A novel synthetic approach to dichlorostyrenes

Article abstract of DOI:10.1016/S0040-4020(00)00606-2

We found that N-unsubstituted hydrazones of aromatic aldehydes can be easily converted to the corresponding 1,1-dichlorostyrenes in the reaction with carbon tetrachloride using copper (I) chloride as catalyst. Factors affecting the route of the reaction and yields of the products were investigated. A proposed mechanism for the reaction is discussed. (C) 2000 Published by Elsevier Science Ltd.

Full text of DOI:10.1016/S0040-4020(00)00606-2

TETRAHEDRON
Pergamon
Tetrahedron 56 (2000) 6557±6563
A Novel Synthetic Approach to Dichlorostyrenes
Alexey V. Shastin,a Vasily N. Korotchenko,b Valentine G. Nenajdenkob, and
*
Elisabeth S. Balenkovab
aInstitute of Problems of Chemical Physics, Chernogolovka, Moscow Region 142432, Russia
bMoscow State University, Department of Chemistry, Leninskie Gory, Moscow 119899, Russia
Received 14 April 2000; revised 12 June 2000; accepted 29 June 2000
AbstractÐWe found that N-unsubstituted hydrazones of aromatic aldehydes can be easily converted to the corresponding 1,1-dichloro-
styrenes in the reaction with carbon tetrachloride using copper (I) chloride as catalyst. Factors affecting the route of the reaction and yields of
the products were investigated. A proposed mechanism for the reaction is discussed. q 2000 Published by Elsevier Science Ltd.
Introduction
Our preliminary results show that the reaction is compli-
cated and the yield of the dichlorostyrene depends
dramatically on the reactions conditions. Here we report
our investigation of the reaction optimisation in order to
reach the maximal yield of the product. We investigated
also the mechanism of the transformation.
The conversion of a carbonyl group into a double C±C bond
is a common problem in synthetic organic chemistry.
Dichlorostyrenes are widely used for the syntheses of
acetylenes and chloroacetylenes as well as some other
types of compounds.1,2 Many approaches to the 1,1-
dihalogenoalkenes synthesis such as Wittig reaction and
its modi®cations,2,3 a-trichloromethylcarbinol ester reduc-
tion,4 reductive coupling of polyhalogenalkanes with
aromatic aldehydes5 and (212) cycloaddition of dichloro-
ketenes to aldehydes have been used.6
Results and Discussion
We have found that the main factors affecting the yield of
dichlorostyrenes are the nature of the catalyst and its
amount, the polarity and the type of solvent used and the
reagent/substrate ratio. The hydrazone of p-nitrobenz-
aldehyde 1a was used as a representative model due to its
stability. In each case the isolated yield of 4-nitrodichloro-
styrene 2a was determined. Since nitrogen is formed during
the reaction, its rate of evolution was used as measure of the
effectiveness of the conditions and completeness of the
transformation.
Recently we have reported that N-unsubstituted hydrazones
of aromatic aldehydes could be easily converted to the
corresponding dichlorostyrenes by the reaction with carbon
tetrachloride in the presence of copper(I) chloride
(Scheme 1).7 Substrates bearing both electron-withdrawing
and electron-donating substituents give the target products
in good yields. Besides the dichlorostyrenes the correspond-
ing azines 3 have been isolated as side products. This
reaction presents a novel, facile and convenient method
for the conversion of the hydrazones of aromatic aldehydes
into dichlorostyrenes.7 Mild conditions (room temperature)
and good yields (up to 84%) make the method be very useful
for synthetic purposes.
Optimization of the reaction conditions
In¯uence of the catalyst nature. Our previous experiments
showed that DMSO is one of the most suitable solvents for
the reaction, therefore in our study DMSO was used as a
Scheme 1.
Keywords: catalysis; copper salts; dichlorostyrenes; hydrazones; carbon tetrachloride.
* Corresponding author. Tel.: 17-095-939-2276; fax: 17-095-932-8846; e-mail: nen@acylium.chem.msu.ru
0040±4020/00/$ - see front matter q 2000 Published by Elsevier Science Ltd.
PII: S0040-4020(00)00606-2

6558
A. V. Shastin et al. / Tetrahedron 56 (2000) 6557±6563
Table 1. In¯uence of the catalyst nature on yield of 2a
such as Ni(II), Fe(II), Hg(II) and Ag(I) salts were found to
be much less active.
