Organic Letters
Letter
butylsulfinamide (30 mol %) as the catalyst can afford
and 99% ee (Table S2, entry 6). Under the same reaction
conditions, a variety of 2,3-dialkylquinoxalines 5c,j−w were
subjected to the asymmetric transfer hydrogenation, which
furnished the desired products 6c,j−w in 58−86% yield with
2015, 137, 10018. (h) Stephan, D. W. Acc. Chem. Res. 2015, 48, 306.
(i) Stephan, D. W. Science 2016, 354, aaf7229.
(3) Chen, D.; Klankermayer, J. Chem. Commun. 2008, 2130.
(4) For reviews, see: (a) Liu, Y.; Du, H. Huaxue Xuebao 2014, 72,
7
71. (b) Feng, X.; Du, H. Tetrahedron Lett. 2014, 55, 6959. (c) Shi, L.;
Zhou, Y.-G. ChemCatChem 2015, 7, 54.
5) (a) Parks, D. J.; Spence, R. E. v. H.; Piers, W. E. Angew. Chem., Int.
(
50:50−75:25 dr and 89−99% ee for the trans isomers (Table 1,
Ed. Engl. 1995, 34, 809. (b) Parks, D. J.; Piers, W. E.; Yap, G. P. A.
entries 2−15). Unfortunately, the ee for the cis isomers were
much lower (Table 1, entries 2−14). Because of the ring strain,
the transfer hydrogenation of quinoxalines 5x and 5y gave meso
isomers as major products (Table 1, entries 16 and 17).
Interestingly, high ee’s can be still obtained for the trans
isomers. When quinoxaline 5z bearing a larger ring was used,
tetrahydroquinoxaline 6z in favor of the trans isomer was
obtained in 93% yield with >99% ee (Table 1, entry 18).
In summary, a metal-free asymmetric transfer hydrogenation
of 2,3-disubstituted quinoxalines with ammonia borane as the
hydrogen source using a chiral frustrated Lewis pair of
HB(C F ) and (R)-tert-butylsulfinamide as the catalyst has
Organometallics 1998, 17, 5492.
(6) For selected examples, see: (a) Chen, D.; Wang, Y.;
Klankermayer, J. Angew. Chem., Int. Ed. 2010, 49, 9475. (b) Sumerin,
V.; Chernichenko, K.; Nieger, M.; Leskela,
Adv. Synth. Catal. 2011, 353, 2093. (c) Lindqvist, M.; Borre, K.;
Axenov, K.; Kotai, B.; Nieger, M.; Leskela, M.; Papai, I.; Repo, T. J. Am.
Chem. Soc. 2015, 137, 4038. (d) Susse, L.; Hermeke, J.; Oestreich, M. J.
̈
M.; Rieger, B.; Repo, T.
́
̈
́
̈
Am. Chem. Soc. 2016, 138, 6940. (e) Ye, K.-Y.; Wang, X.; Daniliuc, C.
G.; Kehr, G.; Erker, G. Eur. J. Inorg. Chem. 2017, 2017, 368.
(7) (a) Liu, Y.; Du, H. J. Am. Chem. Soc. 2013, 135, 6810. (b) Wei, S.;
Du, H. J. Am. Chem. Soc. 2014, 136, 12261. (c) Ren, X.; Li, G.; Wei, S.;
Du, H. Org. Lett. 2015, 17, 990. (d) Zhang, Z.; Du, H. Org. Lett. 2015,
17, 2816. (e) Zhang, Z.; Du, H. Org. Lett. 2015, 17, 6266. (f) Ren, X.;
Du, H. J. Am. Chem. Soc. 2016, 138, 810.
(8) Stephan, D. W.; Greenberg, S.; Graham, T. W.; Chase, P.; Hastie,
J. J.; Geier, S. J.; Farrell, J. M.; Brown, C. C.; Heiden, Z. M.; Welch, G.
C.; Ullrich, M. Inorg. Chem. 2011, 50, 12338.
6
5 2
been successfully achieved. High cis selectivities and 77−86%
ee’s were obtained for the reactions of 2-alkyl-3-arylquinoxa-
lines. Interestingly, when 2,3-dialkylquinoxalines were em-
ployed as substrates, the desired products were obtained in
(9) For reviews, see: (a) Ellman, J. A.; Owens, T. D.; Tang, T. P. Acc.
5
8−93% yield with 28:72−75:25 dr (trans:cis) and 89−99% ee.
Chem. Res. 2002, 35, 984. (b) Robak, M. T.; Herbage, M. A.; Ellman, J.
A. Chem. Rev. 2010, 110, 3600.
Further efforts on searching for novel chiral FLPs and exploring
their applications in asymmetric hydrogenation and transfer
hydrogenation are underway in our laboratory.
(
10) Li, S.; Li, G.; Meng, W.; Du, H. J. Am. Chem. Soc. 2016, 138,
2956.
11) For selected examples using ammonia borane as a hydrogen
source, see: (a) Menard, G.; Stephan, D. W. J. Am. Chem. Soc. 2010,
32, 1796. (b) Yang, X.; Zhao, L.; Fox, T.; Wang, Z.-X.; Berke, H.
