Reactions of α-pentafluorophenylpyrylium salts with hydroxylamine

Article abstract of DOI:10.1007/s11172-008-0064-1

The reactions of α-pentafluorophenylpyrylium salts with hydroxylamine in ethanol afford isoxazoline derivatives and/or pyridine N-oxides depending on the steric characteristics of the substituent in the second α position. The structure of 2-hydroxy-2-pent

Full text of DOI:10.1007/s11172-008-0064-1

Russian Chemical Bulletin, International Edition, Vol. 57, No. 2, pp. 412—417, February, 2008
412
Reactions of αꢀpentafluorophenylpyrylium salts with hydroxylamine
I. Yu. Kargapolova, K. S. Shmuilovich, N. A. Orlova,ꢀ M. M. Shakirov, T. V. Rybalova, and V. V. Shelkovnikov
N. N. Vorozhtsov Novosibirsk Institute of Organic Chemistry, Siberian Branch of the Russian Academy of Sciences,
9 prosp. Akad. Lavrentґeva, 630090 Novosibirsk, Russian Federation.
Fax: +7 (383) 330 9752. Eꢀmail: ona@nioch.nsc.ru
The reactions of αꢀpentafluorophenylpyrylium salts with hydroxylamine in ethanol afford
isoxazoline derivatives and/or pyridine Nꢀoxides depending on the steric characteristics of the
substituent in the second α position. The structure of 2ꢀhydroxyꢀ2ꢀpentafluorophenylꢀ
4ꢀphenylꢀ2,3,5,6,7,8ꢀhexahydroquinoline 1ꢀoxide, which was synthesized by the reaction of
2ꢀpentafluorophenylꢀ4ꢀphenylꢀ5,6,7,8ꢀtetrahydrobenzopyrylium perchlorate with NH2OH,
was established by Xꢀray diffraction.
Key words: αꢀpentafluorophenylpyrylium salts, pentafluorophenacylꢀ2ꢀisoxazolines,
2ꢀpentafluorophenylpyridine Nꢀoxides.
Scheme 1
Pyrylium salts take a special place among heteroaromatic
compounds due to their extremely high reactivity. The
reactions of these compounds with nitrogenꢀcontaining
nucleophiles and particularly with binucleophiles, such as
hydrazine hydrate, phenylhydrazine, and hydroxylamine,
serve as a convenient, and sometimes the only, method
for the synthesis of aromatic and heterocyclic derivatives
that are difficult to synthesize.1 The use of pentafluoroꢀ
phenylpyrylium salts2,3 in these reactions would lead to
the previously unavailable polyfluorinated nitrogenꢀconꢀ
taining heterocyclic compounds as potential biologically
active derivatives.4,5 In addition, investigations of pyrylium
salts containing polyfluoroaryl substituents could provide
new data on the influence of fluorine atoms on the reacꢀ
tivity of pyrylium derivatives.
The reactions of pentafluorophenylpyrylium salts with
ammonia2 and methylamine6 have been studied earlier.
In the present study, we investigated the reaction of these
salts with hydroxylamine. The reaction of 2,4,6ꢀtrisubstiꢀ
tuted pyrylium salts with hydroxylamine has been studied
in sufficient detail.7—9 This reaction was demonstrated to
give isoxazolines and pyridine Nꢀoxides as the major prodꢀ
ucts. The reaction mechanism was suggested as early as
in 1968,7 and investigations of this mechanism were
then continued8,9 (Scheme 1). This mechanism assumes
that the reaction proceeds through 2ꢀpenteneꢀ1,5ꢀdione
1ꢀoximes A, which were the only stable products if the
starting pyrylium salts contained bulky substituents (Ph
or But).8,9 Refluxing of oximes in EtOH or CH3COOH
leads to their cyclization to isoxazolines. Under these
conditions, the reaction of pyrylium salts containing less
bulky groups (for example, methyl) affords pyridine
Nꢀoxides as the major products.8
The difference in the cyclization pathways was attribꢀ
uted8 to the different arrangement of the R and OH groups
Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 2, pp. 402—407, February, 2008.
