Structure and properties of 2,2-dibromovinyl trifluoromethyl ketone

Article abstract of DOI:10.1023/B:RUJO.0000003156.65761.7b

It was established by IR spectroscopy and quantum-chemical calculations along nonempirical DFT method in B3LYP version with the basis set 6-311 G(d,p) that 2,2-dibromovinyl trifluoromethyl ketone consisted of a mixture of s-cis planar conformer and s-tranx-form deviating from a plane by 13°, whereas the s-cis-form is more energetically stable than the s-trans one (ΔE -5.07 kcal mol^-1). Also in 2,2-dibromo-vinyl methyl ketone the planar s-cis conformer is more stable. Chlorine-containing analogs, 2,2-dichlorovinyl trifluoromethyl ketone and 2,2-dichlorovinyl methyl ketone, are more stable in the planar s-trans-conformation. Charge distribution and polarization in the dibromovinyl ketones are analogous to those in dichlorovinyl ketones in agreement with the established reactivity of dibromovinyl trifluoromethyl ketone. By reaction of 2,2-dibromovinyl trifluoromethyl ketone with 2,4-dinitrophenyl-, alkylhydrazines, N,N-dimethylhydrazine, N,N-, N,O-, N,S-binucleophiles were respectively obtained hydrazone, derivatives of pyrazole, imidazole, oxazole, and 1,3-thiazine containing a trifluoromethyl group.

Full text of DOI:10.1023/B:RUJO.0000003156.65761.7b

Russian Journal of Organic Chemistry, Vol. 39, No. 6, 2003, pp. 807 813. Translated from Zhurnal Organicheskoi Khimii, Vol. 39, No. 6, 2003,
pp. 857 863.
Original Russian Text Copyright
2003 by Bozhenkov, Frolov, Toryashinova, Levkovskaya, Mirskova.
Structure and Properties of 2,2-Dibromovinyl
Trifluoromethyl Ketone
G. V. Bozhenkov, Yu. L. Frolov, D. S.- D. Toryashinova, G. G. Levkovskaya, and A. N. Mirskova
Faworsky Irkutsk Institute of Chemistry, Siberian Division, Russian Academy of Sciences Irkutsk, 664033 Russia
e-mail: ggl@irioch.irk.ru
Received May 22, 2002
Abstract It was established by IR spectroscopy and quantum-chemical calculations along nonempirical
DFT method in B3LYP version with the basis set 6-311 G(d,p) that 2,2-dibromovinyl trifluoromethyl ketone
consisted of a mixture of s-cis planar conformer and s-trans-form deviating from a plane by 13 , whereas
1
the s-cis-form is more energetically stable than the s-trans one ( E 5.07 kcal mol ). Also in 2,2-dibromo-
vinyl methyl ketone the planar s-cis conformer is more stable. Chlorine-containing analogs, 2,2-dichlorovinyl
trifluoromethyl ketone and 2,2-dichlorovinyl methyl ketone, are more stable in the planar s-trans-conforma-
tion. Charge distribution and polarization in the dibromovinyl ketones are analogous to those in dichlorovinyl
ketones in agreement with the established reactivity of dibromovinyl trifluoromethyl ketone. By reaction of
2,2-dibromovinyl trifluoromethyl ketone with 2,4-dinitrophenyl-, alkylhydrazines, N,N-dimethylhydrazine,
N,N-, N,O-, N,S-binucleophiles were respectively obtained hydrazone, derivatives of pyrazole, imidazole,
oxazole, and 1,3-thiazine containing a trifluoromethyl group.
We have reported [1] on the synthesis of 2,2-di-
bromovinyl trifluoromethyl ketone (I) by trifluoro-
acetylation of 1,1-dichloroethene in the presence of
aluminum bromide. Prior to our investigations
ketones with a dibromovinyl group were not known,
and their structure and characteristics were not
studied.
In this study the structure of 2,2-dibromovinyl tri-
fluoromethyl ketone (I), trifluoromethyl 2,2-di-
chlorovinyl ketone (II), and conformational equilibr-
ium in these molecules were investigarted by means
1
of H NMR and IR spectroscopy and by quantum-
chemical calculations by method DFT in a version
B3LYP/6-311 G (d,p) (Tables 1, 2). For the sake
of comparison analogous nonempirical quantum-
chemical calculations were also performed (Table 2)
for methyl 2,2-dichloro(dibromo)vinyl ketones (III,
IV). The results obtained were compared with
previous calculations for methyl 2,2-dichlorovinyl
ketone (III) carried out by CNDO/2 procedure [5].
