Synthesis and reactivity of 2-polyfluoroalkylchromene-4(4H)-thiones

Article abstract of DOI:10.1007/s11172-005-0115-9

2-Polyfluoroalkylchromene-4(4H)-thiones, synthesized from 2-polyfluoroalkylchromones and P₂S₅, react with aniline, phenylhydrazines, and hydroxylamine at the C(4) atom and afford corresponding anils, phenylhydrazones, and oximes of c

Full text of DOI:10.1007/s11172-005-0115-9

Russian Chemical Bulletin, International Edition, Vol. 53, No. 10, pp. 2285—2292, October, 2004
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Synthesis and reactivity of 2ꢀpolyfluoroalkylchromeneꢀ4(4H )ꢀthiones
ꢀ
B. I. Usachev, M. A. Shafeev, and V. Ya. Sosnovskikh
A. M. Gorky Ural State University,
51 prosp. Lenina, 620083 Ekaterinburg, Russian Federation.
Fax: +7 (343 2) 61 5978. Eꢀmail: Vyacheslav.Sosnovskikh@usu.ru
2ꢀPolyfluoroalkylchromeneꢀ4(4H )ꢀthiones, synthesized from 2ꢀpolyfluoroalkylchromones
and P2S5, react with aniline, phenylhydrazines, and hydroxylamine at the С(4) atom and
afford corresponding anils, phenylhydrazones, and oximes of chromones. On heating in alcoꢀ
hol in the presence of concentrated HCl, chromone phenylhydrazones and oximes undergo
ring closure to form 3ꢀ(2ꢀhydroxyaryl)ꢀ1ꢀphenylꢀ5ꢀpolyfluoroalkylpyrazoles and 5ꢀhydroxyꢀ
2
3ꢀ(2ꢀhydroxyaryl)ꢀ5ꢀpolyfluoroalkylꢀ∆ ꢀisoxazolines.
Key words: 2ꢀpolyfluoroalkylchromeneꢀ4(4H )ꢀthiones, amines, hydrazines, hydroxylamine;
anils, chromone phenylhydrazones, chromone oximes; pyrazoles, isoxazolines.
In continuation of our studies of the chemical properꢀ
related regioisomeric RFꢀcontaining heterocyclic comꢀ
pounds.
ties of 2ꢀpolyfluoroalkylchromones 1, which turned out
to be highly reactive substrates in reactions with Nꢀ, Sꢀ,
and Сꢀnucleophiles,1 it seemed of interest to synthesize
2ꢀpolyfluoroalkylchromeneꢀ4(4H )ꢀthiones (2) and comꢀ
pare their reactivity toward Nꢀnucleophiles with the reacꢀ
tivity of previously studied 2ꢀpolyfluoroalkylchromones 1.
It is known1—4 that the reactions of chromones with
nucleophilic reagents occur mainly at the С(2) atom
(1,4 addition), regardless of the presence and nature of a
substituent at this atom. The replacement of the carbonyl
oxygen atom by the sulfur atom makes it possible, in some
cases, to direct the attack of an Nꢀnucleophile to the С(4)
atom. For instance, it has been shown5—7 that 2ꢀarylꢀ
chromeneꢀ4(4H )ꢀthiones react with primary amines,
hydroxylamine, and hydrazines at the thione group to
form the corresponding Nꢀsubstituted flavone imines.
Taking into account these data, it could be assumed that
2ꢀRFꢀchromenethiones 2, as 2ꢀRFꢀchromones 1, are valuꢀ
able substrates for syntheses of a wide series of RFꢀconꢀ
taining, including trifluoromethylated, nitrogen heteroꢀ
cycles, which are of interest from the viewpoint of their
potential biological activity.8
In this work, we synthesized for the first time a series
2ꢀpolyfluoroalkylchromeneꢀ4(4H )ꢀthiones 2 by the reꢀ
action of 2ꢀRFꢀchromones 1 with P2S5 and studied their
reactions with different Nꢀnucleophiles. As should be exꢀ
pected in accord with the principle of "hard and soft acids
and bases" and published data on 2ꢀarylchromeneꢀ4ꢀ
thiones,5—7 2ꢀRFꢀchromenethiones 2 react with aniline,
phenylhydrazine, and hydroxylamine at the С(4) atom
(1,2 addition). This enhances substantially the synthetic
significance of the chromone system with a polyfluoroꢀ
alkyl group in position 2 due to a possibility of obtaining
Results and Discussion
Data on the synthesis and chemical properties of
chromenethiones containing a polyhaloalkyl group at the
С(2) atom are lacking. At the same time, the reaction of
2ꢀarylchromeneꢀ4ꢀthione, chromeneꢀ4ꢀthione, 2ꢀmethylꢀ
chromeneꢀ4ꢀthione, and their substituted derivatives with
different Nꢀnucleophiles were studied in detail. For exꢀ
ample, the reagents with the primary amino group were
shown to react with 2ꢀarylchromeneꢀ4ꢀthiones predomiꢀ
nantly at the С(4) atom with the formation of flavone
imines, hydrazones, and oximes.5—7,9 Hydrazine, phenylꢀ
hydrazine, and hydroxylamine react with chromeneꢀ4ꢀ
thiones both at the С(2) atom with pyrone ring openꢀ
ing and formation of the corresponding pyrazoles and
isoxazoles7,10 and at the С(4) atom.7,10,11
We found that reflux of 2ꢀRFꢀchromones 1a—g with
P2S5 in toluene for 4 h affords 2ꢀRFꢀchromenethiones
2a—g in 49—93% yield. Compounds 2a—g (Scheme 1)
are crystals colored from green to violet. The presence of
a halogen atom in position 3 does not prevent the reacꢀ
tion. The replacement of the carbonyl O atom by an
S atom results in a substantial downfield shift of signals
from the Н(3) and Н(5) protons (by ~0.7 and ~0.3 ppm,
respectively), which is related to a high deshielding effect
of the S atom. At the same time, the transition from
chromone 1a to chromenethione 2a only insignificantly
affects the chemical shift of the CF3 group (–72.2 ppm
in 1а and –71.5 ppm in 2а).
On refluxing in butanol for 4 h, chromenethiones 2a,b,f
react with aniline at the С(4) atoms to afford anils 3a,b,f
Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 10, pp. 2188—2195, October, 2004.
1066ꢀ5285/04/5310ꢀ2285 © 2004 Springer Science+Business Media, Inc.

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Russ.Chem.Bull., Int.Ed., Vol. 53, No. 10, October, 2004
Usachev et al.
Scheme 1
system and exerts a shielding effect on the Н(5) proton.