Catalyst
Yield 2a (%)
To summarise these data the best catalyst (higher yield and
optimal reaction rate) are copper (I and II) salts, however in
the case of copper dichloride the reaction rate is too high and
strong evolution of nitrogen results in some inconvenience
due to foaming of the reaction mixture. On the other hand,
using copper(I) chloride as a catalyst the reaction takes
place in optimal time to give the best yield of the target
dichlorostyrene. According to these results, copper (I)
chloride was found to be the best catalyst for the procedure.
CuCl
CuCl2
79
78
61
61
20
16
11
6
CoCl2£6H2O
PdCl2
(NH4)2Fe(SO4)2£6H2O
HgCl2
Ag2SO4
NiCl2£6H2O
MnSO4£5H2O
0
In¯uence of the catalyst quantity. In order to determine
the optimal substrate/catalyst ratio we carried out the
reaction using various amounts of copper(I) chloride (the
other parameters were ®xed the same). As is shown in Fig. 1
the optimal quantity of CuCl is about 5±10%, with any
increase of the catalyst amount leading to lower yields of
dichlorostyrene due to by-product formation.
Solvent nature in¯uence. We have investigated the
in¯uence of the nature of the solvent on the dichlorostyrene
yield and reaction rate (10 mol% copper(I) chloride as
catalyst). Various solvents with different polarity and nature
have been tested. The reaction proceeds rapidly and the best
yield of 2a was obtained in polar solvents with high
solvating ability, characterized by the dipole moment and
dielectric permeability (Table 2). We believe that the forma-
tion of a complex between the copper salt and solvent
molecules plays a signi®cant role in the catalytic activity,
since in the case of hexane and benzene, which do not
solvate copper ions only trace amount of the target product
were isolated; similarly, no reaction occurs using halo-
genated solvents such as CH2Cl2 or CCl.4
Figure 1. Yield of 2a depending on catalyst /substrate ratio.
solvent for the determination of the optimal catalyst.
Standard reaction conditions for the conversion of 1a
(0.01 mol) were a DMSO solution (10 ml) of carbon tetra-
chloride (0.05 mol) and aqueous ammonia (3.33 ml), all the
reactions were carried out at room temperature. A gas
burette was used for the measurement of the nitrogen
volume for the reaction monitoring. It should be noted
that the reaction does not take place without catalyst and
in that case 94% of starting material 1a was recovered.
Different transition metals salts (10 mol%) were tested as
catalysts. As shown in Table 1 the reaction proceeds in the
presence of any metal salts (except for Mn21 salt). The best
However, there is no direct correlation between solvent
properties and the product yield. In most solvents the
reaction proceeds completely (by gas evolution measure-
ment) within 3 h to 3 days. The maximum yield of the target
dichlorostyrene was obtained in DMSO solution.
yields of styrene were found in the case of Pd21, Co21
,
Cu21, Cu1 salts. We found that catalytic activity estimated
by the rate of N2 evolution decreases in the sequence:
CuCl2.PdCl2.CuCl.CoCl2. Other transition metal salts
Reagent/substrate ratio. We have studied the optimal CCl4
(reagent)/substrate (hydrazone 1a) ratio to be taken into the
Table 2. In¯uence of the nature of the solvent
Solvent
Yield 2a (%)
er,8 dielectric permeability
mp1030, (Cpm),8 dipole moment
Formamide
Ethanediol
48
59
61
63
59
53
58
57
79
57
57
12
64
47
10
27
12
8
111.0
37.7
11.2
7.7
5.7
12.9
5.8
5.5
11.9
11.8
13.5
16.0
10.8
13.6
11.7
18.5
5.7
Methyl alcohol
N-methylformamide
Ethyl alcohol
Isopropyl alcohol
Nitromethane
Acetonitrile
DMSO
Sulfolane
DMF
N-methylpyrrolidone
Tetramethyl urea
HMPTA
32.66
182.4
24.55
19.92
35.94
35.94
46.45
43.3
36.71
32.2
23.6
29.6
7.20
7.58
Dimethoxyethane
THF
Benzene
5.8
0.0
0.0
2.27
1.88
Hexane

A. V. Shastin et al. / Tetrahedron 56 (2000) 6557±6563
6559
Figure 2. Dependence of yield of 2a on CCl4/1a ratio.
