5(4)-Chloro-1-(2,4-dinitrophenyl)pyrazoles from 2,4-dinitrophenylhydrazones of chlorovinyl ketones and β,β-dichloroacrolein

Article abstract of DOI:10.1007/s10593-005-0238-9

A method has been developed for obtaining 3-alkyl(phenyl)-4(5)-chloro-1-(2, 4-dinitrophenyl)pyrazoles from appropriate dinitrophenylhydrazones of 1-chloro-, 1,2-, and 2,2-dichlorovinyl ketones by heating the latter in polyphosphoric acid. The structure of

Full text of DOI:10.1007/s10593-005-0238-9

Chemistry of Heterocyclic Compounds, Vol. 41, No. 7, 2005
5(4)-CHLORO-1-(2,4-DINITROPHENYL)-
PYRAZOLES FROM 2,4-DINITROPHENYL-
HYDRAZONES OF CHLOROVINYL KETONES
AND β,β-DICHLOROACROLEIN
G. V. Bozhenkov, G. G. Levkovskaya, A. N. Mirskova, and L. I. Larina
A method has been developed for obtaining 3-alkyl(phenyl)-4(5)-chloro-1-(2,4-dinitrophenyl)pyrazoles
from appropriate dinitrophenylhydrazones of 1-chloro-, 1,2-, and 2,2-dichlorovinyl ketones by heating
1
the latter in polyphosphoric acid. The structure of the pyrazoles was studied by IR and H NMR
spectroscopy.
Keywords: bromoacrolein, dichloroacrolein, 2,4-dinitrophenylhydrazones, 1-(2,4-dinitrophenyl)-
pyrazoles, 4(5)-chloro-1-(2,4-dinitrophenyl)pyrazoles, chlorovinyl ketones, heterocyclization.
1-Alkyl-3-alkyl(aryl)(chloroalkyl)(perfluoroalkyl)-5(4)-chloro(bromo)pyrazoles are promising for
making medicinal preparations, dyestuffs, insecticides, insectoacaricides, etc. [1-8], and are formed in reactions
of the corresponding 1,2-dichloro- and 2,2-dihalovinyl ketones with alkylhydrazines in the presence of base
[9-12]. An extensive series of 3-alkyl-1-methylpyrazoles and 5-chloro(bromo)-1-methylpyrazoles was obtained
by us using new one-stage selective heterocyclization reactions of 2-chloro- and 2,2-dichloro(bromo)vinyl
ketones with unsymmetrical dimethylhydrazine [13-15].
It proved to be possible to synthesize 4(5)-chloro-1-phenylpyrazoles or 1-phenylpyrazoles unsubstituted
in positions 4 and 5 by the intramolecular heterocyclization of previously obtained phenylhydrazones of
1-chlorovinylalkyl(aryl)- and 2,2-dichlorovinyl phenyl ketones [9, 16]. At the same time, only in the one
example of 5-chloro-1-(2,4-dinitrophenyl)-3-phenylpyrazole [17] has the preparation been reported of
1-nitrophenyl-substituted halopyrazoles by the thermal cyclization of the corresponding arylhydrazones of
2,2-dichlorovinyl phenyl ketone. It was shown simultaneously that 2,4-dinitrophenylhydrazones (DNPH) of
aliphatic 2,2-dichlorovinyl ketones are not cyclized on thermolysis into the corresponding 5-chloropyrazoles. In
a systematic study of the structure of DNPH of dichlorovinyl ketones [17, 18] the determining role of the
configuration of the hydrazone was established unequivocally. The DNPH of aliphatic ketones exist preferably
in the s-cis-anti form, but the DNPH of aromatic ketones exist in the s-trans-syn form, capable of achieving
intramolecular heterocyclization. The energy barrier for the transition of one form into the other is fairly high
[17], but as was established in [18] the process of syn-anti conversion of geometric isomers of DNPH is
catalyzed by acids.