As a result, the H(5) proton should appear in a stronger
field (in the series of 4ꢀazafluorene azomethines, a similar
proton is observed at 6.1—6.5 ppm).15,16
Also note that, unlike Nꢀalkylchromeneimines that
are protonated in a CDCl3 solution in the presence of
both CD3CO2D and CF3CO2H,12 compounds 3 form
anilium cations 3´ only with CF3CO2H. In this case,
signals of all protons of the heterocyclic system exhibit a
downfield shift by 0.5—0.6 ppm, and the Н(3) proton is
deshielded to the greatest extent, which is likely related to
an increase in the contribution of aromatic chromilium
cation 3″. At the same time, the chemical shifts of protons
remain unchanged upon the addition of CD3CO2D, indiꢀ
cating a lower basicity of anils 3 and explaining their
incapability, unlike Nꢀalkylchromeneimines,12 of openꢀ
ing to form aminoenones in an ammonium acetate soꢀ
lution.
The reactions of aliphatic primary amines (benzylꢀ
amine, 2ꢀaminoethanol) with chromenethiones 2 ocꢀ
cur ambiguously and afford a complicated mixture of
substances, whose main components are regioisomeric
aminoenones, viz., products of the amino group attack at
the С(2) and С(4) atoms of the chromenethione system
followed by pyrone ring opening. This fact is in contrast
to the behavior of chromones, whose reaction with priꢀ
mary amines at the С(2) atom with the formation of
3ꢀaminoꢀ1ꢀ(2ꢀhydroxyaryl)propꢀ2ꢀenꢀ1ꢀones is one of the
most characteristic.1,2 We failed to isolate individual prodꢀ
ucts in the reactions of substituted anilines, such as
oꢀmercaptoaniline.
a
b
c
d
e
f
g
RF
R
X
CF3
H
H
CF3
6ꢀMe 7ꢀMeO
H
CF3
CF3
H
Cl
CF3 (CF2)2H (CF2)2H
H
Br
H
H
6ꢀMe
H
H
in 55—79% yields (Scheme 2). When compounds 3 are
refluxed in ethanol in the presence of concentrated HCl,
they hydrolyze to chromones 1, whereas in aqueous AcOH
the reaction ceases at intermediate 2ꢀhydroxyꢀ2ꢀtriꢀ
fluoromethylchromanꢀ4ꢀones, as in the case of Nꢀalkylꢀ
4Нꢀchromeneꢀ4ꢀimines recently described by us.12
It should be mentioned that chromones10 and even
2ꢀRFꢀchromones do not react with aromatic amines (exꢀ
cept for 6ꢀnitroꢀ2ꢀtrifluoromethylchromone13 and 5,7ꢀdiꢀ
methylꢀ2ꢀtrifluoromethylꢀ8ꢀazachromone,14 which can
undergo pyrone ring opening under the action of aniline
to form βꢀanilinovinyl ketones). 2ꢀPhenylchromeneꢀ4ꢀ
thione does not either react with aniline, and flavone anil
was obtained only from more reactive 4ꢀmethylthioꢀ
flavilium, which is formed by the methylation of thione at
the sulfur atom under the action of MeI.6
Scheme 2
Compounds 2a,b,g react with phenylhydrazine already
at ~20 °С. The reaction is accompanied by vigorous H2S
evolution and affords (within several min) phenylhydrꢀ
azones 4a,b,g (37—78% yields), whose nonꢀfluorinated
analogs were synthesized earlier from chromeneꢀ4ꢀthiones
and 2ꢀarylchromeneꢀ4ꢀthiones under more drastic conꢀ
ditions.7,10,11 On boiling in ethanol in the presence of
concentrated HCl, phenylhydrazones 4b,g undergo ring
closure to 1ꢀPhꢀ5ꢀRFꢀpyrazoles 5b,g in ~100% yield
(Scheme 3). The RF group is located at the C(5) atom
(not С(3)), which can easily be established if one considꢀ
3
ers the JH,F constant value of the (CF2)2H group in
pyrazole 5g. This constant is 3.2 Hz in a CDCl3 solution
and corresponds to the 5ꢀRF regioisomer17 (3JH,F = 4.5 Hz
was indicated for the 3ꢀRF regioisomer).17 Note that the
structure of 5ꢀ(2ꢀhydroxyphenyl)ꢀ3ꢀmethylꢀ1ꢀphenylꢀ
pyrazole was ascribed to the product of the reaction of
2ꢀmethylchromeneꢀ4ꢀthione with phenylhydrazine.6
Pyrazoles 5 can be obtained directly from chromeneꢀ
thiones 2 when the latter are refluxed in alcohol with
phenylhydrazines. However, from the preparative point
of view, this reaction is better to use only in the case of
solid hydrazines, where solvent should be used and the
process cannot be stopped at the step of phenylhydrꢀ
The 1Н NMR spectra of anils 3 contain only one set of
signals corresponding to the Е configuration of the С=N
bond, which can be concluded from the chemical shift
value of the Н(5) proton (δ 8.13—8.37). Because of unfaꢀ
vorable steric interactions with the periꢀH atom in the
Z isomer, the phenyl substituent should predominantly be
located in the nonplanar position toward the chromone

2ꢀPolyfluoroalkylchromeneꢀ4ꢀthiones
Russ.Chem.Bull., Int.Ed., Vol. 53, No. 10, October, 2004
2287
scribed12,21—23 Nꢀalkylꢀ4Нꢀchromeneꢀ4ꢀimines turned
out to be more appropriate for this purpose. They are
protonated at the imine nitrogen atom even in a weakly
acidic medium and generate iminium cations with an
enhanced electrophilicity of the С(2) atom. We found
that Nꢀbenzylꢀ2ꢀtrifluoromethylꢀ4Нꢀchromeneꢀ4ꢀimine
(7) reacts with PhNHNH2 in a solution of AcOH and
EtOH (~20 °С, 10 min) and gives 1ꢀPhꢀ3ꢀCF3ꢀpyrazole 8
in 50% yield. Compound 8 was obtained earlier19 from
chromone 1а in a yield of 13% only (Scheme 5).
Scheme 3
Scheme 5
azone 4. For example, we obtained 3ꢀ(5ꢀСF3ꢀpyrazolꢀ1ꢀ
yl)pyridazine 6 from chromenethione 2а and 3ꢀhydrazinoꢀ
6ꢀ(2ꢀhydroxyphenyl)pyridazine18 on refluxing in methaꢀ
nol (Scheme 4). This compound belongs to the series of
5ꢀRFꢀpyrazoles, which is indicated by the chemical shifts
of Н(6) protons of the 2ꢀhydroxyphenyl substituents
(δ 7.93 and 8.20) characteristic of a planar conformer stabiꢀ
lized by two intramolecular hydrogen bonds (IMHB)19,20
(in the case of 3ꢀRF regioisomer, no IMHB can be
formed between the phenolic proton and pyrazole ring).
