Azines and azoles: CXXV. New regioselective synthesis of 1-amino-6-methyluracils

Article abstract of DOI:10.1134/S1070363207120134

Readily accessible 5-acetyl-4-hydroxy-3,6-dihydro-2H-1,3-thiazine-2,6-dione reacts with substituted hydrazines and carboxylic acid hydrazides under mild conditions to give the corresponding hydrazones. Under severe conditions (heating in boiling dimethylformamide) the reaction is accompanied by extrusion of COS with formation of substituted 1-amino-6-methyluracils. Reactions of 5-acetyl-4-hydroxy-3,6-dihydro-2H-1,3-thiazine-2,6-dione with monosubstituted alkyl-and arylhydrazines take different pathways, depending on the conditions. Heating of equimolar mixtures of the reactants in ethanol or propan-1-ol leads to the formation of 2-substituted 5-methyl-3-oxo-2,3-dihydro-1H-pyrazole-4- carboxamides rather than 1-amino-6-methyluracil derivatives.

Full text of DOI:10.1134/S1070363207120134

ISSN 1070-3632, Russian Journal of General Chemistry, 2007, Vol. 77, No. 12, pp. 2150 2161.
Pleiades Publishing, Ltd., 2007.
Original Russian Text V.N. Yuskovets, B.A. Ivin, E.N. Kirillova, 2007, published in Zhurnal Obshchei Khimii, 2007, Vol. 77, No. 12, pp. 2007 2017.
Azines and Azoles: CXXV.1 New Regioselective Synthesis
of 1-Amino-6-methyluracils
V. N. Yuskovets, B. A. Ivin, and E. N. Kirillova
St. Petersburg State Chemical and Pharmaceutical Academy,
ul. Prof. Popova 14, St. Petersburg, 197376 Russia
e-mail: oxazin@yahoo.com
Received July 13, 2007
Abstract Readily accessible 5-acetyl-4-hydroxy-3,6-dihydro-2H-1,3-thiazine-2,6-dione reacts with sub-
stituted hydrazines and carboxylic acid hydrazides under mild conditions to give the corresponding hy-
drazones. Under severe conditions (heating in boiling dimethylformamide) the reaction is accompanied by
extrusion of COS with formation of substituted 1-amino-6-methyluracils. Reactions of 5-acetyl-4-hydroxy-3,6-
dihydro-2H-1,3-thiazine-2,6-dione with monosubstituted alkyl- and arylhydrazines take different pathways,
depending on the conditions. Heating of equimolar mixtures of the reactants in ethanol or propan-1-ol leads to
the formation of 2-substituted 5-methyl-3-oxo-2,3-dihydro-1H-pyrazole-4-carboxamides rather than 1-amino-
6-methyluracil derivatives.
DOI: 10.1134/S1070363207120134
Among numerous known syntheses of 1-amino-
uracils, two approaches must be noted. The first of
these includes reactions with semicarbazide deriv-
atives [2 4], and the second is based on direct amina-
tion of uracil derivatives with such reagents as hy-
droxylamine O-sulfonic acid, which leads to mixtures
of 1- and 3-aminosubstituted compounds [5]. As a
rule, amination of 6-methyluracil involves almost
exclusively the N3 atom due to steric hindrances
created by the 6-methyl group.
corresponding hydrazones. Carboxylic acid hydrazides
react similarly to give 90 95% of the corresponding
acylhydrazones even at room temperature. For ex-
ample, in 1 2 min after dissolution of 1 g of thiazine
Ia and 0.9 g of 2-methoxybenzohydrazide in 8 ml of
dimethylformamide at room temperature, the cor-
responding poorly soluble hydrazone quickly se-
parates from the transparent solution.
Under more severe conditions, surprising, much
more interesting, and unpredictable pattern was
observed. Heating of equimolar mixtures of thiazine
Ia and substituted hydrazines in boiling DMF resulted
in the formation of 67 86% of 1-amino-6-methyl-
uracil derivatives IIIa IIIt. The process was accom-
panied by evolution of carbonyl sulfide. With a view
to determine the scope of this novel reaction, it was
performed with various substituted hydrazines.
5-Acetylthiazine Ia reacted with alkyl-, aryl-, and
hetarylhydrazines under analogous conditions to give
1-amino-6-methyluracil derivatives IIIa IIIj (Table
1). Likewise, using carboxylic acid hydrazides we
obtained 60 85% of 1-acylamino-6-methyluracils
IIIk IIIs. Presumably, in all cases the primary
product is the corresponding hydrazone which loses
COS molecule on heating, and open-chain inter-
mediate thus formed undergoes intramolecular ring
closure to 1-amino-6-methyluracil (Scheme 1). In the
reaction of 4-aminobenzohydrazide with 2 equiv of
We recently developed a very simple and con-
venient procedure for the synthesis of 5-acetyl-4-
hydroxy-2H-1,3-thiazine-2,6-dione (Ia) from malonic
acid, potassium thiocyanate, and acetic anhydride in
acetic acid [6, 7]. We showed that 5-acetyl-4-hydroxy-
2H-1,3-thiazine-2,6-dione (Ia) readily reacts under
mild conditions with primary amines at the acetyl
carbonyl group with formation of the corresponding
Schiff bases without opening of the thiazine ring. The
reaction under severe conditions (boiling dimethyl-
formamide) is accompanied by extrusion of COS, and
the products are 1-substituted 6-methyluracils [6, 8, 9].
