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Chemical Science
Page 5 of 6
DOI: 10.1039/C6SC02646J
Journal Name
COMMUNICATION
Bottom view
OMe
synclinal
1 For reviews of enantioselectivity switches using a single chiral
source, see: (a) G. Zanoni, F. Castronovo, M. Franzini, G. Vidari
and E. Giannini, Chem. Soc. Rev., 2003, 32, 115−129. (b) T.
steric
Ph
approach
O
11
O
O
11
O
Ph
O
-
10
face
Re
O
O
O
10
O
N
O
attack
Ph
N
Cl
N
Cl
Cl
Cl
O
O
O
N
Tanaka and M. Hayashi, Synthesis, 2008, 3361
−3376. (c) M.
O-
O
N
O
MeO
Ph
MeO
N
Bartók, Chem. Rev., 2010, 110, 1663−1705. (d) J. Escorihuela, M.
I. Burguete and S. V. Luis, Chem. Soc. Rev., 2013, 42,
5595−5617.
N
7
)-
(
R
A-syn
(favored)
antiperiplanar
approach
major
π π
-
interaction; supported by
molecular simulation
A-anti (less favored)
2 G. Storch and O. Trapp, Angew. Chem., Int. Ed., 2015, 54,
3580−3586.
(b) B-anti transition state assembly
3 Y. Sohtome, S. Tanaka, K. Takada, T. Yamaguchi and K.
Nagasawa, Angew. Chem., Int. Ed., 2010, 49, 9254−9257.
4 S. A. Moteki, J. Han, S. Arimitsu, M. Akakura, K. Nakayama and
K. Maruoka, Angew. Chem., Int. Ed., 2012, 51, 1187−1190.
5 J. Wang, J. Chen, C. W. Kee and C.ꢀH. Tan, Angew. Chem., Int.
Ed., 2012, 51, 2382−2386.
steric
O
11
10
O
O
PhO
O-
N
face
Si
Ph
O
N
O
attack
O
Cl
O
Cl
Ph
O
N
MeO
N
MeO
antiperiplanar
approach
7
( )-
S
minor
steric
6 Z. Wang, Z. Yang, D. Chen, X. Liu, L. Lin and X. Feng, Angew.
Chem., Int. Ed., 2011, 50, 4928ꢀ4932.
B-anti (disfavored)
7 (a) T. Yamamoto, T. Yamada, Y. Nagata and M. Suginome, J. Am.
Chem. Soc., 2010, 132, 7899−7901. (b) Y. Akai, T. Yamamoto, Y.
Nagata, T. Ohmura and M. Suginome, J. Am. Chem. Soc., 2012,
134, 11092−11095.
Fig. 2 Plausible transition state assemblies of Steglich rearrangement by
using (P)-1. (a) A-syn and A-anti transition state assemblies using GaussView
(side view) and ChemDraw (side and bottom views) presentations. (b) B-anti
transition state assembly using ChemDraw (bottom view) presentation.
8 S. Mortezaei, N. R. Catarineu and J. W. Canary, J. Am. Chem. Soc.,
2012, 134, 8054−8057.
9 (a) J. Wang and B. L. Feringa, Science, 2011, 331, 1429−1432. (b)
M. Vlatković, L. Bernard, E. Otten and B. L. Feringa, Chem.
Commun., 2014, 50, 7773−7775. (c) D. Zhao, T. M. Neubauer and
B. L. Feringa, Nature Commun., 2015, 6, 6652.
10 For reviews of photoswitchable catalysis, see: (a) B. M. Neilson
and C. W. Bielawski, ACS Catal., 2013, 3, 1874−1885. (b) R.
Göstl, A. Senf and S. Hecht, Chem. Soc. Rev., 2014, 43,
1982−1996. For representative example of photochemically
modulated enantioselectivity in asymmetric reaction, see : (c) D.
Sud, T. B. Norsten and N. R. Branda, Angew. Chem., Int. Ed.,
2005, 44, 2019−2021.
Conclusions
In summary, we have documented a pseudoꢀenantiomeric pair of
optically switchable helicene catalysts (10R,11R,P)ꢀ1 and
(10R,11R,M)ꢀ1’, which contain a 4ꢀNꢀmethylaminopyridine (MAP)
moiety. The helicene pair underwent complementary, photoꢀ
switching profiles at 290 nm (1/1’, <1/>99) and 340 nm (1/1’, 91/9)
and unidirectional thermoꢀrotation (1/1’, >99/<1), as evidenced by
UVꢀVis difference, CD, and HPLC analyses. They can efficiently
catalyze enantiodivergent Steglich rearrangements of Oꢀ to Cꢀ
o
carboxyazlactones at ꢀ40 C in DME/tAA mixed solvents, resulting
in the formation of either enantiomeric products of bioꢀmedicinal
importance29 in up to 91% (R) and 94% (S) ee, respectively. Control
experiments were performed to understand that the catalytic process
may proceed through a reversible Oꢀcarboxylation and a subsequent
irreversible Cꢀcarboxylation, Molecular simulations of the transition
state assemblies of the incipient ion pairs indicate that synclinal Reꢀ
face attack is favored in catalyst (P)ꢀ1 due to greater HOMOꢀLUMO
interactions with minimal stereoelectronic repulsions. To our
knowledge, this system provides the best complementary
enantioselectivities among several lightꢀ or heatꢀcontrolled
enantiodivergent catalytic reactions. Investigations toward
examining other substrate classes, as well as applications to other
organoꢀcatalytic systems are underway.
11 (a) J. C. Ruble and G. C. Fu, J. Am. Chem. Soc., 1998, 120,
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15 H. Mandai, T Fujiwara, K. Noda, K. Fujii, K. Mitsudo, T.
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16 (a) C. Joannesse, C. P. Johnston, C. Concellon, C. Simal, D. Philp
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Acknowledgements
Financial support from the Ministry of Science of Technology of
Taiwan (MOST 104ꢀ2113ꢀMꢀ007 ꢀ002 ꢀMY3 and 104ꢀ2113ꢀMꢀ007ꢀ
014) was greatly acknowledged.
17 D. Uraguchi, K. Koshimoto, S. Miyake and T. Ooi, Angew.
Chem., Int. Ed., 2010, 49, 5567−5569.
Notes and references
18 Z. Zhang, F. Xie, J. Jia and W. Zhang, J. Am. Chem. Soc., 2010,
132, 15939–15941.
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