Macromolecules
Article
Monomer 10c. In a manner similar to that described above
for 10a, reaction of 4,13-diaza-18-crown-6 (260 mg, 1 mmol) and 17
(570 mg, 2.1 mmol) yielded after chromatographic separation on silica
gel (DCM/MeOH = 95/5) 10c (570 mg, 75%); mp 182−184 °C. 1H
NMR (400 MHz, CDCl3) δ: 1.51 (d, J = 8.1 Hz, 2 H), 1.60 (d, J =
8.1 Hz, 2 H), 2.86−2.94 (m, 4 H), 2.96 (br, 4 H), 3.04−3.12 (m, 4 H),
3.18−3.28 (m, 4 H), 3.58 (br, 8 H), 3.69 (br, 16 H), 6.15 (s, 4 H),
6.35 (d, J = 8.3 Hz, 4 H), 7.25 (d, J = 8.3 Hz, 4 H). 13C NMR (100
MHz, CDCl3) δ: 45.5, 46.6, 50.5, 52.1, 70.1, 70.5, 110.9, 122.5, 128.4,
135.6, 148.1, 172.6. HRMS (FAB) calcd C44H57N4O6 [M + H]:
737.4278; found: 737.4284.
Polymer 12a. A solution of 10a (22 mg, 0.04 mmol) and 7 (3.5 mg,
4 × 10−3 mmol) in DCM (23 mL) was stirred under Ar for 2 h at rt.
Ethyl vinyl ether (2 mL) was then added, and the mixture was stirred
for 10 min. The resulting solution was concentrated, and the polymer
Figure 7. STM images of 12c on HOPG. Panel a2 was acquired by
using an impedance smaller than that of panel a1 to unveil the
underlying HOPG. Panel a3 is a zoomed-in image of panel a1. Imaging
conditions of Ebias, itunneling, and image sizes: (a1) 0.90 V, 50 pA, 13 ×
13 nm; (a2) 0.10 V, 600 pA, 4 × 4 nm; (a3) 0.90 V, 50 pA, 4 × 4 nm.
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was precipitated in Et2O (30 mL) as a white solid (20 mg, 92%). H
NMR (400 MHz, CDCl3) δ: 1.42−1.52 (br, 2 H), 1.81−2.00 (br, 2 H),
2.82−3.23 (br, 16 H), 3.70−3.81 (br, 8 H), 4.12−4.68 (br, 4 H), 5.43−
5.54 (br, 4 H), 6.10−6.80 (br, 4 H), 7.55−8.10 (br, 4 H). 13C NMR
(100 MHz, CDCl3) δ: 35.9, 36.7, 37.7, 39.1, 45.1, 46.9, 47.0, 48.9,
49.3, 49.7, 50.0, 63.9, 64.5, 69.8, 70.8, 70.9, 111.1, 116.8, 125.9, 128.4,
131.3, 133.4, 150.5, 166.5. GPC (CHCl3) Mn = 7800, PDI = 1.2.
Polymer 12b. In a manner similar to that described above for 12a,
reaction of 10b (22 mg, 0.04 mmol) with 7 (3.5 mg, 0.004 mmol)
between two adjacent polynorbornene backbones and between
the polynorbornene strand of a polymer and the crown ether
moieties of the adjacent polymer may not be the same. Such
irregularity on the STM image is therefore not unexpected.
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yielded 12b as a white solid (21 mg, 95%). H NMR (400 MHz,
CDCl3) δ: 1.30−1.65 (br, 2 H), 1.65−2.10 (br, 6 H), 2.48−3.70 (br,
16 H), 4.00−4.56 (br, 4 H), 4.80−5.90 (br, 4 H), 6.00−6.80 (br, 4 H),
7.50−8.20 (br, 4 H). 13C NMR (100 MHz, CDCl3) δ: 25.8, 26.1, 36.7,
38.0, 45.1, 45.4, 46.1, 46.6, 49.9, 63.7, 111.3, 117.2, 125.9, 128.4, 131.1,
131.3, 150.5, 166.6. GPC (CHCl3) Mn = 5300, PDI = 1.3.
