N-Alkylated dinitrones from isosorbide as cross-linkers for unsaturated bio-based polyesters

Article abstract of DOI:10.3762/bjoc.10.88

Isosorbide was esterified with acryloyl chloride and crotonic acid yielding isosorbide diacrylate (9a) and isosorbide dicrotonate (9b), which were reacted with benzaldehyde oxime in the presence of zinc(II) iodide and boron triflouride etherate as catalysts to obtain N-alkylated dinitrones 10a/b. Poly(isosorbide itaconite -co- succinate) 13 as a bio-based unsaturated polyester was crosslinked by a 1,3-dipolar cycloaddition with the received dinitrones 10a/b. The 1,3-dipolar cycloaddition led to a strong change of the mechanical properties which were investigated by rheological measurements. Nitrones derived from methyl acrylate (3a) and methyl crotonate (3b) were used as model systems and reacted with dimethyl itaconate to further characterize the 1,3-dipolaric cycloaddition.

Full text of DOI:10.3762/bjoc.10.88

N-Alkylated dinitrones from isosorbide as
cross-linkers for unsaturated bio-based polyesters
Oliver Goerz and Helmut Ritter*
Full Research Paper
Open Access
Address:
Beilstein J. Org. Chem. 2014, 10, 902–909.
Institut für Organische und Makromolekulare Chemie, Lehrstuhl für
Präparative Polymerchemie, Heinrich-Heine-Universität Düsseldorf,
Universitätsstr. 1, 40225 Düsseldorf, Germany
doi:10.3762/bjoc.10.88
Received: 16 January 2014
Accepted: 27 March 2014
Published: 22 April 2014
Email:
Helmut Ritter* - h.ritter@uni-duesseldorf.de
Associate Editor: P. J. Skabara
* Corresponding author
© 2014 Goerz and Ritter; licensee Beilstein-Institut.
License and terms: see end of document.
Keywords:
bio-based polyesters; cross-linkers; dinitrones; 1,3-dipolar
cycloaddition; isosorbide
Abstract
Isosorbide was esterified with acryloyl chloride and crotonic acid yielding isosorbide diacrylate (9a) and isosorbide dicrotonate
(9b), which were reacted with benzaldehyde oxime in the presence of zinc(II) iodide and boron triflouride etherate as catalysts to
obtain N-alkylated dinitrones 10a/b. Poly(isosorbide itaconite -co- succinate) 13 as a bio-based unsaturated polyester was cross-
linked by a 1,3-dipolar cycloaddition with the received dinitrones 10a/b. The 1,3-dipolar cycloaddition led to a strong change of the
mechanical properties which were investigated by rheological measurements. Nitrones derived from methyl acrylate (3a) and
methyl crotonate (3b) were used as model systems and reacted with dimethyl itaconate to further characterize the 1,3-dipolaric
cycloaddition.
Introduction
Nitrones represent a class of compounds with a versatile use as mers bearing nitrones as photosensitive material [7,8] was also
electron spin traps [1] and in cycloaddition reactions [2]. As described. We focused on the preparation of polynitrones as
nitrones undergo 1,3-dipolar cycloadditions under mild condi- efficient cross-linkers for unsaturated polyesters based on
tions with a variety of unsaturated substances with a catalyst fumaric und maleic acid [9]. In the light of the growing interest
[3,4] or without a catalyst [5] they are important for the syn- in polymers from renewable resources the synthesis of bio-
thetic accessibility of five-membered heterocycles. Efforts have based nitrones as novel cross-linkers for unsaturated bio-poly-
also been undertaken to employ nitrones in the realm of esters [10] offers an interesting access to biocompatible ma-
polymer chemistry. For instance, our former reports describe terials.
the cycloaddition of bis(N-methylnitrone)s and bis(N-phenyl-
maleimide)s , which yielded linear polymers bearing isoxazoli- This paper presents the synthesis of bio-based N-alkylated dini-
dine units with high thermal stability [6]. The synthesis of poly- trones based on isosorbide and the subsequent use of these dini-
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Beilstein J. Org. Chem. 2014, 10, 902–909.
trones as cross-linkers in a 1,3-dipolar cycloaddition with unsat-
urated bio-based polyester poly(isosorbide itaconate -co- succi-
nate).
