Synthesis of 1,4,5,6,7,7-hexachlorobicyclo[2.2.1]hepta-2,5-dienylmethyl haloacetates

Article abstract of DOI:10.1134/S1070427209080199

Hexachlorobicyclo[2.2.1]hepta-2,5-dienylmethyl haloacetates were prepared by [4+2]-cycloaddition of hexachlorocyclopentadiene to the corresponding propargyl haloacetates.

Full text of DOI:10.1134/S1070427209080199

ISSN 1070-4272, Russian Journal of Applied Chemistry, 2009, Vol. 82, No. 8, pp. 1424−1427. © Pleiades Publishing, Ltd., 2009.
Original Russian Text © T.G. Kyazimova, E.G. Mamedbeili, A.V. Nagiev, Kh.I. Gasanov, G.G. Ivanova, 2009, published in Zhurnal Prikladnoi Khimii, 2009,
Vol. 82, No. 8, pp. 1324−1327.
ORGANIC SYNTHESIS
AND INDUSTRIAL ORGANIC CHEMISTRY
Synthesis
of 1,4,5,6,7,7-Hexachlorobicyclo[2.2.1]hepta-2,5-dienylmethyl
Haloacetates
T. G. Kyazimova, E. G. Mamedbeili, A. V. Nagiev, Kh. I. Gasanov, and G. G. Ivanova
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 November 11, 2008
Abstract—Hexachlorobicyclo[2.2.1]hepta-2,5-dienylmethyl haloacetates were prepared by [4+2]-cycloaddition
of hexachlorocyclopentadiene to the corresponding propargyl haloacetates.
DOI: 10.1134/S1070427209080199
Proceeding with studies in the field of the synthesis of
polyhalogenated bicyclic esters [9–14], we prepared and
examined polyhalonorbornadienylmethyl haloacetates.
First, by the esterification procedure, we prepared propargyl
haloacetates IX–XV by the following scheme:
Compounds of the bicyclo[2.2.1]heptene series exhibit
diverse useful properties. Rigid framework structures of
these compounds with fixed substituents are promising
models for studying structure–property relationships
[1].
Polyhalogenated bicyclic esters with other functional
groups are widely used for imparting fireproof properties
to polymeric materials, and also as modifiers, epoxy
resin hardeners, and biologically active substances [2, 3].
Halogen-containing functionally substituted norbornenes
are used as starting compounds for preparing important
commercial chemicals [4–7]. Studies of reactions
involving hexachlorocyclopentadiene (HCCPD) and
its derivatives, along with practical significance, are
of scientific interest for elucidating the mechanism of
Diels–Alder reactions [8].
R = CH2Cl (II, IX), CHCl2 (III, X), CCl3 (IV, IX);
CH2Br (V, XII), CHBr2 (VI, XIII), CBr3 (VII, XIV),
CF3 (VIII, XV).
Table 1. The physicochemical properties of the esters prepared
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SYNTHESIS OF 1,4,5,6,7,7-HEXACHLOROBICYCLO[2.2.1]HEPTA-2,5-DIENYLMETHYL
1425
Table 2. Physicochemical characteristics and elemental analysis of hexachlorobicyclo[2.2.1]hepta-2,5-dienylmethyl
haloacetates
The physicochemical properties of the esters prepared
are given in Table 1.
temperature. Below 100°C, there is virtually no reaction.
With an increase in the temperature from 100 to 160°C,
the yield of adduct XX increases from 10 to 82%. With an
increase in the diene : dienophile molar ratio from 1 : 1 to
3 : 1, the yield of adduct XX increases from 52 to 82%.
Further increase in the molar ratio to 4 : 1 has virtually no
effect on the yield: it increases to only 83%. An increase
in the temperature to 180°C leads to a decrease in the
yield of adduct XX to 71% and to partial tarring of the
reaction mixture.
The target products XVII–XXIII were prepared by
the Diels–Alder reaction of HCCPD XVI with propargyl
haloacetates IX–XV. The reaction follows the scheme
With propargyl mono-, di- and tribromoacetate as
examples, we examined how the number of halogen
atoms in dienophile molecules affects the yield of
the corresponding adducts XX–XXII. Propargyl
monobromo-acetate reacts with hexachlorobutadiene
more readily than do propargyl di- and tribromoacetate.
The adduct yield at 160°C, reaction time of 12 h, and
diene : dienophile ratio of 3 : 1 decreases from 82%
for XX to 78% for XXI and 61% for XXII. That is, the
dienophilic activity decreases with an increase in the
number of halogen atoms:
R = CH2Cl (XVII), CHCl2 (XVIII), CCl3 (XIX), CH2Br
(XX), CHBr2 (XXI), CBr3 (XXII), CF3 (XXIII).
The reaction was performed in the temperature range
100–180°C for 2–14 h at the diene : dienophile molar
ratio of 1 : 1 to 4 : 1. The physicochemical constants of
