Conversion of aromatic aldehydes into 1-aryl-2,2-dichloroethenes

Article abstract of DOI:10.1023/A:1011377504491

A new general one-pot preparative method for the synthesis of 1-aryl(hetaryl)-2,2-dichloroethenes from aldehydes was developed. The method involves successive conversions of the latter into hydrazones followed by treatment with carbon tetrachloride in the

Full text of DOI:10.1023/A:1011377504491

Russian Chemical Bulletin, International Edition, Vol. 50, No. 6, pp. 1047—1050, June, 2001
1047
Conversion of aromatic aldehydes into 1-aryl-2,2-dichloroethenes
V. G. Nenajdenko,a« A. V. Shastinb, V. N. Korotchenkoa, and E. S. Balenkovaa
aDepartment of Chemistry, M. V. Lomonosov Moscow State University,
Leninskie Gory, 119899 Moscow, Russian Federation.
Fax: +7 (095) 932 8846. E-mail: nen@acylium.chem.msu.ru
bInstitute of Problems of Chemical Physics,
142432 Chernogolovka, Moscow Region, Russian Federation.
Fax: +7 (095) 515 3588. E-mail shastin@icp.ac.ru
A new general one-pot preparative method for the synthesis of 1-aryl(hetaryl)-2,2-di-
chloroethenes from aldehydes was developed. The method involves successive conversions of
the latter into hydrazones followed by treatment with carbon tetrachloride in the presence of
copper(I) chloride.
Key words: catalysis, copper salts, dichlorostyrenes, hydrazones, carbon tetrachloride.
1,1-Dihalolalkenes are widely used as synthetic pre-
cursors of alkynes and chloroalkynes.1—4 The classical
approaches to the synthesis of 1,1-dihaloalkenes involve
the Wittig reaction and its modifications,5—8 reduction
of α-trichloromethyl alcohols with metals (zinc, etc.),9—11
reductive coupling of polyhalogenohydrocarbons with
aromatic aldehydes in the presence of the lead—alumi-
num system,12 and [2+2]-cycloaddition of dichloro-
ketenes to aldehydes followed by thermal decarboxyla-
tion of the resulting β-lactones.13 The drawbacks of
these procedures are drastic conditions, the necessity of
using expensive reagents, and the employment of
equimolar amounts of phosphorus reagents or metals as
reductants.
Results and Discussion
The preparation of dichlorostyrenes from hydrazones
is accompanied by elimination of nitrogen and for-
mation of symmetrical aldazines and chloroform
(Scheme 1). Dichlorostyrenes and azines are obtained
in nearly quantitative cumulative yield.15
Scheme 1
NNH2
H
Cu2Cl2
R
+
CCl4
NH3 aq.
Previously, we have found a new redox reaction of
N-unsubstituted hydrazones of aromatic aldehydes with
carbon tetrachloride in the presence of catalytic amounts
of copper(I) chloride giving rise to dichlorostyrenes.14,15
This procedure represents a new approach to the trans-
formation of the C=O bond into the C=C bond using
inexpensive and readily accessible compounds, imposes
minimum demands on equipment, and is characterized
by the simplicity of the reaction procedure and isolation
of the products. It was demonstrated that this procedure
makes it possible to prepare dichlorostyrenes containing
functional groups of different nature. Dichlorostyrenes
containing electron-withdrawing substituents are formed
in high yields, whereas the reactions of aldehyde
hydrazones containing electron-donating substituents (for
example, 4-Me2N or 4-MeO) afford the target products
in low yields (26—49%).15
H
Cl
R
Cl
N N
+
+ N2 +
HCCl3
R
R
H
H
We assumed that the carbenoid copper complex
RCH=Cu analogous to the known carbenoid complexes
of copper and other metals16—22 is formed as the key
intermediate in this reaction (Scheme 2). In the first
stage, copper(I) chloride is oxidized by CCl4, the latter
being reduced to chloroform via the intermediate
trichloromethyl anion (or dichlorocarbene)23 and Cu2Cl2
being converted into CuCl2. Previously, we have dem-
onstrated that the reaction performed in the presence of
CuCl2 as a catalyst was accelerated by approximately
two orders of magnitude resulting in substantial heat
evolution and foaming of the reaction mixture, whereas
the yields of dichlorostyrenes remained virtually un-
changed.15 Hence, we chose Cu2Cl2 as the optimum
catalyst, which made it possible to control the course of
the reaction. In the subsequent stage, CuII reacts with
In the present study, we suggest a mechanism of this
reaction and propose a new catalytic cycle describing the
processes that occur in the reaction system. In addition,
we developed a simplified procedure for the synthesis of
dichlorostyrenes, which, in some cases, enables one to
obtain the target products in substantially higher yields.
Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 6, pp. 1003—1006, June, 2001.
1066-5285/01/5006-1047 $25.00 © 2001 Plenum Publishing Corporation

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Russ.Chem.Bull., Int.Ed., Vol. 50, No. 6, June, 2001
Nenajdenko et al.
Scheme 2
CHCl3
HCl
H
RCHN2•Cu0
RCH NNH2
CCl3
CCl4
N2
N2
CuCl2
Cu2Cl2
RCH Cu
CHR•Cu0
RCH N N
RCH
CCl2 CCl4
RCH N N CHR
+
CCl3
CCl4
the hydrazone to form the carbenoid copper complex
(via the corresponding diazoalkane). In this stage, one
nitrogen molecule and two HCl molecules are elimi-
nated. The reaction of the resulting complex with CCl4
affords the corresponding 1,1-dichloroalkene with re-
generation of CuCl2 and gives rise to a new catalytic
cycle. The other path of decomposition of diazolalkane
affords azine (the side reaction)24 accompanied by elimi-
nation of nitrogen and formation of chloroform. This
process is the major source of chloroform in the system
(we have detected chloroform in the reaction mixture by
1H NMR spectroscopy).
We believe that the major and side reactions share
the key intermediate, both reactions being catalytic (the
completion of each catalytic cycle leads to regeneration
of the catalyst). Hence, the ratio between the reaction
products (1,1-dichloroalkene and azine) depends on the
ratio between hydrazone, CCl4, and the catalysts in a
complicated manner and, as a result, is governed by the
kinetics of the competitive reactions.
Previously,15 we have found the optimum reaction
conditions (the ratios between the reagents, the catalyst,
and the solvent) providing high yields of the target
products in the case of aldehyde hydrazones containing
electron-withdrawing substituents. The synthesis of al-
dehyde hydrazones containing electron-donating sub-
stituents presents difficulties due to their tendency to
undergo oxidative dimerization under the action of at-
mospheric oxygen and problems associated with their
isolation in the pure form.25 One would expect that the
one-pot reactions of such hydrazones will afford the
target products in higher yields. This gave impetus to
the development of a procedure for conversions of
aldehydes into 1,1-dichloroalkenes without intermediate
isolation of hydrazones.
dichlorostyrene 1a has been obtained in the lowest yield
(26%). Preliminary experiments demonstrated that
4-N,N-dimethylaminobenzaldehyde hydrazone, which
was prepared in situ from equimolar amounts of the
aldehyde and hydrazine, was converted under standard
conditions15 into the corresponding dichlorostyrene in
higher yield compared to that obtained in the reaction
of the hydrazone prepared separately. Further investiga-
tion of the conditions of the preparation of hydrazones
showed that the optimum duration of the reaction of
aldehyde with hydrazine is 3 h and that an excess of
hydrazine leads to a decrease in the yield of dichloro-
styrene 1a from 58% (an equimolar ratio) to 29% (a
50% excess of hydrazine). Product 1a was obtained in
the highest yield at ∼20 °C; a decrease or an increase in
the temperature led to a decrease in the yield.
When employing the one-pot procedure developed
by us, we succeeded in obtaining dichlorostyrenes 1a—c
in substantially higher yields (Table 1). It was demon-
strated that the use of this procedure did not lead to a
decrease (in some cases, led to an increase) in the yields
of the corresponding dichlorostyrenes from aromatic
aldehydes containing fluoro, chloro, bromo, nitro, cyano,
methoxy, or hydroxy groups in the aromatic nucleus
(Scheme 3).
Scheme 3
Cl
O
H
Cl
1. N2H4•H2O
Ar(HetAr)
Ar(HetAr)
2. CCl4, Cu2Cl2
H
1a—z
We chose 4-N,N-dimethylaminobenzaldehyde as a
model compound because of the extremely low stability
of its hydrazone.25 Previously, the corresponding
Attempts to perform the reaction involving salicylal-
dehyde failed, but other ortho-substituted benzaldehydes,
including 5-nitrosalicylaldehyde, entered into these re-

Conversion of aromatic aldehydes into dichloroalkenes Russ.Chem.Bull., Int.Ed., Vol. 50, No. 6, June, 2001
1049
Table 1. Synthesis of dichloroalkenes from aldehydes
standard; the chemical shifts are given in the δ scale relative to
Me4Si with an accuracy of 0.01 ppm.
Commercial aldehydes were used as the starting com-
pounds.