Here we report on the reaction of thiazine Ia with
substituted hydrazines and carboxylic acid hydrazides.
We found that thiazine Ia very readily and quickly
(within 5 min) reacts with hydrazines in dimethyl-
formamide, dioxane, or diethyl ether to produce the
1
For communication CXXIV see [1].
2150

AZINES AND AZOLES: CXXV.
2151
Scheme 1.
R
H
H
N
R
O
O
O
O
N
NH
NH
Me
RR NNH2
DMF
Me
O
O
S
O
S
Ia
II
COS
O
R
N
NH
R
O
N
N
N
Me
O
NH
+C
Me
R
H
R
O
IIIa IIIt
II, III, R = H, R = Me (a), R = R = Me (b), R = H, R = PhCH2 (c), Ph (d), 2-MeC6H4 (e), 4-O2NC6H4 (f), 2,4,5-
Cl3C6H2 (g), R = R = Ph (h), R = Ph, R = PhCH2 (i), RR N = Ph2C=N (j), R = H, R = Ac (k), R = R = Ac (l), R = H,
R = PrCO (m), PhCO (n), 2-MeOC6H4CO (o), 3-MeOC6H4CO (p), 3-BrC6H4CO (q), 2-furylCO (r), 4-ClC6H4OCH2CO
(s).
5-acetyl-4-hydroxy-2H-1,3-thiazine-2,6-dione (Ia),
both amino groups in the former are involved, and the
product is bis-uracil derivative IIIt. It should be noted
that, following an analogous mechanism, thiazine Ia
is converted into 6-methyl-2H-1,3-oxazine-2,4-dione
(IV, yield 73%) on heating in pyridine.
Table 1. Yields, melting points, Rf values, and elemental analyses of 1-amino-6-methyluracils IIIa IIIt
Found, %
H
Calculated, %
Comp. Yield,
Rf (acetone
hexane, 1: 1)
mp,
C
Formula
no.
%
C
N
C
H
N
IIIa
64
71
78
84
172 173
186 187
184 185
271 273
(decomp.)
285 287
(decomp.)
283 285
(decomp.)
275 277
227 229
233 235
207 208
237 239
184 185
181 182
239 241
265 267
0.34
0.42
0.56
0.63
46.49
49.64
62.28
60.77
5.84
6.56
5.67
5.11
27.11
24.79
18.19
19.31
C6H9N3O2
46.45
49.70
62.33
60.82
5.85
6.55
5.67
5.10
27.08
24.84
18.17
19.34
IIIb
IIIc
IIId
C7H11N3O2
C12H13N3O2
C11H11N3O2
IIIe
IIIf
71
68
0.58
0.66
62.37
50.45
5.68
3.84
18.15
21.41
C12H13N3O2
C11H10N4O4
62.33
50.38
5.67
3.84
18.17
21.37
IIIg
IIIh
IIIi
IIIj
IIIk
IIIl
IIIm
IIIn
IIIo
66
87
83
81
76
89
62
85
82
0.46
41.18
69.71
70.39
70.76
45.94
48.07
51.12
58.71
56.79
2.51
5.16
5.57
4.94
4.96
4.91
6.21
4.53
4.75
13.12
14.32
13.69
13.77
22.89
18.65
19.84
17.15
15.28
C11H8Cl3N3O2
C17H15N3O2
C18H17N3O2
C18H15N3O2
C7H9N3O3
C9H11N3O4
C9H13N3O3
C12H11N3O3
C13H13N3O4
41.21
69.61
70.34
70.81
45.90
48.00
51.18
58.77
56.72
2.52
5.15
5.58
4.95
4.95
4.92
6.20
4.52
4.76
13.11
14.33
13.67
13.76
22.94
18.66
19.89
17.13
15.27
0.73a
0.52
0.43
0.45a
0.67a
0.49a
0.36a
0.29a
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2152
YUSKOVETS et al.
Found, %
Table 1. (Contd.)
Calculated, %
H
Comp. Yield,
no.
Rf (acetone
hexane, 1: 1)
mp,
C
Formula
%
C
H
N
C
N
IIIp
80
76
69
62
54
271 272
249 251
263 265
239 240
275 276
0.30a
0.32a
0.25a
0.38a
0.16a
56.66
44.48
51.09
50.38
55.25
4.77
3.12
3.87
3.92
4.08
15.29
24.63
17.85
11.44
18.97
C13H13N3O4
C12H10BrN3O3
C10H9N3O4
C13H12ClN3O4
C17H15N5O5
56.72
44.47
51.07
50.42
55.28
4.76
3.11
3.86
3.91
4.09
15.27
24.65
17.87
11.45
18.96
IIIq
IIIr
IIIs
IIIt
a
Benzene acetic acid, 10:1.
Me
O
O
O
H
O
NH
N
H
O
N
N
N
N
Me
O
O
O
H
Me
IIIt
IV
1
The structure of compounds III was confirmed by
The H NMR spectra of compounds IIIa IIIt in
1
elemental analyses (Table 1) and H and 13C NMR,
DMSO-d6 (Table 3) contain three singlets at 11.08
11.76, 5.39 5.74, and 1.87 2.28 ppm from the N3H,
5-H, and 6-CH3 protons, respectively. The 1-NH
proton signal in the spectra of 1-amino-6-methyl-
uracils obtained from monosubstituted hydrazines
appears as a singlet at 10.42 11.37 (R = acyl) or
UV, IR, and mass spectra. 1-Amino-6-methyluracil
derivatives IIIa IIIt showed in the mass spectra
(Table 2) the molecular ion peaks and peaks of frag-
ment ions resulting from cleavage of the N N bond;
the latter are often the most abundant ions.