In the present work were investigated the chemical
properties and structure of 2,2-dibromovinyl trifluoro-
methyl ketone and a comparative analysis was made
of structural parameters and reactivity of this com-
pound and alkyl, aryl, and trifluoromethyl 2,2-di-
chlorovinyl ketones [2].
In the 1H NMR spectrum of 2,2-dibromovinyl
ketone (I) a singlet is observed from the -proton
shifted downfield by 0.6 ppm as compared with a
singlet from the vinyl proton in the 1H NMR spectrum
of its 2,2-dichlorovinyl analog (II) and by 1.2
0.6 ppm relative to the position of the olefin proton
signal for alkyl, aryl 2,2-dichlorovinyl ketones [2].
The larger value of the chemical shift from the signal
We formerly investigated the conformational
structure of important organic synthons, alkyl(aryl)
2,2-dichlorovinyl ketones by using quantum-chemical
calculations SCF MO LCAO by semiempirical
method CNDO/2, calculating atomic vibrations by
1
measuring permettivity, IR, UV, H NMR, 35ClNQR
spectra [2 5]. It was established that aliphatic deriv-
atives existed as mixtures of two planar s-cis, s-trans
conformers, and aromatic 2,2-dichlorovinyl ketones
were present as planar s-cis forms. It was also
demonstrated that the structures of ketones and their
2,4-dinitrophenylhydrazones govern the cyclization
process of the latter into pyrazoles and also the bio-
logical activity thereof [6 8].
1
of olefin proton in the H NMR spectrum of ketone I
(Table 1) is in agreement with the known increase in
the chemical shift value for the proton in position 2
at introduction of a bromine in position 1 of ethane
as compared with 1-chloroethenes [9]. The presence
in vibrational spectra of trifluoromethyl 2,2-dibromo-
1070-4280/03/3906-0807$25.00 2003 MAIK Nauka/Interperiodica

808
BOZHENKOV et al.
Table 1. IR and 1H NMR spectral data for groups C=C, C=O, and =CH of dibromo(dichloro)vinyl ketones
1
1
, cm (CCl4)
, cm (microfilm)
, ppm (CDCl3)
=CH
Compd.
C=C
C=O
= C H
C=C
C=O
CF3C(O)CH= CBr2 (I)
CF3C(O)CH= CCl2 (II)
CH3C(O)CH= CCl2 (III)
C6H5C(O)CH= CCl2
1528
1572.9
1574
1677, 1780
1734, 1782
1676, 1705
1657
3055
3065
3050
3060
1563
1574
1576
1570
1731, 1743 shoulder
1733, 1781
1674, 1704
1670
7.63
7.00
6.45
7.17
1557
Table 2. Total charges, bond lengths, dipole moments, and bond energy in s-cis- and s-trans-conformations
of dihalovinyl ketones
Compd.
no.
E,
Charges
Ccarb
Bond length, nm
1
Rotamer , D
Etotal, ppm kcal mol
C
C
O
C=O C C C=C C CX3
I
B 0
A 166.7
B 0o
A 180
B 0
A 180
B 0o
2.4 5676.1756742
2.4 5676.1675874
5.07
0
4.36
0
0.32
0
0.96
0
0.25
0.26
0.19
0.23
0.18
0.24
0.23
0.27
0.07 0.11 0.25 120.5 147.4 134.2 155.6
0.05 0.08 0.25 120.8 148.1 134.2 155.5
0.04 0.11 0.25 120.5 147.2 134.1 155.6
0.01 0.08 0.25 120.8 147.7 134.2 155.4
II
2.3 1448.3339650
2.2 1448.3270224
2.7 1150.5343024
1.9 1150.5348083
2.6 5378.3771545
2.1 5378.3756207
III
IV
0.07 0.19
0.29 121.2 149.0 133.9 152.2
0.01 0.20 0.29 121.5 149.3 133.6 151.2
0.09 0.20 0.29 121.1 149.5 133.8 151.8
0.06 0.20 0.29 121.6 149.7 133.7 151.1
A 180
(dichloro)vinyl ketones (I, II) of a doublet in the
absorption region of C=O group (Table 1) similarly
to the spectra of alkyl dichlorovinyl ketones is likely
to originate from existence thereof as two rotary
s-cis-, s-trans-conformers [4, 5].
chlorovinyl analog II consist of a mixture of con-
formers: ketone II of planar s-cis- and s-trans-forms,
ketone I of planar s-cis- and deviating from a plane
by 13 s-trans-form (Table 2). Thus the observed
significant increase in the chemical shift of the olefin
proton signal in the spectrum of ketone I (Table 1)
compared to that in ketone II also may be caused by
the existence of dibromoketone I molecule in the non-
planar s-trans-conformation hampering the conjuga-
tion between the double C=O and C=C bonds.
