Gould-jacobs reaction of 5- and 6-amino-2-substituted benzoxazoles. II. Reaction with 3-ethoxymethylene-2,4-pentanedione and ethyl 2-ethoxymethylene-3-oxobutanoate

Article abstract of DOI:10.1135/cccc19960371

Nucleophilic reaction of 5-amino- and 6-amino-2-substituted benzoxazoles 1 and 2 with 3-ethoxymethylene-2,4-pentanedione (3) gave compounds 5 and 6. Compounds 1 and 2 reacted with ethyl ethoxymethylene-3-oxobutanoate (4) under formation of compounds 7 and

Full text of DOI:10.1135/cccc19960371

Gould–Jacobs Reaction
371
GOULD–JACOBS REACTION OF 5- AND 6-AMINO-2-SUBSTITUTED
BENZOXAZOLES. II. REACTION WITH 3-ETHOXYMETHYLENE-2,4-
PENTANEDIONE AND ETHYL 2-ETHOXYMETHYLENE-
3
-OXOBUTANOATE
a
b
b
c
Katarina HELEYOVA , †Dusan ILAVSKY , Vladimir BOBOSIK and Nada PRONAYOVA
a
Research Institute for Drugs, 900 01 Modra, Slovak Republic
Department of Organic Chemistry,
b
Slovak Technical University, 812 37 Bratislava, Slovak Republic
c
Central Laboratory,
Slovak Technical University, 812 37 Bratislava, Slovak Republic
Received September 14, 1995
Accepted September 27, 1995
Nucleophilic reaction of 5-amino- and 6-amino-2-substituted benzoxazoles 1 and 2 with 3-ethoxy-
methylene-2,4-pentanedione (3) gave compounds 5 and 6. Compounds 1 and 2 reacted with ethyl
ethoxymethylene-3-oxobutanoate (4) under formation of compounds 7 and 8. The substitution prod-
ucts 7 and 8 underwent thermal cyclization at high temperature (boiling mixture of diphenyl ether
and biphenyl) to give angularly and linearly annelated derivatives of 5-acetyl-4-oxo-oxazolo[4,5-f]-
quinoline 9 and 7-acetyl-8-oxo-oxazolo[5,4-g]quinoline 10 (from 7), and derivatives of 8-acetyl-9-
oxo-oxazolo[5,4-f]quinoline 11 and 6-acetyl-5-oxo-oxazolo[4,5-g]quinoline 12 (from 8). The
1
structure of the substitution products is discussed on the basis of their spectral characteristics ( H and
1
3
C NMR, IR, UV, MS).
Key words: Gould–Jacobs reaction; Oxazoloquinolones.
1
The Gould–Jacobs reaction , in which a 4-pyridone ring is annelated to a benzoxazole
2
skeleton , represents one of the synthetical approaches to the oxazoloquinolone system.
Much more common is the formation of oxazole skeleton on a substituted quinoline
3
–5
derivative . With isoelectric azoles, the former method leads exclusively to angularly
annelated derivatives, with nonisoelectric ones it enables the preparation of both the
linearly and angularly annelated products, the choice of the substitution derivatives
being, however, more difficult.
6
The present study represents an extension of our preceding paper describing the
reaction of 5- and 6-amino-2-substituted benzoxazoles (with hydrogen, methyl or phenyl in
position 2) with diethyl ethoxymethylenemalonate leading to 3-N-[5- or 6-(2-sub-
stituted benzoxazolyl)]aminomethylenemalonates which under conditions of Gould–
Jacobs reaction were cyclized to give a mixture of angularly and linearly annelated
oxazoloquinolones.
Collect. Czech. Chem. Commun. (Vol. 61) (1996)