Table 2. Mass spectra of 1-amino-6-methyluracils IIIa IIIt
Comp.
no.
m/z (Irel, %)
IIIa
155 M+ (40), 126 (62), 112 (100), 97 (2), 83 (12), 84 (4), 70 (21), 69 (50), 54 (9), 43 (27), 41 (74)
169 M+ (9), 127 (11), 126 (57), 111 (29), 97 (20), 83 (24), 57 (11), 44 (100), 43 (49), 42 (54)
231 M+ (4), 196 (6), 141 (2), 127 (8), 126 (10), 106 (50), 91 (100), 83 (3), 77 (3), 65 (5), 51 (4), 39 (6)
217 M+ (100), 174 (90), 145 (8), 132 (15), 126 (8), 105 (38), 92 (45), 91 (75), 77 (68), 65 (45), 51 (10), 39 (37)
231 M+ (80), 188 (27), 171 (5), 160 (5), 146 (11), 145 (10), 132 (12), 119 (30), 118 (15), 107 (14), 106 (100),
105 (26), 104 (25), 92 (14), 91 (34), 84 (14), 69 (19), 68 (15), 67 (24), 65 (15), 51 (15)
262 M+ (52), 246 (10), 219 (100), 177 (14), 150 (26), 138 (17), 136 (26), 126 (14), 122 (29), 90 (17), 83 (10),
76 (11), 65 (16), 54 (15), 42 (24)
IIIb
IIIc
IIId
IIIe
IIIf
IIIg
323 M+ (19), 321 M+ (41), 319 M+ (45), 278 (28), 276 (28), 243 (38), 241 (57), 211 (10), 209 (36), 207 (36),
198 (32), 197 (26), 196 (96), 195 (47), 194 (100), 193 (30), 181 (13), 179 (14), 171 (9), 169 (28), 167 (29), 160
(13), 158 (15), 145 (7), 133 (5), 124 (8), 109 (10), 107 (8), 97 (11), 88 (10), 82 (9), 74 (8), 67 (10)
293 M+ (60), 250 (13), 233 (4), 201 (5), 180 (3), 168 (100), 167 (44), 125 (3), 115 (3), 91 (4), 77 (22), 51 (12)
307 M+ (8), 182 (30), 181 (86), 180 (19), 173 (18), 126 (3), 115 (3), 105 (6), 106 (4), 104 (8), 91 (100), 77 (60),
65 (11), 51 (10)
IIIh
IIIi
IIIj
305 M+ (100), 262 (40), 261 (95), 247 (6), 233 (4), 221 (8), 195 (10), 185 (20), 180 (60), 165 (42), 152 (3), 144
(5), 139 (6), 131 (8), 118 (4), 104 (3), 84 (13), 77 (80), 67 (12), 54 (10), 51 (30)
183 M+ (22), 141 (96), 98 (59), 70 (11), 43 (100)
IIIk
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AZINES AND AZOLES: CXXV.
2153
Table 2. (Contd.)
Comp.
no.
m/z (Irel, %)
IIIl
225 M+ (22), 183 (50), 141 (96), 98 (59), 83 (6), 70 (11), 54 (7), 43 (100)
211 M+ (11), 142 (4), 141 (33), 98 (24), 71 (89), 43 (100), 41 (22)
245 M+ (6), 105 (100), 77 (40), 51 (14), 45 (12)
IIIm
IIIn
IIIo
IIIp
IIIq
IIIr
IIIs
136 (8), 135 (100), 120 (3), 105 (3), 92 (6), 77 (19), 64 (3), 51 (3), 39 (4)
275 M+ (4), 136 (11), 135 (100), 107 (20), 92 (9), 77 (11), 64 (5), 63 (3), 51 (3)
325 M+ (4), 323 M+ (4), 185 (94), 183 (100), 157 (23), 155 (23), 105 (6), 104 (4), 76 (21), 75 (17), 50 (15)
235 M+ (12), 206 (2), 192 (3), 164 (1), 96 (5), 95 (100), 67 (4), 39 (10)
311 M+ (18), 310 M+ (9), 309 M+ (57), 182 (65), 168 (10), 154 (90), 143 (29), 142 (10), 141 (81), 128 (39), 127
(29), 126 (10), 113 (42), 111 (100), 99 (6), 83 (9), 77 (11), 75 (32), 54 (8), 51 (7)
IIIt
369 M+ (3), 351 (4), 326 (4), 308 (5), 245 (11), 243 (16), 229 (100), 202 (10), 200 (24), 186 (89), 171 (9), 159
(15), 146 (33), 130 (14), 126 (35), 120 (87), 103 (13), 98 (27), 92 (22), 90 (23), 83 (20), 76 (12), 68 (29), 43 (47)
1
Table 3. UV, IR and HNR spectra of 1-amino-6-methylurasils IIIa IIIt
1H NMR spectrum (DMSO-d6), , ppm (J, Hz)
UV spectrum
Comp.
no.
