Synthesis and photostabilizing properties of hexachlorobicyclo[2.2.1]hept- 5-enylmethyl esters of substituted benzoic acids

Article abstract of DOI:10.1134/S107042720803018X

Polychlorinated bicyclic esters of p-substituted benzoic acids were prepared by the Diels-Alder reaction of hexachlorocyclopentadiene with allyl esters of p-substituted benzoic acids. Some of the adducts synthesized were tested as photostabilizers for polyethylene-based polymer formulations.

Full text of DOI:10.1134/S107042720803018X

ISSN 1070-4272, Russian Journal of Applied Chemistry, 2008, Vol. 81, No. 3, pp. 438 442. Pleiades Publishing, Ltd., 2008.
Original Russian Text
No. 3, pp. 453 457.
T.G. Kyazimova, E.G. Mamedov, R.S. Babaev, I.M. Mamedova, 2008, published in Zhurnal Prikladnoi Khimii, 2008, Vol. 81,
ORGANIC SYNTHESIS
AND INDUSTRIAL ORGANIC CHEMISTRY
Synthesis and Photostabilizing Properties
of Hexachlorobicyclo[2.2.1]hept-5-enylmethyl Esters
of Substituted Benzoic Acids
T. G. Kyazimova, E. G. Mamedov, R. S. Babaev, and I. M. Mamedova
Institute of Chemical Problems, National Academy of Sciences of Azerbaijan, Baku, Azerbaijan
Insitute of Petrochemical Processes, National Academy of Sciences of Azerbaijan, Baku, Azerbaijan
Received January 24, 2007
Abstract Polychlorinated bicyclic esters of p-substituted benzoic acids were prepared by the Diels Alder
reaction of hexachlorocyclopentadiene with allyl esters of p-substitutted benzoic acids. Some of the adducts
synthesized were tested as photostabilizers for polyethylene-based polymer formulations.
DOI: 10.1134/S107042720803018X
Hexachlorocyclopentadiene (HCCPD, I) and re-
lated compounds are among unusual objects of the
modern organic chemistry. Thanks to HCCPD, the
theory of X-philic reactions was developed, and the
theory of pericyclic reactions was supplemented by
the reversed Diels Alder reaction. The syn anti iso-
merism of diene condensation adducts was substanti-
ated using data for HCCPD derivatives [1]. Simple
synthesis of dihomocubane compounds from poly-
halogenated cyclopentadienes attracts attention. Hexa-
chlorocyclopentadiene and related compounds, along
with practical significance, are of interest for elucidat-
ing the mechanism of the Diels Alder reaction [2].
fiers and curing agents for epoxy resins and biologi-
cally active substances [3].
Synthesis of various polyhalogenated bicyclic
esters from unsaturated esters of substituted benzoic
acids attracts researchers’ attention [4, 5].
Proceeding with studies in the field of synthesis of
polyhalogenated bicyclic esters [6 9], we prepared,
identified, and examined polyhalonorbornenylmethyl
esters of p-substituted benzoic acids. First, we pre-
pared by a common esterification procedure allyl
esters of p-substituted benzoic acids II VIII. Their
physicochemical properties are given in Table 1.
Target products IX XV were prepared by diene
condensation of HCCPD I with allyl esters of p-sub-
stituted benzoic acids II VIII. The reaction follows
the scheme
Halogen-containing bicyclic esters with other
unique fragments are widely used for imparting flame
resistance to polymeric materials, and also as modi-
,
I
IX XV
II VIII
where R = H (II, IX), CH (III, X), HO (IV, XI),
The reaction was performed in the temperature
range 100 160 C for 4 12 h; the diene : dienophile
molar ratio was from 1 : 1 to 4 : 1. The physicochemi-
3
MeO (V, XII), Cl (VI, XIII), Br (VII, XIV), NO
(VIII, XV).
2
438