Results and Discussion
N-Alkylated dinitrones derived from acrylates and crotonates
were prepared and evaluated in respect to their 1,3-cycloaddi-
tion with itaconic acid containing polyester resins. To study the
course of this cycloaddition the two low molecular model
nitrones methyl 3-[benzylidene(oxido)amino]propanoate (3a)
and methyl 3-[benzylidene(oxido)amino]butanoate (3b), were
prepared from methyl acrylate (2a) and methyl crotonate (2b)
with E-benzaldoxime (1) (Scheme 1), respectively.
Scheme 1: Synthesis of Z-configurated model compounds 3a/b from
E-benzaldoxime and acrylates 2a/b.
The success of the reaction of compounds 3a/b can be easily
verified by 1H NMR spectroscopy (Figure 1). Former multi-
plets of acrylic functionalities in regions of 5.50 ppm to
7.00 ppm vanished after the addition of benzaldoxime. Instead, shows the N–O stretch vibration at 1149 cm−1 (3a) and
the nitron signal can be found around 7.90 ppm. The formation 1147 cm−1 (3b) thereby hinting at the formation of nitrones.
of the Z-configuration of 3a/b is evident from the signal at
7.90 ppm. With the formation of the nitrone with an E-configur- In contrast to previous reports [12], we lowered the catalyst
ation the proton of the nitron group is exposed to a strong amount of ZnI2/BF3∙OEt2 to reduce several side reactions. For
deshielding effect of the N-oxide group, which causes a move- example, it could be determined, that high amounts of catalyst
ment of the signal to higher ppm values [11]. The appearance of led to the oxidation of the oxime to benzaldehyde or the
the Z-isomer can also be explained with steric interactions cleavage of nitrones.
between the phenyl group and the methylene hydrogen atoms of
3a and the methyl group of 3b, respectively. Minor impurities We expected that the cycloaddition of 3a with 4 yields two
in the spectra result from benzaldoxime. FTIR spectroscopy diastereomers for each 4- and 5-substituted isoxazolidines,
Figure 1: 1H NMR spectra of 3a (300 MHz, DMSO-d6).
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Beilstein J. Org. Chem. 2014, 10, 902–909.
resulting in four isomers. The proposed molecular interactions respectively. In contrast to 3a/b, the produced dinitrones lacked
are shown in Scheme 2.
the solubility in toluene and precipitated during the reaction,
resulting in a viscous mass comprised of product, byproducts
The model compounds 3a/b were reacted with an excess of and catalyst. For purification the crude products were washed
dimethyl itaconate (4) obtaining isoxazolidines 5a/b with 2-propanol to dissolve byproducts and catalyst. The pure
(Scheme 3).
compounds were obtained by additionally washing with diethyl
ether.
From the NMR spectra it could be determined that only the
5-substituted isoxazolidine was formed with a ratio of 60/40 of In order to proof the ability of dinitrones to form three-dimen-
Z/E. Although 1,3-dipolar cycloadditions of nitrones with sional networks with itaconate moieties containing polyesters,
alkenes are controlled by molecular orbital interactions, the the bio-based unsaturated polyester 13 was synthesized from
steric character of the molecular structures plays a predominant isosorbide, itaconic acid and succinic acid under acid catalyzed
role. In the case of the formation of the 4-substituted isoxazoli- conditions (Scheme 5). The obtained unsaturated polyester 13
dine the phenyl group of 3a and both esters of 4 are expected to showed
values of 3400 g/mol and a glass transition
approach each other. This causes an electronic repulsion of the temperature of 64 °C. The cross-linking of 10a/b with 13 was
sterically demanding groups. Thus, the formation of the investigated by rheological measurements in oscillatory mode.
5-substituted isoxazolidine is favored due to reduced steric The storage modulus G' and loss modulus G'' which were
interactions of the involved groups. Although 3b shows a recorded at a constant shear rate of 1 s−1 and a shear stress of
slightly different molecular structure the reaction with 4 15 Pa are illustrated in Figure 2.
resulted only in the formation of the 5-substituted isoxazolidine
with a diastereomeric ratio of 30/30/20/20.
