Recyclization of the products of amidine addition to the substituted 5-amino-4-cyano-1,3-oxazole into new derivatives of 5,6-diaminopyrimidin-4-one

Article abstract of DOI:10.1134/S1070363210050233

The products of addition of amidines to accessible 5-arylamino-4-cyano-1,3- oxazoles at heating in acetic acid undergo recyclization and afford new derivatives of 6-amino-5-acylaminopyrimidin-4-one, whose structure was reliably established using X-ray diffraction studies. Pleiades Publishing, Ltd., 2010.

Full text of DOI:10.1134/S1070363210050233

ISSN 1070-3632, Russian Journal of General Chemistry, 2010, Vol. 80, No. 5, pp. 994–1000. © Pleiades Publishing, Ltd., 2010.
Original Russian Text © A.P. Kozachenko, O.V. Shablykin, A.N. Vasilenko, E.B. Rusanov, V.S. Brovarets, B.S. Drach, 2010, published in Zhurnal Obshchei
Khimii, 2010, Vol. 80, No. 5, pp. 824–830.
Recyclization of the Products of Amidine Addition
to the Substituted 5-Amino-4-cyano-1,3-oxazole
into New Derivatives of 5,6-Diaminopyrimidin-4-one
A. P. Kozachenkoa, O. V. Shablykina, A. N. Vasilenkoa,
E. B. Rusanovb, V. S. Brovaretsa, and B. S. Drach† a
a Institute of Bioorganic Chemistry and Petrochemistry, National Academy of Sciences of Ukraine,
ul. Murmanskaya 1, Kiev, 02660 Ukraine
e-mail: brovarets@bpci.kiev.ua
b Institute of Organic Chemistry, National Academy of Sciences of Ukraine, Kiev, Ukraine
Received September 1, 2009
Abstract―The products of addition of amidines to accessible 5-arylamino-4-cyano-1,3-oxazoles at heating in
acetic acid undergo recyclization and afford new derivatives of 6-amino-5-acylaminopyrimidin-4-one, whose
structure was reliably established using X-ray diffraction studies.
DOI: 10.1134/S1070363210050233
13
Derivatives of 5,6-diaminopyrimidin-4-one arise
permanent interest in synthetic chemistry as biolo-
gically active substances and as intermediates in the
synthesis of purine bases [1–7]. Despite the fact that
chemical derivatives of 5,6-diaminopyrimidine have
been well studied [8], some of these compounds are
produced by a complex way, or are not known. There-
fore the search for original, accessible initial substrates
for the synthesis of new representatives of the 5,6-di-
aminopyrimidin-4-one derivatives is an important task.
comparison of C NMR spectra of the compounds Іd
and ІІh (Fig. 1) suggests that oxazole cycle remains
intact at the I → II transformation.
The products II contain labile hydrogen atoms and
therefore are able of prototropism with the formation
of non-aromatic tautomers III containing unsaturated
5-imino azlactone system. At heating the latter in 98%
acetic acid the azlactone system is cleaved by water,
and thus further intramolecular IV → V cyclization is
provided (Scheme 1).
In this paper we report on a method for obtaining
previously unknown derivatives of 5,6-diamino-
pyrimidin-4-one with aryl substituents in positions 2
and 3 of the pyrimidine ring by recyclization of the
products of addition of amidines to accessible 5-
arylamino-4-cyano-1,3-oxazoles (I) [9] by heating
them in acetic acid (Scheme 1). The initial stage of this
process is the addition of amidines to the nitrile group
of compounds I, which like with other nitrile [10, 11]
proceeds with the formation of substrates II. The latter
were isolated in individual state (Table 1). The
structure of adducts II was reliably proved by the data
of elemental analysis, mass spectra, and IR spectra, in
the latter was lacking the band of stretching vibrations
of the cyano group (Table 2). At the same time the
Similar intramolecular cyclization with splitting off
the ammonia molecule and the formation of the
pyrimidine ring is known for a number of compounds
with a characteristic fragment A [12, 13].
The structure of the final products of this complex
N
NH
NH2
O
A
II → V transformation agrees with the mass spectra
that contain a molecular peak greater by unity than for
the substrates II. The elemental analysis data also
indicate that formation of compounds V includes
splitting off ammonia from the product II and adding a
water molecule.
†
Deceased.
994

RECYCLIZATION OF THE PRODUCTS OF AMIDINE ADDITION
995
Table 1. Yields, melting points, data of elemental analysis, and mass spectra of compounds II and V
Comp. Yield,
Found, %
H
Calculated, %
H
mp, °С
Formula
М+
no.
