C O MMU N I C A T I O N S
Scheme 1. Absolute Configuration Determination by
Barbas, C. F., III. J. Org. Chem. 2003, 68, 9624. (i) Chowdari, N. S.;
Ramachary, D. B.; Barbas, C. F., III. Synlett 2003, 1906. Other
examples: (j) Northrup, A. B.; MacMillan, D. W. C. J. Am. Chem. Soc.
a
2002, 124, 2458. (k) List, B. J. Am. Chem. Soc. 2002, 124, 5656. (l)
Kumaragurubaran, N.; Juhl, K.; Zhuang, W.; Bøgevig, A.; Jørgensen, K.
A. J. Am. Chem. Soc. 2002, 124, 6254. (m) Bøgevig, A.; Juhl, K.;
Kumaragurubaran, N.; Zhuang, W.; Jørgensen, K. A. Angew. Chem., Int.
Ed. 2002, 41, 1790. (n) Bøgevig, A.; Gothelf, K. V.; Jørgensen, K. A.
Chem.-Eur. J. 2002, 8, 5652. (o) Brown, S. P.; Brochu, M. P.; Sinz, C.
J.; MacMillan, D. W. C. J. Am. Chem. Soc. 2003, 125, 10808. (p)
Ramachary, D. B.; Chowdari, N. S.; Barbas, C. F., III. Synlett 2003, 1910.
a
Conditions: (a) Oxone, K2CO3, acetone, CH2Cl2, H2O, 0 °C; (b)
(
q) Bøgevig, A.; Poulsen, T. B.; Zhuang, W.; Jørgensen, K. A. Synlett
003, 1915. (r) Zhong, G. Angew. Chem., Int. Ed. 2003, 42, 4247. (s)
Bøgevig, A.; Sund e´ n, H.; C o´ rdova, A. Angew. Chem., Int. Ed. 2004, 43,
DIBAH, toluene, -78 °C; (c) cat. KMnO4, NaIO4, Na2CO3, 1,4-dioxane,
H2O, room temperature; (d) diazomethane, ethyl acetate, 0 °C, 46% (four
steps).
2
1
109. (t) Hayashi, Y.; Yamaguchi, J.; Sumiya, T.; Shoji, M. Angew. Chem.,
Int. Ed. 2004, 43, 1112.
(
5) Other recent examples of secondary amine-catalyzed enantioselective
carbon-carbon bond formation. Friedel-Crafts reactions: (a) Paras, N.
A.; MacMillan, D. W. C. J. Am. Chem. Soc. 2001, 123, 4370. (b) Austin,
J. F.; MacMillan, D. W. C. J. Am. Chem. Soc. 2002, 124, 1172. (c) Paras,
N. A.; MacMillan, D. W. C. J. Am. Chem. Soc. 2002, 124, 7894. (d)
Brown, S. P.; Goodwin, N. C.; MacMillan, D. W. C. J. Am. Chem. Soc.
methylester (4). The absolute configuration of 4 was assigned to
be S by optical rotation. The results demonstrate that (R)-â-
aminoketone (3, R ) Ph) was obtained in the reaction catalyzed
by (R)-1d. This procedure also exhibits the synthetic utility of 3 to
construct an R-amino acid moiety.
1
2003, 125, 1192. Michael reactions: (e) Halland, N.; Hazell, R. G.;
Jørgensen, K. A. J. Org. Chem. 2002, 67, 8331. (f) Halland, N.; Aburel,
P. S.; Jørgensen, K. A. Angew. Chem., Int. Ed. 2003, 42, 661. (g) Halland,
N.; Hansen, T.; Jørgensen, K. A. Angew. Chem., Int. Ed. 2003, 42, 4955.
In summary, we communicated that the phosphoric acid deriva-
tives of general structure 1 serve as highly effective catalysts for
the direct addition of acetyl acetone to N-Boc-protected arylimines.
The beneficial effects of the 3,3′-bisaryl substituents of the catalysts
on the enantioselectivity are greatly appreciated, and thus 1d
functions as an excellent catalyst. The Brønsted acid-catalyzed direct
Mannich reactions presented herein provide an attractive way to
construct â-aminoketones under extremely mild conditions. The
stereochemical course of this reaction was established through the
synthesis of Boc-(S)-phenylglycine methylester (4). The transforma-
tion thus demonstrated is applicable to a useful method for the
synthesis of various phenylglycine derivatives. The development
of other Mannich-type reactions catalyzed by phosphoric acids as
Brønsted acid catalysts is underway in our laboratory.
(
h) Halland, N.; Aburel, P. S.; Jørgensen, K. A. Angew. Chem., Int. Ed.
2004, 43, 1272.
(
6) Schreiner, P. R. Chem. Soc. ReV. 2003, 32, 289.
(7) (a) Huang, Y.; Unni, A. K.; Thadani, A. N.; Rawal, V. H. Nature 2003,
4
24, 146. (b) McDougal, N. T.; Schaus, S. E. J. Am. Chem. Soc. 2003,
125, 12094.
(
8) Some other chiral charged Brønsted acid catalysts were reported, see:
Nugent, B. M.; Yoder, R. A.; Johnston, J. N. J. Am. Chem. Soc. 2004,
126, 3418. See also ref 6.
(9) (a) Sigman, M. S.; Jacobsen, E. N. J. Am. Chem. Soc. 1998, 120, 4901.