CONCLUSIONS
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The chemistry described herein is the first example on the
CMCP reaction of strained biscycloalkenes with flexible linkers.
Single-stranded polybisnorbornenes are thus obtained. This
approach offers an interesting synthesis of hammock-like crown
ether moieties hanging on a hydrophobic polynorbornene
scaffold. It seems likely that the monomeric bisnorbornene may
be folded under the reaction conditions to give the correspond-
ing syn conformer (like syn-10). Intramolecular π−π inter-
actions between the pending aryl groups may take place to
direct the ring closure process (Scheme 2). Such π−π inter-
actions appear to be crucial for the success of the CMCP. The
extension of this reaction for designing polymers of different
structural variety using different kinds of monomeric bis-
cycloalkenes is in progress.
Polymer 12c. In a manner similar to that described above for 12a,
reaction of 10c (30 mg, 0.04 mmol) with 7 (3.5 mg, 0.004 mmol)
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yielded 12c as a white solid (27 mg, 90%). H NMR (500 MHz,
CDCl3) δ: 1.30−1.55 (br, 2 H), 1.60−2.05 (br, 2 H), 2.50−3.05 (br,
8 H), 3.05−3.40 (br, 8 H), 3.40−3.65 (br, 12 H), 3.65−4.20 (br, 12 H),
5.20−5.80 (br, 4 H), 6.20−6.80 (br, 4 H), 7.10−7.60 (br, 4 H). 13C
NMR (125 MHz, CDCl3) δ: 36.2, 45.0, 46.3, 49.9, 70.0, 70.5, 112.1,
123.8, 126.0, 128.5, 131.4, 148.9, 172.6. GPC (CHCl3) Mn = 6500,
PDI = 1.3.
Polymer 12c′. In a manner similar to that described above for 12a,
reaction of 10c (30 mg, 0.04 mmol) and 7 (7.0 mg, 8 × 10−3 mmol)
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yielded 12c′ as a white solid (20 mg, 84%). H NMR (400 MHz,
CDCl3) δ: 1.11−1.71 (br, 2 H), 1.73−2.08 (br, 2 H), 2.50−3.02 (br,
8 H), 3.04−3.35 (br, 8 H), 3.38−4.03 (br, 24 H), 5.17−5.76 (br, 4 H),
6.34−6.75 (br, 4 H), 7.01−7.54 (br, 4 H). 13C NMR (125 MHz,
CDCl3) δ: 35.8, 45.2, 46.2, 49.9, 70.1, 70.6, 111.9, 123.7, 125.9, 128.4,
130.5, 131.5, 135.6, 148.9, 172.5. GPC (CHCl3) Mn = 3700, PDI = 1.2.
General Procedure for the Hydrolysis−Esterification of 12.
Under a N2 atmosphere, to a solution or suspension of 12 (0.07 mmol
of ester group) in THF (anhydrous, 20 mL) was added at rt water
(18 mg, 1 mmol) and KOtBu (1.2 g, 10 mmol). After stirring at rt for
48 h, the mixture was poured into water (30 mL) and extracted with
ethyl ether (50 mL). The aqueous layer was separated and neutralized
with HCl (1 M) at 0 °C to afford a white precipitate, which was
directly used for the next reaction without further purification. A
mixture of the above precipitate, CsF (40 mg, 0.3 mmol) and EtI (82 mg,
0.5 mmol) in DMF (2 mL), was stirred at rt for 24 h. The mixture
was poured into water (20 mL), and 15 was precipitated as yellowish
solid. 1H NMR (400 MHz, CDCl3) δ: 1.10−1.50 (br, 4 H), 1.70−2.00
(br, 1 H), 2.60−2.80 (br, 2 H), 2.80−3.10 (br, 2 H), 3.10−3.60 (br,
4 H), 4.10−4.50 (br, 2H), 5.20−5.60 (br, 2 H), 6.25−6.70 (br, 2 H),
7.60−8.10 (br, 2 H). 13C NMR (100 MHz, CDCl3) δ: 14.5, 35.7, 36.2,
37.5, 39.9, 44.5, 44.8, 46.4, 46.8, 49.4, 49.5, 60.1, 111.4, 117.4, 125.9,
128.4, 131.2, 131.7, 131.8, 150.8, 166.9. 15a (85%): GPC (CHCl3)
Mn = 6700, PDI = 1.2; 15b (85%): Mn = 4600, PDI = 1.2; 15c (75%):
Mn = 5000, PDI = 1.2.
