Edge Article
Chemical Science
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Synthesis of 4-methoxybenzylideneaniline (4)
293 mg (2.15 mmol) of 4-methoxybenzaldehyde and 200 mg
(2.15 mmol) of aniline were dissolved in 4 ml of benzene and
reuxed in a Dean–Stark apparatus for 4 h. The benzene was
then evaporated under reduced pressure and the pure product
was obtained in quantitative yield as a pale yellow solid (454 mg,
2.15 mmol, 100% yield). 1H-NMR (400 MHz, CD3CN): d 8.48 (s,
1H), 7.89 (d, J ¼ 9.0 Hz, 2H), 7.42 (t, J ¼ 9.0 Hz, 2H), 7.26–7.21
(m, 3H), 7.06 (d, J ¼ 9.0 Hz), 3.88 (s, 3H); 13C-NMR (100.6 MHz,
CD3CN): d 163.4, 160.8, 153.4, 131.4, 130.4, 130.2, 126.5, 121.8,
115.2, 56.2; HRMS (ESI+): calcd for C14H13NO–H+ 212.1075;
found 212.1076; FT-IR (thin lm): nmax/cmꢂ1 2258, 2923, 1945,
1605, 1512, 1253, 1164, 1030, 835.
General procedure for the generation of the dynamic libraries
Stock solutions of the diimine 1 (15 mM), of hexylamine 2 (150
mM) and of each diamine 3 (100 mM) were prepared in
deuterated acetonitrile. The aliquots of these solutions were
loaded into NMR tubes and then CD3CN was added in order to
obtain 600 mL of a 1 : 2 : 1 mixture of the substrates (2.5 mM of
ꢄ
1). The system was then le to equilibrate at 25 C. Aer 1–4
days, there was no further change in the 1H-NMR spectrum
showing that the system had reached equilibrium.
Determination of equilibrium constants
The equilibrium constants were determined by using the
concentrations obtained by integration of the H-NMR signals,
1
using the signal of the methyl group of the n-hexyl chain as an
internal reference. The errors in Kref were calculated by
considering a 5% error in the integrals. Errors in K and K1,2 are
quoted as twice the standard deviation of the values obtained
from repeating the experiment twice at different concentrations
of hexylamine (5 mM, 10 mM and 20 mM).
Acknowledgements
`
Thanks are due to the Ministero dell'Istruzione, dell'Universita
e della Ricerca (MIUR, PRIN 2010CX2TLM). This work was also
`
partially supported by Universita di Roma La Sapienza (Progetti
di Ricerca 2012 and Avvio alla Ricerca 2013). The authors also
thank Dr Simon Thorpe for the time and help with the MALDI
experiments.
Notes and references
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(c) Dynamic combinatorial chemistry: in drug discovery,
bioorganic chemistry and material science, ed. B. L. Miller,
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the concentration of a given macrocycle belonging to the DL
can be calculated as [Cn] ¼ xnEMn, where EMn is the effective
molarity of the macrocycle Cn, x is the extent of reaction
expressed as the fraction of reacted groups in the linear
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