1
(EtOH), max, nm
IR spectrum (KBr), , cm
N3H
C5H
Me
R
R1
(
104)
IIIa
IIIb
IIIc
207 (0.93), 267 417, 500, 528, 630, 646, 735, 756, 11.26 s 5.40 s 2.18 s 5.79
q
2.54 d
(0.81)
837, 892, 976, 1033, 1070, 1132,
1167, 1197, 1212, 1378, 1400,
1442, 1510, 1580, 1653, 1701,
1717, 2590, 2995, 3100, 3176,
3320, 3448
(1H, J 5.7) (3H, J 5.7)
206 (1.29), 238 413, 450, 486, 525, 600, 637, 720, 11.10 s 5.39 s 2.13 s
(1.51), 267 (1.25) 759, 875, 924, 980, 1002, 1029,
1045, 1077, 1151, 1200, 1223,
2.82 s (6H)
1263, 1376, 1400, 1441, 1459,
1616, 1669, 1706, 1724, 2796,
2853, 2924, 2962, 3035, 3077, 3432
210 (1.30), 268 427, 482, 507, 526, 605, 632, 652, 11.20 s 5.33 s 1.98 s 6.06 t
7.36 7.29 m
(1.01)
702, 726, 744, 777, 800, 818, 858,
880, 921, 981, 1050, 1090, 1194,
1374, 1389, 1409, 1452, 1470,
1493, 1512, 1605, 1669, 1697,
1717, 2806, 2830, 2850, 2886,
2937, 2975, 3005, 3066, 3084,
3185, 3291, 3410
(1H, J 4.9) (5H), 4.02 d
(2H, J 4.9)
IIId
208 (1.63), 231 428, 492, 508, 530, 593, 618, 635, 11.38 s 5.60 s 2.11 s 8.67 s (1H) 7.21 t (2H,
(1.46), 262 (1.42) 692, 704, 758, 850, 872, 895, 965,
975, 1027, 1035, 1081, 1179, 1198,
1250, 1373, 1392, 1444, 1457,
1496, 1424, 1600, 1677, 1698,
1716, 2793, 2822, 2885, 3019,
3129, 3276, 3289, 3400
J 7.3), 6.83 t
(1H, J 7.3),
6.64 d (2H,
J 7.3)
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2154
YUSKOVETS et al.
Table 3. (Contd.)
1H NMR spectrum (DMSO-d6), , ppm (J, Hz)
N3H C5H R1
Me
UV spectrum
(EtOH), max, nm
104)
Comp.
no.
1
IR spectrum (KBr), , cm
R
(
IIIe
207 (1.63), 229 432, 511, 525, 546, 565, 593, 628, 11.28 s 5.49 d 2.10 s 7.93 s (1H) 7.04 d (2H,
(0.88), 264 (0.93) 639, 673, 719, 754, 784, 857, 935,
977, 1001, 1041, 1079, 1111, 1154,
1184, 1200, 1215, 1252, 1304,
1387, 1430, 1444, 1462, 1486,
1519, 1590, 1609, 1663, 1705,
1897, 1933, 1957, 2060, 2177,
2397, 2466, 2610, 2773, 2943,
2816, 3035, 3085, 3179, 3322, 3431
(J 1.2)
J 7.3),
7.00 d.t (1H,
J 0.8, 7.8),
6.74 d.t (1H,
J 0.7, 7.8),
6.30 d (1H,
J 7.8), 2.16 s
(3H)
IIIf
207 (1.79), 257 414, 431, 496, 516, 526, 554, 582, 11.53 s 5.66 s 2.08 s 9.70 s (1H) 8.11 d (2H,
(0.96), 334 (1.26) 628, 656, 693, 714, 753, 824, 850,
878, 978, 1000, 1049, 1081, 1112,
1181, 1204, 1216, 1279, 1311,
1343, 1377, 1390, 1405, 1426,
1459, 1491, 1501, 1546, 1594,
1672, 1725, 1923, 1958, 3081,
3146, 3292, 3434
J 9.1),
6.83 d (2H,
J 9.1)
IIIg
207 (2.16), 212 424, 454, 483, 527, 557, 567, 578, 11.15 s 5.44 s 2.28 s 8.22 s (1H) 7.31 s (2H)
(1.95), 263 (0.81) 630, 694, 719, 735, 749, 766, 798,
811, 826, 856, 883, 909, 982, 1004,
1041, 1080, 1140, 1182, 1214,
1231, 1258, 1272, 1383, 1404,
1449, 1462, 1503, 1569, 1609,
1680, 1728,1968, 2810, 2834, 2847,
2932, 3009, 3063, 3089, 3152,
3211, 3290, 3434
IIIh
207 (1.92), 267 422, 450, 508, 571, 622, 655, 691, 11.57 s 5.51 s 2.09 s
7.32 7.37 m
(4H), 7.05
7.10 m (6H)
(1.19)
707, 750, 761, 826, 882, 893, 910,
919, 962, 980, 1000, 1030, 1037,
1050, 1169, 1181, 1079, 1156,
1222, 1272, 1323, 1368, 1377,
1390, 1421, 1439, 1459, 1493,
1589, 1625, 1686, 1712, 2975,
3074, 3217, 3406
IIIi
IIIj
211 (1.93), 237 406, 433, 517, 536, 554, 574, 693, 11.45 s 5.42 s 1.87 s 7.34 7.40 m (4H), 7.30
(1.75), 267 (1.32) 704, 716, 754, 773, 821, 879, 898,
978, 1028, 1041, 1081, 1201, 1212,
1276, 1372, 1413, 1454, 1464,
1494, 1583, 1597, 1616, 1666,
1727, 1975, 2341, 2361, 2802,
2823, 2852, 2915, 3006, 3131, 3435
7.33 d.d (1H), 7.25 7.30 d.t
(2H), 7.91 t (1H, J 7.5),
6.78 d (2H, J 7.5), 5.08 d
(1H, J 11.8), 4.66 d (1H,
J 11.8)
207 (2.45), 253 407, 425, 504, 533, 557, 573, 655, 11.08 s 5.52 s 2.23 s 7.59 7.64 t (3H), 7.43
(1.13), 275 (1.31), 667, 694, 727, 746, 767, 777, 795,
7.52 m (5H), 7.22 7.26 d.d
(2H)
320 (0.39)
809, 843, 880, 970, 1001, 1038,
1080, 1175, 1303, 1320, 1373,
1406, 1431, 1444, 1463, 1490,
1561, 1653, 1711, 1969, 2343,
2362, 2787, 2854, 2925, 3029,
3176, 3423
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AZINES AND AZOLES: CXXV.