Product
Aryl (hetaryl)
Yield (%)
Synthesis of dichloroalkenes 1a—z (general procedure). A
solution of an aldehyde (0.01 mol) in DMSO (5 mL) was added
dropwise to a solution of 100% hydrazine hydrate (0.49 mL,
0.01 mol) in DMSO (5 mL). The reaction mixture was stirred
for 3 h. Concentrated NH4OH (3.33 mL) and Cu2Cl2 (100 mg,
1 mmol) were added to the resulting solution of hydrazone in
DMSO. Then CCl4 (5 mL, 50 mmol) was added dropwise at
20 °C for 10 min. The reaction mixture was stirred for 4 h and
0.1 M HCl (300 mL) was added. The reaction products were
extracted with CH2Cl2 (3½50 mL), the extract was dried with
Na2SO4, the solvent was evaporated, and the residue was
purified by column chromatography on SiO2. The spectral
characteristics of compounds 1a—c, 1f—p, 1t, and 1v corre-
spond to the data published in the literature.
A
B
1a
1b
1c
1d
1e
1f
1g
1h
1i
4-Me2NC6H4
Ph
58
74
77
37
36
79
74
72
60
59
75
69
58
57
68
65
52
57
36
40
26
48
41
44
34
45
26
27
49
—
—
79
67
78
70
57
66
74
65
64
79
62
—
—
—
14
—
—
—
—
—
—
4-MeOC6H4
3-MeOC6H4
4-HOC6H4
4-O2NC6H4
3-O2NC6H4
4-NCC6H4
3-NCC6H4
4-BrC6H4
3-BrC6H4
4-ClC6H4
3-ClC6H4
2-ClC6H4
2,6-Cl2C6H3
2,4-Cl2C6H3
4-FC6H4
3-FC6H4
2-FC6H4
2-HO, 5-O2NC6H3
p-Phenylene
1-Naphthyl
3-Pyridyl
4-Pyridyl
2-Thienyl
3-Thienyl
1j
1k
1l
1m
1n
1o
1p
1q
1r
1s
1t
4-(2,2-Dichlorovinyl)-N,N-dimethylaniline (1a): m.p.
70—71 °C (cf. lit. data5: m.p. 70—71 °C).
(2,2-Dichlorovinyl)benzene (1b): nD20 1.5880 (cf. lit. data5:
20
nD 1.5874).
1-(2,2-Dichlorovinyl)-4-methoxybenzene (1c): nD20 1.5978
(cf. lit. data13: nD 1.5975).
20
1-(2,2-Dichlorovinyl)-3-methoxybenzene (1d): nD20 1.5825
(cf. lit. data13: b.p. 156—158 °C (3 Torr)). 1H NMR, δ: 3.77 (s,
3 H, OMe); 6.80 (s, 1 H, —CH=); 6.83 (ddd, 1 H, Ar, J = 8.3,
2.6, and 1.0 Hz); 7.03—7.10 (br.d, 1 H, Ar, J = 7.6 Hz); 7.08
(s, 1 H, CH(2)); 7.25 (dd, 1 H, Ar, J = 8.3 and 7.6 Hz).
13C NMR, δ: 55.1 (Me); 113.4 (Ar); 114.0 (Ar); 121.1 (=CCl2);
121.2 (Ar); 128.4 (—CH=); 129.4 (Ar); 134.5 (Ar); 159.4 (C—O).
4-(2,2-Dichlorovinyl)phenol (1e): m.p. 92—93 °C.
Found (%): C, 51.24; H, 3.26. C8H6Cl2O. Found (%): C, 50.83;
H, 3.20. IR, ν/cm–1: 1620, 1590, 1380, 825. 1H NMR, δ: 5.84
(s, 1 H, —CH=), 6.82 (d, 2 H, Ar, J = 8.6 Hz), 7.43 (d, 2 H,
Ar, J = 8.6 Hz). 13C NMR, δ: 115.6 (Ar), 119.0 (=CCl2), 126.3
(Ar), 127.8 (—CH=), 130.3 (Ar), 155.2 (C—OH).
1-(2,2-Dichlorovinyl)-4-nitrobenzene (1f): m.p. 94 °C (cf.
lit. data5: m.p. 94 °C).
1u
1v
1w
1x
1y
1z
Note. A, the one-pot synthesis; B, from the corresponding
hydrazones.
actions. Terephthalaldehyde gave the corresponding
1,4-bis(2,2-dichlorovinyl)benzene (1u).