3
72
Heleyova, Ilavsky, Bobosik, Pronayova:
The present communication describes the nucleophilic substitution reaction of
5
-amino- (1) and 6-amino-2-substituted (2) benzoxazoles with 3-ethoxymethylene-2,4-
pentanedione (3), leading to products 5 and 6, and with ethyl 2-ethoxymethylene-3-oxo-
butanoate (4), affording products 7 and 8 (Scheme 1). This nucleophilic substitution
proceeds under mild conditions, in refluxing ethanol. Generally, the 6-amino-sub-
stituted benzoxazoles 2 required longer reaction time, the substituent in position 2 having
no marked influence on the reaction course.
The physicochemical properties of the products 5–8 are given in Table I and their IR
and UV spectra in Table II. In all cases, the substitution derivatives showed transoid
1
arrangement of the –NH–CH= grouping (J = 12–14 Hz). Comparison of H NMR sig-
nals of compounds 5–8 is given in Table III. The position of the NH proton signal was
approximately constant (12.57–12.75 ppm) and the signal of the neighbouring C–H
group was at 8.30–8.31 ppm. The acetyl signal appeared at 2.10–2.40 ppm and those of
the ethyl ester group at 1.24–1.29 and 4.10–4.13 ppm.
The 13C NMR spectra of products 5–8 (Table IV) show that in the case of unsymme-
trically substituted ethylenic bond both geometric isomers are formed, the (E)-isomer
invariably predominating (more than 90%). The shift of the acetyl carbons C-10 and
C-12 is enormously high, being 199.50–199.38 and 195.63–195.20 ppm, respectively,
in compounds 5 and 6. In the spectra of derivatives 7 and 8 the signal of the C-12
carbon atom, bearing the ester group, appears mostly at 166.00–166.17 ppm. The carbon
atom C-2 in derivatives 5a–8a resonates at 151.13–155.49 ppm, in the other derivatives
at 162.60–166.22 ppm.
7
7a
6
O
N
O
N
H C O
X
Y
5
2
H 5
R
2
H N
R
+
2
4a
X
4
H
8
N
9
H
Y
1, 2
3, 4
5-8
In formulae 1, 5, 7 : 5-NH2
2
, 6, 8 : 6-NH2
, 5, 6 : X = Y = COCH3
3
4
, 7, 8 : X = COCH , Y = COOC H
3 2 5
1
, 2, 5-8 : a, R = H
b, R = CH3
c, R = C H
6
5
SCHEME 1
Collect. Czech. Chem. Commun. (Vol. 61) (1996)

Gould–Jacobs Reaction
373
TABLE I
Physicochemical properties of substitution products 5–8
Solvent of
Calculated/Found
% H
crystallization
Reaction time,
min
M.p., °C
Yield, %
Formula
M.w.
Compound
% C
% N
5
5
a
toluene
142–143
70
C13H12N2O3
63.91
63.55
4.95
4.78
11.47
11.25
1
5
5
0
0
0
0
244.1
b
toluene
132–135
73
C14H14N2O3
65.09
65.07
5.47
5.48
10.85
10.76
1
258.1
5
c
toluene
170–171
75
C19H16N2O3
71.22
70.93
5.04
5.03
8.75
8.74
3
320.1
6
a
toluene
170–171
67
C13H12N2O3
61.29
61.09
5.15
5.31
10.22
10.28
3
244.1
6
b
toluene
132–134
65
C14H14N2O3
62.48
62.33
5.60
5.54
9.72
9.81
3
258.1
6
7
c
toluene
197–199
65
C19H16N2O3
68.55
68.72
5.18
5.19
8.00
7.97
6
320.1
a
CHCl3–hexane
114–117
80
C14H14N2O4
61.29
61.30
5.15
5.09
10.22
10.19
1
5
0
0
274.1
7
b
toluene
103–106
78
C15H16N2O4
62.48
62.35
5.60
5.69
9.72
9.80
3
288.1
7
c
toluene
134–135
82
C20H18N2O4
68.55
68.31
5.18
5.15
8.00
8.08
6
350.1
8
a
CHCl3–hexane
70–71
65
C14H14N2O4
61.29
61.18
5.15
5.20
10.22
10.29
3
0
0
0
274.1
8
b
toluene
208–211
60
C15H16N2O4
62.48
62.40
5.60
5.54
9.72
9.66
6
288.1
8
c
toluene
173–175
62
C20H18N2O4
68.55
68.60
5.18
5.12
8.00
8.12
6
350.1
Collect. Czech. Chem. Commun. (Vol. 61) (1996)