A rapid increase of the G' and G'' values was observed for
10a/b in the first 120 minutes. Thus, during this period most of
To apply the results described above to bio-based cross-linkers, the network points were formed. The ongoing cross-linking is
isosorbide (6) was esterified with acryloyl chloride (7) yielding accompanied by restrictions in the mobility of the polymer
acrylate 9a. Dicrotonate 9b was prepared from isosorbide (6) chains and the cross-linkers, which results in lowered reaction
and crotonic acid (8, Scheme 4). The obtained compounds 9a/b rates with flattening values for G' and G''. Sample 10b shows a
were transferred into the corresponding dinitrones 10a/b with gel point at about 100 minutes, whereas the gel point of 10a
4 equivalents of benzaldoxime yielding 95% 10a and 60% 10b, shows up after 210 minutes of heating. This observation can be
Scheme 2: Proposed molecular interactions of nitron 3a and dimethyl itaconate (4).
Scheme 3: 1,3-Dipolaric cycloaddition of nitrones 3a/b with dimethyl itaconate (4).
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Beilstein J. Org. Chem. 2014, 10, 902–909.
Scheme 4: Synthetic route to bio-based dinitrones derived from isosorbide.
Scheme 5: Synthesis of poly(isosorbide itaconate -co- succinate) 13 from isosorbide (6), itaconic acid (11) and succinic acid (12).
Experimental
explained with the different solubilities of 10a and 10b in poly-
ester 13. The molten mixture of dinitrone 10a and 13 showed a Materials
slight turbidity due to phase separation. This means that a Acryloyl chloride (97%), crotonic acid (98%), itaconic acid (IA,
certain amount of unsaturated functionalities of the polyester 97%), methyl acrylate (99%), methyl crotonate (98%), succinic
can only be accessed by nitrones after a long reaction time. On acid (SA, 99%), p-toluenesulfonic acid, phenothiazine (98%),
the other hand, 10b was completely soluble in polyester 13, zinc iodide (98%), and boron trifluoride diethyl etherate (46%)
giving a clear solution without any phase separation. Although were purchased from Sigma-Aldrich and used as received.
the reactivity was reduced, higher values for G' and G'' could be Isosorbide (98%) and E-benzaldoxime (97%) were purchased
obtained due to the more rigid structure of 10a.
from Alfa Aesar, and isosorbide was recrystallized from
acetone/ethyl acetate. All used solvents are commercially avail-
able and were used without further purification.
Conclusion
In the present work, bio-based dinitrones were prepared from
acrylated and crotonated isosorbide with benzaldoxime. They Measurements
were employed as cross-linkers for unsaturated bio-based poly- 1H NMR and 13C NMR spectroscopic measurements were
esters from isosorbide, itaconic acid and succinic acid. The performed with a Bruker Avance III spectrometer at 300 MHz
thermal cross-linking could be followed by oscillatory measure- and at 75 MHz in either DMSO-d6 or CDCl3 as solvents.
ments. 1,3-dipolar cycloadditions of model nitrones with Chemical shifts were referenced to the solvent value
dimethyl itaconate confirmed the proposed mechanism of cross- δ = 2.50 ppm for DMSO-d6 and δ = 7.26 ppm for CDCl3. IR
linking.
measurements were performed by using a FTIR spectrometer
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Beilstein J. Org. Chem. 2014, 10, 902–909.
Figure 2: Oscillation measurements during thermal cross-linking of unsaturated polyester 13 with dinitrones 10a and 10b at 120 °C.
(Nicolet 6700 FTIR) equipped with an ATR unit. Molecular (DSC) measurements were performed by using a Mettler
weight distributions were measured by Gel Permeation Chro- Toledo DSC 822 controller apparatus in a temperature range
matography (GPC) with a flow rate of 1 mL/min at room between 0 and 200 °C with a heating rate of 10 °C·min−1. The
temperature and THF (HPLC Grade, unstabilised – Biosolve) as glass transition temperature (Tg) values reported are taken from
an eluent. The GPC System compromises a Scharmbeck SFD the third heating cycle. EIMS spectra were recorded on a
degasser (Gastor BG12), a FLOW pump (Intelligent PUMP GC–MS integrated system Trace DSG by Thermo Finnigan.