The reactions have a general character. We suc-
ceeded in performing the reactions also with poly-
aromatic and heteroaromatic aldehydes. The reaction of
1-naphthaldehyde afforded the corresponding 1,1-di-
chloroalkene in 48% yield. The reactions of aldehydes
of the thiophene and pyridine series also gave rise to the
corresponding dichloroalkenes 1w—z. However, the re-
actions of aldehydes of the pyrrole, furan, and indole
series did not yield the target products.
To summarize, we developed a new convenient and
simple procedure for conversions of aromatic and
heteroaromatic aldehydes into the corresponding
1-aryl(hetaryl)-2,2-dichloroethenes in good yields. The
mechanism of the reaction representing a new approach
to the construction of the C=C bond is proposed.
1-(2,2-Dichlorovinyl)-3-nitrobenzene (1g): m.p. 54 °C (cf.
lit. data13: m.p. 53—55 °C).
4-(2,2-Dichlorovinyl)benzonitrile (1h): m.p. 73—74 °C (cf.
lit. data13: m.p. 75—76 °C).
3-(2,2-Dichlorovinyl)benzonitrile (1i): m.p. 33—34 °C (cf.
lit. data15: m.p. 33—34 °C).
1-Bromo-4-(2,2-dichlorovinyl)benzene (1j): m.p. 24—25 °C
(cf. lit. data15: m.p. 24—25 °C).
17
1-Bromo-3-(2,2-dichlorovinyl)benzene (1k): nD
1.6220
(cf. lit. data15: nD 1.6220).
20
4-Chloro-1-(2,2-dichlorovinyl)benzene (1l): nD20 1.5930 (cf.
lit. data1: nD201.5914).
3-Chloro-1-(2,2-dichlorovinyl)benzene
(1m):
b.p.
103—105 °C (1 Torr) (cf. lit. data13: b.p. 103—105 °C (1 Torr)).
20
2-Chloro-1-(2,2-dichlorovinyl)benzene (1n): nD 1.5793
(cf. lit. data1: nD 1.5793).
20
2,6-Dichloro-1-(2,2-dichlorovinyl)benzene (1o): nD20 1.5850
(cf. lit. data5: nD 1.5853).
20
Experimental
2,4-Dichloro-1-(2,2-dDichlorovinyl)benzene (1p): m.p.
49—50 °C (cf. lit. data15: m.p. 49—50 °C).
17
The IR spectra were recorded on a UR-20 spectrophotom-
eter in thin films for liquids and in Nujol mulls for solids. TLC
was carried out on Silufol UV-254 plates; visualization was
performed with an acidified KMnO4 solution, iodine vapor, or
UV light. The 1H and 13C NMR spectra were measured on a
Varian VXR-400 spectrometer (400 MHz for 1H and 100 MHz
for 13C) in CDCl3 and DMSO-d6 with Me4Si as the internal
1-(2,2-Dichlorovinyl)-4-fluorobenzene (1q): nD 1.5660.
Found (%): C, 50.61; H, 3.04. C8H5Cl2F. Found (%): C, 50.30;
H, 2.64. IR, ν/cm–1: 1610, 1240, 850. 1H NMR, δ: 6.77 (s,
1 H, —CH=); 7.02 (dd, 2 H, Ar, J = 8.8 and 6.8 Hz); 7.48 (m,
2 H, Ar). 13C NMR, δ: 115.4 (Ar, J = 21.8 Hz); 120.8
(=CCl2); 127.4 (—CH=); 129.4 (Ar, J = 3.4 Hz); 130.4 (Ar,
J = 8.1 Hz); 163.1 (C—F, J = 254 Hz).

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Russ.Chem.Bull., Int.Ed., Vol. 50, No. 6, June, 2001
Nenajdenko et al.
17
1-(2,2-Dichlorovinyl)-3-fluorobenzene (1r): nD 1.5685.
Found (%): C, 50.56; H, 2.79. C8H5Cl2F. Found (%): C, 50.30;
H, 2.64. IR, ν/cm–1: 1620, 1590, 1240, 790. 1H NMR, δ: 6.76
(s, 1 H, —CH=); 6.96 (dd, 1 H, Ar, J = 8.3 and 2.5 Hz);
7.16—7.31 (m, 3 H, Ar). 13C NMR, δ: 115.1 (Ar, J = 22.3 Hz);
115.4 (Ar); 122.3 (=CCl2); 124.6 (—CH=); 127.4 (Ar,
J = 2.3 Hz); 129.9 (Ar, J = 8.4 Hz); 135.2 (Ar, J = 8.2 Hz);
162.6 (C—F, J = 245 Hz).
References
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1-(2,2-Dichlorovinyl)-2-fluorobenzene (1s): Found (%):
C, 50.42; H, 2.59. C8H5Cl2F. Found (%): C, 50.30; H, 2.64.
