Synthesis of piperazine-1,4-dipropanoic acid Di(1,2,2,6,6-pentamethyl-4-piperidine)yl ester as a photostabilizer

Article abstract of DOI:10.1134/S1070363214110292

A new type hindered amine light stabilizer (HALS) has been synthesized. The derivatives of piperazine and piperidine have been combined via the transesterification reaction. Effects of such variables as molar ratio, catalyst dosage, reaction time, and temperature were studied and optimized. The structures of all products were elucidated by FT-IR spectroscopy and NMR spectrometry.

Full text of DOI:10.1134/S1070363214110292

ISSN 1070-3632, Russian Journal of General Chemistry, 2014, Vol. 84, No. 11, pp. 2218–2221. © Pleiades Publishing, Ltd., 2014.
Synthesis of Piperazine-1,4-Dipropanoic Acid
Di(1,2,2,6,6-pentamethyl-4-piperidine)yl Ester
as a Photostabilizer1
Xiao Fenga,b, Zhou Yuanlina,b, and Yang Wenbina,b
a State Key Laboratory Cultivation Base for Nonmetal Composite
and Functional Materials Southwest University of Science and Technology, Mianyang, 621010 China
b Department of Material Science and Engineering,
Southwest University of Science and Technology, Mianyang, 621010 China
e-mail: zhouyuanlin@swust.edu.cn
Received September 5, 2014
Abstract—A new type hindered amine light stabilizer (HALS) has been synthesized. The derivatives of
piperazine and piperidine have been combined via the transesterification reaction. Effects of such variables as
molar ratio, catalyst dosage, reaction time, and temperature were studied and optimized. The structures of all
products were elucidated by FT-IR spectroscopy and NMR spectrometry.
Keywords: hindered amine, light stabilizer, transesterification, piperazine, piperidine
DOI: 10.1134/S1070363214110292
Rubber materials are indispensable in our daily life
[1]. Rubber polymers undergo oxidative degradation
under the influence of sunlight throughout their
lifetime [2]due to the unsaturated bonds in their chains
[3], resulting in the discoloration, cracking, stiffening,
and decrease in the physico-mechanical and chemical
ies of rubber characteristics that make their service life
shorter resulting in negative influence on the
environment [4]. Maintaining of the unique properties
of rubber polymers for longer time can be achieved by
blending in a small quantity of a stabilizer [5].
with other acidic components in the system, (4) high
thermal and oxygen resistance. Combined together in a
compound these exhibit pronounced synergic
stabilizing effect [15] making application scope of a
new stabilizer much broader.
In order to combine the derivatives of piperidine
and piperazine in the same molecule we designed and
successfully synthesized piperazine_1,4-dipropanoic
acid di(1,2,2,6,6-pentamethyl-4-piperidine)yl ester via
transesterification of piperazine-1,4-dipropanoic acid
diemthyl ester with 1,2,2,6,6-pentamethyl-4-pipe-
ridinol (Scheme 1). Transesterification of the ester
with piperidinol is more complicated than with ali-
phatic alcohols due to the stereo structure of piperidinol.
Among the efficient light and heat stabilizers are
those of HALS type that are predominantly derivatives
of 2,2,6,6-tetramethyl piperidine [6–9]. They form
nitroxide radicals either reacting with peroxy radicals
or occasionally with atmospheric oxygen [10, 11]. The
nitroxide radicals can regenerate and capture alkyl
radicals efficiently retarding the degradation process
[12, 13]. HALS can be classified as the derivatives of
piperidine, piperazine and imidazolidazolidinone
depending on the structure of a parent molecule [14].
Compared to piperidine derivatives piperazine
derivatives have some advantages: (1) low alkalinity,
(2) high compatibility with resin, (3) weak interactions
Effect of substrate molar ratio. The molar ratio of
substrates, namely piperazine-1,4-dipropanoic acid
dimethyl ester to 1,2,2,6,6-pentamethyl-4-piperidinol
had an impact on the yield of the process (Table 1) due
to specific features of transesterification. The reaction
can be shifted to the right applying an excess of
1,2,2,6,6-pentamethyl-4-piperidinol and removing
small molecular weight byproducts. Methanol can be
removed efficiently by 3A molecular sieves.
Effect of catalyst loading. The catalyst was
studied in the rate range from 1.0% to 3.0% (w/w of
substrates) under otherwise similar conditions.
1 The text was submitted by the authors in English.
2218

