ChemComm
Communication
This research was supported by Grants-in-Aids (11011761)
and Supported program for the Strategic Research Foundation
at Private Universities (2012–2016) from MEXT of Japan for Y.H.
Notes and references
‡ The association constant Ka of [1ꢀ(R)-2a-H][PF6] was not determined
because of the peak broadening in the 1H NMR spectrum. The Ka value
of [1ꢀ(R)-2b-H][PF6] is calculated using 1H NMR titration experiments at
273 K to be 370 Mꢁ1 (Fig. S14, ESI†). The value is smaller than the
[2]pseudorotaxane of dibenzo[24]crown-8 and dibenzylammonium
(27 000 Mꢁ1 at 298 K)11 and is larger than that of chiral crown ether
and benzyl ammonium (3.3 Mꢁ1 at 283 K; Y. Tachibana, N. Kihara,
Y. Ohga, T. Takata, Chem. Lett., 2000, 29, 806).
Fig. 5 CD signals at 261.6 nm of [1ꢀ(R)-2a-H][PF6] and [1ꢀ(S)-2a-H][PF6] with
varying %ee values. [1] = [ammonium salts] = 3.0 mM.
1 D. Philp and J. F. Stoddart, Angew. Chem., Int. Ed. Engl., 1996, 35, 1155.
2 D. B. Amabilino and J. F. Stoddart, Chem. Rev., 1995, 95, 2725.
3 J. Cornelissen, A. E. Rowan, R. J. M. Nolte and N. Sommerdijk, Chem.
Rev., 2001, 101, 4039.
[1ꢀ(R)-2a-H][PF6] and [1ꢀ(S)-2a-H][PF6], respectively. This means
that the [2]pseudorotaxanes containing the chiral sec-ammonium
salts with the same absolute configuration show the same Cotton
effects in CD spectra.
Because good crystals of the [2]pseudorotaxanes suitable for
X-ray crystallography were not obtained, a conformer search
using molecular mechanics and then optimization using semi-
empirical AM1 calculations followed by ab initio B3LYP/6-31G*
calculations of [(R)-2a-H]+ were carried out (Fig. 4d). The
4 M. M. Green, K. S. Cheon, S. Y. Yang, J. W. Park, S. Swansburg and
W. H. Liu, Acc. Chem. Res., 2001, 34, 672–680.
5 L. Pu, Chem. Rev., 2004, 104, 1687.
6 M. A. Mateos-Timoneda, M. Crego-Calama and D. N. Reinhoudt,
Chem. Soc. Rev., 2004, 33, 363.
7 G. A. Hembury, V. V. Borovkov and Y. Inoue, Chem. Rev., 2008, 108, 1.
8 K. Naemura, H. Miyabe, Y. Shingai and Y. Tobe, J. Chem. Soc., Perkin
Trans. 1, 1993, 1073.
9 Y. Habata, J. S. Bradshaw, J. J. Young, S. L. Castle and P. Huszthy,
J. Org. Chem., 1996, 61, 8391.
10 K. Naemura, K. Ogasahara, K. Hirose and Y. Tobe, Tetrahedron:
Asymmetry, 1997, 8, 19.
optimized structure shows that the ammonium salt is incorpo- 11 P. R. Ashton, P. J. Campbell, E. J. T. Chrystal, P. T. Glink, S. Menzer,
D. Philp, N. Spencer, J. F. Stoddart, P. A. Tasker and D. J. Williams,
Angew. Chem., Int. Ed. Engl., 1995, 34, 1865.
12 N. Harada and K. Nakanishi, Circular dichroic spectroscopy: exciton
rated in the crown ether ring, and the two biphenyl moieties
constitute a counterclockwise screw sense with the dihedral
angle of 841. The modeling strongly supports the result of CD
measurements.
coupling in organic stereochemistry, University Science Books, 1983.
13 Circular Dichroism: Principles and Applications, ed. N. Berova,
K. Nakanishi and R. W. Woody, Wiley, 2000.
To evaluate the effectiveness of the [2]pseudorotaxane
system for quantitative enantiomeric excess (ee) determination
of chiral sec-ammonium ions, a calibration curve28–31 was
created using (R)- and (S)-2a-HꢀPF6 with varying ee (ꢁ100,
ꢁ80, ꢁ60, ꢁ40, ꢁ20, 0, +20, +40, +60, +80, +100 %ee of
(R)-2a-HꢀPF6). The CD amplitudes at 261.6 nm were plotted
versus %ee (Fig. 5). The calibration curve shows a linear
relationship with R2 = 0.998. The result indicates that the
system is applicable to quantitative ee determination of chiral
sec-ammonium ions.