Chromone 1а does not react with hydrazinopyridazine.
X = O (1a), NꢀBn (7)
Thus, the replacement of the carbonyl groups in
2ꢀRFꢀchromones 1 by the thione or imino group makes
it possible to synthesize regioisomeric Nꢀsubstituted
pyrazoles. However, anils 3 do not react with phenylꢀ
hydrazine, under these conditions, because of a lower
basicity. The reaction of chromenethione 2b with hydrꢀ
azine hydrate occurs as easily as that of chromone 1b 19
and affords pyrazole 9 in 65% yield (Scheme 6). In this
case, unlike the reaction of phenylhydrazine, we failed to
detect the formation of chromone hydrazone as an interꢀ
mediate product. Nonꢀfluorinated chromenethiones reꢀ
act with hydrazine hydrate to afford both pyrazoles7,10
and hydrazones.7,11
Scheme 4
Scheme 6
X = O (1b), S (2b)
We have previously shown19 that the reaction of
2ꢀRFꢀchromones 1 with phenylhydrazine on refluxing in
ethanol occurs at the С(2) atom and, unlike chromeneꢀ
thiones 2, affords 1ꢀPhꢀ3ꢀRFꢀpyrazoles. However, the
yields of these compounds did not exceed 20% and, hence,
chromones 1 could not be recommended for preparaꢀ
tive synthesis of 1ꢀPhꢀ3ꢀRFꢀpyrazoles. Recently deꢀ
The reactions of chromones with hydroxylamine
are known to give mainly mixtures of regioisomeric
isoxazoles,3,4,24—28 and the formation of chromone oximes
along with isoxazoles was observed only for chromones
unsubstituted in position 2 4,24,28 and flavone.27 The diꢀ
rection of the reaction of chromeneꢀ4ꢀthiones with
NH2OH depends, to a great extent, on the nature of

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Usachev et al.
substituents in positions 2 and 3. In this case, 2ꢀarylchroꢀ
meneꢀ4ꢀthiones give predominantly flavone oximes,6,9
whereas chromone dioximes, isoxazoles, thiazoles, and
oximes were obtained in the reactions with chromeneꢀ
thiones and 3ꢀarylchromeneꢀ4ꢀthiones.26,29
tion from chromones 1 to chromenethiones 2 changes
the direction of the reaction of hydroxylamine with
the chromone system, which makes it possible to obꢀ
tain regioisomeric 5ꢀ and 3ꢀpolyfluoroalkylꢀcontaining
isoxazoles.
We have recently shown30 that 2ꢀRFꢀchromones 1 reꢀ
act with NH2OH at the С(2) atom to form monooximes
of the corresponding βꢀdiketones, which readily undergo
ring closure in an acidic medium to form 3ꢀRFꢀisoxazoles.
In this work, we found that 2ꢀRFꢀchromenethiones 2 reꢀ
act very smoothly and selectively with NH2OH (ethanol,
~20 °С, 5 min) at the thione group to form chromone
oximes 10a,b,f in 72—83% yields. In addition, only
compounds 10 were also obtained from chromeneꢀ
thiones 2 under more drastic conditions (reflux in aqueꢀ
ous ethanol for 1 h). Under these conditions, chromones 1
gave diketone monooximes30 (Scheme 7). According to
It is interesting that, under the conditions of the
Beckmann rearrangement, the reaction of oxime 10a with
PCl5 in ether followed by the hydrolysis of the reaction
mixture affords phosphate 13, whose structure was conꢀ
firmed by the data of elemental analysis and IR and NMR
spectroscopies (Scheme 8).
Scheme 8
1
the Н NMR spectra, oximes 10 are formed almost exꢀ
clusively as Е isomers, in the spectra of which sigꢀ
nals from the Н(5) and Н(3) protons are observed at
δ 7.71—7.94 and 7.15—7.17, respectively. An insignifiꢀ
cant content of the Z isomers (2—3% for 10a,b and
6% for 10f) can be concluded from the downfield signal of
the Н(5) proton at δ 8.95—8.97 and the singlet of the
Н(3) proton at δ 6.40—6.45, which agrees with the pubꢀ
lished data on the chemical shifts of the Н(5) atom in
isomeric 3ꢀmethylchromone oximes (Zꢀoxime: δ 9.13,
Eꢀoxime: δ 7.95).29
The formation of different products on refluxing
anils 3, phenylhydrazones 4, and oximes 10 in alcohol
in the presence of concentrated HCl is explained in
Scheme 9. The acidꢀcatalyzed hydration of the double
bond of the pyrone ring leads to intermediate А existing,
most likely, as an equilibrium mixture of cyclic and open
forms. In the case of anils 3, this intermediate hydrolyzes
to chromanone 12 stable in a weakly acidic medium but
easily dehydrating to chromone 1 in the presence of HCl.
For X = ОН, intermediate А undergoes ring closure to
form isoxazoline 11 stable under the given conditions,30
and at X = NHPh intermediate A forms pyrazoline that
looses a water molecule and transforms into pyrazole 5.
This scheme does not contradict the mechanism of hydroꢀ
lysis of Nꢀalkylchromeneimines to aminoenones and
chromanones12 that has been proposed by us previously.
The different behavior of compounds 1 and 2 in the
reactions with Nꢀnucleophiles agrees well with the semiꢀ
empirical quantumꢀchemical calculations for chromone
1а and chromenethione 2а performed using the PM3
method.31 The results of calculations show that 1а and 2а
differ slightly by LUMO energy (–1.15 and –1.26 eV,
respectively), whereas the atomic coefficients of the
pz orbitals of the С(2) and С(4) atoms in LUMO are equal
to –0.51 and 0.37 (for 1а) and –0.40 and 0.56 (for 2а),
predicting the predominant attack to the C(2) atom of
chromone 1а and to the С(4) atom of chromenethione 2а
by a nucleophilic species. In addition, the calculations of
the reaction routes of addition at the carbonyl and thione
groups for the reaction of compounds 1а and 2а with
hydroxylamine show a much higher activation energy
(45 kcal mol–1) for the attack to the C=O bond by hydrꢀ
Scheme 7
The simple and efficient synthesis of chromone oximes
10 is of doubtless interest, because this class of organic
compounds remained inaccessible and poorly studied up
to recently. On refluxing in alcohol in the presence of HCl,
oxime 10а transforms into isoxazoline 11, which we obꢀ
tained earlier from 2ꢀhydroxyꢀ2ꢀtrifluoromethylchromanꢀ
4ꢀone (12) and used for the synthesis of the correspondꢀ
ing 5ꢀCF3ꢀisoxazole30 (see Scheme 7). Thus, the transiꢀ

2ꢀPolyfluoroalkylchromeneꢀ4ꢀthiones
Russ.Chem.Bull., Int.Ed., Vol. 53, No. 10, October, 2004
2289
Scheme 9
ing of interest for further studies in the field of regioꢀ
controlled synthesis of polyfluoroalkylꢀcontaining heteroꢀ
cyclic compounds.