A s-trans
B s-cis
The most energetically feasible form for di-
bromovinyl ketone I and 2,2-dibromovinyl methyl
ketone (IV) is the s-cis-conformer whereas for their
chloro-substituted analogs II, III these are s-trans-
conformers (Table 2). Energy parameters of ketones
I, II, IV conformers differ considerably.
In the IR spectrum of ketone I a shift is observed of
the stretching bands of the carbonyl group and the
double bond to the region of higher frequencies, and
therewith a reverse of their intensity occurs compared
with the corresponding bands and intensities for
alkyl, aryl, and trifluoromethyl 2,2-dichlorovinyl
ketones [1, 2, 4, 5]. Therewith in the IR spectra of
ketones I and II the frequencies of bands correspond-
ing to groups C=O and C=C differ little likely
because of dominating inductive effect of the tri-
fluoromethyl group.
At the same time the difference in the total energy
of conformers of methyl dichlorovinyl ketone III
1
( E = Es-trans Es-cis = 0.32 kcal mol ) indicates
comparable stability of s-cis- and s-trans-conformers
of this compound in contrast to the previously obtain-
ed [5] by CNDO/2 values that have suggested the
higher energetical stability of the s-trans-conformer
According to performed calculations 2,2-di-
bromovinyl trifluoromethyl ketone (I) and its di-
1
( E = 5.27 kcal mol ).
RUSSIAN JOURNAL OF ORGANIC CHEMISTRY Vol. 39 No. 6 2003

STRUCTURE AND PROPERTIES OF 2,2-DIBROMOVINYL TRIFLUOROMETHYL KETONE
It was demonstrated that the lengths of C=C, C
809
All the above stated testifies to the similar charge
distribution and polarization of C=C and C=O
bonds in compounds I IV, and consequently di-
bromovinyl ketones I, IV should behave in reactions
with nucleophiles analogously to ketones II, III.
C
carb, C=O, C CF3 (CH3) bonds were almost
independent of the conformational structure of
ketones II IV, only a small elongation of the Ccarb
Cmethyl bond is observed in the s-cis-isomer of methyl
dichlorovinyl ketone (III). In the s-cis-, s-trans-con-
formers of ketone I the difference in the length of
C=C, C=O, C CF3 (CH3) bonds is also insig-
nificant, but in its nonplanar s-trans-conformer a
considerable elongation of C Ccarb bond is observed
evidencing increased conjugation between the double
bond and the carbonyl group in this conformation of
ketone I.
The reactivity of dibromovinyl trifluoromethyl
ketone found in this study supports the above con-
clusion.
2,2-Dibromovinyl trifluoromethyl ketone as tri-
fluoromethyl 2,2-dichlorovinyl ketone [2] is extreme-
ly promising for preparation of polyfunctional hetero-
atomic and heterocyclic compounds containing a tri-
fluoromethyl group. Compounds with a perfluoro-
methyl group, especially those belonging to hetero-
cyclic series, exhibit high biological activity, and
some among them are applied as pharmaceuticals,
herbicides etc. [10, 11].
The charges on the atoms calculated for various
conformations of dichlorovinyl ketone II and ketones
III, IV are considerably different unlike almost equal
bond lengths.
The replacement of a methyl group by a trifluoro-
methyl one results in decrease in ketones I, II of the
negative charge on the oxygen of the carbonyl group
compared to that in the nonfluorinated analogs III, IV
in keeping with the large electronegative effect of the
trifluoromethyl group. However it also leads to
reduction in the positive charge on the carbon atom
of the carbonyl group.
Reactivity of ketone I was investigated by
examples of reactions with acetylthioamide, thiourea,
o-phenylenediamine, o-aminophenol, 2,4-dinitro-
phenylhydrazine, and alkylhydrazines.