1066ꢀ5285/08/5702ꢀ0412 © 2008 Springer Science+Business Media, Inc.

Reactions of fluorinated pyrylium salts
Russ.Chem.Bull., Int.Ed., Vol. 57, No. 2, February, 2008
413
Scheme 2
with respect to the C=N bond in oximes A, and it was
suggested that the Z isomer gives Nꢀoxide, whereas the
E isomer produces isoxazoline, the E configuration being
more typical of bulky substituents.
Results and Discussion
In the present study, we investigated the reaction of
four pyrylium salts with general structure 1 containing
one or two C6F5 groups in the α positions of the pyrylium
ring, viz., 2,6ꢀbis(pentafluorophenyl)ꢀ4ꢀphenylpyrylium
(1a), 6ꢀpentafluorophenylꢀ2,4ꢀdiphenylpyrylium (1b),
2ꢀmethylꢀ6ꢀpentafluorophenylꢀ4ꢀphenylpyrylium (1c),
and 2ꢀpentafluorophenylꢀ4ꢀphenylꢀ5,6,7,8ꢀtetrahydroꢀ
benzopyrylium (1d) perchlorates, with hydroxylamine.
Ar = C6F5 (a), Ph (b)
then this compound disappears. After 3 h, the reaction
mixture contains approximately equal amounts of 3ꢀmeꢀ
thylꢀ5ꢀpentafluorophenacylꢀ5ꢀphenylꢀ2ꢀisoxazoline (2c)
and 2ꢀmethylꢀ6ꢀpentafluorophenylꢀ4ꢀphenylpyridine
1ꢀoxide (4c) (Scheme 3).
R1 = H, R2 = C6F5 (a), Ph (b), Me (c), R1 + R2 = (CH2)4 (d)
Scheme 3
The reactions were carried out with a fourfold molar
excess of the reagent in an aqueous ethanolic medium
under the conditions used in the study,7 which allowed
us to compare the reactivities of the fluorinated and
nonfluorinated substrates.
The stirring of salt 1a containing C6F5 groups in both
α positions of the ring for 30 min leads to its complete
transformation into 5ꢀpentafluorophenacylꢀ3ꢀpentaꢀ
fluorophenylꢀ5ꢀphenylꢀ2ꢀisoxazoline (2a). During the
same time, pyrylium salt 1b gives a mixture of 5ꢀpentafluoroꢀ
phenacylꢀ3,5ꢀdiphenylꢀ2ꢀisoxazoline (2b) and an unstable
compound. We failed to isolate the latter product in the
individual state and assigned the structure of 5ꢀpentaꢀ
fluorophenylꢀ1,3ꢀdiphenylpentꢀ2ꢀeneꢀ1,5ꢀdione 1ꢀoxime
(3b) to this compound based on the NMR spectroscopic
data for the mixture (Scheme 2). After 3 h, the reaction
mixture contained only isoxazoline 2b.
The exclusive formation of isoxazolines 2a,b confirms
the role of the steric factor in choosing the reaction pathꢀ
way. It should be noted that the presence of C6F5 groups
in both α positions facilitates an increase in the reaction
rate to an extent that the corresponding oxime 3a cannot
be detected.
Taking into account that compounds 2c and 4c are
generated from the same intermediate and based on the
1H and 19F NMR data, we assigned the acyclic structure
of 1ꢀmethylꢀ5ꢀpentafluorophenylꢀ3ꢀphenylpentꢀ2ꢀeneꢀ
1,5ꢀdione 1ꢀoxime (3c) to this intermediate.