Experimental
IR spectra were recorded on IKSꢀ29 and Perkin—Elmer
1
Spectrum BXꢀII instruments in Nujol or KBr pellets. Н NMR
spectra were obtained on a Bruker DRXꢀ400 spectrometer in
CDCl3 with a working frequency of 400.1 MHz and Me4Si as an
internal standard. The starting chromones 1a—d,f,g 30,36,37 and
chromeneimine 7 22 were described earlier.
3ꢀBromoꢀ2ꢀtrifluoromethylchromone (1е) was synthesized by
a procedure similar to that described for 3ꢀchloroꢀ2ꢀtrifluoroꢀ
methylchromone36 in 72% yield, m.p. 149—150 °С (ethanol),
colorless needleꢀlike crystals. Found (%): С, 41.32; H, 1.37.
C
10H4BrF3O2. Calculated (%): C, 40.99; H, 1.38. IR, ν/cm–1
:
1660 (C=O), 1620 (C=C), 1575 (arom.). 1Н NMR (CDCl3), δ:
7.54 (ddd, 1 H, H(6), Jo = 8.1 Hz, 7.2 Hz, Jm = 1.0 Hz); 7.58 (d,
1 H, H(8), Jo = 8.6 Hz); 7.81 (ddd, 1 H, H(7), Jo = 8.6, 7.2 Hz,
Jm = 1.7 Hz); 8.27 (dd, 1 H, H(5), Jo = 8.1 Hz, Jm = 1.7 Hz).
Synthesis of 2ꢀpolyfluoroalkylchromeneꢀ4(4H )ꢀthiones (2)
(general procedure). A mixture of 2ꢀRFꢀchromone 1 (4.5 mmol)
and P2S5 (1.0 g, 4.5 mmol) in anhydrous toluene (5 mL) was
refluxed with stirring for 4 h. After the reaction mixture cooled
down, it was filtered, the solvent from the filtrate was evapoꢀ
rated, and the residue was recrystallized from hexane (a hot
hexane solution was preliminarily passed through silica gel
(2 cm3)). All synthesized chromenethiones are brightly colored
crystalline substances stable on storing for several weeks.
2ꢀTrifluoromethylchromeneꢀ4ꢀthione (2а). The yield was
93%, m.p. 71—72 °C, dark blue needleꢀlike crystals with metalꢀ
lic luster. Found (%): С, 52.04; H, 2.20. C10H5F3OS. Calcuꢀ
lated (%): C, 52.17; H, 2.19. IR (KBr), ν/cm–1: 3065, 1640,
1605. 1Н NMR (CDCl3), δ: 7.44 (s, 1 H, H(3)); 7.46 (ddd, 1 H,
H(6), Jo = 8.2, 7.1 Hz, Jm = 1.1 Hz); 7.53 (dd, 1 H, H(8), Jo =
8.6 Hz, Jm = 1.1 Hz); 7.78 (ddd, 1 H, H(7), Jo = 8.6, 7.1 Hz,
Jm = 1.6 Hz); 8.48 (dd, 1 H, H(5), Jo = 8.2 Hz, Jm = 1.6 Hz).
19F NMR (376.5 MHz, CDCl3, CFCl3), δ: –71.5 (CF3).
6ꢀMethylꢀ2ꢀtrifluoromethylchromeneꢀ4ꢀthione (2b). The
yield was 60%, m.p. 77—79 °С, light green crystals. Found (%):
С, 53.16; H, 2.89. C11H7F3OS•0.25H2O. Calculated (%):
oxylamine, while for the С=S bond the activation energy
is only 18 kcal mol–1
.
It should be noted in conclusion that with
2ꢀСF3ꢀchromenethione 2a we could not perform the
whole series of reactions that were characteristic of
2ꢀphenylchromeneꢀ4ꢀthione and 2ꢀCF3ꢀchromones 1.
For example, unlike phenylchromenethione, chromeneꢀ
thione 2а, being treated with MeI, is not methylated at
the sulfur atom. Under the conditions where phenylꢀ
chromenethione hydrolyzes to flavone in 65% yield,6
chromenethione 2а gives chromone 1а only in trace
amounts. Chromenethione 2а does not react either
with (trifluoromethyl)trimethylsilane (reacting with
2ꢀCF3ꢀchromones by the type of 1,4 addition32,33), does
not react with ethylmercaptoacetate (in the reaction
with which 2ꢀCF3ꢀchromones afford dihydrothienoꢀ
coumarins34,35), and transforms into resin under the acꢀ
tion of phenyllithuim at –50 °С.
1
C, 53.12; H, 2.84. IR, ν/cm–1: 1635, 1560. Н NMR (CDCl3),
δ: 2.49 (s, 3 H, Me); 7.43 (d, 1 H, H(8), Jo = 8.6 Hz); 7.44
(s, 1 H, H(3)); 7.60 (ddq, 1 H, H(7), Jo = 8.6 Hz, Jm
2.2 Hz, JН,Ме = 0.5 Hz); 8.28 (dq, 1 H, H(5), Jm = 2.2 Hz,
4JН,Ме = 0.5 Hz).
=
4
7ꢀMethoxyꢀ2ꢀtrifluoromethylchromeneꢀ4ꢀthione (2с). The
yield was 75%, m.p. 106—108 °С, lilac crystals. Found (%):
С, 50.83; H, 2.82. C11H7F3O2S. Calculated (%): C, 50.77;
H, 2.71. IR (KBr), ν/cm–1: 1645, 1610, 1500. 1Н NMR (CDCl3),
δ: 3.94 (s, 3 H, MeО); 6.89 (d, 1 H, H(8), Jm = 2.5 Hz); 7.04
(dd, 1 H, H(6), Jo = 9.1 Hz, Jm = 2.5 Hz); 7.36 (s, 1 H, H(3));
8.42 (d, 1 H, H(5), Jo = 9.1 Hz).