14 Comprehensive Chiroptical Spectroscopy, Applications in Stereochemi-
cal Analysis of Synthetic Compounds, Natural Products, and Bio-
molecules, ed. N. Berova, P. L. Polavarapu, K. Nakanishi and
R. W. Woody, Wiley, 2012.
15 V. V. Borovkov, J. M. Lintuluoto and Y. Inoue, J. Am. Chem. Soc.,
2001, 123, 2979.
16 X. F. Huang, N. Fujioka, G. Pescitelli, F. E. Koehn, R. T. Williamson,
K. Nakanishi and N. Berova, J. Am. Chem. Soc., 2002, 124, 10320.
17 R. Katoono, H. Kawai, K. Fujiwara and T. Suzuki, Tetrahedron Lett.,
2006, 47, 1513.
18 H. Degenbeck, A.-S. Felten, E. C. Escudero-Adan, J. Benet-Buchholz,
L. Di Bari, G. Pescitelli and A. Vidal-Ferran, Inorg. Chem., 2012,
51, 8643.
In conclusion, we demonstrated that a combination of 1 and 19 H. Tsukube, H. Fukui and S. Shinoda, Tetrahedron Lett., 2001,
42, 7583.
chiral sec-ammonium salts achieves the chiral transcription
and amplification by forming [2]pseudorotaxanes. In this
20 H. Tamiaki, S. Unno, E. Takeuchi, N. Tameshige, S. Shinoda and
H. Tsukube, Tetrahedron, 2003, 59, 10477.
system, the crown ether forms complexes with chiral sec- 21 G. Fukuhara and Y. Inoue, Chem.–Eur. J., 2010, 16, 7859.
22 S. Shinoda, K. Terada and H. Tsukube, Chem.–Asian J., 2012, 7, 400.
23 M. Asakawa, G. Brancato, M. Fanti, D. A. Leigh, T. Shimizu, A. M. Z.
Slawin, J. K. Y. Wong, F. Zerbetto and S. W. Zhang, J. Am. Chem. Soc.,
2002, 124, 2939.
24 S. Facchetti, D. Losi and A. Iuliano, Tetrahedron: Asymmetry, 2006,
17, 2993.
25 X. Z. Zhu and C. F. Chen, J. Am. Chem. Soc., 2005, 127, 13158.
ammonium ions to make [2]pseudorotaxanes, and the chirality
of the sec-ammonium ion is transcribed into the crown ether.
Since two biphenyl parts in the 20,200-quaterphenyl group rotate
like a co-axial rotor, the chirality of the atropisomers of the
crown ether can be inverted depending on the chirality of
the guest ions. When the crown ether formed the chiral 26 B. H. Northrop, S. J. Khan and J. F. Stoddart, Org. Lett., 2006, 8, 2159.
27 C. Zhang, S. Li, J. Zhang, K. Zhu, N. Li and F. Huang, Org. Lett., 2007,
[2]pseudorotaxane with (R)-sec-ammonium ions, the negative
9, 5553.
first and positive second Cotton effects indicating a counter-
28 L. A. Joyce, M. S. Maynor, J. M. Dragna, G. M. da Cruz, V. M. Lynch,
clockwise screw sense were observed in the CD spectrum. The
chirality transcription and amplification by the formation of
the pseudorotaxane would open a new way to determine the
absolute configuration and ee of chiral sec-amines.
J. W. Canary and E. V. Anslyn, J. Am. Chem. Soc., 2011, 133, 13746.
29 L. You, G. Pescitelli, E. V. Anslyn and L. Di Bari, J. Am. Chem. Soc.,
2012, 134, 7117.
30 M. W. Ghosn and C. Wolf, J. Am. Chem. Soc., 2009, 131, 16360.
31 D. P. Iwaniuk and C. Wolf, J. Am. Chem. Soc., 2011, 133, 2414.
c
2188 Chem. Commun., 2013, 49, 2186--2188
This journal is The Royal Society of Chemistry 2013