Table 3. Reaction of hydrazones 1a±p with CCl4
Substrates, Rˆ
a, 4-NO2
b, 3-NO2
c, 4-CN
d, 3-CN
e, 4-Br
f, 3-Br
g, 4-Cl
h, 3-Cl
Yield (%)
2
3
79
17
67
78
17
70
57
40
66
74
65
Substrates, Rˆ
i, 2-Cl
k, 2,6-Cl
l, 2,4-Cl
m, H
n, Me2N
o, 4-MeO
p, 2-OH, 5-NO2
Yield (%)
2
3
64
79
15
62
27
68
26
49
44
14
80
reaction. The procedure was carried out in DMSO solution
with various amount of carbon tetrachloride. As is shown in
Fig. 2 the optimal CCl4/substrate ratio is about 5. Any
further increase in the carbon tetrachloride quantity does
not lead to a substantially better yield of dichlorostyrene,
but in the case of lower amounts of this reagent the yield of
the target product decreases dramatically. Thus we found
that 5 equiv. of carbon tetrachloride is optimal for the
reaction procedure.
2p was isolated in 14% yield whereas the reaction with
structurally similar hydrazone 1b gives the styrene 2b in
67% yield.
In¯uence of substituents on the reaction rate. We investi-
gated also the dependence of the reaction rate on aromatic
ring substituents (Fig. 3). As is shown in Scheme 1 both
reactions (transformation to styrene or azine) are
accompanied by nitrogen evolution, however the rate of
conversion is approximately in accordance with gas
evolution.
Study of substrate nature. Preparative synthesis of 1,1-
dichlorostyrenes. Having found the optimal reaction con-
ditions we tried to study the scope and limitations of the
technique. A wide range of hydrazones9 of aromatic
aldehydes were converted to the corresponding dichloro-
styrenes having various substituents in the aromatic ring.
In most cases the reaction proceeded smoothly to give the
target product in good yield. The formation of the corre-
sponding azines 3 is the main side reaction. The total yield
of these products (213) is nearly quantitative (Table 3). It
should be noted that the puri®cation of the styrenes is very
simple since the separation of azines proceeds without any
problem due to its low solubility.
As is shown in Fig. 3, at the initial moment of reaction the
rate of nitrogen evolution is almost equal for the substrates
bearing electron withdrawing groups such as 4-NO2 and
4-CN. In the case of hydrazone 1o containing an electron
donating group (4-MeO) more rapid conversion takes place.
It is known that the electron donating groups facilitate the
oxidation of hydrazones whereas electron withdrawing
groups deactivate.11
The hydrazone of 2,6-dichlorobenzaldehyde 1k is much less
active by comparison with other substrates. Evidently the
reaction is sensitive to the steric hindrance of the substrate.
It was found that the yields of dichlorostyrenes were gener-
ally better in the case of hydrazones which contain electron
withdrawing groups such as nitro, cyano and halogen. In the
case of the parent unsubstituted compound as well as elec-
tron rich hydrazones the yield of styrenes decreases and the
formation of azines prevails over the formation of styrenes.
A very low nitrogen evolution rate was observed in the case
of hydrazone 1p, this abnormal result is in agreement with
the predominant formation of the corresponding azine in the
case of this hydrazone. As is shown in Scheme 1, the forma-
tion of azine results in the formation of half a mole of
nitrogen (per mole of hydrazone) but conversion to styrene
gives one molecule of nitrogen.
An abnormal result was obtained in the case of hydrazone
1p having an electron-withdrawing group along with an
electron-donating substituent. The major product was
azine 3p (yield 80%). The corresponding dichlorostyrene
Reaction mechanism. We have found that no gas evolution
and no formation of the products 2a and 3a took place (TLC

6560
A. V. Shastin et al. / Tetrahedron 56 (2000) 6557±6563
Figure 3. Gas evolution rate for different substrates.
monitoring) without copper(I) chloride catalyst or carbon
tetrachloride. Therefore, we assume that the ®rst step of
the reaction is oxidation of copper(I) by carbon tetrachloride
with formation of dichlorocarbene according to Assher and
Vofsi.10 On the other hand, it is well known that transition
metals salts can convert hydrazones into the corresponding
diazoalkanes.11 We supposed that p-nitrophenyldiazo-
methane can be an intermediate in this transformation.
