Chemical conversions of 8,18-disubstituted derivatives of 6,16-diphenyl-1,2,3,11,12,13-hexahydrodibenzo[g,o]-4,14-dioxa-1,5,11, 15-tetraazacyclohexadecine-2,12-diones

Article abstract of DOI:10.1023/A:1024717514329

The chemical properties of 8,18-disubstituted 6,16-diphenyl-1,2,3,11,12,13-tetrahydrodibenzo[g,o]-4,14-dioxa-1,5,11, 15-tetraazahexadecine-2,12-diones have been studied, including their interaction with N-nucleophiles (hydroxylamine, hydrazine, semicarbazide, and thiosemicarbazide), acidic and alkaline hydrolysis, and methylation. A hypothesis has been made from analysis of the mass spectral data of the thiosemicarbazide on the preferred existence of 6-substituted 4-phenylquinazoline-2-carbaldehydes in the gas phase as the linear tautomer.

Full text of DOI:10.1023/A:1024717514329

Chemistry of Heterocyclic Compounds, Vol. 39, No. 4, 2003
CHEMICAL CONVERSIONS OF
8,18-DISUBSTITUTED DERIVATIVES OF
6,16-DIPHENYL-1,2,3,11,12,13-HEXAHYDRO-
g,o
DIBENZO[ ]-4,14-DIOXA-1,5,11,15-TETRA-
AZACYCLOHEXADECINE-2,12-DIONES
O. V. Kulikov, V. I. Pavlovsky, A. V. Mazepa, and S. A. Andronati
The chemical properties of 8,18-disubstituted 6,16-diphenyl-1,2,3,11,12,13-tetrahydrodibenzo[g,o]-
4,14-dioxa-1,5,11,15-tetraazahexadecine-2,12-diones have been studied, including their interaction
with N-nucleophiles (hydroxylamine, hydrazine, semicarbazide, and thiosemicarbazide), acidic and
alkaline hydrolysis, and methylation. A hypothesis has been made from analysis of the mass spectral
data of the thiosemicarbazide on the preferred existence of 6-substituted 4-phenylquinazoline-2-
carbaldehydes in the gas phase as the linear tautomer.
Keywords: dibenzomacrocycle, N-nucleophile, thiosemicarbazone, quinazoline.
We previously reported the synthesis of 8,18-disubstituted 6,16-diphenyl-1,2,3,11,12,13-
hexahydrodibenzo[g,o]-4,14-dioxa-1,5,11,15-tetraazacyclohexadecine-2,12-diones 1-3 from the syn isomers of
2-amino-5-substituted benzophenone oximes and also on their structure and antithrombotic activity [1]. While
continuing investigations in this direction we have studied some chemical conversions of
dibenzomacroheterocycles 1-3. It turned out that, on interacting compounds 1-3 with various N-nucleophiles
(hydroxylamine, hydrazine, semicarbazide, and thiosemicarbazide) in the presence of NaOH, the corresponding
derivatives of 6-substituted 4-phenylquinazoline-2-carbaldehydes 4-6 may be obtained, viz. oximes 7-9,
hydrazones 10-12, semicarbazones 13-15, and thiosemicarbazones 16-18.
Compounds 7-18 were also obtained by the alternate synthesis from the corresponding 6-substituted
4-phenylquinazoline-2-carbaldehydes 4-6 obtained in their turn by thermolysis of 7-substituted 3-hydroxy-5-
phenyl-1,2-dihydro-3H-1,4-dibenzodiazepin-2-ones 19-21 [2] by the procedure of [3].
The study of the possibility of using macrocycles 1-3 is impeded by their extremely insignificant
solubility in the overwhelming majority of organic solvents. The 1,11-dimethyl derivatives 22-24 possess much
higher solubility in organic solvents. We obtained these compounds for the first time by methylating
macrocycles 1-3 with dimethyl sulfate in the presence of NaOMe. Compounds 22-24 did not react with
N-nucleophiles under the conditions described above.
__________________________________________________________________________________________
A. V. Bogatsky Physico-Chemical Institute, National Academy of Sciences of the Ukraine, Odessa
65080; e-mail: oximes.kul@paco.net. Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 4,
pp. 566-573, April, 2003. Original article submitted October 22, 2001.
0009-3122/03/3904-0485$25.00©2003 Plenum Publishing Corporation
485