3ꢀChloroꢀ2ꢀtrifluoromethylchromeneꢀ4ꢀthione (2d). The yield
was 89%, m.p. 72—74 °С, green crystals. Found (%): С, 45.13;
H, 1.54. C10H4ClF3OS. Calculated (%): C, 45.38; H, 1.52. IR,
Thus, unlike earlier studied 2ꢀRFꢀchromones,1
2ꢀRFꢀchromenethiones react with Nꢀnucleophiles mainly
according to the 1,2 addition type, which makes it posꢀ
sible to obtain anils, phenylhydrazones, and oximes of
2ꢀRFꢀchromones inaccessible by other methods and beꢀ
1
ν/cm–1: 1605, 1600. Н NMR (DMSOꢀd6), δ: 7.65 (ddd, 1 H,
H(6), Jo = 8.2, 7.1 Hz, Jm = 1.1 Hz); 7.84 (ddd, 1 H, H(8), Jo =
8.5 Hz, Jm = 1.1 Hz, Jp = 0.4 Hz); 7.99 (ddd, 1 H, H(7),

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Usachev et al.
Jo = 8.5, 7.1 Hz, Jm = 1.6 Hz); 8.42 (ddd, 1 H, H(5), Jo
8.2 Hz, Jm = 1.6 Hz, Jp = 0.4 Hz).
=
(m, 2 H, arom.); 7.56 (ddq, 1 H, H(7), Jo = 8.6 Hz, Jm = 2.2 Hz,
4JH,Me = 0.5 Hz); 8.13 (br.d, 1 H, H(5), Jm ≈ 2.0 Hz).
3ꢀBromoꢀ2ꢀtrifluoromethylchromeneꢀ4ꢀthione (2е). The yield
was 49%, m.p. 88—89 °С, green needleꢀlike crystals. Found (%):
С, 38.79; H, 1.25. C10H4BrF3OS. Calculated (%): C, 38.86;
H, 1.30. IR, ν/cm–1: 1605, 1590. 1Н NMR (CDCl3), δ: 7.54
(ddd, 1 H, H(6), Jo = 8.0, 7.2 Hz, Jm = 1.0 Hz); 7.58 (ddd, 1 H,
H(8), Jo = 8.6 Hz, Jm = 1.0 Hz, Jp = 0.5 Hz); 7.81 (ddd, 1 H,
H(7), Jo = 8.6, 7.2 Hz, Jm = 1.7 Hz); 8.26 (ddd, 1 H, H(5), Jo =
8.0 Hz, Jm = 1.7 Hz, Jp = 0.5 Hz).
Nꢀ(1,1,2,2ꢀTetrafluoroethylꢀ4Hꢀchromenꢀ4ꢀylidene)aniline
(3f). The yield was 77%, m.p. 94—95 °С, yellow needleꢀlike
crystals. Found (%): С, 63.41; H, 3.46; N, 4.36. C17H11F4NO.
Calculated (%): C, 63.56; H, 3.45; N, 4.36. IR, ν/cm–1: 1660,
1590, 1580. 1Н NMR (CDCl3), δ: 6.07 (tt, 1 Н, CF2CF2H,
2JH,F = 53.1 Hz, 3JH,F = 4.2 Hz); 6.59 (s, 1 H, H(3)); 6.88—6.91
(m, 2 Н, arom.); 7.14 (tt, 1 H, arom., Jo = 7.4 Hz, Jm = 1.2 Hz);
7.32 (dd, 1 Н, Н(8), Jo = 8.4 Hz, Jm = 0.9 Hz); 7.36—7.42 (m,
3 H, H(6), arom.); 7.58 (ddd, 1 H, H(7), Jo = 8.5 Hz, 7.2 Hz,
Jm = 1.7 Hz); 8.37 (dd, 1 H, H(5), Jo = 8.0 Hz, Jm = 1.7 Hz).
Synthesis of chromone Nꢀphenylhydrazones (4) (general proꢀ
cedure). A mixture of chromenethione 2 (4.3 mmol) and freshly
distilled phenylhydrazine (0.97 g, 9.0 mmol) was stirred without
a solvent for 15 min (the reaction was accompanied by vigorous
H2S evolution). Then the reaction mixture was thoroughly trituꢀ
rated with water (10 mL) until a crystalline product formed. The
product was filtered off, washed with water, dried, and recrysꢀ
tallized from hexane.
2ꢀ(1,1,2,2ꢀTetrafluoroethyl)chromeneꢀ4ꢀthione (2f). The
yield was 64%, m.p. 63—65 °С, violet needleꢀlike crystals with
metallic luster. Found (%): С, 50.37; H, 2.42. C11H6F4OS. Calꢀ
culated (%): C, 50.38; H, 2.31. IR, ν/cm–1: 1635, 1610. 1Н NMR
2
3
(CDCl3), δ: 6.14 (tt, 1 Н, CF2CF2H, JH,F = 53.0 Hz, JH,F
3.5 Hz); 7.46 (s, 1 H, H(3)); 7.47 (ddd, 1 H, H(6), Jo = 8.2,
7.1 Hz, Jm = 1.1 Hz); 7.51 (ddd, 1 H, H(8), Jo = 8.6 Hz, Jm
=
=
1.1 Hz, Jp = 0.5 Hz); 7.77 (ddd, 1 H, H(7), Jo = 8.6, 7.1 Hz,
Jm = 1.7 Hz); 8.50 (ddd, 1 H, H(5), Jo = 8.2 Hz, Jm = 1.7 Hz,
Jp = 0.5 Hz).
6ꢀMethylꢀ2ꢀ(1,1,2,2ꢀtetrafluoroethyl)chromeneꢀ4ꢀthione
(2g). The yield was 92%, m.p. 96—98 °С, violet needleꢀlike
crystals with metallic luster. Found (%): С, 52.46; H, 3.03.
2ꢀTrifluoromethylꢀ4Hꢀchromenꢀ4ꢀone Nꢀphenylhydrazone
(4a). The yield was 78%, m.p. 128—129 °С, yellow crystals.