IIа
IIb
IIc
IId
IIe
IIf
%
52
81
78
68
50
84
73
64
86
94
91
81
82
95
88
70
C
N
C
N
167–170
200–202
197–199
203–205
193–195
192–194
208–209
138–140d
125–128
241–243
267–269
284–286
199–201
218–220
267–269
291–293
72.97
73.24
60.86
60.83
73.26
73.66
61.42
68.35
72.63
73.07
60.73
60.57
73.24
73.63
61.42
68.34
5.27
5.73
4.30
4.32
5.75
5.87
4.61
5.66
5.01
5.48
4.10
3.96
5.49
5.65
4.42
5.49
17.65
17.19
14.74
14.82
17.02
16.64
14.27
21.09
14.08
13.74
11.88
11.69
13.72
13.15
11.37
16.72
С24Н21N5O
72.89
73.33
60.77
60.77
73.33
73.74
61.48
68.45
72.71
73.15
60.64
60.64
73.15
73.57
61.36
68.25
5.35
5.66
4.25
4.25
5.66
5.95
4.54
5.74
5.08
5.40
4.03
4.03
5.40
5.70
4.33
5.43
17.71
17.10
14.76
14.76
17.10
16.54
14.34
21.01
14.13
13.65
11.79
11.79
13.65
13.30
11.45
16.76
395
409
С25Н23N5O
С24Н20BrN5Oa
С24Н20BrN5Ob
С25Н23N5O
473; 475
473; 475
409
С26Н25N5O
С25Н22BrN5Oc
423
487; 489
333
IIh
IIh
Vа
Vb
Vc
Vd
Ve
Vf
С19Н19N5O
С24Н20N4O2
С25Н22N4O2
С24Н19Br N4O2
С24Н19Br N4O2
С25Н22N4O2
С26Н24N4O2
396
410
e
f
474; 476
474; 476
411
425
g
С25Н21BrN4O2
С19Н18N4O2
488; 490
335
Vg
Vh
a
Found, %: Br 16.93. Calculated, %: Br 16.84. b Found, %: Br 16.92. Calculated, %: Br 16.84. c Found, %: Br 16.28. Calculated, %: Br
16.36. d After recristallyzation from acetonitrile. e Found, %: Br 16.89. Calculated, %: Br 16.81. f Found, %: Br 16.73. Calculated, %: Br
16.81. g Found,%: Br 16.42. Calculated,%: Br 16.33.
Table 2. Spectral data of synthesized compounds
Comp.
no.
IR spectrum (KBr), ν, cm–1
1Н NMR spectrum (DMSO-d6), δ, mmp
1676 (С=N)a, 2200–2300 (bands not observed), 2.29 s (3Н, СН3), 7.09–7.93 m (14Н arom.), 8.80 br.s (1H, NH)b
IIa
IIc
IIe
IIg
IIh
3050–3500 (NH as.)
1675 (С=N)a, 2200–2300 (bands not observed), 2.27 s (3Н, СН3), 7.10–7.88 m (13Н arom.), 8.79 br.s (1H, NH)b
2950–3430 (NH as.)
1681 (С=N)a, 2200–2300 (bands not observed), 2.29 s (3Н, СН3), 2.35 s (3Н, СН3), 7.08–7.94 m (13Н arom.), 8.78 br.s (1H, NH)b
3000–3420 (NH as.)
1677 (С=N)a, 2200–2300 (bands not observed), 2.29 s (3Н, СН3), 2.35 s (3Н, СН3), 7.08–7.89 m (12Н arom.), 8.74 br.s (1H, NH)b
3000–3450 (NH as.)
1674 (С=N)a, 2200–2300 (bands not observed), 2.14 s (3Н, СН3), 2.24 s (3Н, СН3), 7.03–7.14 m (4Н arom.), 7.46–7.94 m (5Н
3020–3460 (NH as.)
arom.), 8.43 br.s (1H, NH)b
2.24 s (3Н, СН3), 6.49 br.s (2H, NH2), 7.01–8.00 m (14Н arom.), 9.16 s (1H, NH)
1642 (С=O)a, 3010–3362 (NH as.)
Va
Vb
1643 (С=O)a, 3143–3397 (NH as.)
2.23 s (3Н, СН3), 2.25 s (3Н, СН3), 6.46 br.s (2H, NH2), 6.98–7.99 m (13Н arom.),
9.15 s (1H, NH)
2.27 s (3Н, СН3), 6.52 br.s (2H, NH2), 7.02–7.52 m (13Н arom.), 9.17 s (1H, NH)
1638 (С=O)a, 3170–3311 (NH as.)