The following reaction between dichlorocarbene and
p-nitrophenyldiazomethane resulted in formation of the
dichlorostyrene 2a (Scheme 2). The reoxidation of the
reduced Cu (I) to Cu (II) with CCl4 takes place to form a
catalytic cycle.
carbene. The corresponding dihaloalkenes were obtained in
yields 28±85%, and the authors also obtained the corre-
sponding azines. The azine formation has been explained
by interaction between two molecules of diazoalkane
(Scheme 3). Only two products 2 and 3 were isolated
from the reaction mixture with nearly quantitative total
yield. The proposed mechanism of the reaction is in
accordance with the experimental data obtained in our work.
For the veri®cation of the proposed mechanism we intro-
duced separately prepared p-nitrophenyldiazomethane into
the reaction. It was found that p-nitrophenyldiazomethane
gave dichlorostyrene 2a in 11% yield, but azine 3a was the
main product of the reaction. p-Nitrobenzaldehyde was
isolated together with 2a and 3a. Probably p-nitrobenzalde-
hyde is formed by hydrolysis of p-nitrophenyldiazomethane
followed by oxidation. Nevertheless, this results show that
the system studied is rather complex.
The reaction between diazoalkanes and dihalocarbenes
produced from haloforms has been described previously.12
The reaction mechanism was suggested to be an electro-
philic attack on the carbon atom of the diazoalkane by the
Scheme 2.
Scheme 3.

A. V. Shastin et al. / Tetrahedron 56 (2000) 6557±6563
6561
83±848C (from EtOH); IR (Nujol) (n, cm21): 1610
(CvN), 2240 (CN). 1H NMR (CDCl3) d 7.80 (s, 1H,
3
2-H), 7.77 (d, Jˆ7.8 Hz, 1H, 4-H), 7.69 (s, 1H, CHvN),
7.61 (d, 3Jˆ7.6 Hz, 1H, 6-H), 7.49 (dd, 3Jˆ7.6 Hz,
3Jˆ7.8 Hz, 1H, 5-H). 13C NMR (CDCl3) d 137.89
(CvN), 135.16 (C-3), 130.40, 129.69, 129.14 and 128.28
(C-2, C-4, C-5 and C-6), 118.79 (CN), 111.66 (C-1). Anal.
Calcd for C8H7N3 (%): C, 66.19; H, 4.86. Found: C, 65.77;
H, 4.82.
Scheme 4.
We assume that formation of dichlorocarbene is
accompanied by chloroform formation in the system
(Scheme 4).
We conducted the reaction using carbon tetrachloride in
DMSO-d6 as solvent and after the completion of nitrogen
evolution the reaction mixture was passed through a column
Hydrazone of 4-bromophenylbenzaldehyde (1e). The
compound was obtained as colourless crystals, yield 72%,
mp 77±788C (from EtOH); IR (Nujol) (n, cm21): 1600
1
1
with silica gel to remove the copper salts. In the H NMR
(CvN). H NMR (CDCl3) d 7.66 (s, 1H, CHvN), 7.47
3
3
spectrum an additional signal with shift 7.64 ppm was
detected, the 13C spectrum has the signal of chloroform at
78.04 ppm. These data are in agreement with our supposi-
tion about dichlorocarbene intermediate formation.
(d, Jˆ8.6 Hz, 2H, 3-H and 5-H), 7.39 (d, Jˆ8.6 Hz, 2H,
2-H and 6-H). 13C NMR (CDCl3) d 141.48 (CvN), 134.07
(C-1), 131.66 (C-3 and C-5), 127.50 (C-2 and C-6), 122.43
(C-4). Anal. Calcd for C7H7BrN2 (%): C, 42.24; H, 3.54.
Found: C, 42.45; H, 3.48.