3
74
Heleyova, Ilavsky, Bobosik, Pronayova:
TABLE II
Infrared and UV spectra of substitution products 5–8
IR spectra
Compound
UV spectra
~
a
~
ν(C=O)
ν(C=C)
5
5
a
1 618
1 585
1 574
1 591
1 591
1 574
1 583
1 583
1 581
1 583
1 581
1 574
1 581
206.6 (3.24), 239.9 (3.12), 335.1 (3.34)
b
1 630
1 618
1 637
1 630
1 614
207.0 (3.72), 241.3 (3.23), 336.0 (3.41)
206.3 (3.70), 266.5 (3.42), 341.5 (3.53)
203.9 (3.22), 245.1 (3.02), 341.5 (3.40)
207.0 (3.72), 241.3 (3.21), 336.9 (3.39)
204.9 (3.74), 337.1 (3.60)
5
6
c
a
6
b
6
7
c
a
1 684, 1 610
1 711, 1 639
1 691, 1 633
1 695, 1 618
1 691, 1 631
1 709, 1 637
206.3 (3.21), 235.8 (3.33), 334.2 (3.36)
207.0 (3.22), 236.7 (3.36), 335.1 (3.36)
201.6 (3.50), 241.3 (3.31), 270.6 (3.33), 339.7 (3.56)
202.9 (3.17), 232.3 (3.11), 341.5 (3.26)
204.9 (3.32), 241.3 (3.18), 348.2 (3.40)
200.0 (3.56), 232.8 (3.30), 379.0 (3.66)
7
b
7
8
c
a
8
b
8
c
a
The long-wavenumber absorption corresponds to the ester carbonyl vibration.
TABLE III
Proton NMR spectra of substitution products 5–8
Compound H-4
H-5
H-6
H-7
H-8
NH COCH3 COCH3 CH2 CH3
R
5
5
a
7.74
7.70
7.79
–
–
–
7.52 7.70 8.44 12.64
7.38 7.62 8.40 12.75
7.50 7.79 8.45 12.62
2.38
2.41
2.40
2.43
2.39
2.10
2.37
2.37
2.38
2.38
2.12
2.30
2.38
2.37
2.41
2.40
2.38
2.10
–
–
–
–
–
–
–
–
–
–
–
–
–
8.76
2.61
b
a
5
6
c
–
a
7.80 7.50
7.65 7.42
7.79 7.49
–
–
–
8.10 8.46 12.64
7.79 8.42 12.63
8.09 8.46 12.64
8.73
2.60
6
b
b
6
7
c
–
a
7.86
7.72
7.90
–
–
–
7.46 7.76 8.46 12.61
7.38 7.66 8.45 12.60
7.46 7.82 8.49 12.62
4.10 1.29 8.72
7
b
–
4.18 1.28 2.60
c
7
8
c
–
4.17 1.29
–
a
7.75 7.34
7.85 6.97
7.82 7.73
–
–
–
7.85 8.35 12.61
7.89 8.30 12.57
7.98 8.51 10.90
–
4.15 1.27 8.66
8
b
–
4.14 1.24 2.60
d
8
c
–
4.10 1.24
–
a
b
c
d
Chemical shifts of o- and (m-, p-)protons, respectively: 8.19, 7.62. 8.15, 7.61. 8.19, 7.62. 8.15, 7.60.
Collect. Czech. Chem. Commun. (Vol. 61) (1996)

