Organic Letters
Letter
Hultzsch, K. C.; Yus, M.; Foubelo, F.; Tada, M. Chem. Rev. 2008, 108,
3795. (c) Nugent, T. C.; El-Shazly, M. Adv. Synth. Catal. 2010, 352,
753. (d) Collet, F.; Lescot, C.; Dauban, P. Chem. Soc. Rev. 2011, 40,
1926.
Scheme 5. Two Possible Paths for the Asymmetric Transfer
Hydrogenation
(3) For recent reviews, see: (a) Tang, W.; Zhang, X. Chem. Rev. 2003,
103, 3029. (b) Xie, J. H.; Zhu, S. F.; Zhou, Q. L. Chem. Soc. Rev. 2012,
41, 4126. (c) Bartoszewicz, A.; Ahlsten, N.; Martín-Matute, B.
Chem.Eur. J. 2013, 19, 7274. (d) Xie, J.; Zhou, Q. Acta Chim.
Sinica 2012, 70, 1427.
(4) For recent reviews, see: (a) Zhou, Y.-G. Acc. Chem. Res. 2007, 40,
1357. (b) Wang, D.-S.; Chen, Q.-A.; Lu, S.-M.; Zhou, Y.-G. Chem. Rev.
2012, 112, 2557. (c) Glorius, F. Org. Biomol. Chem. 2005, 3, 4171.
(d) Kuwano, R. Heterocycles 2008, 76, 909. (e) Fleury-Breg
́
eot, N.; de
la Fuente, V.; Castillon, S.; Claver, C. ChemCatChem 2010, 2, 1346.
́
(f) Chen, Q.-A.; Ye, Z.-S.; Duan, Y.; Zhou, Y.-G. Chem. Soc. Rev. 2013,
42, 497.
Scheme 6. Isotopic Labeling Experiment
(5) For representative reports on asymmetric hydrogenation of
quinolines and 1,10-phenanthrolines, see: (a) Wang, W.-B.; Lu, S.-M.;
Yang, P.-Y.; Han, X.-W.; Zhou, Y.-G. J. Am. Chem. Soc. 2003, 125,
10536. (b) Rueping, M.; Antonchick, A. P.; Theissmann, T. Angew.
Chem., Int. Ed. 2006, 45, 3683. (c) Guo, Q.-S.; Du, D.-M.; Xu, J.
Angew. Chem., Int. Ed. 2008, 47, 759. (d) Zhou, H.; Li, Z.; Wang, Z.;
Wang, T.; Xu, L.; He, Y.; Fan, Q.-H.; Pan, J.; Gu, L.; Chan, A. S. C.
Angew. Chem., Int. Ed. 2008, 47, 8464. (e) Wang, C.; Li, C.; Wu, X.;
Pettman, A.; Xiao, J. Angew. Chem., Int. Ed. 2009, 48, 6524. (f) Wang,
T.; Zhuo, L.-G.; Li, Z.; Chen, F.; Ding, Z.; He, Y.; Fan, Q.-H.; Xiang,
J.; Yu, Z.-X.; Chan, A. S. C. J. Am. Chem. Soc. 2011, 133, 9878.
(g) Chen, Q.-A.; Gao, K.; Duan, Y.; Ye, Z.-S.; Shi, L.; Yang, Y.; Zhou,
Y.-G. J. Am. Chem. Soc. 2012, 134, 2442. (h) Tu, X.-F.; Gong, L.-Z.
Angew. Chem., Int. Ed. 2012, 51, 11346. (i) Wang, T.; Chen, F.; Qin, J.;
He, Y.-M.; Fan, Q.-H. Angew. Chem., Int. Ed. 2013, 52, 7172.
(6) For representative reports on asymmetric hydrogenation of
pyridines and isoquinolines, see: (a) Glorius, F.; Spielkamp, N.; Holle,
S.; Goddard, R.; Lehmann, C. W. Angew. Chem., Int. Ed. 2004, 43,
2850. (b) Legault, C. Y.; Charette, A. B. J. Am. Chem. Soc. 2005, 127,
8966. (c) Lu, S.-M.; Wang, Y.-Q.; Han, X.-W.; Zhou, Y.-G. Angew.
Chem., Int. Ed. 2006, 45, 2260. (d) Rueping, M.; Antonchick, A. P.
Angew. Chem., Int. Ed. 2007, 46, 4562. (e) Shi, L.; Ye, Z.-S.; Cao, L.-L.;
Guo, R.-N.; Hu, Y.; Zhou, Y.-G. Angew. Chem., Int. Ed. 2012, 51, 8286.
(f) Ye, Z.-S.; Chen, M.-W.; Chen, Q.-A.; Shi, L.; Duan, Y.; Zhou, Y.-G.