After 30 min, the reaction of tetrahydrobenzopyrylium
perchlorate 1d with hydroxylamine (4 molar equivalents)
afforded a stable compound. In the IR spectrum of this
compound, the absorption band of the carbonyl group is
absent and, consequently, it is not oxime 3. The Xꢀray
diffraction study showed that the reaction produced
2ꢀhydroxyꢀ2ꢀpentafluorophenylꢀ4ꢀphenylꢀ2,3,5,6,7,8ꢀ
The reaction of 2ꢀmethylꢀsubstituted salt 1c with hyꢀ
droxylamine also proceeds through the formation of an
1
unstable intermediate. Based on the H and 19F NMR
data, this intermediate is formed as the major reaction
product 30 min after the beginning of the reaction, and

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Russ.Chem.Bull., Int.Ed., Vol. 57, No. 2, February, 2008
Kargapolova et al.
hexahydroquinoline 1ꢀoxide (5). When refluxed in ethaꢀ
nol, compound 5 undergoes dehydration to form 2ꢀpentaꢀ
fluorophenylꢀ4ꢀphenylꢀ5,6,7,8ꢀtetrahydroquinoline 1ꢀoxide
(4d). Stability of bicyclic compound 5 can be attributed to
the stabilizing effect of the C6F5 group on the reaction
center at the sp3ꢀhybridized carbon atom,6,10 which hinders
dehydration in highly basic media. Actually, the reaction
with the use of an equimolar ratio of the reagents proꢀ
duces Nꢀoxide 4d within 30 min (Scheme 4).
Scheme 4
Fig. 1. Threeꢀdimensional structure of oxime 3b calculated by
the PM3 method.
ture of isoxazoline 2c and pyridine Nꢀoxide 4c. Presumꢀ
ably, the E,Z isomerism of oximes with respect to the
C(1)—N bond has a certain importance, but it is not
the factor governing the reaction pathway.
The formation of compound 5 is unambiguous
evidence that the primary attack of the reagent occurs on
the αꢀcarbon atom of the pyrylium ring, which is not
bound to the pentafluorophenyl group, i.e., the steric
effect of the C6F5 group prevails over the electronic factor.
The structures of the newly synthesized compounds
Different reaction pathways of pyrylium salts 1 with
hydroxylamine are evidently attributed to the steric effect
of the substituents in the α positions of the pyrylium ring.
The presence of bulky groups in both α positions, such as
pentafluorophenyl substituents (salt 1a) or Ph and C6F5
groups (salt 1b), leads to their mutual repulsion in interꢀ
mediate oximes 3, resulting in a substantial deviation of
the oxime group from the plane of the starting pyrylium
salt. This decreases the possibility of the subsequent
attack of the oxime group on the carbonyl carbon atom
giving rise to Nꢀoxides and promotes the formation of
isoxazolines 2a,b. This assumption is consistent with the
structure of oxime 3b calculated by the PM3 semiempirical
quantum chemical method (Fig. 1). The presence of the
phenyl substituent at the C(1) atom was demonstrated to
cause the twist of the oxime fragment of the molecule
about the C(1)—C(2) bond by 90—110°. To the contrary,
salt 1d containing the fused fragment of the cyclohexane
ring is completely transformed into Nꢀoxide 5. Apparꢀ
ently, the C(1)—C(2) bond, which is fixed by the hydroꢀ
carbon bridge in intermediate oxime 3d and, consequently,
cannot undergo free rotation, holds the oxime fragment
in the vicinity of the carbonyl reaction center, resulting in
the sixꢀmembered ring closure. Evidently, the structure of
oxime 3c derived from methylꢀsubstituted pyrylium salt
1c is less distorted compared to compounds 3a,b and, as a
consequence, compound 3c retains the ability to undergo
cyclization through both possible pathways to give a mixꢀ
1
were determined by H and 19F NMR spectroscopy, IR
spectroscopy, and mass spectrometry and were confirmed
by elemental analysis data. The 1H NMR spectrum of
isoxazoline 2b shows two AB systems belonging to the
protons of the methylene group in the isoxazoline ring
(δ 3.66 and 3.91, J = 17 Hz) and in the phenacyl fragment
(δ 3.57 and 3.66, J = 15 Hz) and multiplets assigned to
two phenyl rings (δ 7.27—7.47 and 7.59—7.66). The posiꢀ
tion of the pentafluorophenyl group is confirmed by a
broadening of the signals of the AB system belonging to
the protons of the phenacyl fragment due to spinꢀspin
coupling with the orthoꢀfluorine atoms of the adjacent
C6F5 group. The 19F NMR spectrum shows signals of the
pentafluorophenyl group at δ 1.50, 12.97, and 21.31 with
an intensity ratio of 2 : 1 : 2. The IR spectrum has bands
in the C=O (1705 cm–1), C=N (1650 cm–1), and C6F5
(1496 cm–1) stretching regions. The molecular weight deꢀ
termined on a highꢀresolution mass spectrometer and the
elemental analysis data confirm the structure of 2b. The
spectroscopic data for isoxazolines 2a and 2c are, on the
whole, similar to the aboveꢀgiven data for 2b. The 1H and
19F NMR spectra of compound 2a provide evidence for
the presence of one phenyl group and two C6F5 groups.
