.;
Chapman & Hall: London, UK, 1996; pp 9-26. (d) Heller, D.; Drexler,
H.-J.; Fischer, C.; Buschmann, H.; Baumann, W.; Heller, B. Angew. Chem.,
Int. Ed. 2000, 39, 495-499. (e) Kitamura, M.; Suga, S.; Niwa, M.; Noyori,
R. J. Am. Chem. Soc. 1995, 117, 4832-4842. (f) Blackmond, D. G. J. Am.
Chem. Soc. 1998, 120, 13349-13353.
Although the detailed reaction mechanism remains un-
known, it can be deduced that there may be a variety of
aggregated catalyst species involved in the catalytic system
Org. Lett., Vol. 4, No. 24, 2002
4351

particular model and the change of the catalytic species may
occur during the course of the reaction with a nonenantiopure
1
7f
catalyst. Further insight into the reaction mechanism and
research on the application of this type of catalyst in other
asymmetric reactions are underway in this laboratory.
In conclusion, a highly efficient enantioselective zinc
binaphthoxide-catalyzed hetero-Diels-Alder reaction of
Danishefsky’s diene with aldehydes has been developed.
Under the optimized conditions, up to a quantitative yield
and 98% ee of the products were achieved with the catalysis
2
of 10 mol % of Zn/3,3′-Br -BINOL.
Acknowledgment. Financial support from the National
Natural Science Foundation of China, Chinese Academy of
Sciences, the Major Basic Research Development Program
of China, and the Ministry of Science and Technology
Commission of Shanghai Municipality is gratefully acknowl-
edged.
Figure 1. Enantioselectivity for the reaction of 4 with 5a catalyzed
by the zinc complexes of partially resolved (R)-L6. The broken
line indicates the expected values when the reactivity difference
between Zn/(R)-L6 and Zn/(S)-L6 was not considered.
Supporting Information Available: Experimental details
and spectral data for 5a-l and the data from the search for
NLE and the solvent effect in the reaction system. This
material is available free of charge via the Internet at
http://pubs.acs.org.
reactions dropped with the decrease of enantiomeric excesses
of (R)-L6. Therefore, the ML -type model is not applicable
n
to the present catalytic system either. All these facts show
that the present catalytic system may not behave in one
OL027034R
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Org. Lett., Vol. 4, No. 24, 2002