SYNTHESIS AND PHOTOSTABILIZING PROPERTIES
Table 1. Constants of allyl esters of p-substituted benzoic acids
439
Compound
Tb, C (1 mm Hg)
n2D0
d240
Yield, %
Allyl benzoate (II)
74 75
90 92
85 87
90 92
85 89
95
1.5156
1.4940
1.5040
1.5010
1.6343
1.5546
1.5420
1.056
80
58
60
60
78
82
58
Allyl p-methylbenzoate (III)
Allyl p-hydroxybenzoate (IV)
Allyl p-methoxybenzoate (V)
Allyl p-chlorobenzoate (VI)
Allyl p-bromobenzoate (VII)
Allyl p-nitrobenzoate (VIII)
0.8861
1.0348
1.0115
1.2055
1.3305
1.1218
128 132
Table 2. Properties and elemental analyses of polychloronorbornenyl esters of substituted benzoic acids
Found, %
H
Calculated, %
Com- Tb, C (P, mm Hg)
n2D0
d240
Formula
pound
or Tm,
C
C
Hlg
C
H
Hlg
IX
X
XI
XII
XIII
XIV
XV
193 194 (1), Tm 50 1.5775
1.4625
1.6340
1.4986
1.5010
41.38
42.36
38.4
2.30
2.55
1.80
1.92
1.92
1.75
1.90
48.97 C15H10Cl6O2
47.06 C16H12Cl6O2
46.4 C15H10Cl6O3
38.7 C16H12Cl6O3
52.56 C15H9Cl7O2
57.0 C15H9Cl6BrO2 34.86
30.02 C15H9Cl6O4 37.64
41.02
42.76
40.0
41.03
38.09
2.15
2.67
2.2
2.58
1.67
1.46
1.58
48.64
47.44
47.2
45.08
52.56
56.74
29.88
207 208 (1)
188 190 (1)
185 186 (2)
97 98
1.5750
1.5800
1.5820
39.6
38.34
35.02
38.06
126
126
cal properties of IX XV are given in Table 2.
[2.2.1]hept-5-ene XVI by the reaction of I with allyl
alcohol according to [10], followed by esterification
of alcohol XVI with p-substituted benzoic acids
XVII XXIII to obtain the corresponding bicyclic
esters IX XV:
We examined the effect of reaction conditions
(temperature, time, reactant ratio) on the yield of the
adducts (Table 3).
As can be seen, with an increase in the temperature
from 100 to 150 C the yield of adduct IX increases from
58.2 to 82.4%. Further increase in the temperature
(160 C) only slightly affects the yield of IX. The data
obtained also show that the optimal conditions of
Table 3. Influence of reaction conditions on the yield of
adducts IX XV
Dieno-
phile
,
h
Diene : dieno- Yield of adducts
T,
C
adduct formation (with the reaction I + II
IX as
phile molar ratio
IX XV, %
example) are as follows: 150 C, 12 h, diene : dieno-
phile ratio 2 : 1.
II
II
II
II
II
II
II
II
100
12
12
12
12
12
12
4
2 : 1
2 : 1
2 : 1
2 : 1
1 : 1
4 : 1
2 : 1
2 : 1
2 : 1
2 : 1
2 : 1
2 : 1
2 : 1
2 : 1
2 : 1
58.2
65.3
82.4
84.2
64.2
69.4
43.3
49.2
85.1
64.1
73.2
90.7
78.8
65.4
82.7
120
150
160
150
150
150
150
150
150
150
150
150
150
150
Under similar optimal conditions (150 C, 12 h,
diene : dienophile molar ratio 2 : 1), we performed the
condensation of HCCPD with allyl esters of other
p-substituted benzoic acids III VIII. The yields of
adducts X XII vary within 65.4 90.7%, with the
lowest yield observed with allyl halobenzoates VI and
VII (78.8 and 65.4%, respectively). On introducing
p-hydroxy, p-methoxy, and p-nitro groups into the
aromatic ring, the yield of the adducts increases (90.7,
88.6, and 82.7%, respectively).
8
II
16
12
12
12
12
12
12
III
IV
V
VI
VII
VIII
The compositions and structures of IX XV were
proved by independent synthesis: preparation of
2-endo-hydroxymethyl-1,4,5,6,7,7-hexachlorobicyclo-
RUSSIAN JOURNAL OF APPLIED CHEMISTRY Vol. 81 No. 3 2008

