Synthesis of 1,4,5,6-tetrachloro-7,7-dimethoxybicyclo[2.2.1]hept-5- enylmethyl haloacetates

Article abstract of DOI:10.1134/S1070427209010194

The possibility of preparing 1,4,5,6-tetrachloro-7,7-dimethoxybicyclo[2.2. 1]hept-5-enylmethyl haloacetates by the reaction of tetrachlorodimethoxycyclopentadiene with allyl haloacetates was examined. The effect of various factors on the product yield was studied, and the optimal synthesis conditions were found.

Full text of DOI:10.1134/S1070427209010194

ISSN 1070-4272, Russian Journal of Applied Chemistry, 2009, Vol. 82, No. 1, pp. 102−106. © Pleiades Publishing, Ltd., 2009.
Original Russian Text © T.G. Kyazymova, E.G. Mamedbeili (Mamedov), O.B. Abdiev, Z.M. Nagiev, S.T. Alieva, A.V. Nagiev, 2009, published in Zhurnal
Prikladnoi Khimii, 2009, Vol. 82, No. 1, pp. 103−107.
ORGANIC SYNTHESIS AND INDUSTRIAL
ORGANIC CHEMISTRY
Synthesis of 1,4,5,6-Tetrachloro-7,7-dimethoxybicyclo[2.2.1]hept-
5-enylmethyl Haloacetates
T. G. Kyazymova, E. G. Mamedbeili (Mamedov), O. B. Abdiev, Z. M. Nagiev,
S. T. Alieva, and A. V. Nagiev
Institute of Chemical Problems, National Academy of Sciences of Azerbaijan, Baku, Azerbaijan
Institute of Petrochemical Processes, National Academy of Sciences of Azerbaijan, Baku, Azerbaijan
Received February 21, 2008
Abstract—The possibility of preparing 1,4,5,6-tetrachloro-7,7-dimethoxybicyclo[2.2.1]hept-5-enylmethyl
haloacetates by the reaction of tetrachlorodimethoxycyclopentadiene with allyl haloacetates was examined. The
effect of various factors on the product yield was studied, and the optimal synthesis conditions were found.
DOI: 10.1134/S1070427209010194
Halogenated bicyclic compounds containing various
substituents are widely used as fire retardants for
commercially important polymeric materials [1] and
are convenient starting compounds for preparing
halogen-substituted sterically hindered phenols [2–4]
XVI
IX−XV
and α-diketones [5, 6]. Therefore, the development of
synthesis procedures and study of properties of new
polyhalogenated bicyclic compounds of the norbornene
series are topical problems.
Here we report on the synthesis of 1,4,5,6-
tetrachloro-7,7-dimethoxybicyclo[2.2.1]hept-5-
enylmethyl haloacetates by the Diels–Alder reaction
of tetrachlorodimethoxycyclopentadiene with allyl
haloacetates. The initial allyl esters IX–XV were prepared
by common esterification of haloacetic acids II–VIII
with allyl alcohol I:
XVII−XXIII
where R = CH2Cl (XVII), CHCl2 (XVIII), CCl3 (XIX),
CH2Br (XX), CHBr2 (XXI), CBr3 (XXII), CF3 (XXIII).
The physicochemical characteristics of the synthesized
adducts XVII–XXIII are given in Table 2.
H+
Benzene,
The reaction was performed in the temperature interval
80–160°C for 2–14 h. The diene : dienophile molar
ratio was 1 : 1 to 4 : 1. We examined the effect of these
parameters on the product yield. The results are given
in Table 3.
refluxing;
IX−XV
I
II−VIII
H2O
where R = CH2Cl (II, IX), CHCl2 (III, X), CCl3 (IV,
XI), CH2Br (V, XII), CHBr2 (VI, XIII), Br3 (VII, XIV),
CF3 (VIII, XV).
With allyl mono-, di-, and trichloroacetates as
examples, we examined how the number of halogen
atoms in dienophile molecules affects the yield of the
adducts (XVII, XVIII, XIX, respectively). We found
that, with an increase in the number of chlorine atoms
The physicochemical data for IX–XV are given in
Table 1.
Target products XVII–XXIII were prepared by the
following scheme:
102