Conclusion
Hydrazone of 3-bromophenylbenzaldehyde (1f). The
compound was obtained as colourless crystals, yield 71%,
mp 92±938C (from EtOH); IR (Nujol) (n, cm21): 1635
(CvN). 1H NMR (CDCl3) d 7.72 (dd, 4Jˆ1.8 Hz,
4Jˆ1.8 Hz, 1H, 2-H), 7.66 (s, 1H, CHvN), 7.45±7.40 (m,
A novel synthesis of 1,1-dichloroalkenes from hydrazones
of aromatic aldehydes has been elaborated. The facile and
ef®cient technique provides the target styrenes in good or
excellent yields under mild conditions.
3
3
2H, 4-H and 6-H), 7.21 (dd, Jˆ7.9 Hz, Jˆ7.9 Hz, 1H,
5-H). 13C NMR (CDCl3) d 140.96 (CvN), 137.30 (C-1),
131.43, 130.11 and 128.88 (C-2, C-4 and C-5), 124.76
(C-6), 122.83 (C-3). Anal. Calcd for C7H7BrN2 (%): C,
42.24; H, 3.54. Found: C, 42.60; H, 3.21.
Experimental
General
Hydrazone of 4-chlorophenylbenzaldehyde (1g). Yield
83%, mp 60±618C (lit.15 57±588C).
Melting points were determined in sealed capillaries and are
uncorrected. NMR spectra were recorded on a Varian VXR-
400 and Bruker AM 400C spectrometers in CDCl3 or
DMSO-d6 with TMS as an internal standard. The IR spectra
were obtained with UR-20 spectrometer. Column chromato-
graphy was performed on silica gel (63±200 mesh, Merck).
Hydrazone of 3-chlorophenylbenzaldehyde (1h). Yield
79%, mp 34±358C (lit.16 Bp 163±1648C/ 20).
Hydrazone of 2-chlorophenylbenzaldehyde (1i). Yield
74%, mp 60±618C (lit.15 57±588C).
General procedure for hydrazone preparation
Hydrazone of 2,6-dichlorophenylbenzaldehyde (1k).
Yield 68%, mp 1358C (lit.9 1348C).
Hydrazones 1a±p were prepared as described in the litera-
ture.13 An aromatic aldehyde (20 mmol) was added to the
solution of of 100% hydrazine hydrate (9.8 ml, 200 mmol)
in ethyl alcohol (20 ml). Reaction mixture was re¯uxed
during 3 h and cooled. The precipitate of hydrazone was
®ltered and recrystalized from EtOH.
Hydrazone of 2,4-dichlorophenylbenzaldehyde (1l).
Yield 78%, mp 83±848C (lit.17 82±848C).
Hydrazone of benzaldehyde (1m). Yield 89%, n2D0 1.6270
(lit.18 n2D0 1.6271).
The known compounds were identi®ed by comparison of
the spectral data and melting point or boiling point with
described in literature.
Hydrazone of 4-dimethylaminophenylbenzaldehyde
(1n). Yield 82%, mp 69±728C (lit.19 69±728C).
Hydrazone of 4-methoxyphenylbenzaldehyde (1o). Yield
86%, mp 167±1688C (lit.20 166±1678C).
Hydrazone of 4-nitrophenylbenzaldehyde (1a). Yield
92%, mp 134±1358C (lit.13 1348C).
2-Hydrazonomethyl-4-nitro-phenol (1p). Yield 67%, mp
186±1888C (lit.21 1868C).
Hydrazone of 3-nitrophenylbenzaldehyde (1b). Yield
87%, mp 107±1088C (lit.13 1078C).
4-Hydrazonomethyl-benzonitrile (1c). Yield 89%, mp
66±678C (lit.14 66±678C).
General procedure for dichlorostyrene preparation
A 25% aqueous solution of ammonia (3.33 ml) and Cu2Cl2
(100 mg, 1 mmol) were added to a solution of hydrazone
1a±p (10 mmol) in DMSO (10 ml). Then CCl4 (5 ml,
3-Hydrazonomethyl-benzonitrile (1d). The compound
was obtained as colourless crystals, yield 77%, mp

6562
A. V. Shastin et al. / Tetrahedron 56 (2000) 6557±6563
50 mmol) was added dropwise over 10 min, maintaining the
temperature at 208C. The reaction mixture was stirred for
4 h and quenched with water (300 ml); any aldazine 3a±p
that precipitated was ®ltered off. The reaction products were
extracted with hexane (50 ml£3). The extracts were dried
over sodium sulphate, hexane was evaporated and the
residue was puri®ed by column chromatography.