O
N
R2
R1
O N
Me
Me
Me2SO4,
NaOMe
R1
N O
N
O
R2
66–72%
R2
O
R1
NH O N
22–24
R1
N O
HN
NH2R3
H
R2
H2NR3, NaOH
O
1–3
N
C
N
R3
54–84%
N
R1
R2
7–18
H2NR3
65–83%
CHO
O
H
N
N
N
t
OH
64–75%
R1
N
R1
R2
R2
19–21
4–6
1, 4, 7, 10, 13, 16, 19, 22 R1 = Br, R2 = Ph; 2, 5, 8, 11, 14, 17, 20, 23 R1 = Br, R2 = o-ClC6H4;
3, 6, 9, 12, 15, 18, 21, 24 R1 = Me, R2 = Ph; 7-9 R3 = OH, 10-12 R3 = NH2,
13-15 R3 = NHCONH2, 16-18 R3 = NHCSNH2
Attempts to synthesize dibenzomacroheterocycle 22 by another method from 5-bromo-2-
methylaminobenzophenone (25) were not successful. On acylating the syn isomer of 5-bromo-2-
methylaminobenzophenone oxime (26) with chloroacetyl chloride under Schotten–Baumann conditions a
mixture was formed of 7-bromo-3-hydroxy-1-methyl-5-phenyl-1,3-dihydro-2H-1,4-benzodiazepin-2-one (28),
described in [4], and a compound, which from data of IR spectroscopy, mass spectrometry, and elemental
analysis, was assigned the structure 8-bromo-1-methyl-6-phenyl-1,3-dihydro-2H-4,1,5-benzoxadiazocin-2-one (29).
The corresponding 2-chloroacetamido oxime derivative 27, by the cyclization of which in the presence of NaOH
we hoped to obtain macrocycle 22 analogously to that described in [1], was not isolated from the reaction mixture.
NHMe
O
NHMe
.
NaOH
(NH2OH)2 H2SO4,
OH
Br
Br
86%
N
Ph
Ph
25
26
O
ClCH2COCl
NaOH
O
Me
Me
N
N
OH
O
Br
Br
N
N
O
75%
Ph
28
Ph
29
18.2%
NaOH
Cl
NMe
OH
22
Br
N
27
Ph
486

The mechanism of the conversion of dibenzomacroheterocycles 1-3 into 7-18 by the action of
N-nucleophiles is not studied specially in the present work. It possibly contains the following stages: 1)
transition of the dibenzoheterocycle into 3-hydroxybenzodiazepine in alkaline medium analogously to that
described for the rearrangement of benzoxadiazocine into 3-hydroxybenzodiazepine [5], and 2) interaction of
the latter with N-nucleophiles, as in [6], leading to the formation of quinazoline-2-carbaldehyde derivatives.
Using 8,18-dibromo-6,16-diphenyl-1,2,3,11,12,13-hexahydrodibenzo[g,o]-4,14-dioxa-1,5,11,15-tetra-
azacyclohexadecine-2,12-dione (1) as example we established that alkaline hydrolysis of the
dibenzomacroheterocycles leads to the formation of 5-substituted 2-aminobenzophenones and a series of
resinous compounds. Study of the acid hydrolysis of dibenzomacroheterocycle 1 showed that, in addition to
2-amino-5-bromobenzophenone (30), the syn isomer of N-(2-amino-5-bromophenylmethylene)iminooxyacetic
acid (31) is formed. Evidently on hydrolysis of compound 1 fission of the amide bond occurs first, which, as
described for the alkaline hydrolysis of benzodiazepin-2-ones [7], leads to the formation of compound 31.
Hydrolytic fission of the azomethine bond then occurs as a result of which aminobenzophenone 30 is obtained.
With the aim of confirming the structure of compound 31 we proposed an independent alternate route of
synthesis, consisting of the interaction of the syn isomer of 2-amino-5-bromobenzophenone oxime (32) with
monobromoacetic acid methyl ester in the presence of NaOMe with subsequent saponification of the resulting
O-alkylation product 33 with the formation of compound 31.
NH2
NH2
O
HCl
+
1
O
O
Br
Br
N
OH
Ph
30
Ph
31
25%
27.4%
82%
NH2
NaOH
NH2
O
BrCH2COOMe,
56%
NaOMe
OH
O
Br
Br
N
N
OMe
Ph
Ph
32
33
In accordance with the data of [8,9] molecules of the thiosemicarbazones of aromatic aldehydes in the
gas phase may be found in a linear I or two cyclic forms, 1,2,4-triazoline-3-thione II or 1,3,4-thiadiazole III.
For each of the tautomeric forms there is a characteristic distinct type of fragmentation under electron impact.
According to the data of [9] the presence in the gas phase of the linear tautomer is confirmed by the presence of
fragment ions formed by breaking C–N and N–N bonds.
Ф1
Ф3
Ф7
HN
Ф5
Ф9
NH2
HN NH
N
PhHC
N
NH
H
H
S
NH2
S
N
H
Ph
S
Ф10
Ph
Ф8
Ф2
Ф4
I
Ф6
II
III
487