Gould–Jacobs Reaction
375
Collect. Czech. Chem. Commun. (Vol. 61) (1996)

3
76
Heleyova, Ilavsky, Bobosik, Pronayova:
Mass spectra of all the substituted derivatives exhibit the molecular ion. The sub-
stitution products 5 and 6 display a peak m/z 112 (100%), corresponding to loss of the
diacetylethylene fragment. In the case of derivatives 7 and 8 we observed two fragmen-
tation paths. The main fragmentation of compounds 7 consisted in loss of ethyl formate
(
M – 74), derivatives 8 lost preferentially the acetyl group (M – 43) with subsequent
fragmentation. The mass spectral data for derivatives 5–8 are given in Table V.
The cyclization of substitution products 7 and 8 takes place at high temperature
(
250–260 °C) in a mixture of diphenyl ether and biphenyl (Scheme 2). The reaction
time was 30–60 min. In most cases the reaction afforded a mixture of angularly and
linearly annelated oxazoloquinolones, only the cyclization of compound 8a gave exclu-
sively the angularly annelated derivative 11a. The cyclization was also greatly in-
TABLE V
Mass spectra of substitution products 5–8
Compound
m/z (relative abundance, %)
+•
5
a
244 (M , 92), 229 (9), 228 (44), 212 (8), 211 (41), 201 (11), 188 (12), 187 (94),
1
6
59 (20), 158 (10), 145 (13), 134 (11), 118 (10), 112 (100), 104 (11), 91 (9), 77 (8),
3 (16), 51 (12), 43 (98), 39 (19), 28 (17)
+•
5
b
258 (M , 58), 243 (23), 225 (38), 215 (11), 202 (10), 201 (38), 197 (9), 160 (13),
47 (32), 132 (20), 112 (100), 104 (11), 91 (11), 63 (8), 43 (57), 32 (12), 28 (28)
1
+
•
5
6
c
320 (M , 49), 305 (59), 287 (30), 277 (12), 263 (22), 235 (15), 209 (50), 160 (20),
32 (26), 112 (100), 104 (24), 91 (16), 77 (22), 63 (20), 43 (85), 39 (9)
1
+•
a
244 (M , 42), 229 (20), 202 (5), 201 (39), 188 (6), 187 (52), 159 (17), 132 (11),
12 (100), 104 (8), 90 (13), 63 (17), 43 (71), 39 (9), 32 (9), 28 (25)
1
+•
6
b
258 (M , 60), 243 (25), 225 (38), 215 (10), 201 (41), 173 (18), 160 (13), 147 (33),
32 (27), 112 (100), 104 (14), 91 (14), 76 (10), 52 (10), 43 (87), 39 (9), 28 (29)
1
+
•
6
7
c
320 (M , 58), 305 (20), 287 (27), 263 (18), 210 (20), 209 (65), 166 (10), 132 (22),
12 (100), 104 (19), 103 (12), 91 (10), 77 (19), 63 (20), 43 (56), 39 (9), 28 (19)
1
+•
a
274 (M , 72), 259 (9), 229 (13), 228 (16), 213 (20), 201 (17), 200 (100), 187 (12),
85 (56), 158 (13), 142 (32), 103 (7), 76 (8), 52 (10), 43 (57), 29 (19), 28 (19)
1
+•
7
b
288 (M , 81), 243 (12), 242 (13), 227 (15), 214 (100), 213 (15), 201 (6), 199 (41),
72 (10), 142 (18), 132 (10), 104 (10), 91 (7), 63 (10), 43 (49), 29 (13), 28 (10)
1
+
•
7
8
c
350 (M , 56), 289 (10), 282 (7), 277 (18), 276 (87), 274 (51), 261 (51), 200 (100),
85 (49), 158 (18), 142 (49), 104 (12), 91 (14), 51 (19), 43 (80), 29 (15), 28 (30)
1
+•
a
274 (M , 15), 157 (11), 142 (10), 104 (7), 103 (9), 90 (10), 77 (9), 63 (13), 51 (10),
3 (100), 29 (46)
4
+•
8
b
288 (M , 38), 243 (10), 242 (17), 227 (13), 215 (16), 214 (100), 200 (7), 199 (53),
73 (7), 172 (17), 142 (28), 104 (28), 103 (10), 77 (10), 63 (7), 43 (30), 28 (12)
1
+•
8
c
350 (M , 10), 104 (13), 103 (23), 91 (5), 77 (8), 63 (33), 51 (19), 43 (100), 29 (17)
Collect. Czech. Chem. Commun. (Vol. 61) (1996)