1-(2,2-Dichlorovinyl)-2,6-dichlorobenzene 2k. Yield 79%,
n2D0 1.5850 (lit.2 n2D0 1.5853).
1-(2,2-Dichlorovinyl)-2,4-dichlorobenzene
2l.
The
compound was obtained as colourless crystals, yield 62%,
mp 49±508C. IR (Nujol) (n, cm21) 1620 (CvC). 1H NMR
(CDCl3) d 7.65 (dd, 3Jˆ8.5 Hz, 5Jˆ0.6 Hz, 1H, CH-6), 7.43
(d, 4Jˆ2.1 Hz, 1H, CH-3), 7.28 (dd, 3Jˆ8. 5 Hz, 4Jˆ2.1 Hz,
1H, CH-5), 6.99 (s, 1H, Ar±CHvC). 13C NMR (CDCl3) d
134.80 (C-2), 134.21 (C-4),130.78 (C-3), 130.44 (C-1),
129.39 (C-5), 127.02 (C-6), 124.70 (C-10), 124.28 (CCl2).
Anal. Calcd for C8H4Cl4 (%): C, 39.72; H, 1.67. Found: C,
40.18; H, 1.56.
The known compounds 2a, 2b, 2c, 2g, 2h, 2i, 2k, 2m, 2n,
2o, 3a, 3c, 3e, 3k, 3m, 3o and 3p were identi®ed by com-
parison of the spectral data and melting point or boiling
point with those described in the literature.
1-(2,2-Dichlorovinyl)-4-nitrobenzene 2a. Yield 79%, mp
948C (lit.2 948C).
1-(2,2-Dichlorovinyl)-benzene 2m. Yield 27%, n2D0 1.5880
(lit.2 n2D0 1.5874).
1-(2,2-Dichlorovinyl)-3-nitrobenzene 2b. Yield 67%, mp
548C (lit.6 53±558C).
4-(2,2-Dichlorovinyl)-N,N-dimethylaniline 2n. Yield
26%, mp 70±718C (lit.2 mp 70±718C).
4-(2,2-Dichlorovinyl)-benzonitrile 2c. Yield 78%, mp
73±748C (lit.6 75±768C).
1-(2,2-Dichlorovinyl)-4-methoxybenzene 2o. Yield 49%,
n2D0 1.5978 (lit.6 n2D0 1.5975).
3-(2,2-Dichlorovinyl)-benzonitrile 2d. The compound was
obtained as colourless crystals, yield 70%, mp 33±348C
(from EtOH); IR (Nujol) (n, cm21): 2240 (CN), 1620
(CvC). 1H NMR (CDCl3) d 7.83 (dd, 4Jˆ1.8 Hz,
2-(2,2-Dichlorovinyl)-4-nitrophenole 2p The compound
was obtained as colourless crystals, yield 14%, mp 153±
1558C. IR (Nujol) (n, cm21) 1630 (CvC), 1530 (NO2),
3
4
1
4Jˆ1.8 Hz, 1H, CH-2), 7.73 (ddd, Jˆ8.0 Hz, Jˆ1.8 Hz,
1380 (O±H). H NMR (CDCl3) d 10.96 (s, 1H, OH), 8.62
4Jˆ1.8 Hz, 1H, CH-6), 7.59 (ddd, 3JHHˆ7.8 Hz,
(d, 4Jˆ2.8 Hz, 1H, CH-3), 8.04 (dd, 3Jˆ9.0 Hz, 4Jˆ2.8 Hz,
1H, CH-5), 7.09 (s, 1H, CH), 7.01 (d, 1H, CH-6,
3Jˆ9.0 Hz). 13C NMR (CDCl3) d 160.47 (C-1), 139.12
(C-4), 124.76 (C-10), 124.20 (C-5), 121.78 (C-3), 121.62
(CCl2), 120.15 (C-2), 114.92 (C-6). Anal. Calcd for
C8H5Cl2NO3 (%): C, 41.06; H, 2.15. Found: C, 41.32; H,
2.30.