In view of the above we have developed a convenient method of obtaining 1-(2,4-dinitrophenyl)-
pyrazoles by the thermal heterocyclization of the corresponding 2,4-dinitrophenylhydrazones of 2-chlorovinyl,
1,2-, and 2,2-dichlorovinyl ketones, and of 2,2-dichloroacrolein in an acidic medium. We have established that
__________________________________________________________________________________________
A. E. Favorsky Irkutsk Institute of Chemistry, Siberian Branch of the Russian Academy of Sciences,
Irkutsk 664033; e-mail: ggl@irioch.irk.ru. Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 7,
pp. 1012-1019, July, 2005. Original article submitted April 2, 2003.
854
0009-3122/05/4107-0854©2005 Springer Science+Business Media, Inc.

2,4-dinitrophenylhydrazones of available alkyl(phenyl) chlorovinyl ketones are cyclized into the corresponding
pyrazoles on heating solutions of them in polyphosphoric acid (PPA) in 45-93% yield (Table 1).The cyclization
process takes place at 100-150°C in 20-40 min. The developed method is based on available starting materials,
enabling the structure of the product to be varied, including the introduction of halogen atoms at positions 4 or 5
of the heterocycle.
R
X
X
R
X
C
C
N
R
Y
N
Y
Y
C
N
100–150 oC
NO2
–
+
N
N
N
Cl
NO2
H
Cl
H
NO2
–HCl
NO2
NO2
NO2
2a–g
1a–g
1, 2 a X = Y = H, R = Pr, b-d X = H, Y = Cl, b R = H, c R = Pr, d R = Ph,
e-g X = Cl, Y = H, e R = Me, f R = Et, g R = Pr
The following compounds were obtained in high yield on carrying out the process with
2,4-dinitrophenylhydrazones
dinitrophenyl)pyrazole (2b),
1a-g:
1-(2,4-dinitrophenyl)-3-propylpyrazole
(2a),
(2c),
5-chloro-1-(2,4-
5-chloro-1-(2,4-
5-chloro-1-(2,4-dinitrophenyl)-3-propylpyrazole
dinitrophenyl)-3-phenylpyrazole (2d), and 3-alkyl-4-chloro-1-(2,4-dinitrophenyl)pyrazoles 2e-g.
TABLE 1. Physicochemical Characteristics of Compounds 1-3
Found, %
Calculated, %
——————
Com-
pound
Empirical
formula
mp, °С
Yield, %
C
H
Hal
N
1a
1e
1f
C12H13ClN4O4
C10H8Cl2N4O4
C11H10Cl2N4O4
C12H12Cl2N4O4
C12H12N4O4
46.12
46.09
37.65
37.64
39.64
39.66
41.53
41.52
52.20
52.17
40.22
40.24
46.36
46.39
52.25
52.27
42.53
42.50
44.55
44.53
46.35
46.39
34.33
34.31
4.23
4.19
2.56
2.53
3.07
3.03
3.46
3.48
4.45
4.38
1.89
1.88
3.45
3.57
2.68
2.63
2.49
2.50
3.09
3.06
3.49
3.57
2.22
2.24
11.35
11.34
22.20
22.22
21.26
21.28
20.43
20.42
17.93
17.92
17.55
17.56
16.80
16.82
16.13
16.14
20.26
20.28
20.79
20.86
18.09
18.03
16.29
16.25
19.85
19.82
18.85
18.89
17.98
18.03
17.77
17.78
130-132
205-206
204
98
98
97
98
92
45
90
78
85
87
93
98
1g
2a
2b
2c
2d
2e
2f
75
—
88-90
115
C9H5ClN4O4
C12H11ClN4O4
C15H9ClN4O4
C10H7ClN4O4
C11H9ClN4O4
C12H11ClN4O4
C9H7BrN4O4
13.25
13.20
11.52
11.41
10.30
10.28
12.57
12.54
11.97
11.95
11.47
11.41
25.36
25.38
73-75
136
96
87-89
103-105
163
2g
3
855

We have established that the action of bases (amines, alkalis, alkali metal alcoholates) on the DNPH of
alkyl 2,2- and 1,2-dichlorovinyl ketones, and also heating them in various solvents (DMF, DMSO, acetonitrile,
alcohols) in the presence of bases, varying the temperature from 70 to 140°C, and the process time up to 10 h,
did not lead to a heterocyclization reaction with the formation of pyrazoles.