1
The H NMR spectrum of isoxazoline 2c shows a singlet
at δ 1.95 belonging to the protons of the CH3 group.

Reactions of fluorinated pyrylium salts
Russ.Chem.Bull., Int.Ed., Vol. 57, No. 2, February, 2008
415
F(3)
in a ratio of 70 : 30. The dihydropyridine ring has
a distorted halfꢀchair conformation in both independent
molecules. The C(10)C(4)C(17)C(22) and C(10A)C(4A)ꢀ
C(17A)C(22A) torsion angles characterizing the orientation
of the phenyl rings C(17)—C(22) and C(17A)—C(22A)
are 46.5(3) and 69.4(3)° in the molecules A and B,
respectively. The pentafluorophenyl substituent is in
the axial position. The N(1)C(2)C(11)C(12) and
N(1A)C(2A)C(11A)C(12A) torsion angles are 0.0(3) and
7.4(3)°, respectively. The independent molecules A and B form
dimeric pairs via two hydrogen bonds, O(2A)—H...O(1)
and O(2)—H...O(1A), with the H...O distances of 1.81(3)
and 1.77(3) Е and the O—H...O angles of 164(3) and
169(3)°, respectively. It should be noted that there are
shortened O(1A)...C(11) and O(1A)...C(16) distances in
these dimers (2.977(3) and 3.075(3) Å, respectively; the
sum of the van der Waals radii11 is 3.35 Å). These dimeric
pairs form shortened pairwise F(3)...F(1A) contacts with
the adjacent dimeric pair (2.745(2) Å; the sum of the
van der Waals radii is 2.92 Å). In the crystal structure,
the dimeric pairs form (1,1,0) layers (2D architecture), in
which the pairwise C(6A)—H(6A)...π(C(17A)—C(22A))
interaction12 (the distance to the plane Dpln = 2.91 Å and the
angle θ = 27.9°) and the C(21A)—H(21A)...π(C(11)—C(16))
interaction (Dpln = 2.86 Å and θ =35.3°) are observed.
To summarize, the reactions of αꢀpentafluorophenylꢀ
substituted pyrylium salts with hydroxylamine in aqueous
ethanolic media afford the corresponding pentafluoroꢀ
phenacylisoxazolines and pyridine Nꢀoxides or their mixꢀ
tures, which is, on the whole, consistent with the reaction
pathway of nonfluorinated pyrylium salts. Pyrylium salts
containing the bulky Ph or C6F5 group in the second
α position of the pyrylium ring give exclusively isoxazoline
derivatives. The fluorineꢀcontaining derivatives have a
higher reactivity, which is manifested in lower stability of
intermediate oximes. A new stable product, 2ꢀhydroxyꢀ
tetrahydropyridine Nꢀoxide 5, was isolated in the reaction
of tetrahydrobenzopyrylium salt 1d with NH2OH. This
product undergoes dehydration under heating.
F(4)
C(14)
C(19)
F(2)
C(15)
C(20)
C(21)
C(18)
C(13)
F(5)
C(17)
C(12)
C(16)
C(11)
C(2)
F(1)
C(22)
C(5)
C(4)
C(6)
C(3)
C(10)
C(9)
C(6´)
C(7)
O(2)
N(1)
O(1)
C(8)
Fig. 2. Threeꢀdimensional structure of molecule A of compound 5.