2155
Table 3. (Contd.)
1H NMR spectrum (DMSO-d6), , ppm (J, Hz)
UV spectrum
(EtOH), max, nm
104)
Comp.
no.
1
IR spectrum (KBr), , cm
N3H
C5H
Me
R
R1
(
IIIk
209 (2.19), 259 428, 492, 529, 556, 625, 652, 737, 11.22 s 5.42 s 2.04 s 10.44 s
2.01 s (3H)
(2.75)
753, 841, 897, 946, 982, 1000,
1014, 1027, 1043, 1089, 1111,
1228, 1243, 1278, 1370, 1400,
1435, 1466, 1519, 1627, 1686,
1708, 1970, 2195, 2300, 2419,
2451, 2496, 2812, 2839, 2897,
2923, 3005, 3095, 3274
(1H)
IIIl
210 (2.01), 261 419, 442, 512, 559, 573, 598, 614, 11.76 s 5.74 s 2.02 s
2.35 s (6H)
(2.65)
636, 656, 687, 733, 755, 859, 895,
945, 975, 1003, 1032, 1043, 1057,
1084, 1198, 1236, 1293, 1370,
1383, 1406, 1439, 1460, 1493,
1626, 1672, 1724, 1736, 1954,
2092, 2181, 2410, 2832, 2890,
2934, 3029, 3453
IIIm
208 (0.84), 259 426, 508, 528, 578, 652, 657, 734, 11.39 s 5.54 s 1.99 s 10.57 s
2.23 m (2H),
1.58 m (2H),
0.91 t (3H,
J 7.3)
(0.94)
752, 789, 814, 849, 872, 902, 958,
984, 1010, 1036, 1050, 1086, 1115,
1186, 1236, 1279, 1376, 1396,
1456, 1504, 1625, 1671, 1731,
1967, 2192, 2249, 2295, 2419,
2632, 2789, 2873, 2932, 2963,
3210, 3448
(1H)
IIIn
IIIo
206 (2.09), 231 433, 540, 606, 690, 706, 796, 877, 11.50 s 5.64 s 2.08 s 11.22 s
7.93 d (2H,
J 7.9), 7.65 t
(1H, J 7.9),
7.56 d (2H,
J 8.4)
(1.59)
908, 923, 932, 1001, 1030, 1075,
1120, 1160, 1284, 1308, 1449,
1487, 1536, 1579, 1605, 1632,
1671, 1805, 1902, 1960, 2999,
3052, 3160, 3201, 3426
(1H)
211 (2.07), 241 407, 427, 484, 526, 541, 565, 597, 11.25 s 5.47 s 2.13 s 10.42 s
(1.11), 258 (1.31), 632, 650, 668, 698, 721, 751, 788, (1H)
7.88 d.d (1H,
J 7.9, 1.9),
7.50 7.54 m
(1H), 7.12 d
(1H, J 8.4),
7.06 t (1H,
J 7.5), 3.98 s
(3H)
299 (0.42)
813, 826, 892, 915, 985, 1012,
1044, 1115, 1162, 1184, 1240,
1258, 1296, 1388, 1418, 1466,
1480, 1498, 1603, 1678, 1732,
2815, 2854, 2930, 2953, 3012,
3221, 3436
IIIp
214 (2.20), 257 419, 447, 469, 507, 523, 553, 577, 11.32 s 5.50 s 2.11 s 11.04 s
7.52 d (1H,
J 7.7),
(1.58), 296 (0.36) 628, 673, 685, 727, 743, 757, 781,
802, 836, 870, 887, 903, 928, 945,
968, 1040, 1086, 1096, 1229, 1298,
1322, 1382, 1398, 1435, 1454,
1484, 1507, 1580, 1610, 1629,
1667, 1685, 1726, 2406, 2600,
3070, 3212
(1H)
7.47 d (1H,
J 1.5), 7.39 t
(1H, J 7.7),
7.11 d.d (1H,
J 7.7, 1.5),
3.86 s (3H)
RUSSIAN JOURNAL OF GENERAL CHEMISTRY Vol. 77 No. 12 2007

2156
YUSKOVETS et al.
Table 3. (Contd.)
1H NMR spectrum (DMSO-d6), , ppm (J, Hz)
UV spectrum
(EtOH), max, nm
104)
Comp.
no.