Gould–Jacobs Reaction
377
fluenced by dilution of the starting solution. The concentration of choice was 1 g of the
compound in 50 g of the solvent. Greater concentrations resulted in darkening of the
mixture, with lower concentrations the isolation of the products was very difficult. The
purity and yields of the cyclocondensation reaction depended also on the purity of the
starting substitution products, good yields being achieved only with recrystallized com-
pounds. The obtained cyclic oxazoloquinolones were extraordinarily insoluble and
melted above 250 °C. The low solubility made the NMR spectral measurements diffi-
cult and, more importantly, made impossible the separation of the angularly and li-
nearly annelated products.
O
H
R
1
1
10
N
CH OC
3
N
H
CH CH OOC
3
2
14
13
12
7, 8
O
COCH3
O
R
H
N
N
N
O
N
H
O
R
COCH3
9
11
+
+
O
H
CH OC
N
3
O
N
O
R
R
N
N
H
CH OC
3
O
10
12b, 12c
In formulae 7-12 : a, R = H
b, R = CH3
c, R = C H5
6
SCHEME 2
Collect. Czech. Chem. Commun. (Vol. 61) (1996)

3
78
Heleyova, Ilavsky, Bobosik, Pronayova:
The analytical data, yields and IR spectra of the cyclocondensation products 9–12 are
given in Table VI. Except the derivative 11a, all the products are mixtures of angularly
and linearly annelated compounds; the data are given only to characterize the obtained
1
mixtures and not the individual compounds. The H NMR spectra (Table VII) of these
mixtures of angularly and linearly annelated products show some doubled signals, e.g.
those of acetyl group, the proton or methyl group in position 2 of the oxazole nucleus,
and in some cases also of the CH–NH protons. The spectra further exhibited charac-
teristic doublets for angularly annelated derivatives 9 (for H-8 and H-9) and 11 (for H-4
and H-5) and singlets, attributable to the H-4 and H-9 protons of the linearly annelated
derivatives 10a–10c and 12b, 12c. The ratio of the angular to linear isomers was deter-
1
mined by the H NMR spectra. Mass spectra of the cyclic products (Table VIII) show
the molecular ions. In most cases, the molecules lose preferentially the methyl group.
EXPERIMENTAL
The melting points are uncorrected. Proton and 13C NMR spectra were measured on a Varian VXR-300
1
13
instrument (300 MHz for H, 75 MHz for C) in hexadeuteriodimethyl sulfoxide with tetramethylsi-
lane as internal standard. IR spectra were taken on an M-80 (Zeiss, Jena) spectrometer using the KBr
TABLE VI
Physicochemical properties of cyclocondensation products 9–12
Compound
or
mixture
Calculated/Found
% H
IR spectra
~
Formula
M.w.
Yield, %
~
%
C
% N
ν(CO)
ν(C=C)
9
a
22
25
38
20
20
33
C12H8N2O3
228.2
63.16
63.00
3.53
3.50
12.28
12.24
1 581, 1 664
1 543
1
1
0a
9b
C13H10N2O3
64.46
64.41
4.16
4.11
11.56
11.51
1 581, 1 666
1 624, 1 662
1 628, 1 666
1 635, 1 662
1 587, 1 622
1 539
1 541
1 543
1 541
1 539
0b
242.2
9
c
C18H12N2O3
71.05
71.15
3.97
4.02
9.21
9.11
1
0c
304.3
1
1a
C12H8N2O3
63.16
63.51
3.35
3.40
12.28
12.32
2
28.2
1
1
1b
2b
C13H10N2O3
64.46
64.39
4.16
4.09
11.56
11.49
242.2
1
1
1c
2c
C18H12N2O3
71.05
69.87
3.97
3.90
9.21
9.18
304.3
Collect. Czech. Chem. Commun. (Vol. 61) (1996)

