8458
F.-X. Chen et al. / Tetrahedron Letters 48 (2007) 8456–8459
(
Table 2, entry 1). It is noteworthy that both yield and
Extension of this procedure to other reactions is under-
way in this laboratory.
enantioselectivity for compound 5l (Table 2, entry 11)
are fairly low. A possible explanation for this observa-
tion might be due to the exchange of the sodium ion
between the phenolic catalyst 2b and the unprotected
para-hydroxy nitrostyrene. Isopropyl malonate ester
also has a moderate enantioselectivty though obtained
in low yield possibly due to steric hindrance (Table 2,
entry 17), but the benzyl malonate ester has a good yield
and moderate enantioselectivity (Table 2, entry 18).
Compared with the previously reported catalytic proce-
Acknowledgments
This work was supported by the grants from the
National Natural Science Foundation of China (Nos.
2
0525206, 20472026 and 20621091) and Chang Jiang
Scholar Program of the Ministry of Education of China.
5
dures, the yield and enantioselectivity are similar. How-
Supplementary data
ever, the unique features of the current system such as
transition metal-free, low catalyst loading, and the aque-
ous reaction media make this procedure more attractive.
Taking advantage of the big difference in solubility
between sodium demethylquinine salt and the products
in water, recycling of the catalyst can be easily accom-
plished. Thus, after the first reaction was completed as
monitored by TLC, the reaction mixture was extracted
References and notes
1
. (a) Berner, O. M.; Tedeschi, L.; Enders, D. Eur. J. Org.
Chem. 2002, 1877; (b) Ono, N. Nitro Group in Organic
Synthesis; Wiley-VCH: New York, 2001; (c) Okino, T.;
Hoashi, Y.; Takemoto, Y. J. Am. Chem. Soc. 2003, 125,
by PE/Et O several times until the product was com-
2
pletely removed. Then the substrates were added to
the aqueous phase containing the catalyst and stirred
vigorously to conduct the reaction again. In the case
of 5 mol % catalyst loading this recycling could be
repeated seven times without loss in enantioselectivity,
while the yield was slightly decreased (Table 3). Com-
1
2672; (d) Okino, T.; Hoashi, Y.; Furukawa, T.; Xu, X.;
Takemoto, Y. J. Am. Chem. Soc. 2005, 127, 119.
2
. The function group transferred from Nitro group, see (a)
Pinnick, H. W. Org. React. 1990, 38, 655; (b) Tamura, R.;
Kamimura, A.; Ono, N. Synthesis 1991, 423; (c) Poupart,
M. A.; Fazal, G.; Goulet, S.; Mar, L. T. J. Org. Chem.
8
pared with the polymer-supported catalysts, this sepa-
ration process through solvent extraction is much
more convenient and economical. When the tertiary
amine of demethylquinine salt 2b was alkylated with a
1
999, 64, 1356; (d) Kamlet, M. J.; Kaplan, L. A.; Dacons, J.
C. J. Org. Chem. 1961, 26, 4371; (e); (e) Mukayama, T.;
Hoshino, T. J. Am. Chem. Soc. 1960, 82, 5339.
9
benzyl group to form a kind of PTC catalyst, the result-
3. (a) Johnson, T. A.; Jang, D. O.; Slafer, B. W.; Curtis, M.
D.; Beak, P. J. Am. Chem. Soc. 2002, 124, 11689; (b)
Sch a¨ fer, H.; Seebach, D. Tetrahedron 1995, 51, 2305.
ing quaternary ammonium salt provided poor enantio-
selectivity though in high yield.
4
. (a) Kobayashi, N.; Iwai, K. J. Org. Chem. 1981, 46, 1823;
b) Luchaco-Cullis, C. A.; Hoveyda, A. H. J. Am. Chem.
(
In conclusion, soluble demethylquinine salt 2b has been
shown as a kind of efficient novel catalyst for asymmet-
ric Michael addition of malonate to nitroalkenes in
water. The environmental friendly solvent and simple
recycling procedure make this protocol attractive.
Soc. 2002, 124, 8192; (c) Alexakis, A.; Benhaim, C.; Rosset,
S.; Humam, M. J. Am. Chem. Soc. 2002, 124, 5262; (d) Ji,
J.; Barnes, D. M.; Zhang, J. S.; King, A.; Wittemberg, S. J.;
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a
Table 3. Recycling of 2b under 5 mol %
NO2
CO Et
2
5
. Michael addition catalyzed by organocatalyst, see (a)
Albrecht, B.; Harald, G. Asymmetric Organocatalysis—
From Biomimetic Concepts to Applications in Asymmetric
Synthesis; Wiley-VCH: New York, 2005; (b) List, B.;
Pojarliev, P.; Martin, H. J. Org. Lett. 2001, 3, 2423; (c)
Hayashi, Y.; Gotoh, T.; Hayasji, T.; Shoji, M. Angew.
Chem., Int. Ed. 2005, 44, 4212; (d) Ender, D.; Seki, A.
Synlett 2002, 26; (e) Mase, N.; Thayumanavan, R.; Tanaka,
F.; Barbas, C. F.; III. Org. Lett. 2004, 6, 2527; (f) Wang,
W.; Wang, J.; Li, H. Angew. Chem., Int. Ed. 2005, 43, 1369;
EtO C
NO2
2
2
b
EtO C
CO Et
2
2
+
H O, RT
2
4
b
3
5
p
Entry
Recycle time
Yield (%)
ee (%)
1
2
3
4
5
6
7
8
0
1
2
3
4
5
6
7
94
89
87
89
85
79
77
74
89
89
90
88
85
87
88
76
(
g) Kotrusz, P.; Toma, S.; Schmalz, H. S.; Adler, A. Eur. J.
Org. Chem. 2005, 1577; (h) Schreiner, P. R. Chem. Soc. Rev.
003, 32, 289; (i) Sigman, M. S.; Jacobsen, E. N. J. Am.
2
Chem. Soc. 1998, 120, 4901; (j) Berkessel, A.; Cleemann, F.;
Mukherjee, S.; M u¨ ller, T. N.; Lex, J. Angew. Chem., Int.
Ed. 2005, 44, 807; (k) Huang, H. B.; Jacobsen, E. N. J. Am.
Chem. Soc. 2006, 128, 7170; (l) Pansare, S. V.; Pandya, K.
J. Am. Chem. Soc. 2006, 128, 9624; (m) Andrey, O.;
Alexakis, A.; Bernardinelli, G. R. Org. Lett. 2003, 5, 2559;
a
The reaction was carried out with 1 equiv of 3 and 2.5 equiv of 4b in
the presence of 5 mol % of catalyst at room temperature on a scale of
.4 mmol of 3. All reactions were run for 10 h.
0