AL-12) and a Scharmbeck SFD (Model S5200) sampler. For The instrument was calibrated in the m/z range of 1050 Da.
detection a Waters 486 Turnable Absorbance Detector and a
Schambeck SFD RI 2000 detector were used. A set of columns Synthesis of methyl 3-[benzylidene(oxido)amino]propanoate
packed with porous styrene–divinylbenzene–copolymer beads (3a): Methyl acrylate (2a, 0.86 g, 10 mmol) and benzaldoxime
was used for the separation of the analytes (MZ Analysen- (1, 2.42 g, 20 mmol) were placed in a 100 mL round bottom
technik GmbH, 1 × guard column 100 Å, 3 × columns with flask and dissolved in 20 mL toluene. Zinc iodide (0.32 g,
10.000, 1000 und 100 Å). The system was calibrated with poly- 1 mmol) and boron triflouride diethyl etherate (0.30 g, 1 mmol)
styrene standards with a molecular range from 575 g/mol to were added. The flask was closed with a plug and the reaction
3,114,000 g/mol. Toluene was added to the analytes as an mixture was heated to 80 °C for 24 h. The solvent was evapo-
internal standard. Rheologial measurements were performed by rated and the crude product dissolved in 20 mL of
using a Haake Mars II rheometer by ThermoFisher Scientific. dichloromethane. Filtration and subsequent purification by
For rotation measurements a plate–plate construction (PP35 Ti, column chromatography over silica gel (ethyl acetate/petrol
D = 35; MP35) was used. The temperature was measured with ether 1:1) afforded the pure product in 66% yield. 1H NMR
an accuracy of ±0.5 ° C in the measuring plate. The control of (300 MHz, DMSO-d6) δ (ppm) 8.27–8.21 (m, 2H, Ar-H), 7.91
the thermostat (Haake DC30 or Haake AC 200-G50) was (s, 1H, -CH=N-), 7.46–7.39 (m, 3H, Ar-H), 4.19 (t, 3J = 6.4 Hz,
controlled by the software. Differential scanning calorimetry 2H, -CH2-CH2-) 3.61 (s, 3H, -CH3), 2.92 (t, 3J = 6.5 Hz, 2H,
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Beilstein J. Org. Chem. 2014, 10, 902–909.
-CH2-CH2-); 13C NMR (125 MHz, DMSO-d6) δ (ppm) 171 MHz, DMSO-d6) δ (ppm) 172–169 (-C=O), 129–127 (Ar-C),
(C=O), 134 (-C=N-), 131 (Ar-C), 130 (Ar-C), 128 (4C, Ar-C), 81 (-C-), 69 (Ar-CH-), 53–51 (-O-CH3), 48 (Ar-CH-CH2-), 42
61 (-CH2-CH2-), 53 (-O-CH3), 31 (-CH2-CH2-); FTIR (-C-CH2-C=O), 41 (-N-CH2-CH2-), 32 (-N-CH2-CH2-); FTIR
(diamond) (cm−1): 3059, 2996, 2952 (ν, -CH3, -CH2), 1731 (diamond) (cm−1): 2953, 2917, 2850 (ν, -CH3, -CH2), 1733
(ν, -C=O), 1172 (ν, -C-O-C-), 1581 (ν, C=N), 1149 (ν, N-O) (ν, -C=O), 1195 (ν , N-O), 1173 (ν, -C-O-C-), 756, 701 (ν, -Ar);
753, 691 (ν, -Ar); EIMS m/z: 221 [M+], 205 [M+ − ESIMS m/z: 366 [M+].
C12H15NO2], 190 [M+ − C11H13NO2], 132 [M+ −C9H10N], 104
[M+ − C7H6N].
Methyl 5-(2-methoxy-2-oxoethyl)-2-(4-methoxy-4-oxobut-2-
yl)-3-phenylisoxazolidine-5-carboxylate (5b): 1H NMR
Synthesis of methyl 3-[benzylidene(oxido)amino]butanoate (300 MHz, DMSO-d6) δ (ppm) 7.4–7.25 (m, 5H, Ar-H),
(3b): Methyl crotonate (2b, 1 g, 10 mmol) and benzaldoxime 4.25–3.80 (m, 1H, Ar-CH-), 3.72–3.48 (m, 9H, -O-CH3),
(1, 2.42 g, 20 mmol) were placed in a 100 mL round bottom 3.27–2.98 (m, 1H, -N-CH-CH2-), 3.06–2.84, (m, 2H, -C-CH2-
flask and dissolved in 40 mL toluene. Zinc iodide (0.48 g, C=O), 3.02–2.27 (m, 2H, Ar-CH-CH2-), 2.90–2.13 (m, 2H,
1.5 mmol) and boron triflouride diethyl etherate (0.44 g, -N-CH-CH2-), 1.04–0.90 (m, 3H, -CH-CH3-); 13C NMR (125
1.5 mmol) were added. The flask was closed with a plug, and MHz, DMSO-d6) δ (ppm) 173–169 (-C=O), 129–127 (Ar-C),
the reaction mixture was heated to 80 °C for 24 h. The solvent 81–80 (-C-), 69 (Ar-CH-), 56 (-N-CH-CH2-), 53–51 (-O-CH3),
was evaporated, and the crude product dissolved in 20 mL of 48–46 (Ar-CH-CH2-), 42 (-C-CH2-C=O), 36 (-N-CH-CH2-),
dichloromethane. Filtration and subsequent purification by 20–12 (-CH-CH3); FTIR (diamond)
(cm−1): 2953, 2920,
column chromatography over silica gel (ethyl acetate/petrol 2847 (ν, -CH3, -CH2), 1731 (ν, -C=O), 1197 (ν , N-O), 1170 (ν,
ether 1:2) afforded the pure product in 46% yield. 1H NMR -C-O-C-), 757, 701 (ν, -Ar); ESIMS m/z: 380 [M+].