The structures of the intermediates, 1,3ꢀdiphenylꢀ
5ꢀpentafluorophenylpentꢀ2ꢀeneꢀ1,5ꢀdione 1ꢀoxime (3b)
and 1ꢀmethylꢀ5ꢀpentafluorophenylꢀ3ꢀphenylpentꢀ2ꢀeneꢀ
1,5ꢀdione 1ꢀoxime (3c), were determined by comparing
the chemical shifts of the corresponding signals in the
1H NMR spectra of the reaction mixtures with the specꢀ
troscopic data for 1,3,5ꢀtriphenylpentꢀ2ꢀeneꢀ1,5ꢀdione
1ꢀoxime published in the literature.9 The spectrum of comꢀ
pound 3c in CDCl3 shows, in addition to the signals of
the Ph group, a singlet of the CH3 group at δ 2.30, a
broadened singlet for two methylene protons H(4) at
δ 3.68, and a singlet for the methine proton H(2) at δ 6.42.
The 19F NMR spectrum of compound 3c has signals of
the pentafluorophenyl group at δ 1.19, 9.43, and 23.24
1
with an intensity ratio of 2 : 1 : 2. The similar H NMR
spectrum is observed for oxime 3b in CD3CN. This specꢀ
trum shows signals for the proton H(4) at δ 3.97, the
proton H(2) at δ 6.71, and the proton of the oxime group
at δ 9.28 as well as signals for the aromatic protons.
The 19F NMR spectrum of compound 5 has signals
belonging to one C6F5 group; the 1H NMR spectrum,
multiplets for the protons of the fused cyclohexane ring at
δ 1.54, 1.79, 2.41, and 2.83, a broadened singlet at δ 3.45
assigned to two protons at the C(3) atom, and signals for
five aromatic protons. The IR spectrum of compound 5 in
CCl4 shows absorption bands at 2500—3400 (O—H), 1651
(C=N), 1490, 1524 (C—F), and 1223 cm–1 (N→O). The
threeꢀdimensional molecular structure of compound 5
was established by Xꢀray diffraction. There are two indeꢀ
pendent molecules per asymmetric unit. The geometry of
one molecule is presented in Fig. 2. The bond lengths in
the independent molecules are equal within experimental
error. The C(6) atom in the first molecule (A) and the
C(6A) atom in the second molecule (B) are disordered in
a ratio of 70 : 30 and, consequently, the cyclohexane fragꢀ
ment adopts distorted halfꢀchair and sofa conformations
Experimental
The NMR spectra were recorded on Bruker ACꢀ200
(200.13 MHz for 1H and 188.2 MHz for 19F) and Bruker DRXꢀ500
(500.13 MHz for 1H) spectrometers in CDCl3 and CD3CN with
the use of the signals for the residual protons of CDCl3 (7.24 ppm)
and CD3CN (1.96 ppm) for 1H NMR spectra and C6F6 for
19F NMR spectra as the internal standard. The chemical shifts
are given on the δ scale. The IR spectra were measured on a
Vector 22 instrument. The highꢀresolution mass spectra were
recorded on a Finnigan MAT 8200 instrument using a direct
inlet probe; the ionization chamber temperature was 314 °C,
and the ionizing electron energy was 70 eV. The quantum chemiꢀ
cal calculations were carried out with the use of the Hyperchem
program package (Hypercube, Inc.).

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Kargapolova et al.