A
scheme for the proposed fragmentation of 6-bromo-4-phenylquinazoline-2-carbaldehyde
thiosemicarbazide (16) is given below as an example. The presence in the mass spectrum of fragment ions with
m/z 325 and 310 corresponding to fragments Φ4 and Φ2 and the absence of fragment ions characteristic of the
cyclic tautomeric forms permits the assumption that thiosemicarbazone 16 is found in the linear form in the gas
phase. The stability of the linear form, according to [8], may be explained by the effective linear π-p-π
conjugation chain in it.
+
N
C
N H
N
Br
Ph
m/z
310
H
.
.
N
C N NH NH2
S
+
+
N
H
N
N
Br
m/z
Br
m/z
Ph
Ph
385
284
.
– Br
+
+
H
+
H
N
N
C N NH
H
N C
N
N
Br
Br
N
Ph
Ph
Ph
m/z 325
m/z 205
m/z 296
– N2
N
+
+
N
CH2
CH3
.
.
N
– Br
N
Br
m/z
Ph
218
Ph
m/z
297
The fragmentation of thiosemicarbazones 17 and 18 is analogous to the above.
EXPERIMENTAL
The IR spectra were recorded on a Specord IR-75 spectrometer in CHCl3 solution. The UV spectra were
obtained on a SF-56 spectrophotometer in ethyl alcohol at a concentration of 3 × 10-5 M at a cell thickness of
10 mm. The mass spectra were recorded on a MX-1321 mass spectrometer using direct insertion of samples into
the ion source, the energy of the ionizing electrons was 70 eV, ionization chamber temperature was 150°C.
The characteristics of the compounds synthesized are given in Tables 1 and 2.
488

TABLE 1. 6-Substituted 4-Phenylquinazoline-2-carbaldehydes 4-6, Their
Oximes
7-9,
Hydrazones
10-12,
Semicarbazones
13-15,
Thiosemicarbazones
16-18,
and 1,11-Dimethyl-8,18-disubstituted
6,16-Diphenyl-1,2,3,11,12,13-hexahydrodibenzo[g,o]-4,14-dioxa-1,5,11,15-
tetraazacyclohexadecine-2,12-diones 22-24
Found, %
——————
Com-
pound
Empirical
formula
Yield, %
(method)
Calculated, %
mp, °С
C
H
N
S
C15H9BrN2O
C15H8BrClN2O
C16H12N2O
57.48
57.53
2.27
2.90
8.97
8.95
4
5
6
7
—
—
—
—
163-165
168-170
164-165
251-253
72
75
64
51.79
2.28
8.02
51.83
77.36
77.40
2.32
4.90
4.87
8.06
11.32
11.28
C15H10BrN3O
70 (A),
73 (B)
54.87
3.04
12.77
54.90
3.07
12.80
C15H9BrClN3O
C16H13N3O
82 (A),
8
49.72
49.68
2.46
2.50
11.56
11.59
—
—
—
—
—
—
—
—
290-295
228-230
173-175
163-168
174-175
212-215
220–223
221-224
222-224
223-225
84 (B)
73.02
65 (A),
67 (B)
9
4.95
15.99
72.99
4.98
15.96
C15H11BrN4
С15H10BrClN4
C16H14N4
55.02
55.06
75 (A),
10
11
12
13
14
15
16
17
18
3.42
3.39
17.17
17.12
65 (B)
49.86
83 (A),
70 (B)
2.76
15.53
49.82
2.79
15.49
73.22
73.26
72 (A),
5.41
5.38
21.33
21.36
63 (B)
C16H12BrN5O
C16H11BrClN5O
C17H15N5O
51.89
68 (A),
56 (B)
3.29
18.89
51.91
3.27
18.92
47.52
47.49
70 (A),
2.78
2.74
17.35
17.31
62 (B)
66.89
73 (A),
58 (B)
4.89
22.97
66.87
4.95
22.94
C16H12BrN5S
C16H11BrClN5S
C17H15N5S
49.72
49.75
69 (A),
3.18
3.13
18.15
18.13
8.27
8.30
54 (B)
45.65
74 (A),
58 (B)
2.59
16.70
7.63
45.68
2.64
16.65
7.62
63.56
63.53
72 (A),
4.73
4.70
21.82
21.79
9.95
9.98
182-185
385-390
387-391
383-385
60 (B)
C32H26Br2N4O4
C32H24Br2Cl2N4O4
C34H32N4O4
55.65
3.77
8.13
22
23
24
—
—
—
66
72
70
55.67
3.80
8.12
50.59
50.62
3.21
3.19
7.40
7.38
72.82
5.72
9.97
72.84
5.75
9.99
TABLE 2. Spectral Characteristics of Compounds 4-18 and 22-24
IR spectrum, ν, cm-1
UV spectrum,
Com-
pound
1
M+,
m/z
λmax, nm (log ε)
N–H
2
OH
3
C=O
4
C=N
5
C=S
6
7
8
—
—
—
—
—
—
1725
1725
1730
1600
1595
1605
—
—
—
232 (4.44), 274 (3.71),
326 (3.54)
312
4
233 (4.53), 271 (3.62),
346
248
5
6
320 (3.50)
229 (4.37), 274 (3.59),
325 (3.56)
489