(300 MHz, DMSO-d6) δ (ppm) 8.28–8.22 (m, 2H, Ar-H), 7.95
(s, 1H, -N=CH-Ar), 7.44–7.39 (m, 3H, Ar-H), 4.60 (m, 1H, Synthesis of 2,5-di-O-acryloyl-1,4:3,6-dianhydro-D-glucitol
-CH-CH3), 3.57 (s, 3H, -O-CH3), 3.00 (dd, 2J = 16.7, 3J = 8.9 (9a): A 250 mL round bottom flask was charged with isosor-
Hz, 1H, -CH-CH2-), 2.67 (dd, 2J = 16.7, 3J = 4.6 Hz, 1H, -CH- bide (7.31 g, 50 mmol) dissolved in 100 mL of
CH2-), 1.37 (d, 3J = 6.6 Hz, 3H, -CH-CH3); 13C NMR (125 dichloromethane. Then triethylamine (11.69 g, 115 mmol) was
MHz, DMSO-d6) δ (ppm) 171 (C=O), 133 (-C=N), 132 (Ar-C), added and the reaction mixture was cooled to 0 °C. Acryloyl
130 (Ar-C), 129 (2 C, Ar-C), 128 (2 C, Ar-C), 67 (-CH-CH3), chloride (10.26 g, 110 mmol) was dissolved in 50 mL
52 (-O-CH3), 38 (-CH-CH2-), 19 (-CH-CH3); FTIR (diamond) dichloromethane and added via a dropping funnel under
(cm−1): 3056, 2986, 2951 (ν, -CH3, -CH2), 1733 (ν, -C=O), vigorous stirring. The reaction mixture was stirred for addition-
1175 (ν, -C-O-C-), 1148 (ν, N-O), 753, 691 (ν, -Ar); EIMS m/z: al 24 h after complete addition. Precipitated ammonium chlo-
207 [M+], 192 [M+ − C11H13NO2], 134 [M+ − C9H12N], 132 ride was removed by filtration and the obtained solution was
[M+ − C9H10N], 91 [M+ − C7H7].
washed with 2 × 50 mL of saturated sodium hydrogen carbonate
solution. The pure product was received after drying of the
General procedure for 1,3-dipolaric cycloaddition of nitrons organic layer over magnesium sulfate and subsequent removal
3a/b with dimethyl itaconate (4): A vial was charged with of the solvent under reduced pressure. Yield: 94%. 1H NMR
2 mmol of nitron 3a or 3b and 20 mmol of dimethyl itaconate (300 MHz, CDCl3) δ (ppm) 6.58–6.33 (m, 2H, H2C=CH-),
(4). The reaction mixture was stirred at 120 °C for 1 h and puri- 6.22–6.01 (m, 2H, H2C=CH-), 5.89–5.80 (m, 2H, H2C=CH-),
fied via column chromatography (ethyl acetate/petrol ether 1:4). 5.29–5.16 (m, 2H, -CH-O-CO-), 4.87 (t, 3J = 5 Hz, 1H, -CH-
Yield: 74–75%.