Table 1. Reactions of pyrylium salts 1a—d with hydroxylamine
Pyryꢀ
lium
salt
1 : NH2OH
mol/mol
τ/ha Reaction
Yield
(%)
M.p./°С
Found
Calculated
Molecular
formula
MSc
(%)
product
(solvent)b
C
H
F
N
1а
1b
1c
1 : 4
1 : 4
1 : 4
0.5
3
2а
2b
66
82
112—115
(heptane)
53.24
52.99
2.00
1.74
36.46
36.45
2.90
2.69
С23Н9F10NO2
С23Н14F5NO2
521.0474
521.0473
107—110
(ethanol)
64.07
64.08
3.20
3.27
22.05
22.02
3.20
3.25
431.0929
431.0944
3
2c
4с
50d
45
95—98
(hexane)
58.34
58.54
3.24
3.28
25.74
25.72
3.80
3.79
С18Н12F5NO2
С18Н10F5NO
368.0713
368.0710
145—148
(ethanol)
61.62
61.54
2.80
2.87
27.40
27.04
3.92
3.99
—
1d
1 : 4
1 : 1
0.5
0.5
5
86
83
119—122
(hexane)
61.91
61.61
4.33
3.94
22.71
23.20
3.38
3.42
С21Н16F5NO2
С21Н14F5NO
408.1037
408.1023
4d
128—130
(hexane)
64.58
64.45
3.58
3.61
24.13
24.28
3.56
3.58
—
a
τ is the reaction time.
b The solvent for recrystallization.
с Found/calculated, m/z, [M]+/M.
d The yields of compounds 2c and 4c were calculated from the 19F NMR spectrum of the reaction mixture. In the pure form, these
compounds were isolated by preparative TLC on silica gel using a diethyl ether—petroleum ether mixture (b.p, 40—70 °C) as the eluent.
1
Table 2. H and 19F NMR (CDCl3) and IR spectra of compounds 2a—c, 4c—d, and 5
Comꢀ
pound
IR, ν/cm–1
(solvent)
1H NMR,
δ (J/Hz)
19F NMR,
δ*
2a
2b
2c
4с
4d
5
1708 (C=O); 1650 (C=N);
1496, 1524 (C6F5)
(CHCl3)
3.58, 3.67 (АВ system, 2 Н, C6F5COCH2, J = 15.0);
3.68, 3.96 (АВ system, 2 Н, Н(4), J1 = 17.0,
J2 = J3 = 1.0); 7.28—7.43 (m, 5 H, Ph)
1.10, 1.82, 11.28,
13.52, 21.30, 25.21
(2 : 2 : 1 : 1 : 2 : 2)
1705 (C=O); 1650 (C=N);
1496, 1522 (C6F5)
(CHCl3)
3.57, 3.66 (АВ system, 2 Н, C6F5COCH2, J = 15.0);
3.66, 3.91 (АВ system, 2 Н, Н(4), J1 = 17.0);
7.27—7.66 (m, 10 H, 2 Ph)
1.50, 12.97, 21.31
(2 : 1 : 2)
1703 (C=O); 1653 (C=N);
1494, 1523 (C6F5)
(KBr)
1.95 (s, 3 Н, Me); 3.19, 3.48 (АВ system, 2 Н, Н(4),
J1 = 17.0); 3.38, 3.58 (АВ system, 2 Н, C6F5COCH2,
J = 14.0); 7.26—7.39 (m, 5 H, Ph)
1.37, 12.83, 21.07
(2 : 1 : 2)
1651 (C=N); 1498,
1522 (C6F5); 1269 (N→O)
(KBr)
2.63 (s, 3 Н, Me); 7.45—7.61 (m, 7 Н, Ph, H(3), H(5))
0.17, 9.99, 24.36
(2 : 1 : 2)
1658 (C=N); 1502,
1520 (C6F5);1318 (N→O)
(KBr)
1.65—1.78, 1.88—2.00, 2.70, 3.03 (all m, 2 Н each,
4 СН2); 7.15 (br.s, 1 Н, Н(3)); 7.28—7.46 (m, 5 Н, Ph)
0.00, 9.42, 24.32
(2 : 1 : 2)
2500—3400 (О—Н); 1651 (C=N);
1490, 1524 (C6F5), 1223 (N→O)
(KBr)
1.54, 1.79, 2.41, 2.83 (all m, 2 Н each, 4 СН2);
3.45 (br.s, 2 Н, Н(3)); 7.00—7.05 (m, 2 Н, Н(Ar));
7.27—7.37 (m, 3 Н, Н(Ar))
0.97, 8.31, 18.95
(2 : 1 : 2)
* The intensity ratio is given in parentheses.
flask. Then salt 1a—d (2 mmol or 8 mmol) was added. The
reaction mixture was magnetically stirred at room temperature
and then kept in a freezing chamber for 30 min. The precipitate
that formed was filtered off, washed with water, and dried in air.