Since heating solutions of hydrazones 1a-g in PPA leads to the formation of the corresponding
pyrazoles, it may be proposed that in PPA solution the DNPH of 2,2- and 1,2-dichlorovinyl ketones undergo
isomerization resulting in the anti form going over to the syn isomer which is then cyclized into a pyrazole.
The mechanism of the reaction probably includes an intramolecular nucleophilic attack by the
2,4-dinitrophenylamine fragment at the β-carbon atom of the vinyl group. The N-(2,4-dinitrophenyl)-
pyrazolinium halide formed in this way is dehydrochlorinated on heating to give the aromatic pyrazole.
Nucleophilic addition of the 2,4-dinitrophenylamine fragment to the double bond, with the formation of
the corresponding pyrazolines and their subsequent dehydrohalogenation with isolation of the corresponding
pyrazoles, is probably not brought about. On attempting to carry out the heterocyclization of the
2,4-dinitrophenylhydrazone of α-bromoacrolein 3 in PPA neither 4-bromo-1-(2,4-dinitrophenyl)-2-pyrazoline
nor 1-(2,4-dinitrophenyl)pyrazole were formed.
Br
O
CBr=CH2
CH2=CBr
C
H
N
C
N
H
N
NH
+
O2N
NO2
H NH
N
2
NO2
NO2
NO2
NO2
3
–HBr
N
N
O2N
NO2
Undoubtedly the method found for obtaining 1-(2,4-dinitrophenyl)pyrazoles makes these compounds
available and an interesting subject for further investigations. The use in pyrazole synthesis of alkyl(aryl)
1,2-dichloro- and alkyl(aryl) 2,2-dichloro(bromo)vinyl ketones with various groups and 2-haloacroleins enables
a wide variation of both the structure of the substituent at position 3 of the heterocycle, and of the position and
nature of the halogen atoms in pyrazoles.
It should be noted that previously several approaches used for the synthesis of 1-nitrophenyl-substituted
pyrazoles, were limited by the poor availability of the initial compounds permitting no variation in the structure
of the desired 1-(2,4-dinitrophenyl)pyrazoles, including pyrazoles with a halogen atom in the ring and with
various substituents at position 3 of the pyrazole ring. The known methods of obtaining 1-nitrophenylpyrazoles
include the nitration of previously obtained 1-phenylpyrazoles [19-21], the condensation of acetylacetone with
nitrophenylhydrazines [22, 23], the arylation of 1-unsubstituted pyrazoles with dinitrochlorobenzene [19], or the
reaction of malondialdehyde with 2,4-dinitrophenylhydrazine [24].
The synthesized 1-(2,4-dinitrophenyl)pyrazoles are promising intermediates for developing the
chemistry of potential biologically active compounds of the pyrazole series.