CH-), 4.51 (d, 3J = 4.9 Hz, 1H, -CH-CH-), 4.00–3.80 (m, 4H,
-CH-CH2-, -CH-CH2-); 13C NMR (125 MHz, CDCl3) δ (ppm)
Methyl 5-(2-methoxy-2-oxoethyl)-2-(3-methoxy-3-oxo- 165 (2C, C=O), 132 (2C, H2C=CH-), 128 (2C, H2C=CH-), 86
propyl)-3-phenylisoxazolidine-5-carboxylate (5a): cis- (1C, -CH-CH-), 81 (1C, -CH-CH-), 78 (1C, -CH-O-CO-), 74
isomer: 1H NMR (300 MHz, DMSO-d6) δ (ppm) 7.39–7.28 (m, (1C, -CH-O-CO-), 73 (1C, -CH-CH2-), 70 (1C, -CH-CH2-);
5H, Ar-H), 3.92 (m, 1H, Ar-CH-), 3.70–3.52 (m, 9H, -O-CH3), FTIR (diamond) (cm−1): 2980, 2876 (ν, -CH3, -CH), 1721 (ν,
3.02–2.92 (m, 2H, -C-CH2-C=O), 2.95 (m, 2H, Ar-CH-CH2-), -C=O), 1634 (ν, C=C), 1179 (ν, -C-O-C-); EIMS m/z: 255 [M+],
2.89 (m, 2H, -N-CH2-CH2-), 2.48 (m, 2H, -N-CH2-CH2-), 2.42 183 [M+ − C9H11O4], 128 [M+ − C6H8O3].
(m, 2H, Ar-CH-CH2-); trans-isomer: 1H NMR (300 MHz,
DMSO-d6) δ (ppm) 7.3–7.28 (m, 5H, Ar-H), 3.82 (m, 1H, Synthesis of 1,4:3,6-dianhydro-2,5-di-O-but-2-enoyl-D-
Ar-CH-), 3.70–3.52 (m, 9H, -O-CH3), 3.02–2.92 (m, 2H, glucitol (9b): A 250 mL round bottom flask was charged with
-C-CH2-C=O), 2.89 (m, 2H, -N-CH2-CH2-), 2.72 (m, 2H, isosorbide (7.31 g, 50 mmol), crotonic acid (9.04 g, 105 mmol),
Ar-CH-CH2-), 2.48 (m, 2H, -N-CH2-CH2-); 13C NMR (125 p-toluenesulfonic acid (0.86 g, 5 mmol), phenothiazine (0.02 g,
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Beilstein J. Org. Chem. 2014, 10, 902–909.
0.1 mmol) and 80 mL of toluene. The flask was fitted with a diethyl ether. Yield: 60%. 1H NMR (300 MHz, DMSO-d6) δ
Dean–Stark apparatus and the mixture was heated under reflux (ppm) 8.34–8.16 (m, 4H, Ar-H), 7.98–7.91 (m, 2H, -CH=N-),
for 72 h. The solution was washed with 2 × 40 mL of saturated 7.45–7.37 (m, 6H, Ar-H), 5.12–4.93 (m, 2H, -CH-O-CO-),
sodium hydrogen carbonate solution and the organic layer was 4.69–4.51 (m, 3H, -CH-CH-, -CH-CH3), 4.37–4.22 (m, 1H,
dried over magnesium sulfate. The pure product was obtained -CH-CH-), 3.94–3.59 (m, 4H, -CH-CH2-, -CH-CH2-),
by evaporation of the solvent. Yield: 92%. 1H NMR (300 MHz, 3.10–2.87 (m, 2H, O-N-CH-CH2-), 2.75–2.57 (m, 2H, O-N-
CDCl3) δ (ppm) 7.11–6.94 (m, H3C-HC=CH-), 5.96–5.79 (m, CH-CH2-), 1.37 (d, 3J = 6.5 Hz, 6H, -CH-CH3); 13C NMR (75
1H, H3C-HC=CH-), 5.33–5.08 (m, 2H, -CH-O-CO-), 4.86 (t, 3J MHz, DMSO-d6) δ (ppm) 170 (2C, C=O), 134 (2C, -CH=N-),
= 5 Hz, 1H, -CH-CH-), 4.53 (d, 3J = 4.6 Hz, 1H, -CH-CH-), 132 (2C, Ar-C), 131 (2C, Ar-C), 128 (8C, Ar-C), 85 (1C, -CH-
4.07–3.79 (m, 4H, -CH-CH2-, -CH-CH2-), 1.93–1.85 (m, 6H, CH-), 82 (1C, -CH-CH-), 78 (1C, -CH-O-CO-), 72 (2C, -CH-O-
H3C-HC=CH-); 13C NMR (125 MHz, DMSO-d6) δ (ppm) δ CO-, -CH-CH2-), 71 (1C, -CH-CH2-), 67 (2C, O-N-CH-CH2-),
165 (2C, C=O), 145 (2C, H3C-HC=CH-), 122 (2C, H3C- 31 (2C, O-N-CH-CH2-), 19 (2C, -CH-CH3); FTIR (diamond)
HC=CH-), 86 (1C, -CH-CH-), 81 (1C, -CH-CH-), 78 (1C, -CH- (cm−1): 2975, 2936, 2876 (ν, -CH3, -CH2), 1734 (ν, -C=O),
O-CO-), 74 (1C, -CH-O-CO-), 74 (1C, -CH-CH2-), 70 (1C, 1580 (ν, C=N), 1176 (ν, -C-O-C-), 1148 (ν, N-O), 755, 692 (ν,
-CH-CH2-), 18 (2C, H3C-HC=CH-); FTIR (diamond) (cm−1): Aryl); ESIMS m/z: 525 [M+].
