Letter
We have, therefore, demonstrated a new, versatile scaffold
NJC
5 S. Kubik, Chem. Soc. Rev., 2009, 38, 585.
6 K. Brak and E. N. Jacobsen, Angew. Chem., Int. Ed., 2013, 52, 534.
7 K. E. Trejo-Huizar, R. Ortiz-Rico, M. de los Angeles Pena-
Gonzalez and M. Hernandez-Rodriguez, New J. Chem., 2013,
37, 2610.
8 (a) M. B. Foreiter and K. R. Seddon, New J. Chem., 2013,
37, 515; (b) M. B. Foreiter, H. Q. N. Gunaratne, P. Nockemann,
K. R. Seddon and G. Srinivasan, Phys. Chem. Chem. Phys.,
2014, 16, 1208.
for chiral ILCs based on the cationic thiouronium hydrogen bond
donor, which allows for facile attachment of different mesogens.
Most synthesised compounds displayed SmA* phases. In the case
of the benzoate ester compounds (5), melting points and meso-
phase ranges can be tuned by the choice of anion, and to a lesser
degree by the length of the alkyl chains. The biphenyl motif was
not as versatile, with some non-mesomorphic salts, but others
giving enantiotropic ILCs. As a proof of concept for catalytic
applications, chiral recognition and sufficient strength of hydrogen
bonding interaction with a chiral model substrate were demon-
strated via the formation of diastereomeric adducts. Due to the low
melting point and the weakly-coordinating nature of the anion,
which frees up the area around the catalytic thiourea, compound 5c
Tf2N in particular is a promising candidate for use as a co-catalytic,
anisotropic reaction medium and investigations into its use
are ongoing. Additionally, while the current study focuses on
symmetrically substituted thioureas, unsymmetric compounds
can be easily synthesised by adding just one more step to the
reaction sequence. This increases the freedom in the design of
optimum catalysts and has the potential to lead to interesting
LC phase behaviour.
´
9 (a) B. Pegot, G. Vo-Thanh, D. Gori and A. Loupy, Tetrahedron
Lett., 2004, 45, 6425; (b) T. K. T. Truong and G. Vo-Thanh,
Tetrahedron, 2010, 66, 5277.
10 R. Gausepohl, P. Buskens, J. Kleinen, A. Bruckmann,
C. W. Lehmann, J. Klankermeyer and W. Leitner, Angew.
Chem., Int. Ed., 2006, 45, 3689.
11 (a) K. R. Sharma and R. M. Noyes, J. Am. Chem. Soc., 1975,
97, 204; (b) J. A. Marshall and M. Lewellyn, J. Am. Chem. Soc.,
1977, 99, 3510.
˜
12 A. Nunez, T. Hollebiik and M. M. Labes, J. Am. Chem. Soc.,
1992, 114, 4925–4926; W. J. Leigh and D. S. Mitchell, J. Am.
Chem. Soc., 1988, 110, 1311.
13 (a) K. V. Axenov and S. Laschat, Materials, 2011, 4, 206;
(b) K. Goossens, K. Lava, C. W. Bielawski and K. Binnemans,
Chem. Rev., 2016, 116, 4643.
Conflicts of interest
14 D. W. Bruce, Y. Gao, J. N. Canongia Lopes, K. Shimizu and
J. M. Slattery, Chem. – Eur. J., 2016, 22, 16113.
There are no conflicts to declare.
15 D. T. Do and A. R. Schmitzer, ChemistrySelect, 2016, 1, 2448.
16 E. I. Jimenez, W. E. Vallejo Narvaez, C. A. Roman-Chavarria,
J. Vazquez-Chavez, T. Rocha-Rinza and M. Hernandez-
Rodriguez, J. Org. Chem., 2016, 81, 7419.
Acknowledgements
We thank the University of York for funding.
17 M. Hennum, H. Fliegl, L. Gundersen and O. Eisenstein,
J. Org. Chem., 2014, 79, 2514.
18 D. W. Bruce, D. A. Dunmur, S. A. Hudson, E. Lalinde, P. M.
Maitlis, M. P. McDonald, R. Orr, P. Styring, A. S. Cherodian,
R. M. Richardson, J. L. Feijoo and G. Ungar, Mol. Cryst. Liq.
Cryst., 1991, 206, 79.
19 (a) A. El-ghayoury, L. Douce, A. Skoulios and R. Ziessel, Angew.
Chem., Int. Ed., 1998, 37, 2205–2208; (b) K. Binnemans, Yu.
G. Galyametdinov, S. R. Collinson and D. W. Bruce, J. Mater.
Chem., 1998, 8, 1551.
Notes and references
1 P. R. Schreiner and A. Wittkopp, Org. Lett., 2002, 4, 217.
2 (a) T. Okino, Y. Hoashi and Y. Takemoto, J. Am. Chem. Soc.,
2003, 125, 12672; (b) C. Curti, G. Rassu, V. Zambrano,
L. Pinna, G. Pelosi, A. Sartori, L. Battistini, F. Zanardi and
G. Casiraghi, Angew. Chem., Int. Ed., 2012, 51, 6200.
3 J. Wang, H. Li, X. Yu, L. Zu and W. Wang, Org. Lett., 2005,
7, 4293.
4 (a) S. J. Connon, Synlett, 2009, 354; (b) A. Wittkopp and 20 P. J. Bailey, K. J. Grant and S. Parsons, Acta Crystallogr., Sect.
P. R. Schreiner, Chem. – Eur. J., 2003, 9, 407. C: Cryst. Struct. Commun., 1997, 53, 247.
New J. Chem.
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