856

1
TABLE 2. IR and H NMR Spectra of Dinitrophenylhydrazones 1a,e-g, 3
and Pyrazoles 2a-g
O2N
H
2
N
2' 3'
R
3
1
N
NO2
4
1'
4'
X
5
6' 5'
Y
H
H
Com-
pound
IR spectrum (KBr),
1Н NMR spectrum (acetone-d6), δ, ppm. (J, Hz)*
ν,cm-1
1a
3305 (NH); 3100,
3075 (=C−H); 1610 (C=N);
1590, 1315 (NO2);
1400 (C=C)
11.07 (1H, s, NH); 8.84 (1H, d, 4J = 2.4, H-3'); 8.38 (1H,
dd, 4J = 2.4, 3J = 9.5, H-5'); 7.88 (1H, d, 3J = 9.5, H-6');
7.34 (1H, d, 3J = 13.7, =CH); 6.64 (1H, d, J = 13.7, =CHCl);
2.60 (2H, t, 3J = 7.4, CH2); 1.59 (2H, m, CH2); 1.01 (3H, t,
J = 7.4, CH3)
1e
1f
3320 (NH); 3080 (=C−H);
1600 (C=N); 1300, 1330,
1500, 1580 (NO2);
11.18 (1H, s, NH); 9.02 (1H, d, 4J = 2.6, H-3'); 8.48 (1H,
dd, 4J = 2.6, 3J = 9.5, H-5'); 8.13 (1H, d, 3J = 9.5, H-6');
7.53 (1H, s, =СН); 2.41 (3H, s, CH3)
1430 (C=C)
3300 (NH); 1620 (C=N);
1300, 1330, 1575 (NO2);
1490 (C=C)
11.15 (1H, s, NH); 8.92 (1H, d, 4J = 2.6, H-3'); 8.43 (1H,
dd, 4J = 2.6, 3J = 9.4, H-5'); 8.02 (1H, d, 3J = 9.4, H-6');
7.68 (1H, s, =CH); 2.78 (2H, q, J = 7.6, CH2);
1.20 (3H, t, J = 7.6, CH3)
1g
2a
3300 (NH); 1620 (C=N);
1300, 1330, 1575 (NO2);
1490 (C=C)
11.42 (1H, s, NH); 9.14 (1H, d, 4J = 2.5, H-3'); 8.38 (1H,
dd, 4J = 2.5, 3J =9.5, H-5'); 8.06 (1H, d, 3J = 9.5, H-6');
7.01 (1H, s, =CH); 2.64 (2H, t, J = 7.8, CH2);
1.70 (2H, m, CH2); 1.11 (3H, t, J = 7.8, CH3)
3145, 3120, 3090 (C=H);
1600 (C=N); 1550,
1345 (NO2)
8.79 (1H, d, 4J = 2.6, H-3'); 8.56 (1H, dd, 4J = 2.6, 3J= 9.0,
H-5'); 8.39 (1H, d, J = 2.6, Y); 8.07 (1H, d, 3J= 9.0, H-6');
6.50 (1H, d, J = 2.6, X); 2.53 (2H, t, J = 7.4, CH2);
1.60 (2H, m, CH2); 0.90 (3H, t, J = 7.4, CH3)
2b
2c
2d
2e
2f
3150, 3100, 3050 (=CH);
1600 (C=N); 1530,
1345 (NO2)
9.07 (1H, d, 4J = 2.5, H-3'); 8.92 (1H, dd, 4J = 2.5, 3
J = 8.7, H-5'); 8.29 (1H, d, 3J= 8.7, H-6'); 6.95 (1H, d,
J = 1.8, H-3); 6.80 (1H, d, J = 1.8, X)
8.86 (1H, s, H-3'); 8.70 (1H, d, 3J = 8.8, H-5'); 8.06 (1H, d,
3J = 8.8, H-6'); 6.43 (1H, s, X); 2.57 (2H, t, J = 7.3, CH2);
1.66 (2H, m, J = 7.3, CH2); 0.93 (3H, t, J = 7.3, CH3)
8.97 (1H, d, 4J = 2.6, H-3'); 8.80 (1H, dd, 4J = 2.6, 3
J = 8.7, H-5'); 8.25 (1H, d, 3J = 8.7, H-6'); 7.85, 7.45 (5H,
m, C6H5); 7.17 (1H, s, X)
8.76 (1H, d, 4J = 2.5, H-3'); 8.63 (1H, dd, 4J = 2.5, 3
J = 8.9, H-5'); 8.43 (1H, s, Y); 8.08 (1H, d, 3J = 8.9, H-6');
2.22 (3H, s, CH3)
3150, 3105, 3090 (=CH);
1600 (C=N); 1520,
1340 (NO2)
3145, 3125 (=CH);
1600 (C=N); 1535,
1345 (NO2)
3145 (=CH); 1600 (C=N);
1540, 1350 (NO2)
3145, 3080 (=CH);
1600 (C=N); 1550, 1525,
1365 (NO2)
8.80 (1H, d, 4J = 2.5, H-3'); 8.66 (1H, dd, 4J = 2.5,
3J = 8.9, H-5'); 8.47 (1H, s, Y); 8.13 (1H, d, 3J = 8.9, H-6');
2.66 (2H, к, J = 7.5, CH2); 1.23 (3H, t, J = 7.5, CH3)
2g
3145, 3075 (=CH);