IR, ν/cm–1: 1610, 1590, 1240, 850. 1H NMR, δ: 6.96 (s, 1 H,
—CH=); 7.04 (ddd, 1 H, Ar, J = 9.9, 8.4, and 1.2); 7.12 (ddd,
1 H, Ar, J = 8.7, 7.7, and 1.2); 7.27 (m, 1 H, Ar); 7.76 (ddd,
1 H, Ar, J = 9.2, 7.7, and 1.5 Hz). 13C NMR, δ: 115.4 (Ar,
J
= 21.9 Hz); 121.1 (—CH=, J = 5.9 Hz); 121.4 (Ar,
J = 12.7 Hz); 123.2 (Ar, J = 1.7 Hz); 123.9 (=CCl2, J = 3.7 Hz);
129.2 (Ar, J = 2.1 Hz); 130.1 (Ar, J = 8.4 Hz); 159.7 (C—F,
J = 251 Hz).
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1,4-Bis(2,2-dichlorovinyl)benzene (1u): m.p. 77—78 °C.
IR, ν/cm–1: 1610. 1H NMR, δ: 6.75 (s, 2 H, —CH=); 7.47 (s,
4 H, Ar). 13C NMR, δ: 122.5 (=CCl2); 128.6 (—CH=); 129.4
(Ar); 134.1 (Ar). Found (%): C, 45.16; H, 2.40. C10H6Cl4.
Found (%): C, 44.82; H, 2.26.
1-(2,2-Dichlorovinyl)naphthalene (1v): m.p. 42 °C (cf. lit.
12. H. Tanaka, S. Yamashita, M. Yamanoue, and S. Torii,
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data26: m.p. 42 °C).
20
3-(2,2-Dichlorovinyl)pyridine (1w): nD
1.5985 (cf. lit.
13. H. O. Krabbenhoft, J. Org. Chem., 1978, 43, 1305.
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data27: nD20 1.5976). Found (%): C, 48.34; H, 3.10. C7H5Cl2N.
Found (%): C, 48.31; H, 2.90. IR, ν/cm–1: 1620, 1590, 830.
1H NMR, δ: 6.84 (s, 1 H, —CH=); 7.33 (dd, 1 H, Py, J = 8.1
and 4.3 Hz); 7.97 (br.d, 1 H, Py, J = 8.1 Hz); 8.55 (d, 1 H,
C(6)H, J = 4.3 Hz); 8.68 (s, 1 H, C(2)H). 13C NMR, δ: 123.2
(—CH=); 125.2 (Py); 129.0 (=CCl2); 130.8 (Py); 134.9 (Py);
149.1 (Py); 149.8 (Py).
4-(2,2-Dichlorovinyl)pyridine (1x): a very unstable color-
less oil, which rapidly blackened in air. 1H NMR, δ: 6.79 (s,
1 H, —CH=); 7.41 (d, 2 H, Py, J = 5.9 Hz); 8.62 (d, 2 H, Py,
J = 5.9 Hz). 13C NMR, δ: 122.5 (Py); 126.2 (—CH=); 128.6
(=CCl2); 140.4 (Py); 150.0 (Py).
2-(2,2-Dichlorovinyl)thiophene (1y): m.p. 35—36 °C.
Found (%): C, 40.40; H, 2.33. C6H4Cl2S. Found (%): C, 40.24;
H, 2.25. IR, ν/cm–1: 1610, 850. 1H NMR, δ: 7.00—7.04 (m,
1 H, Het); 7.02 (s, 1 H, —CH=); 7.17 (br.d, 1 H, Het,
J = 3.7 Hz); 7.36 (br.d, 1 H, Het, J = 5.1 Hz). 13C NMR,
δ: 118.6 (=CCl2); 122.8 (—CH=); 126.6 (Het); 127.2 (Het);
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129.3 (Het); 136.2 (Het).
17
3-(2,2-Dichlorovinyl)thiophene (1z): nD
1.5795.
Found (%): C, 40.18; H, 2.37. C6H4Cl2S. Found (%): C, 40.24;
H, 2.25. IR, ν/cm–1: 1620, 1580, 840. 1H NMR, δ: 6.82 (s,
1 H, —CH=); 7.25—7.31 (m, 2 H, Het); 7.54 (m, 1 H, Het).
13C NMR, δ: 119.6 (=CCl2); 122.8 (—CH=); 125.0 (Het);
127.3 (Het); 133.8 (Het).
This work was financially supported by the Russian
Foundation for Basic Research (Project No. 00-03-
32760a).
Received November 17, 2000;
in revised form February 9, 2001