1650 (С=O)a, 3049–3410 (NH as.)
1649 (С=O)a, 3061–3297 (NH as.)
Vc
Vd
Ve
2.38 s (3Н, СН3), 6.52 br.s (2H, NH2), 7.15–7.90 m (13Н arom.), 9.08 s (1H, NH)
2.23 s (3Н, СН3), 2.38 s (3Н, СН3), 6.59 br.s (2H, NH2), 7.03–7.94 m (13Н arom.),
9.15 s (1H, NH)
1651 (С=O)a, 2917–3355 (NH as.)
1632 (С=O)a, 3040–3480 (NH as.)
1645 (С=O)a, 2984–3421 (NH as.)
2.23 s (3Н, СН3), 2.26 s (3Н, СН3), 2.38 s (3Н, СН3), 6.42 br.s (2H, NH2), 6.98–
7.90 m (12Н arom.), 9.06 s (1H, NH)
Vf
Vg
Vh
2.27 s (3Н, СН3), 2.38 s (3Н, СН3), 6.47 br.s (2H, NH2), 7.02–7.90 m (12Н arom.),
9.08 s (1H, NH)
1.98 s (3Н, СН3), 2.22 s (3Н, СН3), 6.43 br.s (2H, NH2), 7.00–7.28 m (9Н arom.),
8.76 s (1H, NH)
a Band with shoulder. b In exchange for NH, NH2.
RUSSIAN JOURNAL OF GENERAL CHEMISTRY Vol. 80 No. 5 2010

996
KOZACHENKO et al.
Scheme 1.
C
N
N
NH
+
Ar1
R
NHAr
O
Ia_Id
NH2
NH
NH2
N
O
N
N
N
R
R
Ar1
O
H2N
H2N Ar1
NH
Ar
N
Ar
IIa_IIh
IIIa_IIIh
H2O
Δ
H
N
H
NH2
NH2
R
N
R
MeCOOH, Δ
N
N
Ar1
_MeCOONH4
O
O
Ar1
O
O
N
NH H2N
Ar
Va_Vh
Ar
IVa_IVh
I: R = Ph, Ar = 4-MeC6H4 (a); R = 4-MeC6H4, Ar = Ph (b); R = 4-MeC6H4, Ar = 4-MeC6H4 (c); R = Me, Ar = 4-MeC6H4
(d); II–V: R = Ar1 = Ph, Ar = 4-MeC6H4 (а); R = Ph, Ar = Ar1 = 4-MeC6H4 (b); R = Ph, Ar = 4-MeC6H4, Ar1 = 4-BrC6H4
(c); R = 4-MeC6H4, Ar = Ph, Ar1 = 4-BrC6H4 (d); R = Аr = 4-MeC6H4, Ar1 = Ph (e); R = Ar = Ar1 = 4-MeC6H4 (f); R =
Аr = 4-MeC6H4, Ar1 = 4-BrC6H4 (g); R = Me, Ar = 4-MeC6H4, Ar1 = Ph (h).
1
The H NMR spectra of compounds V contain the
signals of the amide and the primary amino group
protons in typical positions (9.06–9.16 and 6.42–
6.52 ppm, respectively). Furthermore, the comparison
of the 13C NMR spectra of compounds IIh and
Vh indicates the transformation of oxazole ring (cf.
the signals of carbon atoms of the methyl group in
Fig. 1).
NH
Ph
H
N
NH2
N
NC
H2N
4-CH3C6H4NH
IIh
N
H3C
N
N
4-CH3C6H4NH
O
O
CH3
O
CH3
N
O
Ph
Id
C6H4CH3-4
Vh
δC 21.08
δC 14.93
δC 21.01
δC 13.93
δC 23.59 δC 21.27
25
20
15
25
20
15
25
20
15
Fig. 1. Fragments of 13C NMR spectra of compounds Іd, ІІh, and Vh.
RUSSIAN JOURNAL OF GENERAL CHEMISTRY Vol. 80 No. 5 2010

RECYCLIZATION OF THE PRODUCTS OF AMIDINE ADDITION
H
997
2.37
H
166.39
21.70
H
141.71
H
c
6.59
NH2
O
132.47
H
135.94
H
97.15
7.30
128.30
158.41
H
N
6
7.92
1 N
7.25
5
4
128.66
7.33
129.27
a
3
9.14
2
H
H
129.37
N
O
H
160.27
157.60
7.04
135.82
b
129.84
7.23
d
129.76
7.08
H
137.92
129.67
H
H
H
2.23
21.29
Fig. 2. The main correlations (shown by arrows) and the assignment of signals (ppm) in the 1H and 13C NMR spectra of compound
Ve.