1600 (C=N); 1535,
1345 (NO2)
8.77 (1H, d, 4J = 2.6, H-3'); 8.63 (1H, dd, 4J = 2.6, 3J = 8.9,
H-5'); 8.45 (1H, s, Y); 8.10 (1H, d, 3J = 8.9, H-6');
2.60 (2H, t, J = 7.3, CH2); 1.67 (2H, m, J = 7.3, CH2,);
0.94 (3H, t, J = 7.3, CH3)
3
3275 (NH); 1615 (C=N);
1510, 1320 (NO2)
11.72 (1H, s, NH); 8.84 (1H, d, 4JH-3-H-5 = 2.5, H-3');
8.44 (1H, s, C(O)H); 8.42 (1H, dd, 4J = 2.5, 3J = 9.5, H-5');
7.91 (1H, d, 3J = 9.5, H-6'); 6.49 (1H, d, 2J = 1.8, =CH);
6.29 (1H, d, 2J = 1.8, =CH)
_______
* The 1H NMR spectra were taken in DMSO-d6 (compounds 1a, 1f, and 2a)
or in CDCl3 (compound 1g).
857

DNPH 1b-d and pyrazole 2d have been described previously and their physicochemical properties
corresponded to the literature [17, 18]. The structures of hydrazones 1a,e-g, 3 and pyrazoles 2a-c,e-g obtained
for the first time were demonstrated by IR and NMR spectroscopic methods (Table 2), and the compositions
were confirmed by elemental analysis (Table 1).
In the IR spectra of DNPH 1a,e-g, 3 absorption bands were observed for N–H, C–Haryl, alkyl, C=N, C=C
bonds, and the NO2 group. In the 1H NMR spectra of DNPH 1a,e-g, 3 the presence was noted of singlet signals
for the protons of the NH group, the HC=C bond, and in the case of the DNPH of α-bromoacrolein (3) there
were also two singlets for the =CH, and CH=N fragments.
Absorption bands were observed in the IR spectra of the obtained pyrazoles 2a-g for the =C–H bond of
the pyrazole ring, for aryl and hetaryl C=N, C=C bonds and for the NO2 group (Table 2).
Mention should be made of the presence in the IR spectra of pyrazoles 2a-g of bands at 3145-3150 cm-1
characterizing the stretching vibrations of C(4)–H and C(5)–H bonds of the heterocycle. The absorption bands of
the C=C bond of the heterocycle is displayed in the IR spectra at 1470-1575 cm-1. The intense absorption band at
3300 cm-1, assigned to the NH group absorption of the initial hydrazones, disappears from the IR spectra of
compounds 2a-g.
1
In the H NMR spectra of pyrazoles 2a-d the resonance signals of the H(4) protons are displayed at
5.9-6.5 ppm, and in pyrazoles 2e-g the H(5) proton signals are found at 8.43-8.45 ppm. As was to be expected, the
introduction of a dinitrophenyl group at position 1 of the heterocycle leads to a displacement of the H(5) signal in
the 1H NMR spectrum of 4-chloropyrazoles 2e-g of 1 ppm towards low field in comparison with the H(5) shift in
the 1H NMR spectra of 1-alkyl-4-chloropyrazoles (7.23-7.49 ppm) [10]. At the same time the position of the H(4)
signal in compounds 2b-d is displaced towards low field to a lesser extent in comparison with its position in the
1H NMR spectra of 5-chloro-1-methylpyrazoles (5.92-6.58 ppm) [15].
