Paper
Organic & Biomolecular Chemistry
nitrile (5 mL) under N2. The mixture was heated at 70 °C with Cleavage and reformation of dynamic covalent bonds
stirring for 24 h. The mixture was washed with water and monitored by 1H NMR and fluorescence spectroscopy
extracted by dichloromethane (10 mL). The organic layer was
collected and dried over anhydrous magnesium sulfate. After
concentrating under reduced pressure, the crude product was
purified by silica gel column chromatography (ethyl acetate/
The adduct 3 (41.1 mg, 0.061 mmol) was dissolved in toluene
(1 mL), and heated at 100 °C with stirring. 40 μL of the above
toluene reaction solution of 3 was placed in a NMR tube at
specific time intervals. This sample solution in the NMR tube
was dried in vacuo for over 24 h. Deuterochloroform (CDCl3)
(0.5 mL) was added in each NMR sample tube for NMR
measurements. 25 μL of the CDCl3 solution of 3 was trans-
ferred from each NMR sample tube into 20 mL bottles, and
petroleum ether = 1/1, v/v) giving a white solid (0.20 g, 41%).
1H NMR (400 MHz, CDCl3): δ = 8.14 (d, J = 7.7 Hz, 2H), 7.62
(dd, J = 60.9, 8.6 Hz, 4H), 7.47 (d, J = 8.1 Hz, 2H), 7.42 (t, J = 7.4
Hz, 2H), 7.30 (t, J = 7.2 Hz, 2H), 6.23 (s, 1H), 5.20 (s, 1H), 4.17
(d, J = 6.0 Hz, 2H), 3.81–3.43 (m, 12H), 3.23 (s, 2H), 2.73 (s,
diluted to 10 mL with dichloromethane for fluorescence
measurements.
1H), 2.38 (t, J = 7.5 Hz, 2H), 1.93–1.77 (m, 2H), 1.22 (t, J = 7.0
Hz, 3H). 13C NMR (100 MHz, CDCl3): δ = 175.32, 175.24,
152.57, 140.55, 138.08, 130.35, 130.20, 127.96, 127.54, 126.12,
123.56, 120.38, 120.32, 109.78, 92.72, 83.76, 70.71, 70.65,
70.31, 69.86, 66.68, 61.20, 49.94, 49.72, 27.20, 24.27, 15.20. IR
(cm−1): 3463, 2865, 1774, 1704, 1599, 1515, 1478, 1451, 1387,
1356, 1317, 1228, 1181, 1103, 977, 927, 831, 750, 723. HRMS
(ESI): m/z calculated for C36H38N2O7 [M + Na]+: 633.2571,
found: 633.2572.
Exchange of furan moieties between 2 and 3
Compound 2 (30.5 mg, 0.05 mmol) was dissolved in deutero-
acetonitrile (CD3CN) (1 mL), and then furfuryl alcohol (5 mg,
0.05 mol) was added. The mixture solution was heated at
75 °C with stirring. 20 μL of the above solution was taken and
placed in
a
NMR tube at specific time intervals.
Deuterochloroform (CDCl3) (480 μL) was then added respect-
Maleimide–furan adduct 3 was synthesized in the same
manner as 2, except for [4-(3-{2-[2-(ethoxy)ethoxy]ethoxy}
propyl)furan-2-yl]methanol replaced with furfuryl alcohol
(0.1 mL). The crude product was purified by silica gel column
chromatography (ethyl acetate/petroleum ether = 1/1, v/v) to
give a white solid (0.12 g, 27%). 1H NMR (400 MHz, CDCl3): δ =
8.14 (d, J = 7.7 Hz, 2H), 7.62 (dd, J = 59.6, 8.6 Hz, 4H), 7.46 (d, J
= 8.1 Hz, 2H), 7.41 (t, J = 7.5 Hz, 2H), 7.30 (t, J = 7.3 Hz, 2H),
6.66 (dd, J = 29.5, 5.7 Hz, 2H), 5.43 (s, 1H), 4.21 (s, 2H), 3.20
(dd, J = 17.6, 6.6 Hz, 2H), 2.72 (s, 1H). 13C NMR (100 MHz,
CDCl3): δ = 175.08, 174.97, 140.61, 138.58, 138.18, 137.21,
130.22, 127.93, 127.57, 126.13, 123.61, 120.37, 120.34, 109.77,
91.96, 81.52, 60.87, 50.13, 48.29, 25.38. IR: 2372, 1776, 1700,
1599, 1544.17, 1517, 1478, 1453, 1404, 1363, 1338, 1316.94,
1301, 1282, 1232, 1207, 1194, 1056, 1019, 757. HRMS (ESI): m/z
ively in each NMR sample tube for NMR measurements.
Conflicts of interest
There are no conflicts to declare.
Acknowledgements
The authors acknowledge the financial support of the National
Natural Science Foundation of China (Grant No. 21674079)
and the Tianjin Research Program of Application Foundation
and Advanced Technology (No. 15JCYBJC20400), and acknowl-
edge Xiaoxin Zhao for the kind help with NMR measurements.
calculated for C27H20N2O4 [M
459.1315.
+
Na]+: 495.1315, found
Maleimide–furan adduct 4 was synthesized in the same
manner as 2, except for [4-(3-{2-[2-(ethoxy)ethoxy]ethoxy}
propyl)furan-2-yl]methanol replaced with 3-(3-{2-[2-(ethoxy)
ethoxy]ethoxy}propyl)furan (0.15 g, 0.6 mmol). The crude
product was purified by silica gel column chromatography
(ethyl acetate/petroleum ether = 3/2, v/v) to give a pale yellow
solid (0.2 g, yield 69%). 1H NMR (400 MHz, CDCl3): δ =
8.17–8.10 (m, 2H), 7.72–7.53 (m, 4H), 7.49–7.45 (m, 2H),
7.36 (m, 4H), 6.12 (q, J = 1.7 Hz, 1H), 5.37 (s, 1H), 5.20 (s,
1H), 3.73–3.48 (m, 12H), 3.10 (dd, J = 19.2, 6.6 Hz, 2H),
2.37 (t, J = 7.6 Hz, 2H), 1.91–1.76 (m, 2H), 1.22 (t, J = 7.0 Hz,
Notes and references
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3H). 13C NMR (100 MHz, CDCl3):
δ = 175.63, 175.47,
152.03, 140.59, 137.92, 130.46, 128.71, 128.04, 127.51, 126.10,
123.54, 120.35, 120.26, 109.80, 83.85, 82.41, 77.24, 70.64,
70.34, 70.32, 69.86, 66.68, 49.40, 47.34, 27.29, 24.10, 15.20. IR
(cm−1): 2863, 1707, 1600, 1515, 1478, 1451, 1385, 1356, 1334,
1229, 1179, 1104, 1016, 936, 870, 825, 750, 723. HRMS (ESI):
m/z calculated for C35H36N2O6 [M + Na]+: 603.2466, found:
603.2466.
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