Reactions of ketone I with thiourea and thioacet-
amide in alcoholic media at the reagents ratio 1: 2
gave rise to 1-amino- and 1-methyl-1,3-thiazine-6-
thiones (V, VI) respectively in up to 70% yield.
Atoms C in compounds I IV of both conforma-
tions are negatively charged, and the absolute charge
value is greater in the dibromovinyl derivatives.
In both conformers of trifluoromethyl ketone I the
charges on atoms C and O are almost equal (Table2).
At the same time in methyl 2,2-dichlorovinyl and
2,2-dibromovinyl ketones III, IV, and in ketone II
the highest electron density is located on the oxygen
of the carbonyl group (Table 2). The charges on
carbon atoms of the double bond C and C in two
conformers of nonfluorinated methyl 2,2-dibromo-
vinyl ketone IV and methyl 2,2-dichlorovinyl ketone
III are notably different, and only the oxygens of the
carbonyl groups have the same negative charge.
R = NH2 (V), CH3 (VI).
The arising compounds V, VI are similar to thi-
azines obtained by reaction of 2,2-tricloromethyl
ketone II with thiourea and thioacetamide [2].
Reaction of ketone I with o-phenylenediamine is
similar to that of compound II and occurs with
simultaneous substitution of geminal bromine atoms
and heterocyclization into 2-(trifluoroacetonyl)benz-
imidazole (VII), whose properties and structure has
been described in detail before [2].
The comparison of calculation results for methyl
2,2-dichlorovinyl ketone obtained by CNDO/2 [5]
and by nonempirical method used in this study show
considerable difference in the values of bond lengths
and in their polarization depending on the calculation
procedure used. For instance, it was shown before [5]
that C atom is less positively charged than the
carbon of the carbonyl group. In this study calcula-
tions evidence that the double bond in , -dihalovinyl
ketones is polarized in direction of the C carbon.
Analogously the exothermic reaction of ketone I
with o-aminophenol proceeded with replacement of
The dipole moments calculated ab initio also are
in better agreement with the experimental data for
methyl 2,2-dichlorovinyl ketone [5].
X = NH (VII), O (VIII).
RUSSIAN JOURNAL OF ORGANIC CHEMISTRY Vol. 39 No. 6 2003

810
BOZHENKOV et al.
Table 3. Yields, melting points, IR and NMR spectral data for compounds I, V XI
Compd. Yield,
mp,
(bp, C)
C
IR spectra (in pellets with KBr and
1H, 19F, 13C NMR spectra, solvent,
1
no.
%
microfilm), , cm
, ppm, J, Hz
I
74
(146)
1047 1333(CF3)[15], 1563 (C=C), 1729 CDCl3: 1H: 7.63 (=CH); 19F: 79.80 (CF3)b;
(C=O), 3055 (=C-H)a
13C: 116.48 (=CBr2), 115.22 q(CF3, JC F 291.3),
125.59 (=CH), 175.97 q (C=O, JC 36.9)
CF
V
68
78
177 179 1290 (C=S), 1490, 1560, (C=C), 1635 CD3OD: 6.85s (=CH), 19F 70.15 s (CF3)b
(C=N), 3100 (=C H), 3285 (NH2)
VI
53 55 1300 (C=S), 1510, 1590 (C=C, C=N), CD3OD: 7.23 s (1H, =CH), 2.61 s (3H, CH3);
2930, 2970 (CH3), 3045 (=C H), 2925, 19F 69.93 s (CF3)b
2970 (CH3)
VII
71
98
289 290 1480(C=C), 1600 (C=N), 1635 (C=O), DMSO-d6: 7.50 m, 7.20 m (5H, C7H5), 5.40
3040, 3080 (=C-H), 2650 2930(NH-, (1H, =CH), 12.0 (NH)
Calk H), 3250 (N H)
VIII
186
1320, 1340, 1510, (NO2), 1620 (C=N), DMSO-d6: 6.39 s (=CH), 9.46 (NH), 7.52 d,
3060, 3100 (=C-H), 3270 (NH)
8.34 d, 9.34 d (C6H3, J 10)
8.34 d, 9.34 d (C6H3, J 10)
IX
Xc
XI
61
56
85
(145)
(c)
1060 1230 (CF2 F) [15], 1470 (C=C), CD3Cl: 3.91 s (3H, NCH3), 6.47 s (1H, =CH);
2960 (CH3), 3150 (=C H)b 19F 63.40 s (CF3)b
1465, 1570 (C=C, C=N), 3145 (=C H) 1.44 t (3H, CH3), 4.24 q (2H, NCH2) (J 11.64),
6.52 (1H, = C 4 H)
158d
1090 1230 (CF3) [15], 1470, 1530, 1580, 6.06 s (1H, =C-H), 7.34 m, 7.49 d, 7.58 d
1620 (C=C, C N, C=N), 1640 (C=O), (J 7.0) (2H, 1H, 1H, C7H4), 10.05 br (1H,
3160 (N H)
OH), 19F 75.26 (CF3)b
a
IR spectra recorded from microfilm of substance.