1
IR spectrum (KBr), , cm
N3H
C5H
Me
R
R1
(
IIIq
IIIr
IIIs
IIIt
207 (1.87), 258 412, 427, 446, 490, 517, 547, 558, 11.34 s 5.51 s 2.11 s 11.21 s
8.12 d (1H,
J 1.6),
7.94 d (1H,
J 7.7),
7.74 d (1H,
J 7.7), 7.46 t
(1H, J 7.7)
(0.89)
627, 645, 656, 675, 712, 743, 761,
811, 829, 884, 929, 1041, 1051,
1067, 1081, 1157, 1202, 1219,
1241, 1275, 1304, 1371, 1386,
1406, 1426, 1435, 1450, 1547,
1631, 1680, 1732, 2844, 2976,
3040, 3187, 3433
(1H)
205 (1.95), 227 429, 477, 513, 532, 555, 577, 589, 11.50 s 5.62 s 2.05 s 11.12 s
7.99 s (1H),
7.35 d (1H,
J 3.3),
6.73 d.d
(1H, J 3.3,
1.5)
(1.70), 274 (0.65) 661, 730, 750, 765, 797, 879, 933,
979, 1012, 1047, 1067, 1093, 1157,
1227, 1288, 1376, 1391, 1459,
1466, 1500, 1588, 1648, 1655,
1701, 1730, 1734, 1970, 2191,
2414, 2784, 2923, 2973, 3159,
3296, 3420
(1H)
204 (1.59), 226 428, 442, 503, 519, 534, 632, 653, 11.29 s 5.45 s 2.03 s 10.81 s
7.26 d (1H,
J 8.9),
7.01 d (1H,
J 8.9),
4.73 d (1H,
J 15.2),
4.68 d (1H,
J 15.2)
(1.43), 259 (1.17) 665, 704, 757, 799, 824, 841, 874,
893, 956, 983, 1006, 1072, 1092,
1102, 1169, 1242, 1280, 1410,
1437, 1465, 1489, 1509, 1585,
1596, 1622, 1699, 1717, 1739,
2830, 2853, 2901, 2923, 3011,
3086, 3126, 3335
(1H)
205 (1.50), 270 419, 435, 488, 499, 511, 542, 600, 11.51
(0.91), 297 (1.12) 620, 638, 654, 720, 745, 775, 817, br.s
890, 916, 937, 1229, 1258, 1287,
1312, 1410, 1431, 1464, 1489,
1518, 1557, 1594, 1620, 1684,
1707, 1746, 2805, 2835, 2850,
2899, 2923, 2939, 3013, 3135,
3300, 3450
5.65 s 2.81 s 11.37 br.s 8.03 d (2H,
(2H)
J 7.8),
7.60 d (2H,
J 7.8),
5.69 s (1H),
2.10 s (3H)
7.93 8.67 ppm (R = Ar, Alk). In the 13C NMR spectra
of 1-amino-6-methyluracils IIIa IIIt (Table 4),
or propan-1-ol we obtained the corresponding 2-sub-
stituted 5-methyl-3-oxo-2,3-dihydro-1H-pyrazole-4-
carboxamides Va Vg rather than 1-amino-6-methyl-
uracil derivatives III. A probable mechanism is given
in Scheme 2. The process is also accompanied by
evolution of carbonyl sulfide, but in this case the
C2OS rather than C6OS fragment is likely to be lost
(in contrast to the reaction in boiling DMF). However,
detailed study on the mechanism of this reaction was
not performed in the present work.
carbon nuclei characteristically resonated at
99.4
C
100.4 (C5), 161.8 162.3 (C2), 153.0 156.9 (C4),
149.3 150.6 (C6), and 17.5 18.7 ppm (6-CH3). The
observed chemical shifts are consistent with limited
published data for structurally related compounds
synthesized previously by other methods [2 5].
Our further studies showed that the reaction of
5-acetyl-4-hydroxy-2H-1,3-thiazine-2,6-dione
(Ia)
with monosubstituted alkyl- and arylhydrazines takes
different pathways, depending on the conditions. By
heating equimolar mixtures of the reactants in ethanol
The reaction is quite sensitive to steric and elec-
tronic factore. For example, no pyrazolone derivatives
were formed in the reactions with 2-tolylhydrazine
RUSSIAN JOURNAL OF GENERAL CHEMISTRY Vol. 77 No. 12 2007

AZINES AND AZOLES: CXXV.
2157
Scheme 2.
O
H
Me
OH
NH
O
S
O
Me
HN
NH2
NH
1-PrOH
COS
RNHNH2
Me
N
O
NH
N
R
O
S
O
O
R
O
Va Vg
R = H (a), Me (b), CH2COOEt (c), CH2Ph (d), Ph (e), 4-MeOC6H4 (f), 2-pyridyl (g).
and 2,4,6-trichlorophenylhydrazine: the process
stopped at the stage of formation of the corresponding
hydrazone, while under more severe conditions (boil-
ing DMF) 1-amino-6-methyluracils were obtained.
lone derivative Vg was formed in the reaction of Ia
with 2-pyridylhydrazine.
The structure of compounds Va Vg was confirmed
1
by the data of elemental analysis (Table 5), H and
The presence of a nitro group in the para position
of phenylhydrazine reduces nucleophilicity of the NH
nitrogen atom so that pyrazole ring closure does not
occur, and the product is the corresponding hydrazone
which is converted into 1-amino-6-methyluracil under
drastic conditions. By contrast, nucleophilicity of the
NH nitrogen atom in 4-methoxyphenylhydrazine is so
high that the formation of pyrazolone Vf becomes the
only reaction direction (no 1-aminouracil is formed
even on heating in boiling DMF). Likewise, pyrazo-
13C NMR, UV, and IR spectroscopy, and mass spec-
trometry. The mass spectra of 2-substituted 5-methyl-
3-oxo-2,3-dihydro-1H-pyrazole-4-carboxamides Va
Vg (Table 6) contained the molecular ion peaks and
peaks from the [M
elimination of hydroxyl. In the H NMR spectra of
17]+ ions resulting from
1
Va Vg in CDCl3 DMSO-d6 (10:1) (Table 7), the NH
proton in the pyrazole ring resonated at
11.46
12.43 ppm as a broadened singlet, and two slightly
Table 4. 13C NMR spectra of 1-amino-6-methyluracils IIIa IIIt in DMSO-d6, C, ppm
Comp.
no.