As a result of the investigations carried out a new simple method has been developed for obtaining
1-alkyl(aryl)-4(5)-chloro-1-(2,4-dinitrophenyl)pyrazoles from readily available starting materials.
EXPERIMENTAL
1
The H NMR spectra were obtained on Bruker DPX 400 (400 MHz) and Jeol FX 90 Q (90 MHz)
instruments, internal standard was HMDS (δ 0.05 ppm for 1H and 2.00 ppm for 13C in relation to TMS). The IR
spectra were taken on a Specord IR 75 spectrophotometer in KBr disks.
The previously known 2,4-dinitrophenylhydrazones 1b-d were obtained by the usual procedure of [25],
their physicochemical characteristics corresponded with the data of [26].
2,4-Dinitrophenylhydrazones 1a,e-g (General Procedure). The appropriate 2-chlorovinyl ketone
(10 mmol) was added dropwise with stirring to a solution of 2,4-dinitrophenylhydrazine (10 mmol) in ethanol
(50 ml) and 50% H2SO4 (10 ml). The product precipitating as a solid was filtered off, washed with ethanol
(10 ml), and dried.
Preparation of 1-(2,4-Dinitrophenyl)pyrazoles (General Procedure). A solution of chlorovinyl
ketone 2,4-dinitrophenylhydrazone in PPA was heated with stirring at 100-150°C for 20-40 min. The reaction
mixture was cooled, and poured onto ice. The precipitated solid was filtered off, washed with water to neutral
reaction, and dried over P2O5.
1-(2,4-Dinitrophenyl)-3-propylpyrazole (2a) was obtained from the DNPH of 2-chlorovinyl propyl
ketone (2.2 g, 7 mmol) in PPA (16 g) with stirring and heating at 100-110°C for 20 min. Yield 1.78 g.
5-Chloro-1-(2,4-dinitrophenyl)pyrazole (2b) was obtained from the DNPH of β,β-dichloroacrolein
(7.64 g, 25 mmol) and PPA (60 g) at 130-150°C, reaction time was 40 min. Yield 3.02 g.
5-Chloro-1-(2,4-dinitrophenyl)-3-propylpyrazole (2c) was obtained from the DNPH of
2,2-dichlorovinyl propyl ketone (2 g, 5.76 mmol) in PPA (40 g) at 130°C, reaction time was 20 min. Yield
1.59 g.
858

5-Chloro-1-(2,4-dinitrophenyl)-3-phenylpyrazole (2d) was obtained from the DNPH of
2,2-dichlorovinyl phenyl ketone (0.85 g, 2.23 mmol) in PPA (20 g) at 140-150°C, reaction time was 30 min.
Yield 0.6 g.
4-Chloro-1-(2,4-dinitrophenyl)-3-methylpyrazole (2e) was obtained from the DNPH of
1,2-dichlorovinyl methyl ketone (1.24 g, 3.9 mmol) in PPA (20 g) at 130-150°C, reaction time was 30 min.
Yield 0.93 g.
4-Chloro-1-(2,4-dinitrophenyl)-3-ethylpyrazole (2f) was obtained from the DNPH of
1,2-dichlorovinyl ethyl ketone (0.62 g, 1.86 mmol) in PPA (20 g) at 120-125°C, reaction time was 30 min.
Yield 0.48 g.
4-Chloro-1-(2,4-dinitrophenyl)-3-propylpyrazole (2g) was obtained from the DNPH of
1,2-dichlorovinyl propyl ketone (0.57 g, 1.6 mmol) in PPA (20 g) at 130-140°C, reaction time was 30 min.
Yield 0.46 g.
α-Bromoacrolein 2,4-Dinitrophenylhydrazone (3) was obtained analogously to compound 1 from
dinitrophenylhydrazine (3.36 g, 17 mmol) and α-bromoacrolein (2.35 g, 17 mmol). Yield 5.24 g.