SYNTHESIS OF 1,4,5,6-TETRACHLORO-7,7-DIMETHOXYBICYCLO[2.2.1]HEPT-5-ENYLMETHYL...
103
of XVII increases from 13.4 to 73.2%. Further increase
in the reaction time to 14 h does not lead to a significant
increase in the yield (75.1%).
Table 1. Physicochemical characteristics of allyl haloacetates
IX–XV
A study of the effect of the reaction temperature on
the adduct yield, with the reaction of XVI with allyl
trichloroacetate XI as example, showed that the yield of
XIX strongly depended on temperature and increased
from 11.2 to 95.1% with an increase in the temperature
from 80 to 160°C. With an increase in the diene :
dienophile molar ratio from 1 : 1 to 3 : 1, the yield of
XIX increased from 71.4 to 95.1%. Further increase in
the molar ratio to 4 : 1 adversely affected the yield: it
decreased to 80.2%.
IX
X
XI
XII
XIII
XIV
XV
Thus, the optimal conditions for the synthesis of
adducts XVII–XXIII are as follows: temperature 160°C,
time 10 h, and diene : dienophile molar ratio 3 : 1.
The structure of adducts XVII–XXIII was proved
by independent synthesis. By the reaction of tetra-
chlorodimethoxycyclopentadiene with allyl alcohol I,
following the procedure from [7], we prepared 2-endo-
hydroxymethyl-1,4,5,6-tetrachloro-7,7-dimethoxybicyc
lo[2.2.1]hept-5-ene XXIV. Its subsequent esterification
with haloacetic acids II–VIII yielded bicyclic esters
XVII–XXIII (see Scheme
in dienophile molecules, at equal reaction temperature
(160°C), time (10 h), and diene : dienophile ratio (3 :
1), the product yield increases (73.2% for XVII, 78.1%
for XVIII, 95.1% for XIX), i.e., the dienophilic activity
increases with an increase in the number of chlorine
atoms. As seen from Table 3, the reaction time strongly
affects the yield of 1,4,5,6-tetrachloro-7,7-dimethoxybi
cyclo[2.2.1]hept-5-enylmethyl monochloroacetate XVII
in the reaction of XVI with allyl monochloroacetate IX.
As the reaction time is increased from 2 to 10 h, the yield
All the physicochemical characteristics of compounds
XVII–XXIII prepared by alternative routes are
identical.
The structures of XVII–XXIII were confirmed by
elemental analysis (Table 2) and by IR and 1H NMR
Table 2. Properties of 1,4,5,6-tetrachloro-7,7-dimethoxybicyclo[2.2.1]hept-5-enylmethyl haloacetates XVII–XXIII
XVII
XVIII
XIX
XX
XXI
XXII
XXIII
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104
KYAZYMOVA et al.
Scheme.
H+
XVI + I
Benzene, refluxing;
–H2O
XXIV
II−VII
XVII−XXIII
In the 1H NMR spectra of the adducts, in the
high-field region, there are signals at 1.60–1.65 and
2.40–2.50 ppm, corresponding to HA and HB protons,
with the geminal coupling constant J = –12 Hz. The
vicinal coupling constants are JAC = 4 and JBC = 9 Hz.
The HC proton gives a multiplet at 3.0–3.1 ppm. Two
strong singlets of syn- (s) and anti- (a) OCH3 groups are
observed at 3.40–3.45 and 3.55–3.60 ppm, respectively.
Two protons of the –CH2OOCR group give a multiplet
at 3.62–4.3 ppm.
spectra. The purity was checked by TLC. We found
that the reactions yield exclusively endo isomers of the
adducts.
In the IR spectra of XVII–XXIII, there are strong
absorption bands at 1760–1770 cm–1, characteristic
of the carbonyl group, and bands at 1275–1050 cm–1
characteristic of the ester C–O–C fragment. The C–Cl
vibration bands are observed at 850–650 cm–1. In the IR
spectra of the bromo derivatives, there are strong C–Br
absorption bands at 660–550 cm–1. The ν(C–F) band in the
spectrum of XXIII is observed at 1040 cm–1. The ethylene
moiety of the norbornene ring gives rise to vibration
bands at 1556–1550 [ν(C=C)] and 3050–3045 cm–1
[ν(C–H) at double bond].
The synthesized halogenated bicyclic esters were tested
for fireproofing activity toward high-density polyethylene
(HDPE). We found that these compounds impart to HDPE
self-extinction and improve its physicomechanical and
dielectric properties.
Table 3. Influence of the conditions of the Diels–Alder reac-
tion of tetrachlorodimethoxycyclopentadiene XVI with allyl
haloacetates IX–XV on the yield of adducts XVII–XXIII
To make HDPE fireproof, we mainly used the
halogenated compounds with synergistic additives