C2
C4
C5
C6
Me
R
IIIa
IIIb
IIIc
IIId
IIIe
IIIf
IIIg
IIIh
IIIi
162.2
162.3
162.15 156.5
156.0
156.8
99.2
99.4
99.1
99.9
150.9
150.1
151.1
150.6
18.1 36.7
18.7 42.8
18.4 136.9, 129.2, 128.3, 127.5, 53.2
17.9 147.3, 129.1, 120.0, 111.9
17.8 144.7, 130.4, 126.8, 122.0, 119.9, 109.8, 17.0
17.6 153.1, 139.8, 125.8, 111.3
19.2 138.3, 129.0, 128.8, 124.9
162.2
162.2
162.1
162.1
162.0
162.0
161.9
162.1
161.8
162.2
162.2
162.2
156.9
156.9
155.9
156.8
156.1
156.7
153.0
155.4
153.7
153.3
99.96 150.5
100.7
100.1
101.5
100.1
99.1
99.6
101.8
99.8
150.2
150.2
150.0
149.9
146.3
149.7
149.5
149.7
17.8 143.5, 129.4, 123.1, 118.0
18.1 147.9, 135.65, 129.3, 129.0, 128.5, 127.8, 120.3, 112.7, 55.1
18.5 178.3, 135.4, 133.9, 132.2, 129.8, 128.8, 128.6, 128.1, 127.4
17.5 169.4, 20.0
17.1 170.5, 24.2
17.5 172.3, 34.7, 18.1, 13.3
17.5 166.2, 132.65, 131.0, 128.7, 127.6
17.7 164.9, 157.5, 133.7, 130.7, 120.6, 119.8, 112.2, 56.0
17.5 165.9, 159.3, 132.2, 129.9, 119.8, 118.5, 112.7, 55.3
17.5 164.8, 135.4, 133.1, 131.0, 130.2, 126.8, 121.9
17.55 157.2, 146.6, 144.8, 116.4, 112.2
17.5 167.8, 156.2, 129.2, 125.2, 116.6, 66.1
17.5 165.5, 162.7, 153.1, 151.15, 140.35, 131.4, 129.68, 129.63,
128.8, 128.62, 101.1, 20.25
IIIj
IIIk
IIIl
IIIm
IIIn
IIIo
IIIp
IIIq
IIIr
IIIs
IIIt
155.45 100.15 149.8
155.6
99.8
100.2
100.2
100.16 149.7
100.1
100.2
149.6
149.8
149.7
162.15 155.4
162.1
162.1
162.1
162.1
155.3
155.4
155.1
155.3
149.4
149.7
RUSSIAN JOURNAL OF GENERAL CHEMISTRY Vol. 77 No. 12 2007

2158
YUSKOVETS et al.
Table 5. Yields, melting points, Rf values, and elemental analyses of 2-substituted 5-methyl-3-oxo-2,3-dihydro-1H-pyra-
zole-4-carboxamides Va Vg
Found, %
H
Calculated, %
H
Comp. Yield,
Rf (acetone
hexane, 2: 1)
mp,
C
Formula
no.
%
C
N
C
N
Va
Vb
Vc
Vd
Ve
Vf
68
65
72
83
74
82
73
261 263
278 279
96 98
217 218
227 228
207 209
256 257
0.26a
0.37
0.44
0.33
0.29
0.31
0.17a
42.47
46.41
47.65
62.25
60.87
58.47
55.16
4.99
5.86
5.77
5.68
5.09
5.29
4.63
29.79
27.13
18.52
18.13
19.31
16.97
25.65
C5H7N3O2
C6H9N3O2
42.55
46.45
47.57
62.33
60.82
58.29
55.04
5.00
5.85
5.77
5.67
5.10
5.30
4.62
29.77
27.08
18.49
18.17
19.34
16.99
25.68
C9H13N3O4
C12H13N3O2
C11H11N3O2
C12H13N3O3
C10H10N4O2
Vg
a
Benzene acetic acid, 10:1.
Table 6. Mass spectra of 2-substituted 5-methyl-3-oxo-2,3-dihydro-1H-pyrazole-4-carboxamides Va Vg
Comp.
no.
m/z (Irel, %)
Va
Vb
Vc
Vd
141 M+ (53), 124 (100), 67 (30), 56 (44), 44 (12), 39 (12)
155 M+ (78), 138 (100), 96 (42), 67 (47), 56 (6), 44 (15), 39 (12)
227 M+ (10), 210 (34), 154 (5), 137 (100), 124 (4), 69 (45), 67 (14), 42 (27)
231 M+ (32), 214 (26), 186 (20), 172 (7), 158 (12), 145 (4), 137 (5), 117 (6), 105 (6), 104 (8), 91 (100), 89 (3),
84 (5), 77 (6), 67 (16), 65 (20), 55 (7), 44 (10)
Ve
Vf
Vg
217 M+ (24), 200 (100), 132 (27), 103 (5), 91 (98), 77 (25), 67 (20), 51 (18), 44 (15)
247 M+ (4), 232 (100), 217 (31), 215 (10), 204 (9), 189 (11), 147 (6), 134 (7), 122 (10), 107 (8), 92 (7), 80 (9)
218 M+ (7), 175 (100), 160 (20), 134 (24), 118 (4), 119 (4), 93 (6), 79 (27), 52 (9), 52 (9), 44 (9)
1
Table 7. UV, IR, and H NMR spectra of 2-substituted 5-methyl-3-oxo-2,3-dihydro-1H-pyrazole-4-carboxamides Va Vg
1H NMR spectrum (DMSO-d6), , ppm (J, Hz)
UV spectrum
Comp.
no.