Gould–Jacobs Reaction
379
TABLE VII
Proton NMR spectra of cyclocondensation products 9–12
Compound
H-4
H-5
H-6
H-7
H-8
H-9
NH CH CO
R
3
a
f
9
a
–
11.12
–
–
–
12.18
12.25
10.08
10.08
8.40
8.40
–
–
–
11.66 11.43 12.33
11.84 12.62
9.15 10.17 10.17
5.94
6.02
3.57
3.77
2.52
2.62
2.50
2.75
2.75
2.85
2.88
–
f
1
0a
–
–
b
9
b
–
–
3.48
3.52
1
0b
c
9.48
–
–
–
–
8.23
–
10.17 10.17
9
c
–
–
8.59
8.59
–
8.59
8.59
8.81
8.48
8.48
8.62
8.62
8.28–8.22
7.64–7.58
8.92
1
0c
1a
7.85
8.09
8.10
9.30
8.17
9.97
–
–
1
7.65
7.98
–
8.48
8.29
8.29
8.55
8.55
–
d
1
1b
–
–
8.26
2.49
1
2b
–
–
–
2.49
e
a
1
1c
2c
7.70
–
–
–
–
8.28–8.22
7.68–7.55
1
–
–
–
a
b
c
d
e
f
Population of isomers in the mixture: 3 : 1. 3 : 2. 1 : 1. 2 : 1. 3 : 2. Signal not obvious.
TABLE VIII
Mass spectra of cyclocondensation products 9–12
Compound
m/z (relative abundance, %)
+•
9a
228 (M , 77), 214 (13), 213 (100), 185 (8), 157 (5), 145 (34), 130 (21), 129 (5)
1
1
0a
103 (5), 102 (9), 75 (15), 63 (7), 62 (8), 53 (15), 52 (8), 43 (30), 28 (10)
+•
9b
242 (M , 60), 228 (14), 227 (100), 199 (10), 171 (5), 159 (22), 158 (7), 144 (7)
0b
130 (5), 120 (5), 102 (5), 75 (7), 53 (5), 43 (27), 28 (5)
+•
9c
304 (M , 68), 290 (20), 289 (100), 278 (5), 277 (10), 270 (49), 263 (7)
1
0c
261 (27), 234 (8), 210 (7), 170 (12), 142 (11), 130 (7), 104 (14), 103 (14), 91 (7),
7
7 (27), 76 (12), 63 (14), 53 (12), 52 (10), 51 (22), 43 (35), 39 (11)
+•
1
1a
228 (M , 32), 214 (5), 213 (47), 171 (13), 170 (100), 169 (13), 154 (59), 153 (18),
1
5
52 (13), 145 (12), 142 (34), 140 (49), 115 (18), 77 (35), 76 (12), 63 (12), 51 (42),
0 (14), 43 (10), 39 (19), 28 (7)
+
•
1
1
1b
2b
242 (M , 62), 228 (14), 227 (100), 199 (8), 171 (5), 170 (15), 159 (25), 158 (5)
154 (11), 77 (11), 76 (11), 43 (20), 39 (7), 28 (13)
+
•
1
1
1c
2c
304 (M , 100), 290 (17), 289 (78), 286 (7), 261 (9), 223 (7), 221 (13), 206 (7)
170 (26), 154 (17), 141 (14), 130 (12), 104 (10), 103 (12), 102 (15), 77 (22), 76 (9),
7
5 (11), 63 (7), 51 (15), 43 (12), 39 (7)
Collect. Czech. Chem. Commun. (Vol. 61) (1996)