(Sb2O3). Samples of polymeric materials were prepared
by mixing the components on laboratory rolls
(10–15 min at 150–160°C), followed by pressing into
plates at 150°C.
Dieno-
phile
XVII−XXIII, %
IX
X
XI
The fire resistance of polymeric compounds was
evaluated by the fire pipe method. Compounds were
rated as self-extinguishing if after double ignition with
flame for 10 s the combustion ceased before reaching
the depth of 120 mm. No self-extinction was observed
without synergistic additive (Sb2O3). Introduction of
Sb2O3 into HDPE as the only additive did not enhance
the fire resistance, either. However, the use of Sb2O3
in combination with XVII–XXIII gave rise to the
fireproofing effect. The self-extinction may be due to
formation of antimony trihalide in the combustion zone.
IX
The results of testing 1,4,5,6-tetrachloro-7,7-dimetho
xybicyclo[2.2.1]hept-5-enylmethyl trichloroacetate XIX
for the flame-extinguishing activity are given in Table 4.
With the other adducts, the results were similar. The new
fireproofing compounds can find use in electronics, cable
industry, and other fields.
XII
XIII
XIV
XV
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SYNTHESIS OF 1,4,5,6-TETRACHLORO-7,7-DIMETHOXYBICYCLO[2.2.1]HEPT-5-ENYLMETHYL...
105
Table 4. Properties of polymeric compounds based on adduct XIX
XIX
''
''
''
* The melt flow index (MFI) was determined according to GOST (State Standard) 11645-73/78–93.
EXPERIMENTAL
167–168°C (1 mm Hg), nD20 = 1.5299, d420 = 1.5014.
IR spectrum, ν, cm–1: 1760 (C=O), 1110 (C–O), 800
The IR spectra were recorded on a UR-20 spectrometer
in the range 4000–400 cm–1, and the 1H NMR spectra, on
a Tesla BS-48 spectrometer (80 MHz) in CCl4, internal
reference HMDS. The TLC analysis was performed
according to [8], with Al2O3 (Brockmann grade II) as
sorbent and heptane–acetone as eluent. The spots were
developed by UV irradiation from a mercury lamp
equipped with a color filter.
(C–Cl).
Found, %:
C 35.87; H 3.04; Cl 44.21
C 36.14; H 3.26; Cl 44.54
Calculated, %:
Adducts XVII–XXIII were prepared similarly (the
synthesis conditions and results are given in Table 3, and
the physicochemical characteristics, in Table 2).
Independent synthesis of XVII–XXIII was performed
by esterification of bicyclic alcohol XXIV with appropriate
carboxylic acids II–VIII, following the standard
procedure.
5,5-Dimethoxytetrachlorocyclopenta-1,3-diene XVI
was prepared by the procedure described in [9] from
hexachlorocyclopentadiene, bp 108–110°C (11 mm Hg),
nD20 = 1.5288, d420 = 1.5010.
2-endo-Hydroxymethyl-1,4,5,6-tetrachloro-7,7-
dimethoxybicyclo[2.2.1]hept-5-ene XIV was prepared
by Diels–Alder reaction of tetrachlorodimethoxy-
cyclopentadiene with allyl alcohol, as described in [7].
Allyl haloacetates II–VIII were prepared by the
common procedure, esterification in the presence of
an acid catalyst (H2SO4, 5% of the reaction mixture
volume) in refluxing benzene. After the reaction
completion (when the water release ceased), the mixture
was washed and dried over MgSO4. The benzene was
distilled off, and the residue was distilled in a vacuum.
The physicochemical properties of esters IX–XV are
given in Table 1.
CONCLUSIONS
(1) Polyhalogenated norbornenylmethyl esters
were prepared by [4+2]-cycloaddition of tetra-
chlorodimethoxycyclopentadiene to allyl haloacetates.
(2)The optimal conditions for preparing target products
are as follows: 160°C, 10 h, diene : dienophile ratio 3 :
1. Under these conditions, the adducts (exclusively endo
isomers) are obtained in 73–92% yield.
1,4,5,6-Tetrachloro-7,7-dimethoxybicyclo[2.2.1]hept-
5-enylmethyl monochloroacetate XVII. A mixture of
7.92 g (0.03 mol) of tetrachlorodimethoxycyclopentadiene
XVI and 1.34 g (0.01 mol) of allyl monochloroacetate IX
was heated at 160°C for 10 h. After vacuum distillation,
we obtained 2.91 g of adduct XVII; yield 73.2%, bp
(3) Polychlorobicyclic esters of haloacetic acids in
combination with a synergistic additive (Sb2O3), when
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KYAZYMOVA et al.
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