TABLE 2 (continued)
1
2
3
4
5
6
7
8
—
—
3545
3560
—
—
1595
1595
—
—
257 (4.50), 297 (4.03),
335 (3.70)
327
361
7
8
9
255 (4.59), 295 (4.10),
332 (3.66)
—
3565
—
—
—
1600
1600
1595
1595
1600
1595
1575
—
—
—
—
—
—
—
256 (4.51), 299 (3.80),
332 (3.65)
263
326
360
262
369
403
305
3285, 3435
3295, 3440
3280, 3425
264 (4.25), 306 (4.41),
10
11
12
13
14
15
360 (3.69)
—
—
265 (4.28), 309 (4.48),
359 (3.80)
—
—
263 (4.16), 297 (4.25),
358 (3.57)
3315, 3380,
3440, 3495
—
1690
1700
1695
265 (4.37), 302 (4.57),
361 (3.82)
3330, 3395,
—
267 (4.34), 306 (4.57),
3485, 3515
362 (3.78)
3335, 3400,
3455, 3520
—
255 (4.25), 292 (4.46),
359 (3.66)
3310, 3350,
—
—
—
—
—
—
1595
1575
1580
1095
1090
1095
249 (4.24), 281 (4.26),
385
419
312
16
17
18
3485
333 (4.53)
3315, 3355,
3490
231 (4.43), 277 (4.23),
335 (4.55)
3325, 3365,
252 (4.24), 274 (4.25),
3500
330 (4.50)
—
—
—
—
—
—
1660
1655
1655
1590
1580
1585
—
—
—
201 (4.65), 262 (4.21)
205 (4.68), 262 (4.25)
203 (4.67), 262 (4.24)
688
756
560
22
23
24
6-Bromo-4-phenylquinazoline-2-carbaldehyde (4). Compound 19 (0.1 g, 0.302 mmol) was heated at
194-196°C until gas evolution ceased. The melt was cooled to room temperature. The oil obtained was triturated
with hexane. The resulting white solid was filtered off, dried, and recrystallized from hexane. Compound 4
(0.68 g, 72%) was obtained.
Compounds 5 and 6 were obtained analogously from compounds 20 and 21.
6-Bromo-4-phenylquinazoline-2-carbaldehyde Oxime (7). A. Hydroxylamine sulfate (0.052 g,
0.319 mmol) was added to a solution of compound 4 (0.1 g, 0.319 mmol) in ethanol (20 ml) and the mixture
stirred for 15 min. The precipitated white solid was filtered off, dried, washed with water, and recrystallized
from ethanol. Yield of oxime 7 0.074 g.
B. A solution of 2 N NaOH (0.32 ml) was added to a suspension of compound 1 (0.1 g, 0.151 mmol)
and hydroxylamine sulfate (0.05 g, 0.302 mmol) in ethanol (11 ml) and the mixture boiled for 30 min. The
reaction mixture was then poured into water, the precipitated amorphous white solid was filtered off, and
recrystallized from ethanol. Yield of 7 0.072 g.
Compounds 8-18 were obtained by the interaction of 1-3 and 4-6 with the appropriate nitrogenous
bases by a procedure analogous to the above using hydroxylamine, hydrazine hydrate, and the hydrochlorides of
semicarbazide and thiosemicarbazide as nucleophilic agent.
g,o
1,11-Dimethyl-8,18-dibromo-6,16-diphenyl-1,2,3,11,12,13-hexahydrodibenzo[ ]-4,14-dioxa-1,5,11,15-
tetraazacyclohexadecine-2,12-dione (22). Dimethyl sulfate (0.03 ml, 0.302 mmol) was added with stirring to a
suspension of compound 1 (0.2 g, 0.302 mmol) and NaOMe (0.033 g, 0.604 mmol) in 1,4-dioxane (30 ml).
490