An important confirmation of the structure of
compounds V was also obtained by a comprehensive
analysis using two-dimensional NMR spectroscopy,
which included homonuclear experiments COSY and
NOESY, and heteronuclear HMBC and HMQC. Basic
correlations for compound Ve are shown in Fig. 2, and
all the found correlations are listed in Table 3. The
two-dimensional HMBC spectrum revealed the
interaction of the CONH proton (9.14 ppm) with the
carbon nuclei CONH (166.39 ppm), C5a (97.15 ppm),
C4a (160.27 ppm) and C6a (158.41 ppm), proving the
cleavage of the oxazole cycle.
are turned by 82° and 72° respectively. The bonds C2N3
1.352(3) and C5N4 1.350(3) Å are significantly shorter
compared with the standard [14] length of a single
C–N bond (average 1.45 Å), which is associated with
conjugation of the lone electron pair of nitrogen atoms
N3 and N4 with the π-system of the heterocycle and the
carbonyl bond, respectively.
The compound Ve crystallizes with one molecule
of water. In the crystal a formation of the hydrogen
bonds O3–N31O···O1 and N3–H31N···N2 is observed with
the following parameters: O3H31O 0.83(4), O3···O1
2.9545(18) Å, O3–H31O–O1 143(4 )°, and N3–H31N
0.90(3), N3···N2 3.038(3) Å, N3–H31N–N2 173(2)°.
But all these data are still not sufficient to exclude
other alternative structures. Therefore, for the unequi-
vocal proof of the structure of compounds V, one of
them (R = Ar = 4-MeC6H4, Ar1 = Ph) was used for the
X-ray diffraction analysis (Fig. 3). The distribution of
bond lengths and angles in the pyrimidine cycle has no
special features and is characteristic of such systems
(Fig. 3). The heterocycle is almost planar, the mean
deviation of atoms from the mean plane is 0.016 Å.
Phenyl groups C13–C18 and C20–C25 at the heterocycle
Since the intermediate compounds IV were not
identified, it is possible that the synthesis of
compounds V can also proceed along the path II →
VI → VII → V (Scheme 2). A key role in this
transformation play compounds VII, which are
unstable in acidic medium and can be easily split with
water like other oxazole[5,4-d]pyrimidines [15,16], but
we believe that the preferable way of the formation of
compounds V is the one shown in Scheme 1.
RUSSIAN JOURNAL OF GENERAL CHEMISTRY Vol. 80 No. 5 2010

998
KOZACHENKO et al.
Table 3. The list of correlations in the COSY, NOESY, HMQC, and HMBC spectra of compound Vea
1H, δ
13C, δ(C3bH, C5bH)
HMBC
1H, δ
COSY
7.33
NOESY
7.33
HMQC
129.76
129.37
7.23 (C4bH)
129.27 (C2b, C6b)
129.37 (C3b, C5b), 135.94 (C1b)
129.27 (C2b, C6b), 157.60 (C2a), 129.76 (C4b)
–
7.33 (C3bH, C5bH)
7.25 (C2bH, C6bH)
6.59 (NH2)
7.23, 7.25
7.23, 7.25
7.33
–
7.33
–
129.27
–
2.37 (CH3C4c)
–
7.30
21.70
128.30
128.66
141.71 (C4c), 128.30 (C3c, C5c)
128.30 (C3c, C5c), 21.70 (CH3C4c), 132.47 (C1c)
128.66 (C2c, C6c), 166.39 (CONH)
7.30 (C3cH, C5cH)
7.92 (C2cH, C6cH)
7.92
7.30
7.92, 2.37
7.30, 9.14
9.14 (CONH)
2.23 (CH3C4d)
–
–
7.92
7.08
–
166.39 (CONH), 97.15 (C5a), 160.27 (C4a), 158.41 (C6a)
129.67 (C3d, C5d), 137.92 (C4d)
21.29
7.08 (C3dH, C5dH)
7.04 (C2dH, C6dH)
7.04
7.08
2.23, 7.04
7.08
129.67
129.84
135.82 (C1d), 21.29 (CH3C4d), 129.67 (C3d,C5d)
137.92 (C4d), 129.84 (C2d, C6d)
a For the numbering of carbon atoms see Fig. 2.