2975, 2876 (ν, -CH3, -CH), 1717 (ν, -C=O), 1656 (ν, C=C),
1172 (ν, -C-O-C-); ESIMS m/z: 283 [M+].
Synthesis of poly(isosorbide itaconate -co- succinate) 13: A
250 mL round bottom flask was charged with isosorbide
Synthesis of 1,4:3,6-dianhydro-2,5-bis-O-{3-[benzyl- (5.85 g, 40 mmol), itaconic acid (2.60 g, 20 mmol), succinic
idene(oxido)amino]propanoyl}-D-glucitol (10a): Compound acid (2.36 g, 20 mmol), p-toluenesulfonic acid (0.04 g,
9a (1.27 g, 5 mmol) and benzaldoxime (1, 2.42 g, 20 mmol) 0.2 mmol), phenothiazine (0.02 g, 0.1 mmol) and 80 mL
were placed in a 100 mL round bottom flask and dissolved in toluene. The flask was fitted with a Dean–Stark apparatus and
20 mL toluene. Zinc iodide (0.32 g, 1 mmol) and boron the solution was heated under reflux for 72 h. The solution was
triflouride diethyl etherate (0.30 g, 1 mmol) were added. The concentrated after cooling to room temperature and the crude
flask was closed with a plug and the reaction mixture was product was dissolved in a small amount of dichloromethane
heated to 80 °C for 24 h. The solvent was evaporated and the and precipitated in 300 mL methanol. The product was again
crude product washed with 50 mL of isopropanol and 50 mL of dissolved in dichloromethane and the pure polyester was
diethyl ether. Yield: 95%. 1H NMR (300 MHz, DMSO-d6) δ isolated by removing the solvent under reduced pressure.
(ppm) 8.29–8.17 (m, 4H, Ar-H), 7.90 (s, 2H, -CH=N-), 1H NMR (300 MHz, CDCl3) δ (ppm) 6.39 (m, 1H), 5.78 (m,
7.48–7.37 (m, 6H, Ar-H), 5.16–5.02 (m, 2H, -CH-O-CO-), 4.72 1H), 5.20 (m, 2H), 4.82 (m, 1H), 4.47 (m, 1H), 3.90 (m, 4H),
(t, 3J = 5.3 Hz, 1H, -CH-CH-), 4.39 (d, 3J = 5.3 Hz, 1H, -CH- 3.39 (s, 1H), 3.33 (s, 1H), 2.67 (m, 2H); FTIR (diamond)
CH-), 4.25–4.13 (m, 4H, O-N-CH2-CH2-), 3.85–3.70 (m, 4H, (cm−1): 2977, 2935, 2877 (ν, -CH2), 1729 (ν, C=O), 1639 (ν,
-CH-CH2-, -CH-CH2-), 3.05–2.85 (m, 4H, O-N-CH2-CH2-); C=C), 1151 (ν, C-O); GPC (THF):
13C NMR (125 MHz, DMSO-d6) δ (ppm) 170 (2C, C=O), 134 Tg = 64 °C.
(2C, -CH=N-), 131 (2C, Ar-C), 130 (2C, Ar-C), 128 (8C,
= 3452; D = 1.69; DSC:
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