3
80
Heleyova, Ilavsky, Bobosik, Pronayova:
technique (1 mg in 300 mg KBr). Electronic absorption spectra were recorded on a UV-VIS M-40
–4
–3
spectrophotometer (Zeiss, Jena) in methanol, concentration 1 . 10 mol dm . Mass spectra were obtained
5
,7–11
with an MS 902S (AEI Kratos) instrument. The nitrobenzoxazoles were prepared according to refs
.
Preparation of Aminobenzoxazoles 1 and 2
A mixture of the nitro compound (0.01 mol), Raney nickel (10% of weight of the nitro derivative)
and ethanol (100 ml) was hydrogenated for 24–120 h, the reaction being monitored by TLC and hy-
drogen consumption. After filtration, the obtained alcoholic solution of the amine was immediately
used in the further reaction.
Preparation of Substitution Derivatives 5–8
The alcoholic solution of the amine, obtained in the above experiment, was mixed with 3-ethoxy-
methylene-2,4-pentanedione (3) or ethyl 2-ethoxymethylene-3-oxobutanoate (4) (0.01 mol-equivalent).
The mixture was refluxed for 15–60 min and the reaction was monitored by TLC. The reaction mix-
ture was concentrated in vacuo on a rotatory evaporator and the product was crystallized from an
appropriate solvent. The yields, reaction times, melting points and crystallization solvents are given
1
13
in Table I, their IR and UV spectra in Table II, H NMR spectra in Table III, C NMR spectra in
Table IV and mass spectra in Table V.
Preparation of Cyclocondensation Products 9–12
A mixture of the substitution product 7 or 8 (1 g) and Dowtherm (50 g) was heated at 250–260 °C
for 30–60 min. In most cases, cooling of the mixture afforded a gelatinous mass which was washed
with hexane and ether to remove the residual solvent. The physicochemical data for compounds 9–12
1
and their IR spectra are given in Table VI, their H NMR spectra in Table VII and mass spectra in
Table VIII.
The authors are indebted to Dr J. Lesko for measurement of the mass spectra and to Mrs S. Marku-
sová for the IR and UV spectral measurements.
REFERENCES
1. Yanagisawa I., Murakami M., Nega Y.: Japan. Kokai 7 472 297 (1975); Chem. Abstr. 83,
1
31573 (1975).
2. Mullock B. B., Suschitzky H.: J. Chem. Soc., C 1968, 1937.
3. Hammam A. S., Yanni A. S., Khalil Z. H., Abdel-Hafez A. A.: J. Chem. Technol. Biotechnol.
3
2, 485 (1982).
4
5
6
7
8
9
. Osman A. M., Khalil Z. H., Yanni A. S.: Appl. Chem. Biotechnol. 27, 33 (19977).
. Roussos M., Lacomte J.: Ger. 1 124 499; Chem. Abstr. 57, 9858 (1962).
. Ilavsky D., Heleyova K., Nadaska J., Bobosik V.: Collect. Czech. Chem. Commun. 61, 268 (1996).
. Passarini R.: J. Chem. Soc. 1954, 2256.
. Stephenson F. F., Bower J. D.: J. Chem. Soc. 1949, 2971.
. Stephenson F. F., Bower J. D.: J. Chem. Soc. 1950, 1722.
1
1
0. Newbery G., Philips M. A.: J. Chem. Soc. 1928, 122.
1. Garner R., Mullock E. B., Suschitzky H.: J. Chem. Soc., C 1966, 1960.
Collect. Czech. Chem. Commun. (Vol. 61) (1996)