In conclusion, we note that the transformation of
compounds I → V is of interest not only as an unusual
transformation of the oxazole ring into the pyrimidine
one, but also as a preparative method of synthesis of
previously unknown derivatives of 5,6-diaminopyr-
imidin-4-one, the intermediates in the synthesis of
purine bases. Their possible use in this direction will
be considered by us in the future.
1100/DAD/MSD VL G1965 instrument. The melting
points were measured on a Fisher–Johns unit.
The X-ray diffraction study of a single crystal of
compound Ve with linear dimensions 0.04×0.08×
0.46 mm was carried out at room temperature on a
Bruker Smart Apex II diffractometer (λМоKα radiation,
graphite monochromator, θmax 26.40°, sphere segment
–15 ≤ h ≤ 8, –7 ≤ k ≤ 7, –36 ≤ l ≤ 37). Overall number
of measured reflections 12,733, of which 4.573 were
independent (R-factor of averaging 0.0532). Crystals
of compound Ve: C25H23N4O2.5, M = 419.47, are
monoclinic, space group P2/c, a = 12.0149(7), b =
6.1862(4), c = 30.3489(17) Å, β = 97.266(3)°, V =
2237.6(2 ) Å3, Z = 4, dcalc = 1.245, μ = 0.082 mm–1,
F(000) = 884. The structure was solved by the direct
method and refined by full-matrix least-mean- squares
method in an anisotropic approximation using the
EXPERIMENTAL
The IR spectra of the compounds were recorded on
a Vertex 70 spectrometer from tablets with KBr, the 1H
NMR spectra were taken on a Varian-300 instrument,
1
and the H and 13C NMR spectra of compounds Id,
IIh, Vh, and Ve, on a Varian Mercury-400 instrument
in DMSO-d6 with internal reference TMS. The mass
spectra of compounds were recorded on an Agilent
Scheme 2.
NH
NH
NH
N
O
N
MeCOOH, Δ
H2O, MeCOOH
MeCOOH, Δ
_MeCOONH4
N
IIa_IIh
Va_Vh
R
R
NH2
Ar1
Δ
N
N
Ar1
O
Ar
VIa_VIh
Ar
VIIa_VIIh
RUSSIAN JOURNAL OF GENERAL CHEMISTRY Vol. 80 No. 5 2010

RECYCLIZATION OF THE PRODUCTS OF AMIDINE ADDITION
999
C12
C9
C10
O3
C11
C19
C15
C16
C17
O1
C4
C14
C8
C5
C7
C6
N4
C3
C13
N1
O2
C18
C21
C2
C1
N3
C22
C20
N2
C25
C23
C24
Fig. 3. General view of the molecule Ve and the main bond lengths and angles.
programs SHELXS97 and SHELXL97 [17, 18]. For
the refinement 4573 reflections were used with I > 2σ(I),
(355 refined parameters, number of reflections per a
parameter 12.9, the weight scheme was used, ω =
1/[σ2(Fo2) + (0.0598P)2], where P = (Fo2 + 2Fc2)/3,
the ratio of maximum (average) shift to the error in
final cycle was 0.10(0.005). The extinction correction
was introduced using the program SADABS (ratio of
water, and a compound IIa–IIh formed was purified
by recrystallization from ethanol.
6-Amino-5-acylamino-2,3-diaryl-3H-pyrimidin-
4-ones (Va–Vh). A solution of 0.04 mol of a com-
pound IIa–IIh in 20 ml of 98% acetic acid was
refluxed for 2 h, 150 ml of water was then added, the
precipitate formed was filtered off, and compound Va–
Vh formed was crystallized from ethanol–water 9:1
mixture.
minimum to maximum corrections Tmin/Tmax
=
0.656381). The hydrogen atoms of methyl groups were
localized geometrically, other hydrogen atoms were
identified and refined isotropically. The final values of
divergence factors are as follows: R1(F) = 0.0531,
wR2(F2) = 0.1085, GOF = 0.953, over the reflections
with I > 2σ(I). Residual electron density obtained from
the difference Fourier series after the last cycle of
refinement was 0.18 and –0.18 e/Å3.
REFERENCES
1. Lunt, E., in Comprehensive Organic Chemistry, Bar-
ton, D. and Ollis, W.D. Eds., London: Pergamon Press,
1979.