Found (%): С, 63.14; H, 3.66; N, 9.04. C16H11F3N2O. Calcuꢀ
lated (%): C, 63.16; H, 3.64; N, 9.21. IR (KBr), ν/cm–1: 3320,
1665, 1640, 1605, 1585, 1560, 1505. 1Н NMR (CDCl3), δ: 6.62
(s, 1 H, H(3)); 6.91 (tt, 1 H, arom., Jo = 7.3 Hz, Jm = 1.2 Hz);
7.16—7.33 (m, 7 H, H(6), H(8), NH, arom.); 7.37 (ddd, 1 H,
H(7), Jo = 8.3, 7.3 Hz, Jm = 1.7 Hz); 8.14 (dd, 1 H, H(5), Jo =
7.9 Hz, Jm = 1.7 Hz).
C12H8F4OS. Calculated (%): C, 52.17; H, 2.92. IR, ν/cm–1
:
1635, 1565. 1Н NMR (CDCl3), δ: 2.49 (s, 3 H, Me); 6.13 (tt,
1 Н, CF2CF2H, 2JH,F = 53.0 Hz, 3JH,F = 3.5 Hz); 7.41 (d, 1 H,
H(8), Jo = 8.6 Hz); 7.46 (s, 1 H, H(3)); 7.59 (ddq, 1 H, H(7),
Jo = 8.6 Hz, Jm = 2.2 Hz, 4JН,Ме = 0.5 Hz); 8.29 (dq, 1 H, H(5),
Jm = 2.2 Hz, 4JН,Ме = 0.5 Hz).
Synthesis of 2ꢀpolyfluoroalkylchromone anils (3) (general proꢀ
cedure). A mixture of the corresponding 2ꢀRFꢀchromeneꢀ4ꢀ
thione 2 (6.5 mmol) and freshly distilled aniline (0.75 g,
8.1 mmol) in anhydrous butanol (5 mL) was refluxed for 4 h.
Then the reaction mixture was placed in a Petri dish, and after
the solvent evaporated, the residue was recrystallized from ethaꢀ
nol or hexane.
6ꢀMethylꢀ2ꢀtrifluoromethylꢀ4Hꢀchromenꢀ4ꢀone Nꢀphenylꢀ
hydrazone (4b). The yield was 37%, m.p. 160—161 °С, yellow
crystals. Found (%): С, 64.16; H, 3.92; N, 8.80. C17H13F3N2O.
Calculated (%): C, 64.15; H, 4.12; N, 8.80. IR (KBr), ν/cm–1
:
3325, 1660, 1600, 1565, 1505. 1Н NMR (CDCl3), δ: 2.41 (s,
3 Н, Me); 6.62 (s, 1 H, H(3)); 6.91 (t, 1 H, arom., Jo = 7.3 Hz);
7.07 (d, 1 Н, Н(8), Jo = 8.4 Hz); 7.17 (br.dd, 1 Н, Н(7), Jo
=
Nꢀ(2ꢀTrifluoromethylꢀ4Hꢀchromenꢀ4ꢀylidene)aniline (3а).
The yield was 79%, m.p. 103—104 °С, yellow crystals.
Found (%): С, 66.07; H, 3.59; N, 4.91. C16H10F3NO. Calcuꢀ
lated (%): C, 66.44; H, 3.48; N, 4.84. IR (KBr), ν/cm–1: 1665,
1640, 1615, 1600, 1590, 1580. 1Н NMR (CDCl3), δ: 6.57 (s,
1 H, H(3)); 6.87—6.90 (m, 2 Н, arom.); 7.14 (tt, 1 H, arom.,
Jo = 7.4 Hz, Jm = 1.2 Hz); 7.35—7.42 (m, 4 H, H(6),
H(8), arom.); 7.60 (ddd, 1 H, H(7), Jo = 8.4, 7.2 Hz,
8.4 Hz, Jm ≈ 1.7 Hz); 7.18—7.21 (m, 2 H, arom.); 7.29—7.33
(m, 3 H, arom., NH); 7.93 (br.d, 1 H, H(5), Jm ≈ 1.5 Hz).
6ꢀMethylꢀ2ꢀ(1,1,2,2ꢀtetrafluoroethyl)ꢀ4Hꢀchromenꢀ4ꢀone
Nꢀphenylhydrazone (4g). The yield was 54%, m.p. 135—136 °С,
yellow crystals. Found (%): С, 61.49; H, 3.78; N, 8.09.
C18H14F4N2O. Calculated (%): C, 61.72; H, 4.03; N, 8.00. IR,
ν/cm–1: 1655, 1605, 1560. 1Н NMR (CDCl3), δ: 2.40 (s 3 Н,
Ме); 6.11 (tt, 1 Н, CF2CF2H, 2JH,F = 53.1 Hz, 3JH,F = 4.5 Hz);
6.59 (s, 1 H, H(3)); 6.90 (t, 1 H, arom., Jo = 7.3 Hz); 7.02 (d,
1 Н, Н(8), Jo = 8.4 Hz); 7.15 (br.dd, 1 Н, Н(7), Jo = 8.4 Hz,
Jm ≈ 1.7 Hz); 7.18—7.21 (m, 2 H, arom.); 7.29—7.33 (m, 3 H,
arom., NH); 7.93 (br.d, 1 H, H(5), Jm ≈ 1.5 Hz).
Jm = 1.7 Hz); 8.36 (dd, 1 H, H(5), Jo = 8.0 Hz, Jm
=
1.7 Hz). 1Н NMR (CDCl3+CF3CO2H), δ: 7.16 (s, 1 H, H(3));
7.42—7.45 (m, 2 Н, arom.); 7.57—7.64 (m, 3 H, arom.);
7.83—7.88 (m, 2 H, H(6), H(8)); 8.11 (ddd, 1 H, H(7), Jo
=
8.6, 7.3 Hz, Jm = 1.4 Hz); 8.85 (dd, 1 H, H(5), Jo = 8.1 Hz,
Jm = 1.4 Hz).
Heating of anil 3а in aqueous AcOH under the conditions
described for hydrolysis of chromeneimines12 gave chromanone
12 in 72% yield and m.p. 153—154 °С (cf. Ref. 12: m.p.
153—154 °С).
Nꢀ(6ꢀMethylꢀ2ꢀtrifluoromethylꢀ4Hꢀchromenꢀ4ꢀylidene)aniꢀ
line (3b). The yield was 55%, m.p. 119—121 °С, yellow crystals.
Found (%): С, 67.40; H, 3.96; N, 4.47. C17H12F3NO. Calcuꢀ
lated (%): C, 67.33; H, 3.99; N, 4.62. IR, ν/cm–1: 1660, 1600,
1585. 1Н NMR (acetoneꢀd6), δ: 2.47 (s, 3 Н, Ме); 6.59 (s, 1 H,
Ring closure of NꢀNꢀphenylhydrazones 4b,g to 1ꢀPhꢀ5ꢀ
RFꢀpyrazoles 5b,g (general procedure). Phenylhydrazone 4
(0.9 mmol) was refluxed for 1 h in ethanol (3 mL) acidified with
3 droplets of concentrated HCl. After the solvent evaporated,
the residue was diluted with water (5 mL), a precipitate was
filtered off, washed with water, dried, and recrystallized from
hexane. The yield of pyrazole 5b described in Ref. 19 was 89%.