Chemical shift in the spectrum determined relative to CCl3F.
The product purified by column chromatography.
b
c
d
Publ. [13]: mp 202 205 C (Table), 165 166 C (EXPERIMENTAL).
halogen atoms and formation of 2-(trifluoroacetonyl)-
benzoxazole (VIII) in 85% yield. The reaction was
carried out at equimolar reagents ratio in alcohol in
the presence of 2 equiv of alkali.
In reaction with 2,4-dinitrophenylhydrazine ketone
I affords the corresponding hydrazone IX. In contrast
in the reaction of ketone I with alkylhydrazones we
failed to isolate the corresponding hydrazones, and as
reaction products formed 5-bromo-1-alkylpyrazoles
X, XI. The reactions were carried out as well as at
equivalent amounts of reagents and at the double
excess of alkylhydrazine.
Benzoxazole VIII was obtained formerly [12] in
80% yield at heating o-aminophenol with fluoroacet-
yldiethoxyketene for 3 h at 90 95 C. Taking into
account the accessibility of ketone I, milder condi-
tions of the process, and higher yield of the target
product the developed procedure for preparation of
benzoxazole VIII has significant advantages before
the known method [12].
1
In the IR, H and 13C NMR spectra were observed
signals indicating that compound VIII exists in solid
state as ketone and in solution as enol (Table 3). Thus
1
in the H NMR spectrum appeared a singlet from the
Alk = CH3 (X), C2H5 (XI).
olefin proton, signals from the four protons of the
benzoxazole ring, and a signal from a proton of OH
group. The observed long-wave shift of the stretching
vibrations band of the carbonyl group in the IR
spectrum of 2-trifluoroacetonylbenzoxazole (VIII)
reveals the presence of the hydrogen bonds.
The reaction between 2,2-dibromovinyl trifluoro-
methyl ketone (I) with 1,1-dimethylhydrazine resulted
in formation of 5-bromo-1-methyl-3-trifluoromethyl-
pyrazole (X) in 70% yield. The reaction was carried
out in organic solvents at the reagents ratio 1: 2 with
RUSSIAN JOURNAL OF ORGANIC CHEMISTRY Vol. 39 No. 6 2003

STRUCTURE AND PROPERTIES OF 2,2-DIBROMOVINYL TRIFLUOROMETHYL KETONE
811
heat evolution. As the second reaction product was
isolated 1,1,1-trimethylhydrazinium bromide (XII)
in up to 90% yield. At equimolar ratio of reagents
also was obtained pyrazole X, trimethylhydrazinium
bromide, and unreacted 2,2-dibromovinyl ketone I
was recovered. The likely reaction path consists
first in formation of 2,2-dibromovinyl ketone di
methylhydrazone followed by an intramolecular
attack of the nucleophilic dimethylamine fragment
on the -carbon of the vinyl group. The arising
N,N-dimethylpyrazolinium bromide under the
action of 1,1-dimethylhydrazine suffers dequaterniz-
ation into the target product with elimination of
salt XII.
XII
An alternative mechanism including the primary
formation of a quaternary salt 1-[1-bromo-2-trifluoro-
acetylvinyl]-1,1-dimethylhydrazinium bromide fol-
lowed by heterocyclization is hardly probable. This
assumption is supported by formation of quaternary
salts of dimethylhydrazine having similar structure:
1-[1-bromo-2-benzoyl(2-thenoyl)vinyl]-1,1,-dimethyl-
hydrazinium bromides from the corresponding bromo-
acetylene ketones and 1,1-dimethylhydrazine whose
structure has been determined by X-ray diffraction
analysis [13]; these salts do not undergo cyclization
into pyrazoles.