440
KYAZIMOVA et al.
p
XVII XXIII
XVI
,
Benzene,
refluxing
p
IX XV
where R = H, CH , HO, MeO, Cl, Br, NO .
chloronorborn-5-ene-2-carboxylate was confirmed by
single crystal X-ray diffraction [16].
3
2
All the physicochemical characteristics of com-
pounds IX XV prepared by both procedures are iden-
tical.
The synthesized compounds IX XV were tested as
photostabilizers for polymer formulations based on
high-density polyethylene (HDPE). These compounds
were added in amounts of 0.2, 0.5, and 0.8%. Com-
pounds IX and XIV appeared to be the most active.
On adding stabilizer IX to HDPE, the relative break-
ing elongation of the irradiated samples increased by
a factor of almost 2 compared to the pure polymer,
which is due to good compatibility of the stabilizer
with HDPE. The results of the tests are given in
Table 5.
The compositions and structures of IX XV are
1
confirmed by IR and H NMR spectra. The purity was
checked by TLC. In the IR spectra of IX XV, there
are characteristic bands of the C=O bond at 1720
1740, ester C O bond at 1000 1200, and C Cl bonds
1
at 750 cm . The C=C vibrations have somewhat
1
decreased frequency, 1575 1685 cm , because of the
1
presence of chlorine atoms at the double bond. The H
NMR data for IX XV are given in Table 4.
After UV irradiation for 200 h, the stabilized for-
mulations exhibited considerably better properties
than straight high-density polyethylene. The breaking
1
The H NMR spectra of polychlorinated norbor-
nenylmethyl derivatives show an ABX pattern. The
lowest-field signal was assigned to the proton adjacent
tensile stress ( ) of the initial polymer decreased
B
X
to the electronegative substituent, H . As indicated in
upon irradiation by 70%, and that of the stabilized
polymer, by only 10 13%. The dielectric loss tangent
(tan ) of the stabilized samples also varied signifi-
cantly. The lack of degradation of the stabilized
HDPE after UV irradiation is confirmed by the results
of UV studies. The suggested photostabilizers are
light yellow, and their performance meets the require-
ments of the modern standards.
X
A
[11], the coupling constants of H with protons H
B
and H differ by a factor of approximately 2. The
2
endo orientation of the substituent at C is confirmed
1
by the H NMR spectra (Table 4) whose parameters
are similar to those of the spectra of the known chlori-
nated analogs [12], hexabromonorbornenes [13], and
1,4,5,6-tetrabromo-7,7-dimethoxynorbornenes
[14].
2
The endo orientation of the CN substituent at the C
atom of the hexabromonorbornene core is confirmed
by comparison of the experimental and calculated
dipole moments [13]. In addition, it is known that, in
the case of exo orientation of the CN substituent at the
EXPERIMENTAL
The IR spectra were recorded on a UR-20 spectro-
1
photometer in the range 4000 400 cm , and the
2
C atom of pentachloronorbornene, the parameters of
1
H NMR spectra, on a Tesla BS-48 spectrometer
1
the H NMR spectrum are essentially different [15].
(80 MHz) in CCl , internal reference hexamethyldi-
4
The endo configuration of 2S-( )-menthyl hexa-
siloxane. The TLC analysis was performed by the
RUSSIAN JOURNAL OF APPLIED CHEMISTRY Vol. 81 No. 3 2008