EXPERIMENTAL SECTION
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Monomer 10a. To a solution of triethylene glycol (194 mg, 1
mmol) and Et3N (300 mg, 3 mmol) in DCM (5 mL) at 0 °C was
added a solution of the acid chloride 17 (570 mg, 2.1 mmol) in DCM
(5 mL). The mixture was gradually warmed to rt and stirred for 10 h,
poured into water (100 mL), and extracted with DCM (100 mL × 2).
The organic layer was washed with brine (100 mL × 2), dried
(MgSO4), filtered, and evaporated in vacuo. The residue was chro-
matographed on silica gel (EtOAc/hexane = 1/1) to afford 10a (425 mg,
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68%); mp 120−123 °C. H NMR (400 MHz, CDCl3) δ: 1.51 (d, J =
8.0 Hz, 2 H), 1.61 (d, J = 8.0 Hz, 2 H), 2.91−2.96 (m, 8 H), 3.05−3.09
(m, 4 H), 3.23−3.28 (m, 4 H), 3.69 (s, 4 H), 3.79 (t, J = 4.8 Hz, 4 H),
4.38 (t, J = 4.8 Hz, 4 H), 6.13 (s, 4 H), 6.35 (d, J = 9.0 Hz, 4 H), 7.86 (d,
J = 9.0 Hz, 4 H). 13C NMR (100 MHz, CDCl3) δ: 45.4, 46.6, 50.4, 52.1,
63.3, 69.5, 70.7, 110.7, 116.0, 131.2, 135.6, 150.2, 166.7. HRMS (FAB)
calcd C38H45N2O6 [M + H]: 625.3278; found: 625.3268.
Monomer 10b. In a manner similar to that described above for
10a, reaction of butane-1,4-diol (90 mg, 1 mmol) and 17 (570 mg,
2.1 mmol) yielded after chromatographic separation on silica gel (hexane/
DCM = 1/3) 10b (350 mg, 62%); mp 218−219 °C. 1H NMR (400 MHz,
CDCl3) δ: 1.51 (d, J = 8.1 Hz, 2 H), 1.61 (d, J = 8.1 Hz, 2 H), 1.88 (m,
J = 2.8 Hz, 4 H), 2.92−3.00 (m, 8 H), 3.04−3.12 (m, 4 H), 3.22−3.32
(m, 4 H), 4.29 (m, 4 H), 6.14 (s, 4 H), 6.36 (d, J = 8.8 Hz, 4 H), 7.84
(d, J = 8.8 Hz, 4 H). 13C NMR (100 MHz, CDCl3) δ: 26.2, 45.6, 46.9,
50.6, 52.3, 63.8, 110.6, 116.2, 130.8, 135.3, 149.8, 166.4. HRMS (FAB)
calcd for C36H40N2O4: 564.2988; found: 564.2994.
Monomer 24. To a solution of 2-aza-1,2-dihydro-endo-dicyclo-
pentadiene (284 mg, 2.1 mmol) and Et3N (300 mg, 3 mmol) in DCM
(5 mL) at 0 °C was added a solution of the succinic acid dichloride,
prepared from succinic acid (118 mg, 1 mmol) and oxalyl chloride
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dx.doi.org/10.1021/ma302293q | Macromolecules 2013, 46, 656−663