REFERENCES
1.
2.
3.
4.
5.
6.
7.
8.
Jpn. Pat. 0656792 (1994); Chem. Abstr., 122, 31573 (1995).
A. F. Granov, Usp. Khim., 68, 773 (1999).
A. Pawer and A. A. Patil, Indian J. Chem., 33B, 156 (1994).
D. E. Butler and H. A. De Wald, J. Org. Chem., 36, 2542 (1971).
M. Nazarinia, A. Sharifian, and A. Shafiee, J. Heterocycl. Chem., 32, 223 (1995).
US Patent 3823157 (1974); Ref. Zh. Khim., 12O253P (1975).
West German Patent 2423642 (1974); Chem. Abstr., 83, 206345 (1975).
F. Shen, R. Pein'e, Zh.-P. Vor, Zh. Mort'e, R. Kantegrii, and D. Krauze, Russian Fed. Pat. 2072991
(1997); Byull. Izobret., No. 4, 194 (1997).
9.
10.
A. E. Pohland and W. R. Benson, Chem. Rev., 66, 161 (1966).
G. V. Bozhenkov, Abstracts, Young Persons Scientific School-Conference on Organic Chemistry,
Ekaterinburg (2002), p. 96.
11.
12.
G. G. Levkovskaya, G. V. Bozhenkov, L. A. Larina, I. T. Evstaf'eva, and A. N. Mirskova, Zh. Org.
Khim., 37, 684 (2001).
G. G. Levkovskaya, G. V. Bozhenkov, and A. N. Mirskova, Abstracts 1st International Conference
"Chemistry and Biological Activity of Synthetic and Natural Compounds. Nitrogen Heterocycles and
Alkaloids", Moscow (2001), p. 184.
13.
14.
15.
G. G. Levkovskaya, G. V. Bozhenkov, R. N. Malyushenko, and A. N. Mirskova, Zh. Org. Khim., 37,
1836 (2001).
G. G. Levkovskaya, G. V. Bozhenkov, A. N. Mirskova, and A. P. Tantsyrev, Russian Fed. Pat. 2186772
(2002); Byull. Izobret., No. 22, 439 (2002).
G. G. Levkovskaya, G. V. Bozhenkov, L. I. Larina, and A. N. Mirskova, Zh. Org. Khim., 38, 1554
(2002).
16.
17.
A. Roedig and H.-J. Becker, Liebigs Ann. Chem., 597, 214 (1955).
I. D. Kalikhman, G. G. Levkovskaya, L. I. Lavlinskaya, A. N. Mirskova, and A. S. Atavin, Izv. Akad.
Nauk SSSR, Ser. Khim., 2235 (1973).
18.
I. D. Kalikhman, L. I, Lavlinskaya, G. G. Levkovskaya, A. N. Mirskova, A. S. Atavin, and
V. A. Pestunovich, Izv. Akad. Nauk SSSR, Ser. Khim., 1402 (1974).
I. L. Finar and R. J. Hurlock, Liebigs Ann, Chem., 597, 3024 (1957).
V. Parrini, Ann. Chim., 929 (1957); Ref. Zh. Khim., 32484 (1958).
19.
20.
859

21.
22.
23.
24.
25.
26.
Dal-Monte-Casoni Dea, Gazz. Chim. Ital., 1539 (1959); Ref. Zh. Khim., 17873 (1960).
H. G. Gard and S. Joshis, J. Org. Chem., 26, 946 (1961); Ref. Zh. Khim., 24Zh148 (1961).
K. Conrow, J. Am. Chem. Soc., 81, 5461 (1959); Ref. Zh. Khim., 65307 (1960).
R. Hüttel, Chem. Ber., 74, 1825 (1941).
Organicum, Vol. 2 [Russian translation], Mir, Moscow (1992), p. 71.
A. N. Mirskova, G. G. Levkovskaya, P. V. Lidina, and M. G. Voronkov, Khim.-farm. Zh., 11, No. 3, 74
(1977).
860