Under these conditions, pyrazoles 5b,g were synthesized from
chromenethiones 2b,g and phenylhydrazine in ~60% yield, and
anils 3a,b hydrolyze to chromones 1a,b in ~70% yield.
3ꢀ(2ꢀHydroxyꢀ5ꢀmethylphenyl)ꢀ1ꢀphenylꢀ5ꢀ(1,1,2,2ꢀtetraꢀ
fluoroethyl)pyrazole (5g). The yield was 85%, m.p. 69—70 °С,
colorless needleꢀlike crystals. Found (%): С, 61.45; H, 4.01;
H(3)); 6.91—6.94 (m, 2 H, arom.); 7.15 (tt, 1 H, arom., Jo
=
7.4 Hz, Jm = 1.1 Hz); 7.40 (d, 1 Н, Н(8), Jo = 8.6 Hz); 7.39—7.43

2ꢀPolyfluoroalkylchromeneꢀ4ꢀthiones
Russ.Chem.Bull., Int.Ed., Vol. 53, No. 10, October, 2004
2291
N, 7.98. C18H14F4N2O. Calculated (%): C, 61.72; H, 4.03;
2ꢀTrifluoromethylꢀ4Hꢀchromenꢀ4ꢀone oxime (10а). The yield
was 72%, m.p. 155—156 °С, colorless needleꢀlike crystals.
Found (%): С, 52.17; H, 2.65; N, 5.92. C10H6F3NO2. Calcuꢀ
lated (%): C, 52.41; H, 2.64; N, 6.11. IR, ν/cm–1: 3150, 1670,
1620, 1605. 1Н NMR (CDCl3), δ: 7.17 (s, 1 H, H(3)); 7.25—7.30
(m, 2 Н, Н(6), H(8)); 7.47 (ddd, 1 Н, Н(7), Jo = 8.3, 7.3 Hz,
Jm = 1.7 Hz); 7.92 (ddd, 1 Н, Н(5), Jo = 7.8 Hz, Jm = 1.7 Hz,
Jp = 0.6 Hz); 8.21 (s, 1 H, OH).
N, 8.00. IR, ν/cm–1: 3150, 1635, 1600, 1565. 1Н NMR (CDCl3),
2
δ: 2.34 (s, 3 Н, Me); 5.84 (tt, 1 Н, CF2CF2H, JH,F = 53.4 Hz,
3JH,F = 3.2 Hz); 6.93 (d, 1 Н, Н(3), Jo = 8.3 Hz); 7.08 (dd, 1 Н,
Н(4), Jo = 8.3 Hz, Jm = 2.0 Hz); 7.14 (s, 1 H, =СН); 7.40 (br.d,
1 Н, Н(6), Jm ≈ 1.7 Hz), 7.51 (s, 5 H, Ph); 10.00 (s, 1 H, ОН).
6ꢀ(2ꢀHydroxyphenyl)ꢀ3ꢀ[2ꢀ(hydroxyphenyl)ꢀ5ꢀtrifluoroꢀ
methylꢀ1Hꢀpyrazolꢀ3ꢀyl]pyridazine (6). A mixture of chromeneꢀ
thione 2а (0.18 g, 0.78 mmol) and 3ꢀhydrazinoꢀ6ꢀ(2ꢀhydroxyꢀ
phenyl)pyridazine monohydrate18 (0.12 g, 0.54 mmol) in methaꢀ
nol (2.5 mL) was refluxed for 1 h. A precipitate that formed
when the mixture cooled down was filtered off, washed with
methanol, and dried. Compound 6 was obtained in 28% yield
(0.05 g) as colorless crystals with m.p. 254—255 °С. Found (%):
С, 59.46; H, 3.37; N, 13.68. C20H13F3N4O2•0.25H2O. Calcuꢀ
lated (%): C, 59.63; H, 3.38; N, 13.91. IR, ν/cm–1: 3265,
1660, 1615, 1595, 1565, 1520, 1495. 1Н NMR (DMSOꢀd6), δ:
6.94—6.98 (m, 2 H, H(3), H(5)); 7.31 (ddd, 1 H, H(4), Jo = 8.2,
7.4 Hz, Jm = 1.5 Hz); 7.37—7.42 (m, 2 H, H(3´), H(5´)); 7.53
(ddd, 1 H, H(4´), Jo = 8.2, 7.4 Hz, Jm = 1.6 Hz); 7.82 (s, 1 H,
pyraz.); 7.93 (d, 1 H, H(6), Jo = 7.9 Hz); 7.93 (d, 1 H, pyrid.,
J = 9.6 Hz); 8.20 (dd, 1 H, H(6´), Jo = 7.9 Hz, Jm = 1.5 Hz);
8.36 (d, 1 H, pyrid., J = 9.6 Hz); 11.47, 13.16 (both s,
1 H each, OH).
Reflux of oxime 10а (0.20 g, 0.87 mmol) in a mixture of
ethanol (4 mL) and concentrated HCl (1 mL) for 1 h gave
2
5ꢀhydroxyꢀ3ꢀ(2ꢀhydroxyphenyl)ꢀ5ꢀtrifluoromethylꢀ∆ ꢀisoxazoꢀ
line (11) in 70% yield (0.15 g) with m.p. 123—124 °С (cf. Ref. 30:
m.p. 122—123 °С).
6ꢀMethylꢀ2ꢀtrifluoromethylꢀ4Hꢀchromenꢀ4ꢀone oxime (10b).
The yield was 75%, m.p. 191—193 °С, colorless needleꢀlike
crystals. Found (%): С, 54.40; H, 3.35; N, 5.77. C11H8F3NO2.
Calculated (%): C, 54.33; H, 3.32; N, 5.76. IR (KBr), ν/cm–1
:
3275, 1675, 1630, 1615, 1495. 1Н NMR (CDCl3), δ: 2.39 (s,
3 H, Me); 7.15 (s, 1 H, H(3)); 7.16 (d, 1 Н, H(8), Jo = 8.5 Hz);
4
7.27 (ddq, 1 Н, Н(7), Jo = 8.5 Hz, Jm = 2.1 Hz, JH,Ме
=
0.4 Hz); 7.71 (br.d, 1 Н, Н(5), Jm ≈ 1.8 Hz); 7.73 (s, 1 H, OH).
2ꢀ(1,1,2,2ꢀTetrafluoroethyl)ꢀ4Hꢀchromenꢀ4ꢀone oxime (10f).
The yield was 83%, m.p. 148—149 °С, colorless needleꢀlike
crystals. Found (%): С, 50.50; H, 2.85; N, 5.24. C11H7F4NO2.