Stirring was continued for 2 h at room temperature, and the reaction mixture was poured into water, the
precipitated white amorphous solid was filtered off, washed with water, dried, and crystallized from dioxane.
Compound 22 (0.138 g) was obtained.
Compounds 23 and 24 were synthesized analogously.
syn
A solution of NaOH (1.38 g) in
Isomer of 5-Bromo-2-methylaminobenzophenone Oxime (26).
water (5 ml) was added to a mixture of compound 25 (10 g, 35 mmol) and hydroxylamine sulfate (2.83 g,
17 mmol) in ethanol (50 ml). The mixture was boiled for 6 h, poured into water, and acidified to pH ~7. The
precipitated white clotted solid was filtered off, washed with water, dried, and recrystallized from a benzene–
hexane mixture. The syn isomer of oxime 26 was obtained, yield 9.047 g (86%); mp 155-157°C. IR spectrum
(CHCl3), ν, cm-1: 3555 (O–H), 3430 (N–H), 1590 (C=N). UV spectrum, λmax, nm (log ε): 250 (4.29), 319 (3.27).
Mass spectrum, m/z: 304 [M]+, 286 [M-H2O]+, 272 [M-H2NO]+, 271 [M-H2O-CH3]+, 207 [M-H2O-Br]+, 193
[M-H2NO-Br]+. Found, %: C 55.12; H 4.31; N 9.21. C14H13BrN2O. Calculated, %: C 55.10; H 4.29; N 9.18.
7-Bromo-3-hydroxy-1-methyl-5-phenyl-1,3-dihydro-2H-1,4-benzodiazepin-2-one (28) and 8-Bromo-
1-methyl-6-phenyl-1,3-dihydro-2H-4,1,5-benzoxadiazocin-2-one (29). Chloroacetyl chloride (2.66 ml,
33 mmol) and NaOH (2.64 g) in water (10 ml) were added alternately with stirring to a solution of the syn
isomer of oxime 26 (10 g, 33 mmol) in 1,4-dioxane (10 ml) so that the medium remained neutral or weakly
alkaline but the temperature did not rise above 5°C. The mixture was stirred for 2 h to 2 h 30 min, then poured
into water. The precipitated solid was separated, washed with water, and dried. Fractional crystallization from a
mixture of benzene–hexane gave compound 28 (0.994 g, 18%) and compound 29 (4.095 g, 75%). The properties
of compound 28 are described in [4]. Compound 29 had mp 140-142°C. IR spectrum, ν, cm-1: 1650 (C=O), 1585
(C=N). UV spectrum, λmax, nm (log ε); 224 (4.45), 285 (3.52). Mass spectrum, m/z: 344 [M]+, 314 [M-CH2O]+,
299 [M-CH2O-CH3]+, 286 [M-COCH2O]+, 272 [M-COCH2ON]+, 207 [M-COCH2O-Br]+, 193 [M-COCH2ON-
Br]+. Found, %: C 55.65; H 3.82; N 8.11. C16H13BrN2O2. Calculated, %: C 55.67; H 3.80; N 8.12.
syn
A solution of
Isomer of N-(2-Amino-5-bromodiphenylmethylene)iminooxyacetic Acid (31).
NaOH (0.84 g) in water (2 ml) was added to a solution of N-(2-amino-5-bromodiphenylmethylene)-
iminooxyacetic acid methyl ester (syn isomer) (33) (5 g, 14 mmol) in 1,4-dioxane (15 ml). The suspension
obtained was boiled for 30 min. The reaction mixture was poured into water, acidified to pH ~7, the precipitated
white solid was filtered off, washed with water, dried, and recrystallized from a benzene–hexane mixture.
Compound 31 (4 g, 82%) was obtained; mp 170-172°C. IR spectrum, ν, cm-1: 3445 (NH2 antisym), 3340 (NH2 sym),
1725 (C=O), 1620 (C=N). UV spectrum, λmax, nm (log ε): 246 (4.11), 318 (3.12). Mass spectrum, m/z: 348 [M]+,
272 [M-OHCH2COOH]+, 257 [M-NH2OCH2COOH]+, 193 [M-OHCH2COOH-Br]+, 178 [M-NH2OCH2COOH-
Br]+. Found, %: C 51.58; H 3.76; N 8.02. C15H13BrN2O3. Calculated, %: C 51.60; H 3.75; N 8.02.
The synthesis of compound 33 from 32 was described in [1].
Acid Hydrolysis of Macrocycle 1. Conc. hydrochloric acid (2 ml) was added to a solution of
compound 1 (1 g, 2 mmol) in 1,4-dioxane (7 ml). The suspension obtained was boiled for 2 h. The reaction
mixture was poured into water, the precipitated solid was filtered off, washed with water, dried, and dissolved in
a benzene–hexane 1:1 mixture (10 ml). The insoluble solid was filtered off, recrystallized from benzene, and
compound 31 (0.175 g, 25%) was obtained. The mother liquor was evaporated, the precipitated solid was
filtered off, crystallized from hexane, and 2-amino-5-bromobenzophenone (30) (0.151 g, 27%), described
previously in [10], was obtained.
Alkaline Hydrolysis of Macrocycle 1. A solution of NaOH (0.32 g) in water (2 ml) was added to a
solution of compound 1 (1 g, 2 mmol) in 1,4-dioxane (5 ml). The suspension obtained was boiled for 5 h. The
reaction mixture was poured into water, the precipitated solid was filtered off, washed with water, dried, and
recrystallized from hexane. Compound 30 (0.817 g, 74%) was obtained.
Compounds 1-3, 19-21, and 25 were synthesized analogously to those described in [1,2,10].
491