(b) Vachal, P.; Jacobsen, E. N. Org. Lett. 2000, 2, 867. (c) Sigman, M.
S.; Vachal, P.; Jacobsen, E. N. Angew. Chem., Int. Ed. 2000, 39, 1279.
d) Su, J. T.; Vachal, P.; Jacobsen, E. N. AdV. Synth. Catal. 2001, 343,
97. (e) Vachal, P.; Jacobsen, E. N. J. Am. Chem. Soc. 2002, 124, 10013.
f) Wenzel, A. G.; Lalonde, M. P.; Jacobsen, E. N. Synlett 2003, 1919.
(10) Wenzel, A. G.; Jacobsen, E. N. J. Am. Chem. Soc. 2002, 124, 12964.
(
1
(
(
11) See also: (a) Okino, T.; Hoashi, Y.; Takemoto, Y. J. Am. Chem. Soc.
2
003, 125, 12672. (b) Okino, T.; Nakamura, S.; Furukawa, T.; Takemoto,
Y. Org. Lett. 2004, 6, 625.
Acknowledgment. This work was partially supported by a
Grant-in-Aid for Scientific Research from the Ministry of Education,
Culture, Sports, Science, and Technology, Japan and the Nagase
Science and Technology Foundation. We also acknowledge The
JSPS Research Fellowship for Young Scientists (D.U.) from the
Japan Society for the Promotion of Sciences.
(
12) During the preparation of this manuscript, Akiyama et al. reported similar
phosphoric acid-catalyzed Mannich reactions between N-aryl protected
imines and silyl ketene acetals. Akiyama, T.; Itoh, J.; Yokota, K.; Fuchibe,
K. Angew. Chem., Int. Ed. 2004, 43, 1566.
(13) For an excellent review of catalytic asymmetric direct Mannich reactions,
see: C o´ rdova, A. Acc. Chem. Res. 2004, 37, 102.
(
14) Cu complex-catalyzed similar transformation was reported, see: Marigo,
M.; Kjærsgaard, A.; Juhl, K.; Gathergood, N.; Jørgensen, K. A. Chem.-
Eur. J. 2003, 9, 2359.
Supporting Information Available: Representative experimental
procedure and spectral data for 1d and 3. This material is available
free of charge via the Internet at http://pubs.acs.org.
(15) Metal catalyst-mediated asymmetric direct Mannich reactions, see: (a)
Trost, B. M.; Terrell, L. R. J. Am. Chem. Soc. 2003, 125, 338. (b)
Matsunaga, S.; Kumagai, N.; Harada, S.; Shibasaki, M. J. Am. Chem.
Soc. 2003, 125, 4712. (c) Bernardi, L.; Gothelf, A. S.; Hazell, R. G.;
Jørgensen, K. A. J. Org. Chem. 2003, 68, 2583.
(
a
16) The pK of diethyl phosphate is 1.39. See: Quin, L. D. A Guide to
References
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(
(
(
1) List, B.; Lerner, R. A.; Barbas, C. F., III. J. Am. Chem. Soc. 2000, 122,
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2
1346 and references therein.
2
3) Reviews, see: (a) Dalko, P. I.; Moisan, L. Angew. Chem., Int. Ed. 2001,
(17) Binaphthol monophosphoric acid derivatives have been used as an effective
ligand for transition or rare earth metal catalysis, see: (a) Furuno, H.;
Hayano, T.; Kambara, T.; Sugimoto, Y.; Hanamoto, T.; Tanaka, Y.; Jin,
Y. Z.; Kagawa, T.; Inanaga, J. Tetrahedron 2003, 59, 10509. (b) Davies,
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(
e) Jarvo, E. R.; Miller, S. J. Tetrahedron 2002, 58, 2481. (f) Duthaler,
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(
4) Recent examples of enantioselective organocatalysis via enamine forma-
tion. Aldol reactions: (a) Northrup, A. B.; MacMillan, D. W. C. J. Am.
Chem. Soc. 2002, 124, 6798. (b) Tang, Z.; Jiang, F.; Yu, L.-T.; Cui, X.;
Gong, L.-Z.; Qiao, A.; Jiang, Y.-Z.; Wu, Y.-D. J. Am. Chem. Soc. 2003,
(18) Binaphthol monophosphoric acid derivatives have been used as effective
1
25, 5262. (c) Pidathala, C.; Hoang, L.; Vignola, N.; List, B. Angew.
Chem., Int. Ed. 2003, 42, 2785. (d) Martin, H. J.; List, B. Synlett 2003,
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(19) The results of the reaction in other solvents were as follows: CHCl
3
(98%,
i
1
93% ee), toluene (94%, 86% ee), Pr
2
O (92%, 86% ee), and Et O (97%,
2
W. T.; Martin, H. J. J. Am. Chem. Soc. 2002, 124, 827. (f) Hayashi, Y.;
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Chem., Int. Ed. 2003, 42, 3677. (g) Hayashi, Y.; Tsuboi, W.; Shoji, M.;
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F.; Watanabe, S.-i.; Chowdari, N. S.; Turner, J. M.; Thayumanavan, R.;
88% ee).
(20) Medina, E.; Moyano, A.; Pericas, M. A.; Riera, A. HelV. Chim. Acta 2000,
83, 972.
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J. AM. CHEM. SOC.
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