Organic Letters
ORCID
Letter
Shibasaki, M. Angew. Chem., Int. Ed. 2015, 54, 6236. (f) Arteaga, F. A.;
Liu, Z.; Brewitz, L.; Chen, J.; Sun, B.; Kumagai, N.; Shibasaki, M. Org.
Lett. 2016, 18, 2391.
(
10) (a) Shibasaki, M.; Yoshikawa, N. Chem. Rev. 2002, 102, 2187.
(b) Kanai, M.; Kato, N.; Ichikawa, E.; Shibasaki, M. Synlett 2005, 1491.
(c) Yamamoto, H.; Futatsugi, K. Angew. Chem., Int. Ed. 2005, 44, 1924.
(d) Paull, D. H.; Abraham, C. J.; Scerba, M. T.; Alden-Danforth, E.;
Notes
The authors declare no competing financial interest.
Lectka, T. Acc. Chem. Res. 2008, 41, 655. (e) Yamamoto, H.; Ishihara,
K. Acid Catalysis in Modern Organic Synthesis; Wiley-VCH: Weinheim,
Germany, 2008. (f) Kumagai, N.; Shibasaki, M. Angew. Chem., Int. Ed.
ACKNOWLEDGMENTS
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This work was financially supported by JST ACT-C and JSPS
KAKENHI (25713002, JP16H01043). Dr. Tomoyuki Kimura
at the Institute of Microbial Chemistry is gratefully acknowl-
edged for technical assistance with X-ray crystallographic
analysis of 4a.
2
011, 50, 4760. (g) Peters, R. Cooperative Catalysis; Wiley-VCH:
Weinheim, Germany, 2015.
11) Trost, B. M.; Li, C.-J. Modern Alkyne Chemistry: Catalytic and
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Atom-Economic Transformations; Wiley: Hoboken, NJ, 2014.
(12) (a) Tsuda, T.; Yazawa, T.; Watanabe, K.; Fujii, T.; Saegusa, T. J.
Org. Chem. 1981, 46, 192. (b) Meyer, E. M.; Gambarotta, S.; Floriani,
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(13) The conjugate base of 9 is more basic than that of common
phenol derivatives because of the electron-donating groups on the
aromatic ring. The Cu(I) phenoxide of 9 would be formed in the
catalytic cycle and sufficiently basic to promote enolization.
(
(14) Unfortunately, 7-azaindoline amides bearing longer alkyl chains
(
at the α-position failed in the reaction, which is the subject of future
study.
(15) The reaction with octanal proceeded in a highly enantioselective
(
manner, albeit with low conversion and diastereoselectivity. Con-
(
ditions: 10 mol% [Cu(CH CN) ]/L6/Li salt of 9, DMF, −40 °C, 18
3
4
h; 14% yield, dr 63:37, 98% ee (major diastereomer).
(16) The use of 9 gave no beneficial effect for the reactions of
aromatic aldehydes 3.
(
d) Trost, B. M.; Ito, H. J. Am. Chem. Soc. 2000, 122, 12003.
(
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̊
Stereoselective Synthesis; Molander, G. A., Ed.; Thieme: Stuttgart,
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(
6) For direct catalytic asymmetric aldol(-type) reactions using aldol
donors in the carboxylic acid oxidation state without electron-
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Kanai, M.; Shibasaki, M. Org. Lett. 2005, 7, 3757. Activated amides:
(
b) Saito, S.; Kobayashi, S. J. Am. Chem. Soc. 2006, 128, 8704−8705.
β,γ-Unsaturated esters: Yamaguchi, A.; Matsunaga, S.; Shibasaki, M. J.
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Takimoto, G.; Sugimura, T. J. Am. Chem. Soc. 2010, 132, 6286.
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2
2
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Am. Chem. Soc. 2003, 125, 8706.
(
7) There are numerous examples of direct aldol reactions using aldol
donors bearing electron-withdrawing α-substituents that are readily
enolized under mild basic conditions. For a pioneering study using α-
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(
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(
(
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D
Org. Lett. XXXX, XXX, XXX−XXX