2. Kimura, T., Takase, Y., Tanaka, H., Ohtsuka, I., Seeki, T.,
Kogushi, M., Yamada, T., Fujimori, T., Saitou I., and
Akasaka, K., J. Med. Chem., 1993, vol. 36, no. 11,
p. 1630.
3. Chorvat, R.J., Bakthavatchalam, R., Beck, J.P., Gilli-
gan, P.J., Wilde, R.G., Cocuzza, A.J., Hobbs, F.W.,
Cheeseman, R.S., Curry, M., Rescinito, J.P., Krenitsky, P.,
Chidester, D., Yarem, J.A., Klaczkiewicz, J.D.,
Hodge, C.N., Aldrich, P.E., Wasserman, Z.R., Fernan-
dez, Ch., Zaczek, R., Fitzgerald, L.W., Huang, Sh.-M.,
Shen, H.L., Wong, Y.N., Chien, B.M., Quon, Ch.Y.,
and Arvanitis, A., J. Med. Chem., 1999, vol. 42, no. 5,
p. 833.
A complete set of X-ray data for compound Ve is
deposited in the Cambridge Structural Database
(CCDC 742460).
N-[(2-Aryl-5-arylamino-1,3-oxazol-4-yl)(imino)-
methyl]arylamidines (IIa–IIh). To a solution of
0.04 mol of oxazole Ia–Id [9] in 10 ml of anhydrous
ethanol was added 0.08 mol of arylamidine, the
mixture was refluxes for 4 h, the separated orange pre-
cipitate was filtered off, washed with ethanol and
RUSSIAN JOURNAL OF GENERAL CHEMISTRY Vol. 80 No. 5 2010

1000
KOZACHENKO et al.
4. Brakta, M., Murthy, D., Ellis, L., and Phattare, S.,
Bioorg. and Med. Chem. Lett., 2002, vol. 12, no. 11,
p. 1489.
12. Takahashi, T., Hirokami, S., Kato, K., Nagata, M., and
Yamazaki, T., J. Org. Chem., 1983, vol. 48, no. 17,
p. 2914.
5. Bhushan, R.G. and Vince, R., Bioorg. and Med. Chem.
Lett., 2002, vol. 10, no. 7, p. 2325.
6. Biagi, G., Giorg, I., Leonardi, M., Livi, O., Pacchini, F.,
Scartoni, V., Costa, B., and Lucacchini, A., Eur. J. Med.
Chem., 2003, vol. 38, no. 9, p. 810.
7. Laufer, S.A., Domeyer, D.M., Scior, T.R.F., Albrecht, W.,
and Hauser, D.R.J., J. Med. Chem., 2005, vol. 48, no. 3,
p. 710.
8. Brown, D.J., The Pyrimidines. In: The Chemistry of
Heterocyclic Compounds, Weissberger, A., Ed., suppl. 2,
New York: Wiley, 1985.
9. Kozachenko, A.P., Shablykin, O.V., Rusenov, E.B.,
Vasilenko, A.N., and Brovarets, V.S., Zh. Obshch.
Khim., 2009, vol. 79, no. 5, p. 824.
10. McCasland, G.E. and Torbell, D.S., J. Am. Chem. Soc.,
1946, vol. 68, no. 11, p. 2393.
13. Shishoo, C.J., Devani, M.B., Ananthan, S., Jain, K.S.,
Bhadti, V.S., Mohan, S., and Patel, L., Indian J. Chem.,
Sect. B, 1989, vol. 28, p. 1039.
14. Allen, F.H., Kennard, O., Watson, D.G., Brammer, L.,
Orpen, A.G., and Tailor, R., J. Chem. Soc., Perkin
Trans. 2,1987, p. 1.
15. Falco, E.A., Elion, G.B., Burgi, E., and Hitchings, H.,
J. Am. Chem. Soc., 1952, vol. 74, no. 19, p. 4897.
16. Melik-Ogandzhanyan, R.G., Khachaturyan, T.A.,
Mirzoyan, V.S., and Arsenyan, F.G., Khim. Geterotsikl.
Soedin., 1983, no.1, p. 112.
17. Sheldric, G.M., SHELXS97, Program for the Solution of
Crystal Structure, University of Göttingen, Göttingen,
1997.
18. Sheldric, G.M., SHELXL97, Program for the Refinement
of Crystal Structures, University of Göttingen, Göttingen,
1997.
11. Backer, H.J. and Wanmaker, W.L., Rec. Trav. Chim.,
1951, vol. 70, p. 638.
RUSSIAN JOURNAL OF GENERAL CHEMISTRY Vol. 80 No. 5 2010