the synthesized adducts XVII–XXIII are given in Table
2, and the influence of reaction conditions (temperature,
time, reactant ratio) on the adduct yield is illustrated by
Table 3.
CH2Br > CHBr2 > CBr3
82%
78% 67%
To determine how the kind of the halogen atoms in
the dienophile molecule affects their activity and adduct
yield, we compared the reactions of [4+2]-cycloaddition
of hexachlorocyclopentadiene to propargyl trihaloacetates
XI, XIV, and XV under similar conditions (160°C, 12 h,
diene : dienophile molar ratio 3 : 1). As judged from the
yields, the compounds can be ranked in the following
As seen from Table 3, one of the main parameters
affecting the adduct formation rate is temperature. The
influence of temperature was examined in the range 100–
180°C, with the reaction of hexachlorocyclopentadiene
with propargyl monobromoacetate XII as example.
The yield of XX appeared to be strongly dependent on
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1426
KYAZIMOVA et al.
(XI)
(XIV)
(XV)
XVII–XXIII:
order with respect to the dienophilic activity:
This trend is apparently associated with an in-
crease in the electronegativity of the substituent and
a decrease in the nucleophilicity of the triple bond.
Hexachlorocyclopentadiene reacts more readily with the
more nucleophilic dienophile XIV (yield 83%) than with
XI (47%) and XV (40%).
Thus, the optimal conditions for preparing adducts
XVII–XXIII are 160°C, 12 h, and diene : dienophile
molar ratio of 3 : 1.
The structures of the synthesized adducts XVII–XXII
were confirmed by independent synthesis. By the reaction
of hexachlorocyclopentadiene with propargyl alcohol I,
following the procedure from [15], we prepared 2-hy-
droxymethyl-1,4,5,6,7,7-hexachlorobicyclo[2.2.1]-hepta-
2,5-diene XXIV. The subsequent esterification of XXIV
with haloacetic acids II–VIII, performed as described in
[16], yielded hexachloronorbornadiene-containing esters
All the physicochemical properties of compounds
XVII–XXIII prepared by the two procedures are
identical.
The structures of XVII–XXIII were confirmed by
1
elemental analysis (Table 2) and by IR and H NMR
spectra. The purity was checked by TLC.
In the IR spectra of the compounds, there are strong
absorption bands in the ranges 1760–1730 cm–1, char-
acteristic of the C=O group, and 1200–1050 cm–1,
characteristic of the ester C–O group. The C–Cl bands
are observed at 840–650 cm–1. The ethylene fragments
absorb at 1600–1580 cm–1, and the C–H groups at the
double bond, at 3050–3045 cm–1. The absorption bands of
C–Br bonds in XX–XXII are observed at 640–600 cm–1,
and those of C–F bonds in XXIII, at approximately
1300 cm–1.
Table 3. Influence of reaction conditions on the yield of adducts
XVII–XXIII
1
In the H NMR spectra of the adducts, the C=C–H
protons in the norbornene ring (C3) give multiplets at δ
6.15–6.45 ppm. Two protons of the CH2OOCR fragment
give a triplet at δ 4.05–4.20 ppm, and protons of the CR
substituent, a triplet at δ 3.30–3.70 ppm.
EXPERIMENTAL
The IR spectra of the compounds were recorded on
a UR-20 spectrophotometer in the range 4000–400 cm–1.
1
The H NMR spectra were taken on a Tesla BS-48
spectrometer (80 MHz) from solutions in CCl4; the
chemical shifts are given relative to TMS. TLC analysis
was performed according to [17]. As a sorbent we used
Al2O3 of Brockmann grade II. Heptane–acetone was
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SYNTHESIS OF 1,4,5,6,7,7-HEXACHLOROBICYCLO[2.2.1]HEPTA-2,5-DIENYLMETHYL
1427
an eluent. The plates were developed by irradiation with
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dienylmethyl monochloroacetate XVII. A mixture of
8.19 g (0.03 mol) of HCCPD and 1.33 g (0.01 mol) of
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1
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C 29.13; H 1.16, Hlg 61.04. Calculated, %: C 29.63; H 1.24;
Hlg 61.23.
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(1) Polyhalogenated norbornadienylmethyl esters
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(2) The optimal conditions for preparing the target
products were found: 160°C, 12 h, diene : dienophile
molar ratio 3 : 1. Under these conditions, the yield of the
adducts is 40–82%.
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