Angew. Chem., Int. Ed. 2012, 51, 10181. (g) Guo, R.-N.; Cai, X.-F.; Shi,
L.; Ye, Z.-S.; Chen, M.-W.; Zhou, Y.-G. Chem. Commun. 2013, 49,
8537. (h) Iimuro, A.; Yamaji, K.; Kandula, S.; Nagano, T.; Kita, Y.;
Mashima, K. Angew. Chem., Int. Ed. 2013, 52, 2046. (i) Ye, Z.-S.; Guo,
R.-N.; Cai, X.-F.; Chen, M.-W.; Shi, L.; Zhou, Y.-G. Angew. Chem., Int.
Ed. 2013, 52, 3685.
reaction mainly proceeded via the endocyclic imine inter-
mediate C (path b), and a dynamic kinetic resolution process
was involved.
In conclusion, we have developed a chiral phosphoric acid
catalyzed asymmetric transfer hydrogenation of aromatic
amines, quinolin-3-amines, with up to 99% ee. To supplement
our previous work on Ir-catalyzed asymmetric hydrogenation of
2-alkyl substituted quinolin-3-amines, a number of 2-aryl
substituted substrates were reduced to provide a series of
valuable chiral exocyclic amines with high yields and
enantioselectivities. Preliminary mechanistic studies indicate
that the reaction mainly proceeds via an endocyclic imine
intermediate, and a dynamic kinetic resolution process is
involved. Further work will be devoted to the synthetic
application of the developed strategy.
ASSOCIATED CONTENT
* Supporting Information
■
S
Experimental details and full spectroscopic data for all new
compounds. This material is available free of charge via the
(7) For representative reports on asymmetric hydrogenation of
quinoxalines, thiophenes, and indolizines, see: (a) Bianchini, C.;
Barbaro, P.; Scapacci, G.; Farnetti, E.; Graziani, M. Organometallics
1998, 17, 3308. (b) Tang, W.; Xu, L.; Fan, Q.-H.; Wang, J.; Fan, B.;
Zhou, Z.; Lam, K.-H.; Chan, A. S. C. Angew. Chem., Int. Ed. 2009, 48,
9135. (c) Rueping, M.; Tato, F.; Schoepke, F. R. Chem.Eur. J. 2010,
16, 2688. (d) Chen, Q.-A.; Wang, D.-S.; Zhou, Y.-G.; Duan, Y.; Fan,
H.-J.; Yang, Y.; Zhang, Z. J. Am. Chem. Soc. 2011, 133, 6126.
(e) Urban, S.; Beiring, B.; Ortega, N.; Paul, D.; Glorius, F. J. Am.
Chem. Soc. 2012, 134, 15241. (f) Ortega, N.; Tang, D.-T. D.; Urban,
S.; Zhao, D.; Glorius, F. Angew. Chem., Int. Ed. 2013, 52, 9500.
(8) For representative reports on asymmetric hydrogenation of
indoles and pyrroles, see: (a) Kuwano, R.; Sato, K.; Kurokawa, T.;
Karube, D.; Ito, Y. J. Am. Chem. Soc. 2000, 122, 7614. (b) Kuwano, R.;
Kashiwabara, M.; Ohsumi, M.; Kusano, H. J. Am. Chem. Soc. 2008,
130, 808. (c) Wang, D.-S.; Chen, Q.-A.; Li, W.; Yu, C.-B.; Zhou, Y.-G.;
Zhang, X. J. Am. Chem. Soc. 2010, 132, 8909. (d) Wang, D.-S.; Ye, Z.-
S.; Chen, Q.-A.; Zhou, Y.-G.; Yu, C.-B.; Fan, H.-J.; Duan, Y. J. Am.
Chem. Soc. 2011, 133, 8866.
AUTHOR INFORMATION
Corresponding Author
■
Notes
The authors declare no competing financial interest.
ACKNOWLEDGMENTS
■
We are grateful for financial support from the National Natural
Science Foundation of China (21125208 and 21032003) and
the National Basic Research Program of China
(2010CB833300).
REFERENCES
■
(1) (a) Xie, J.-H.; Zhu, S.-F.; Zhou, Q.-L. Chem. Rev. 2011, 111, 1713.
(b) Nugent, T. C. Chiral Amine Synthesis; Wiley-VCH: Weinheim,
2010.
(2) For selected reviews on the synthesis of chiral exocyclic amines
using other methods, see: Reference 1b; see also: (a) Trost, B. M.;
(9) For reports on asymmetric hydrogenation of furans, imidazoles,
and axazoles, see: (a) Kaiser, S.; Smidt, S. P.; Pfaltz, A. Angew. Chem.,
Int. Ed. 2006, 45, 5194. (b) Kuwano, R.; Kameyama, N.; Ikeda, R. J.
Am. Chem. Soc. 2011, 133, 7312. (c) Ortega, N.; Urban, S.; Beiring, B.;
Crawley, M. L. Chem. Rev. 2003, 103, 2921. (b) Muller, T. E.;
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