SYNTHESIS OF PIPERAZINE-1,4-DIPROPANOIC ACID
2219
O
O
O
O
.
N
O
O
O
N
NH 6H2O
HN
I
II
OH
N
O
N
O
N
O
N
N
III
Scheme 1. Synthesis of piperazine-1,4-dipropanoic acid di(1,2,2,6,6-pentamethyl-4-piperidine)yl ester.
According to Table 2, the yield increased with an
increase in the catalyst loading from 1.0% to 3.0%
gradually. 2.0% CH3ONa was singled out as an
optimum rate in the process.
Toluene was distilled freshly over benzophenone-
sodium. 3A molecular sieves were activated by
heating. TLC was performed on GF254 glass-backed
silica gel plates and visualized in an iodine chamber.
NMR was recorded by a Bruker AVANCE 600 spec-
trometer [1H (600 MHz) 13C (151 MHz)], Switzerland,
in CDCl3 with TMS as an internal standard. FT-IR
were recorded in the solid state as KBr pellets by a
Spectrum One (Version BM) spectrometer of US PE
Instrument Company. Elemental analyses was carried
out by a Vario EL CUBE of Elementar Analysen-
systeme GmbH.
Effect of temperature. Heating improved the rate
of conversion of piperazine-1,4-dipropanoic acid
dimethyl ester and 1,2,2,6,6-pentamethyl-4-piperidinol
in the endothermic reaction (Table 3). The yield
increased from 86.2% to 92.0% within the temperature
range 120 to 150°C The temperature 150°C was
maintained in the subsequent experiments.
Effect of reaction time. Yield of the product
gradually increased with longer reaction time. But it
did not improve after 12 h of heating probably due to
an equilibrium of the reaction reached (Table 4).
Piperazine-1,4-dipropanoic acid dimethyl ester
(II). A mixture of piperazine hexahydrate (0.1942 g,
1 mmol), methyl acrylate (0.2152 g, 2.5 mmol) and
graphene oxide dispersion in water (5 mL) were loaded
in a 50 mL three-neck round-bottom flask. The
reaction mixture was vigorously stirred at room
temperature for 30 min. Progress of the reaction was
EXPERIMENTAL
All chemicals and solvents were used without
additional purification unless otherwise specified.
Table 1. Effect of n(ester) : n(alcohol) ratio on trans-
esterification. Reaction conditions: n(ester) : n(alcohol) =
1 : 2.2, 150°C, 12 h
Table 2. Effect of the catalyst rate on transesterification.
Reaction conditions: n(ester) : n(alcohol) = 1 : 2.2, 150°C,
12 h
n(ester) : n(alcohol)
1 : 2.0
Yield, %
88.3
Catalyst mass fraction, %
Yield, %
81.6
1.0
1.5
2.0
2.5
3.0
1 : 2.1
91.2
88.7
1 : 2.2
92.6
92.0
1 : 2.3
92.8
92.4
1 : 2.4
92.9
92.6
RUSSIAN JOURNAL OF GENERAL CHEMISTRY Vol. 84 No. 11 2014

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XIAO FENG et al.
Table 3. Effect of the reaction temperature on trans-
esterification. Reaction conditions: ω(CH3ONa) = 2.0%,
n(ester) : n(alcohol) = 1 : 2.2, 12 h
Table 4. Effect of reaction time on transesterification. Reac-
tion conditions: ω(CH3ONa) = 2.0%, n(ester) : n(alcohol) =
1 : 2.2, 12 h
Temperature, °C
Yield, %
86.2
Time, h
Yield, %
83.7
120
130
140
150
160
8
89.1
10
12
14
16
89.2
90.8
92.0
92.0
92.2
92.1
92.3
monitored by TLC. Upon completion of the procesrs
the reaction mixture was extracted repeatedly with
ethyl acetate and the organic lay dried over anhydrous
sodium sulfate and concentrated in vacuum to yield a
white solid compound. FT-IR, ν, cm–1: 2957, 2873,
1379 (CH3), 2940, 2829, 1460 (CH2), 1733 (C=O),
CH3), 1.06 s (12H, piperidine CH3). 13C NMR spect-
rum, δC, ppm: 20.88, 26.20, 32.80, 33.24, 45.96, 52.99,
53.72, 55.45, 67.90, 172.30. Found, %: C 67.05; H
10.48; N 10.32; O 12.15. C30H56N4O4. Calculated, %:
C 67.13; H 10.52; N 10.44; O 11.92.
1
1265 (C–O), 1149 (C–O–C), 1195 (C–N). H NMR
CONCLUSIONS
spectrum, δ, ppm: 3.67 s (6H, CH3), 2.68 d.d (4H,
CH2C=O), 2.55–2.35 m [12H, (CH2)2NCH2]. 13C NMR
spectrum, δC, ppm: 32.13, 51.66, 52.90, 53.55, 172.92.
Found, %: C 56.04; H 8.37; N 24.80; O 10.79.
C12H22N2O2. Calculated, %: C 55.80; H 8.58; N 24.78;
O 10.84.
Piperazine_1,4-dipropanoic acid di(1,2,2,6,6-penta-
methyl-4-piperidine)yl ester was successfully syn-
thesized in the process of transesterification. The
optimum reaction conditions were 150°C, reaction
time 12 h, CH3ONa rate 2.0% (w/w of substrates), and
1 : 2.2 ester : alcohol molar ratio, toluene media with
3A molecular sieves. The optimal condition led to the
yield 92.0%.
Piperazine-1,4-dipropanoic acid di(1,2,2,6,6-penta-
methyl-4-piperidine)yl ester (III). Piperazine-1,4-di-
propanoic acid dimethyl ester (0.2585 g, 1.002 mmol),
1,2,2,6,6-pentamethyl-4-piperidinol (0.3781 g,
2.208 mmol), toluene (10 mL), CH3ONa (0.0127 g,
0.2356 mmol, 2% of the total amount of reactants) and
3A molecular sieves were loaded in a 50 mL round
bottom flask the reaction mixture was refluxed at 150°C
for 12 h. The reaction was monitored by TLC. Upon
completion of the reaction the solvent was evaporated
in vacuum and the residue washed with hot water. The
organic layer was separated and the aqueous phase
extracted with ethyl acetate. The combined extracts
and organic phase were dried over sodium sulfate and
concentrated under vacuum. The product was
recrystallized from hot petroleum ether in the form of a
white solid. FT-IR, ν, cm–1: 2972, 1349 (CH3), 2806,
1457 (CH2), 1728 (C=O), 1298 (C–O), 1008 (C–O–C),
ACKNOWLEDGMENTS
We express thanks to Zhai, W.-Q the University of
Science and Technology of China for carrying out
NMR. We are also thankful for the financial support
from NSAF of China (no. 11176026).
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