1
(
ASSOCIATED CONTENT
Supporting Information
́
■
1
*
S
Angew. Chem., Int. Ed. 2010, 49, 2058. (c) Yang, X.; Fox, T.; Berke, H.
Chem. Commun. 2011, 47, 2053. (d) Chong, C. C.; Hirao, H.; Kinjo, R.
Angew. Chem., Int. Ed. 2014, 53, 3342. (e) Fu, S.; Chen, N.-Y.; Liu, X.;
Shao, Z.; Luo, S.-P.; Liu, Q. J. Am. Chem. Soc. 2016, 138, 8588.
Procedure for the asymmetric transfer hydrogenation,
characterization of products, and data for the determi-
(
2
f) Zhou, Q.; Zhang, L.; Meng, W.; Feng, X.; Yang, J.; Du, H. Org. Lett.
016, 18, 5189.
12) For reviews, see: (a) Glorius, F. Org. Biomol. Chem. 2005, 3,
171. (b) Zhou, Y.-G. Acc. Chem. Res. 2007, 40, 1357. (c) Kuwano, R.
(
4
Heterocycles 2008, 76, 909. (d) Wang, D.-S.; Chen, Q.-A.; Lu, S.-M.;
Zhou, Y.-G. Chem. Rev. 2012, 112, 2557. (e) Zheng, C.; You, S.-L.
Chem. Soc. Rev. 2012, 41, 2498.
AUTHOR INFORMATION
(13) For selected examples, see: (a) Jacobsen, E. J.; Stelzer, L. S.;
Belonga, K. L.; Carter, D. B.; Im, W. B.; Sethy, V. H.; Tang, A. H.;
VonVoigtlander, P. F.; Petke, J. D. J. Med. Chem. 1996, 39, 3820.
ORCID
(b) Sikorski, J. A. J. Med. Chem. 2006, 49, 1. (c) Eary, C. T.; Jones, Z.
Notes
S.; Groneberg, R. D.; Burgess, L. E.; Mareska, D. A.; Drew, M. D.;
Blake, J. F.; Laird, E. R.; Balachari, D.; O’Sullivan, M.; Allen, A.; Marsh,
V. Bioorg. Med. Chem. Lett. 2007, 17, 2608. (d) Borrok, M. J.; Kiessling,
L. L. J. Am. Chem. Soc. 2007, 129, 12780.
The authors declare no competing financial interest.
(14) For selected examples, see: (a) Murata, S.; Sugimoto, T.;
Matsuura, S. Heterocycles 1987, 26, 763. (b) Qiu, L.; Kwong, F. Y.; Wu,
J.; Lam, W. H.; Chan, S.; Yu, W.-Y.; Li, Y.-M.; Guo, R.; Zhou, Z.; Chan,
A. S. C. J. Am. Chem. Soc. 2006, 128, 5955. (c) 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. (d) Chen, Q.-A.; Wang, D.-S.; Zhou, Y.-
G.; Duan, Y.; Fan, H.-J.; Yang, Y.; Zhang, Z. J. Am. Chem. Soc. 2011,
ACKNOWLEDGMENTS
■
We are grateful for the financial support from the National
Natural Science Foundation of China (21572231, 21502199,
and 21521002).
1
33, 6126. (e) Chen, Q.-A.; Gao, K.; Duan, Y.; Ye, Z.-S.; Shi, L.; Yang,
Y.; Zhou, Y.-G. J. Am. Chem. Soc. 2012, 134, 2442. For examples of
transfer hydrogenations, see: (f) Rueping, M.; Tato, F.; Schoepke, F. R.
Chem. - Eur. J. 2010, 16, 2688. (g) Shi, F.; Tan, W.; Zhang, H.-H.; Li,
M.; Ye, Q.; Ma, G.-H.; Tu, S.-J.; Li, G. Adv. Synth. Catal. 2013, 355,
REFERENCES
■
(
1) For a seminal work, see: Welch, G. C.; San Juan, R. R.; Masuda, J.
D.; Stephan, D. W. Science 2006, 314, 1124.
2) For reviews, see: (a) Kenward, A. L.; Piers, W. E. Angew. Chem.,
Int. Ed. 2008, 47, 38. (b) Stephan, D. W.; Erker, G. Angew. Chem., Int.
Ed. 2010, 49, 46. (c) Soos, T. Pure Appl. Chem. 2011, 83, 667.
d) Erker, G. Pure Appl. Chem. 2012, 84, 2203. (e) Paradies, J. Angew.
(
3
715.
15) Qin, J.; Chen, F.; Ding, Z.; He, Y.-M.; Xu, L.; Fan, Q.-H. Org.
Lett. 2011, 13, 6568.
16) Zhang, Z.; Du, H. Angew. Chem., Int. Ed. 2015, 54, 623.
(
́
(
(
Chem., Int. Ed. 2014, 53, 3552. (f) Stephan, D. W.; Erker, G. Angew.
Chem., Int. Ed. 2015, 54, 6400. (g) Stephan, D. W. J. Am. Chem. Soc.
C
Org. Lett. XXXX, XXX, XXX−XXX