SYNTHESIS AND PHOTOSTABILIZING PROPERTIES
Table 4. 1H NMR spectra of IX XV
441
B
A
X
Chemical shift, , ppm
Coupling constant, Hz
Com-
pound
R
HA, q
HB, q
HX, m
OCH2 (2H), t
JAX
JBX
JAB
IX
X
XI
XII
XIII
XIV
XV
H
CH3
OH
OMe
Cl
Br
NO2
1.73
2.00
2.15
2.10
1.90
1.93
2.10
2.60
2.73
2.80
2.86
2.70
2.70
2.80
3.17
3.25
3.40
3.30
3.30
3.25
3.50
4.20
4.20
4.30
4.50
4.14
4.30
4.30
8.3
8.5
8.4
8.1
8.4
8.2
8.5
4.80
4.25
4.15
4.29
4.15
4.10
4.25
11.90
12.10
12.31
12.27
12.60
12.50
12.70
Table 5. Properties of stabilized formulations based on compounds IX and XIV
Parameter value after irradiation for 200 h
Stabilizer
Formulation
content, %
2
4
B, kgf cm
80
shrinkage, % MFI, g/10 min tan
10
, %
HDPE
HDPE + stabilizer:
IX
IX
IX
XIV
XIV
XIV
0.2
0.5
0.8
0.2
0.5
0.8
120
150
130
240
230
230
8
8
12
16
16
14
0.14
0.05
0.08
0.11
0.21
0.46
8.7
2.2
2.0
2.1
2.0
2.0
11.8
20.0
5.6
8.8
10.9
19
procedure described in [17]. Alumina (Brockmann
grade II) was used as sorbent, and heptane acetone,
as eluent. The spots were visualized by irradiation
with a mercury lamp equipped with a light filter.
tuted benzoic acids IX XV were prepared by diene
synthesis from HCCPD and the corresponding dieno-
philes II VIII.
1,4,5,6,7,7-Hexachlorobicyclo[2.2.1]hept-2-enyl-
methyl benzoate IX. A mixture of 1.6 g (0.01 mol)
of II and 5.46 g (0.02 mol) of HCCPD was heated at
150 C for 12 h. Adduct IX was obtained; yield 3.58 g
(83%). Adducts X XV were prepared similarly. The
conditions and results are given in Tables 2 and 3.
Hexachlorocyclopentadiene I was prepared by the
procedure described in [18], bp 104 C/9 mm Hg;
20
20
n
= 1.5652, d = 1.719.
D
4
Allyl esters of p-substituted benzoic acids II VIII
were prepared by the standard procedure, esterification
in benzene in the presence of an acid catalyst (sulfuric
acid, 5 wt % relative to the reaction mixture). The
endo-2-Hydroxymethyl-1,4,5,6,7,7-hexachlorobi-
cyclo[2.2.1]hept-5-ene XVI was prepared according
to [19]. Independent synthesis of IX XV was per-
formed by esterification of alcohol XVI with the cor-
responding benzoic acids XVII XXIII in the presence
of an acid catalyst (5% H SO ) in refluxing benzene
mixture was washed with a NaHCO solution and
3
water, dried over MgSO , and distilled. The physico-
4
chemical parameters of the esters are given in Table 1.
Hexachloronorbornenylmethyl esters of p-substi-
2
4
RUSSIAN JOURNAL OF APPLIED CHEMISTRY Vol. 81 No. 3 2008

442
KYAZIMOVA et al.
with azeotropic distillation of water. All the physico-
chemical parameters of compounds IX XV prepared
by independent synthesis are identical to those of the
respective compounds prepared by the condensation
of HCCPD with allyl esters II VIII.
6. Mamedov, E.G., Zh. Prikl. Khim., 2005, vol. 78, no. 9,
pp. 1577 1579.
7. Mamedov, E.G., Azerb. Khim. Zh., 2001, no. 2,
pp. 60 64.
8. Mamedov, E.G., Zh. Org. Khim., 2000, vol. 36, no. 12,
pp. 1785 1787.
CONCLUSIONS
9. Mamedov, E.G., Zh. Org. Khim., 2002, vol. 38, no. 1,
pp. 25 28.
(1) The Diels Alder reaction of allyl esters of
p-substituted benzoic acids with hexachlorocyclopen-
tadiene, performed at 150 C for 12 h at the diene :
dienophile ratio of 2 : 1, gave in good yields (65
90%) the corresponding adducts, exclusively in the
form of endo isomers.
10. Fields, E.K., J. Am. Chem. Soc., 1954, vol. 76, no. 27,
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11. Laszlo, P. and Schleyer, P., J. Am. Chem. Soc., 1963,
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12. Akhmedov, I.M., Peynircioglu, B., Mamedov, E.G.,
et al., Tetrahedron, 1994, vol. 50, no. 7, pp. 2099
2106.
(2) It was demonstrated by the example of high-
density polyethylene that polychlorobicyclic esters of
p-substituted benzoic acids are effective photostabi-
lizers.
13. Mustafaev, A.M., Alekperov, N.A., Guseinov, M.M.,
et al., Zh. Org. Khim., 1985, vol. 21, no. 8, pp. 1691
1696.
14. Mustafaev, A.M., Imamaliev, A.B., and Gusei-
nov, M.M., Zh. Org. Khim., 1989, vol. 25, no. 9,
pp. 1908 1915.
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