Reaction of Nꢀbenzylꢀ2ꢀtrifluoromethylꢀ4Нꢀchromeneꢀ4ꢀ
imine (7) with phenylhydrazine. Chromeneimine 7 22 (0.20 g,
0.66 mmol) was added to a solution of phenylhydrazine (0.09 g,
0.83 mmol) in an AcOH—EtOH (1 : 1) mixture (2 mL), and the
resulting reaction mixture was stirred at ~20 °С for 10 min.
Then concentrated HCl (0.5 mL) and water (10 mL) were added
to the mixture, and an oil that precipitated was triturated to
crystallization. The product was filtered off, washed with water,
dried, and recrystallized from hexane. 5ꢀ(2ꢀHydroxyphenyl)ꢀ1ꢀ
phenylꢀ3ꢀtrifluoromethylpyrazole (8) was obtained in 50% yield
(0.10 g) as colorless crystals with m.p. 143—144 °С. Pyrazole 8
was synthesized previously19 from chromone 1а in 13% yield
with m.p. 144—145 °С.
Reaction of 6ꢀmethylꢀ2ꢀtrifluoromethylchromeneꢀ4ꢀthione
(2b) with hydrazine hydrate. A mixture of chromenethione 2b
(0.20 g, 0.82 mmol) and hydrazine hydrate (0.20 g, 4.0 mmol) in
ethanol (1 mL) was stirred at ~20 °С for 1 h. Then the reaction
mixture was diluted with water (5 mL), and the precipitate
was filtered off, washed with water, dried, and recrystallized
from toluene. 3(5)ꢀ(2ꢀHydroxyꢀ5ꢀmethylphenyl)ꢀ5(3)ꢀtrifluoroꢀ
methylpyrazole (9) was obtained in 65% yield (0.13 g) as colorꢀ
less crystals with m.p. 211—212 °С. Pyrazole 9 was syntheꢀ
sized previously19 from chromone 1b in 66% yield with m.p.
210—211 °С.
Calculated (%): C, 50.59; H, 2.70; N, 5.36. IR (KBr), ν/cm–1
:
3200, 1665, 1615, 1595, 1570. 1Н NMR (CDCl3), δ: 6.09 (tt,
3
1 Н, CF2CF2H, 2JH,F = 53.1 Hz, JH,F = 4.2 Hz); 7.16 (s, 1 H,
H(3)); 7.22 (ddd, 1 Н, H(8), Jo = 8.4 Hz, Jm = 1.2 Hz, Jp
=
0.4 Hz); 7.27 (ddd, 1 Н, H(6), Jo = 8.0 Hz, 7.3, Jm = 1.2 Hz);
7.46 (ddd, 1 Н, Н(7), Jo = 8.4 Hz, 7.3 Hz, Jm = 1.7 Hz); 7.60 (s,
1 H, OH); 7.94 (ddd, 1 Н, Н(5), Jo = 8.0 Hz, Jm = 1.7 Hz,
Jp = 0.4 Hz).
Oxo(tris{[(2ꢀtrifluoromethylꢀ4Hꢀchromenꢀ4ꢀylidene)amiꢀ
no)]oxy})phosphorane (13). Phosphorus pentachloride (0.54 g,
2.6 mmol) was added to a solution of oxime 10 (0.30 g, 1.3 mmol)
in Et2O (10 mL), and the resulting mixture was stirred for
0.5 h at ~20 °С. A plentiful white precipitate (presumably,
the product of substitution of three chlorine atoms in PCl5 by
oxime residues) formed. Then water (5 mL) was added dropwise
to the reaction mixture (the precipitate dissolved), and the
resulting mixture was diluted with water (25 mL). The soluꢀ
tion was extracted with ether (15 mL), the ethereal layer was
separated and evaporated, and the residue was recrystalꢀ
lized from a toluene—hexane (1 : 2) mixture. The yield was
0.17 g (54%), colorless powder without distinct melting temꢀ
perature (melts in an interval of 160—170 °С). Found (%):
С, 48.75; H, 2.09; N, 5.85. C30H15F9N3O7P. Calculated (%):
C, 49.26; H, 2.07; N, 5.75. The substance contains 0.7% Cl,
which corresponds to 8.0% admixture of a nonhydrolyzed
dichlorosubstituted derivative. IR (KBr), ν/cm–1: 1665, 1615,
Synthesis of 2ꢀpolyfluoroalkylchromone oximes (10) (general
procedure). Hydroxylamine hydrochloride (7.5 mmol), KOH
(7.0 mmol), and chromenethione 2 (2.0 mmol) were added sucꢀ
cessively to ethanol (5 mL), and the resulting mixture were
stirred at ~20 °С for 5 min (the reaction was accompanied by
vigorous H2S evolution). Then the reaction mixture was diluted
with water (10 mL), and the precipitate was filtered off, washed
with water, dried, and recrystallized from heptane.
1
1595, 1570. Н NMR (DMSOꢀd6), δ: 7.28 (s, 1 H, H(3)); 7.45
(ddd, 1 Н, Н(6), Jo = 8.1, 7.3 Hz, Jm = 1.0 Hz); 7.59 (dd, 1 Н,
Н(8), Jo = 8.5 Hz, Jm = 1.0 Hz); 7.76 (ddd, 1 Н, Н(7), Jo = 8.5,
7.3 Hz, Jm = 1.6 Hz); 7.96 (dd, 1 Н, Н(5), Jo = 8.1 Hz, Jm
=
1.6 Hz). The singlet at 7.28 ppm does not disappear upon
CD3CO2D addition.
In addition, oximes 10 are formed in ~75% yield in the
reaction of chromenethiones 2 with NH2OH•HCl in the
presence of AcONa according to a procedure described earꢀ
lier for the synthesis of βꢀdiketone monooximes from
This work was financially supported by the Russian
Foundation for Basic Research (Project No. 02ꢀ03ꢀ
32706), the Civil Research and Development Foundation
(CRDF) of the USA, and the Ministry of Education and
chromones 1 30
.

2292
Russ.Chem.Bull., Int.Ed., Vol. 53, No. 10, October, 2004
Usachev et al.
17. V. Ya. Sosnovskikh, Izv. Akad. Nauk, Ser. Khim., 2003, 1977
[Russ. Chem. Bull., Int. Ed., 2003, 52, 2087].
18. V. Ya. Sosnovskikh, B. I. Usachev, and I. I. Vorontsov,
J. Org. Chem., 2002, 67, 6738.
Science of the Russian Federation (Grants EKꢀ005ꢀX1
and Y1ꢀ005ꢀ04).
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Received March 31, 2004