NH groups (Table 3). In the IR spectra of pyrazoles
X, XI should be first of all mentioned an absorption
band characteristic of 5-bromopyrazoles in the region
3140 3150 cm (=CH). In the H NMR spectra
alongside the signals of alkyl groups appears also a
singlet from the pyrazole ring proton H4 at 6.52
6.54 ppm. In the spectrum of 5-choro analog of pyr-
azole X the signal of H4 is observed at 6.47 ppm.
1
1
Thus we have demonstrated that 2,2-dibromovinyl
trifluoromethyl ketone is a highly reactive poly-
functional reagent, and it can find wide applica-
tion in the organic synthesis. Its chemical properties
originate from the presence of highly reactive
bromine and highly electrophilic carbonyl group. In
reactions with ambidentate S,N-, N,N-binucleophiles
and hydrazines both bromine atoms and the oxygen of
carbonyl group can simultaneously undergo substitu-
tion generating respectively derivatives of 1,3-thi-
azine and pyrazole; in reaction with o-phenylenedi-
amine and o-aminophenol only halogen atoms are
replaced, and arise derivatives of benzimidazole and
benzoxazole.
Thus the reaction of 2,2-dibromovinyl trifluoro-
methyl ketone with 1,1-dimethylhydrazine may be
suggested as an efficient procedure for preparation of
5-bromo-1-methyl-3-trifluoromethylpyrazole, a very
promising semiproduct for building up heterocyclic
compounds possessing practically useful properties:
pharmaceuticals, dyes, insectoacaricides etc. [10, 11].
The second product of this reaction, trimethyl-
hydrazinium bromide, is of interest as a biologically
active substance and an aminating reagent [14].
The structure of products prepared from 2,2-di-
bromovinyl trifluoromethyl ketone was proved by
physicochemical methods, by elemental analysis, and
also for compounds V VIII by comparison of their
physicochemical parameters (Table 3) with the data
of these compounds obtained before [2, 12].
EXPERIMENTAL
1H, 13C, 15N, 19F NMR spectra were registered
on spectrometers Bruker DPX-400 (at 400.6, 100.61,
376 MHz for 1H, 13C, 19F respectively) and Jeol
1
FX-90 Q (at 90 and 84 MHz for H and 19F respecti-
vely), internal reference HMDS.
Thiazinethiones V, VI are yellow or orange
powders with a characteristic odor. Their IR and
1H NMR spectra (Table 3) are similar to the spectra
of thiazinethiones prepared previously from ketone II
[2]. All characteristics of benzimidazole VIII are
consistent with the published data [2].
IR spectra were recorded on spectrophotometers
Bruker IFS 25 and Specord 75IR from KBr pellets,
microfilms, and from solutions in CCl4.
In experiments was used molten aluminum
bromide of pure for analysis grade.
2,2-Dibromovinyl trifluoromethyl ketone (I). To
a dispersion of 40 g (0.15 mol) of AlBr3 and 0.35g of
In the IR spectrum of hydrazone IX appear the
characteristic absorption bands of C=N, NO2, and
RUSSIAN JOURNAL OF ORGANIC CHEMISTRY Vol. 39 No. 6 2003

812
BOZHENKOV et al.
anhydrous FeCl3 in 150 ml of anhydrous ethyl
bromide or dibromomethane at 50... 60 C was
added through a bubbler 0.1 mol of trifluoroacetyl
chloride or bromide, and to the mixture was added
dropwise 12.6 g (0.12 mol) of vinylidene chloride.
The reaction mixture was stirred for 3 h at 50...
60 C, then it was warmed to room temperature, and
for 15 min it was maintained at 25 30 C. The reac-
tion mixture was treated with ice, the water layer was
extracted with chloroform, the organic solution was
dried with CaCl2 and distilled. Yield of ketone 21.1 g
(75%) [1].
bromovinyl trifluoromethyl ketone in 5 ml of alcohol.
On completion of heat evolution the stirring continu-
ed for 3 h. Then the reaction mixture was poured into
water, the separated precipitate of benzoxazole was
filtered off and dried in air. Yield 1.95 g. Found, %:
C 52.64; H 2.29; F 24.68; N 6.58. C10H6F3NO2.
Calculated, %: C 52.64; H 2.64; F 4.87; N 6.11.