4
3
4Jˆ1.5 Hz, Jˆ1.5 Hz, 1H, CH-4), 7.49 (dd, Jˆ8.0 Hz,
3Jˆ7.8 Hz, 1H, CH-5), 6.85 (s, 1H, Ar±CHvC). 13C
NMR (CDCl3) d 134.50 (C-1), 132.60 (C-2), 131.84
(C-6), 131.66 (C-4), 129.38 (C-5), 126.40 (C-10), 123.85
(CCl2), 118.25 (CN), 112.84 (C-3). Anal. Calcd for
C9H5Cl2N (%): C, 54.58; H, 2.54. Found: C, 54.38; H, 2.48.
1-(2,2-Dichlorovinyl)-4-bromobenzene 2e. The compound
was obtained as colourless crystals, yield 57%, mp 24±258C
(from EtOH); IR (Nujol) (n, cm21) 1620 (CvC). 1H NMR
(CDCl3) d 7.45 (d, 3Jˆ8.6 Hz, 2H, CH-2,6), 7.35 (d,
3Jˆ8.6 Hz, 2H, CH-3,5), 6.74 (s, 1H, Ar±CHvC). 13C
NMR (CDCl3) d 132.12 (C-1), 131.59 (C-3,5), 130.04
(C-2,6), 127.41 (C-10), 122.46 (C-4), 121.73 (CCl2). Anal.
Calcd for C8H5Cl2Br (%): C, 38.14; H, 2.00. Found: C,
38.42; H, 2.01.
4-Nitrobenzaldehyde (4-nitrobenzylidene)hydrazone 3a.
Yield 17%, mp 296±2978C (lit.22 296±2978C).
4-Formylbenzonitrile
4-cyanobenzylidene)hydrazone
3c. Yield 17%, mp 318±3208C (lit.23 296±2978C).
4-Bromobenzaldehyde (4-bromobenzylidene)hydrazone
3e. Yield 40%, mp 222±2248C (lit.24 223.5±224.58C).
2,6-Dichlorobenzaldehyde (2,6-dichlorobenzylidene)hy-
1-(2,2-Dichlorovinyl)-3-bromobenzene 2f. The compound
was obtained as colourless liquid, yield 66%, n1D7 1.6220. IR
(Nujol) (n, cm21) 1630 (CvC). 1H NMR (CDCl3) d 7.63 (s,
drazone 3k. Yield 15%, mp 152±1538C (lit.25 1538C).
Benzaldehyde (benzylidene)hydrazone 3m. Yield 68%,
mp 92±938C (lit.26 93±948C).
3
1H, CH-2), 7.40 (m, 2H, CH-4,6), 7.18 (dd, Jˆ8.0 Hz,
3Jˆ8.0 Hz, 1H, CH-5), 6.73 (s, 1H, Ar±CHvC). 13C
NMR (CDCl3) d 135.11 (C-1), 131.30 (C-6), 131.25
(C-4), 129.82 (C-5), 127.09 (C-10), 127.06 (C-2), 122.44
(CCl2). Anal. Calcd for C8H5Cl2Br (%): C, 38.14; H, 2.00.
Found: C, 38.16; H, 1.96.
4-Methoxybenzaldehyde (4-methoxybenzylidene)hydra-
zone 3o. Yield 44%, 167±1688C (lit.27 168±1698C).
2-Hydroxy-5-nitro-benzaldehyde
(2-hydroxy-5-nitro-
benzylidene)hydrazone 3p. Yield 80%, mp 2988C (lit.21
3008C).
1-(2,2-Dichlorovinyl)-4-chlorobenzene 2g. Yield 74%, nD20
1.5930 (lit.1 nD20 1.5914).
1-(2,2-Dichlorovinyl)-3-chlorobenzene 2h. Yield 65%, bp
103±1058C/1 Torr, n1D7 1.5970 (lit.6 103±1058C/1 Torr).
Acknowledgements
Financial support from the Russian Foundation for Basic
Research (Grant No. 00-03-32760a) is gratefully acknowl-
edged.
1-(2,2-Dichlorovinyl)-2-chlorobenzene 2i. Yield 64%, nD20
1.5793 (lit.1 nD20 1.5793).

A. V. Shastin et al. / Tetrahedron 56 (2000) 6557±6563
13. Curtius, T.; Lublin, A. Chem. Ber. 1900, 33, 2464.
6563
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