Reaction of pyrylium salts 1a—d with hydroxylamine (general
procedure). A solution of hydroxylamine hydrochloride (0.56 g,
8 mmol) and sodium hydroxide (0.32 g, 8 mmol) in a mixture of
H2O (2.4 mL) and ethanol (20 mL) was placed in a conical

Reactions of fluorinated pyrylium salts
Russ.Chem.Bull., Int.Ed., Vol. 57, No. 2, February, 2008
417
Table 3. Crystallographic parameters of compound 5
The coordinates, equivalent isotropic thermal parameters of
the nonhydrogen atoms, and the geometric parameters of two
molecules of compound 5 were deposited with the Cambridge
Structural Database13 (CCDC 634274).
Parameter
Characteristics
Molecular formula
Molecular weight
С21H16F5NO2
409.35
This study was financially supported by the Federal
Contract No. 02.513.11.3167 and the Integration Projects
of the Siberian Branch of the Russian Academy of Sciences
(Project Nos 15, 17, 33, and 65).
Crystal dimensions/mm
Crystal system
Space group
a/Å
b/Å
c/Å
α/deg
β/deg
0.95×0.64×0.16
Triclinic
–
P1
10.808(1)
11.244(1)
16.426(2)
73.470(9)
75.062(8)
80.807(9)
1840.9(3)
4
1.477
0.129
6391
4741
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7. A. T. Balaban, Tetrahedron, 1968, 24, 5059.
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The filtrate was poured into water, extracted with diethyl ether,
and dried over CaCl2. The solvent was removed on a rotary
1
evaporator. The reaction products were analyzed by H and 19
F
NMR spectroscopy. The pure products were isolated by recrysꢀ
tallization of the precipitate. The reagent ratios, reaction times,
yields, melting points, and elemental analysis data for the reacꢀ
tion products are given in Table 1. The IR and NMR spectroꢀ
scopic data are presented in Table 2.
Xꢀray diffraction study. The Xꢀray diffraction data for comꢀ
pound 5 were collected at room temperature on a Bruker P4
diffractometer (MoꢀKα radiation, graphite monochromator,
θ/2θꢀscanning technique, 2θ < 50°). The crystallographic
parameters are given in Table 3. The structure of compound 5
was solved by direct methods using the SHELXSꢀ97 program
package and refined by the leastꢀsquares method with anisotroꢀ
pic and isotropic (for hydrogen atoms) displacement parameters
using the SHELXLꢀ97 program package. The absorption corꢀ
rection was applied based on the crystal shape (transmission was
0.93—0.99). The hydrogen atoms of the hydroxy groups were
located in difference electron density maps. The other hydrogen
atoms were positioned geometrically.
9. C. Uncu a, A. Tudose, M. T. C proiu, M. Pl ve i,
R. KakouꢀYao, Tetrahedron, 1999, 55, 15011.
10. T. N. Gerasimova, E. P. Fokin, Usp. Khim., 1980, 49, 1057
[Russ. Chem. Rev., 1980, 49 (Engl. Transl.)].
11. R. S. Rowland, R. Taylor, J. Phys. Chem., 1996, 100, 7384.
12. H. Suezawa, T. Yoshida, M. Hirota, H. Takahashi,
Y. Umezawa, K. Honda, S. Tsuboyama, M. Nishio, J. Chem.
Soc., Perkin Trans. 2, 2001, 2053.
13. Cambridge Structural Database, University of Cambridge,
Cambridge, UK, Version 5.27.
Received June 14, 2007;
in revised form October 2, 2007