2,4-Dinitrophenylhydrazone of 2,2-dibromovinyl
trifluoromethyl ketone (IX). To a solution of 1.76 g
(0.01 mol) of 2,4-dinitrophenylhydrazine in 15 ml of
anhydrous methanol and 0.5 ml of concn. H2SO4 was
added at stirring 2.81 g (0.01 mol) of ketone I. On
completion of heat evolution the stirring continued
for 15 min at heating to 60 C. The separated pre-
cipitate was filtered off and dried in a vacuum-desic-
cator. Yield 2.30 g Found, %: C 25.89; H 1.21;
Br 34.39; N 12.05. C10H5Br2F3N4O4. Calculated, %:
C 26.00; H 1.09; Br 34.59; N 12.13.
2-Amino-4-trifluoromethyl-1,3-thiazine-6-thione
(V). To a solution of 1.52 g (0.02 mol) of thiourea in
50 ml of ethanol was added dropwise at stirring
2.81 g (0.01 mol) of 2,2-dibromovinyl trifluoro-
methyl ketone. On completion of heat evolution the
stirring continued for 4 h at heating to 40 C. Then the
reaction mixture was poured into cold water, the
separated yellow flakes were filtered off and dried in
a vacuum-desiccator. Yield of reaction product is
1.7 g. Found, %: C 27.79; H 1.72; N 13.25; S29.60.
C5H3F3N2S2. Calculated, %: C 28.29; H 1.41;
N 13.20; S 30.17.
5-Bromo-1-methyl-3-trifluoromethylpyrazole
(X). (a) To a solution of (0.02 mol) of methylhydr-
azine in 40 50 ml of anhydrous ether was added drop-
wise 5.62 g (0.02 mol) of dibromovinyl ketone I. The
mixture self-heated, and a precipitate of methyl-
hydrazinium bromide separated. On completion of
heat evolution the stirring continued for 1 2 h, the
methylhydrazinium bromide was filtered off, and
from the filtrate on removing the solvents was isolat-
ed pyrazole X in 2.96 g (61%) yield. Found, %:
C 26.18; H 1.64; N 12.09. C5H4BrF3N2. Calculated,
%: C 26.22; H 1.76; N 12.23.
2-Methyl-4-trifluoromethyl-1,3-thiazine-6-thione
(VI). In 32 ml of methanol was dissolved at stirring
1.5 g (0.02 mol) of thioacetamide. To the solution
was added dropwise 2.81 g (0.01 mol) of 2,2-di-
bromovinyl trifluoromethyl ketone. On completion of
heat evolution the stirring continued for 3 h at heating
to 50 C. Then the reaction mixture was poured into
water, the separated precipitate was filtered off and
dried in a vacuum-desiccator. Yield 1.05 g. Found,
%: C 34.24; H 1.82; N 5.80; S 29.50. C6H4F3NS2.
Calculated, %: C 34.12; H 1.91; N 6.63; S 30.36.
(b) To a solution of 1.20 g (0.02 mol) of N,N-di-
methylhydrazine in 50 100 ml of anhydrous hexane
or ether was slowly added dropwise 2.81 g (0.01mol)
of 1,1,1-trifluoro-4,4-dibromo-3-buten-2-one. On
completion of heat evolution the stirring continued for
1 2 h. The separated precipitate of trimethylhydr-
azinium bromide XII was filtered off and dried in a
vacuum over P2O5. Yield of the salt 1.35 g (87.5%),
mp 238 242 C (decomp.). (Publ. [16]: mp 242 C
with decomp, from MeOH Me2C=O). Found, %:
C 32.58; H 10.24; Br 31.97; N 25.37. C3H11BrN2.
Calculated, %: C 32.58; H 10.03; Br 32.06; N25.33.
Trifluoroacetonylbenzimidazole (VII). To
a
solution of 1.12 g (0.01 mol) of o-phenylenediamine
in 60 ml of anhydrous ethyl ether was added drop-
wise 2.81 g (0.01 mol) of 2,2-dibromovinyl trifluoro-
methyl ketone. On completion of heat evolution the
stirring continued for 3 h. The separated precipitate of
trifluoroacetonylbenzimidazolinium
hydrobromide
1
was treated with sodium carbonate solution, the
obtained precipitate of compound VII was filtered off
and dried. Yield 1.65 g. Found, %: C 52.37; H 3.42;
N 12.14. C10H7F3N2O. Calculated, %: C 52.46;
H 3.09; N 12.28.