REFERENCES
1.
O. V. Kulikov, S. A. Andronati, V. I. Pavlovskii, A. V. Mazepa, and T. A. Kabanova, Vestn. Odessa
Nauchn. Univ., Iss. 2, 68 (2000).
2.
3.
4.
K. S. Andronati, Dissertation for Candidate of Chemical Sciences, Odessa (2000).
T. Kovac, B. Belin, T. Fajdiga, and V. Sunjic, J. Heterocycl. Chem., 18, 59 (1981).
S. A. Andronati, K. S. Andronati, D. P. Neshchadin, Yu. A. Simonov, V. Kh. Kravtsov, and
Ya. Lipkovskii, Dokl. Natl. Akad. Nauk. Ukraine, 149 (1999).
5.
6.
7.
8.
A. Stempel, I. Douvan, E. Reeder, and L. H. Sternbach, J. Org. Chem., 32, 2417 (1967).
S. C. Bell and S. J. Childress, J. Org. Chem., 29, 506 (1964).
L. H. Sternbach and E. Reeder, J. Org. Chem., 26, 4936 (1961).
K. N. Zelenin, O. B. Kuznetsova, P. B. Terent'ev, V. N. Torocheshnikov, V. V. Lashin, and
V. V. Alekseev, Khim. Geterotsikl. Soedin., 1689 (1992).
9.
P. B. Terent'ev, V. V. Lashin, V. V. Ovcharenko, G. A. Bulakhov, N. A. Klyuev, M. G. Korotkov,
K. N. Zelenin, and O. B. Kuznetsova, Khim. Geterotsikl. Soedin., 1554 (1993).
V. V. Danilin, Dissertation for Candidate of Chemical Sciences, Odessa (1982).
10.
492