IR spectrum (in ¤Br), cm : 3200, 3100, 3005, 2700
(NH), 2950 (CH3), 1480, 1630 (C N).
5-Bromo-1-ethyl-3-trifluoromethylpyrazole (XI).
To a solution of 2.4 g (0.04 mol) of ethylhydrazine
in 40 50 ml of anhydrous ether was slowly added
dropwise 5.62 g (0.02 mol) of dibromovinyl ketone I.
The reaction mixture self-heated, and ethylhydrazin-
ium bromide precipitated. On completion of heat
evolution the stirring continued for 1 2 h. The
Trifluoroacetonylbenzoxazole (VIII). To a solu-
tion of 1.1 g (0.01 mol) of o-aminophenol and 0.8 g
(0.02 mol) of NaOH in 20 ml of methanol or ethanol
was added dropwise 2.81 g (0.01 mol) of 2,2-di-
RUSSIAN JOURNAL OF ORGANIC CHEMISTRY Vol. 39 No. 6 2003

STRUCTURE AND PROPERTIES OF 2,2-DIBROMOVINYL TRIFLUOROMETHYL KETONE
813
precipitate of the ethylhydrazinium bromide was
filtered off. From the filtrate on removing the
solvents 2.72 g of pyrazole XI was isolated.
skaya, G.G., Mirskova, A.N., Atavin, A.S., and
Pestunovich, V.A., Izv. Akad. Nauk SSSR, Ser. Khim.,
1974, p. 1402.
8. Mirskova, A.N., Levkovskaya, G.G., Lidina, P.V.,
and Voronkov, M.G., Khim.-Farm. Zh., 1977, p. 74.
9. Gordon, A.J. and Ford, R.A., The Chemist, s Compa-
nion, New York: Wiley, 1972. Translated under the
title Sputnik khimika, Moscow: Mir, 1976, pp. 200
225.
REFERENCES
1. Bozhenkov, G.V, Levkovskaya, G.G., and Mirsko-
va, A.N., Zh. Org. Khim., 2002, vol. 38, p. 140.
2. Levkovskaya, G.G., Bozhenkov, G.V., Larina, L.A.,
Evstaf’eva I.T., and Mirskova A.N., Zh. Org. Khim.,
2001, vol. 37, p. 684.
3. Levkovskaya, G.G., Mirskova, A.N., Bryukho-
va, E.V., Kazakov V.P., and Atavin, A.S., Izv. Akad.
Nauk SSSR, Ser. Khim., 1975, p. 793.
4. Gavrilova, G.A., Keiko, V.V., Levkovskaya, G.G.,
Mirskova, A.N., and Frolov, Yu.L., Izv. Akad. Nauk
SSSR, Ser. Khim., 1978, p. 84.
5. Shainyan, B.A., Levkovskaya, G.G., and Mirsko-
va, A.N., Izv. Akad. Nauk SSSR, Ser. Khim., 1978,
p. 934.
10. Nenaidenko, V.G., Sanin, A.V., and Balenkova, E.S.,
Usp. Khim., 1999, 68, p. 483.
11. Granov, A.F., Usp. Khim., 1999, 68, p. 773.
12. Narsaiah, N., Sivaprasad, A., and Venkatarat-
nam, R.V., J. Fluorine Chemistry., 1994, pp. 66, 47.
13. Elokhina, V.N., Nakhmanovich, A.S., Larina, L.I.,
Shishkin, O.V., Baumer, V.N., and Lopyrev, V.A.,
Izv. Russian Akad. Nauk, Ser. Khim., 1999, p. 1536.
14. Belyaev, E.Yu., N,N-Dimetilgidrazin v organiches-
kom sinteze, (N,N-Dimethylhydrazine in Organic
Chemistry), Krasnoyarsk: Sib. Gos. Tekhn. Univ.,
1999.
15. Berney, C.V. and Cormier, A.D., Spectrochim.
Acta, 1977, 33A, p. 929.
16. Klages, F. and Wolf, H., Chem. Ber., 1959, 92,
p. 1842.
6. Kalikhman, I.D., Levkovskaya, G.G., Lavlin-
skaya, L.I., Mirskova, A.N., and Atavin, A.S., Izv.
Akad. Nauk SSSR, Ser. Khim., 1973, p. 2235.
7. Kalikhman, I.D., Lavlinskaya, L.I., Levkov-
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