1
(EtOH),
,
IR spectrum (KBr), , cm
max
nm ( 104)
NH
CONH2
Me
R
Va
Vb
Vc
207 (1.11), 412, 467, 592, 635, 670, 718, 783, 11.50 br.s 6.94 br.s (2H) 2.32 s
262 (0.70)
988, 1052, 1125, 1175, 1265, 1369,
1385, 1406, 1430, 1543, 1578,
1630, 1648, 2520, 2924, 2963,
3252, 3305, 3405
205 (1.10), 445, 544, 603, 642, 721, 736, 787, 11.46 br.s 6.85 br.s,
225 (0.84), 870, 1038, 1124, 1193, 1280, 1347, 6.78 br.s (2H)
2.39 s 3.51 s (3H)
241 (0.82)
1372, 1407, 1455, 1506, 1576,
1630, 1651, 2516, 2577, 2754,
2814, 2944, 3192, 3311, 3447
209 (1.44), 420, 520, 594, 643, 679, 755, 794, 12.43 br.s 7.74 br.s (1H), 2.37 s 4.56 s (2H), 4.15 q
262 (0.91) 881, 925, 957, 1023, 1051, 1090,
1111, 1220, 1237, 1308, 1342,
6.85 br.s (1H)
(2H, J 7.1), 1.20 t
(3H, J 7.1)
1392, 1426, 1542, 1581, 1626,
1746, 2595, 2734, 2921, 2973,
3300,
3322,
3405,
3548
RUSSIAN JOURNAL OF GENERAL CHEMISTRY Vol. 77 No. 12 2007

AZINES AND AZOLES: CXXV.
2159
Table 7. (Contd.)
1H NMR spectrum (DMSO-d6), , ppm (J, Hz)
NH CONH2 Me
UV spectrum
(EtOH),
nm ( 104)
Comp.
no.
1
,
IR spectrum (KBr), , cm
max
R
Vd
210 (1.75), 444, 521, 557, 698, 741, 751, 822, 12.07 br.s 8.20 br.s (1H), 2.36 s 7.19 7.28 m (5H),
262 (0.57), 838, 852, 894, 1072, 1101, 1156, 5.64 br.s (1H) 4.91 s (2H)
300 (1.15)
1219, 1331, 1358, 1371, 1407, 1415,
1429, 1440, 1457, 1466, 1496,
1567, 1607, 1631, 1675, 2839,
3007, 3037, 3064, 3170, 3450
Ve
208 (1.49), 407, 423, 461, 499, 579, 615, 652, 12.33 br.s 8.14 br.s (1H), 2.48 s 7.55 7.62 m (2H),
248 (1.77)
694, 750, 768, 789, 839, 909, 999,
1040, 1092, 1119, 1211, 1240,
1304, 1350, 1369, 1412, 1502,
1542, 1574, 1630, 1650, 1797,
1874, 1954, 2924, 3078, 3241,
3286, 3367
5.85 br.s (1H)
7.34 7.39 m (2H),
7.17 7.21 m (1H)
Vf
206 (1.88), 519, 588, 595, 682, 690, 754, 788, 12.75 br.s 7.88 br.s (1H), 2.44 s 7.53 d (2H, J 9.0),
229 (1.15), 829, 853, 910, 1023, 1100, 1174,
6.95 br.s (1H)
7.05 d (2H, J 9.0),
252 (1.35)
1215, 1255, 1301, 1370, 1410,
1426, 1455, 1509, 1536, 1583,
1593, 1616, 1645, 1672, 2037,
2765, 2934, 3013, 3291, 3400
3.78 s (3H)
Vg
204 (1.80), 443, 478, 513, 562, 607, 672, 707, 13.35 br.s 7.74 br.s (1H), 2.49 s 8.45 d (1H, J 4.7),
245 (2.04), 760, 845, 904, 1007, 1065, 1086,
7.00 br.s (1H)
8.37 d (1H, J 8.4),
7.96 d.t (1H, J 1.7,
6.9), 7.26 7.30 m
(1H)
289 (1.30)
1131, 1162, 1212, 1304, 1342,
1400, 1502, 1424, 1462, 1481,
1514, 1586, 1641, 3101, 3128,
3298, 3403
Table 8. 13C NMR spectra of 2-substituted 5-methyl-3-oxo-2,3-dihydro-1H-pyrazole-4-carboxamides Va Vg in
DMSO-d6, C, ppm
Comp. no.
C5
C4
C3
CONH2
Me
R
Va
Vb
Vc
Vd
Ve
Vf
165.2
164.7
167.5
165.0
164.9
164.9
164.4
97.3
97.6
96.7
97.0
97.2
97.3
97.5
144.1
142.6
148.3
147.6
150.0
148.9
150.5
160.8
158.5
162.1
161.8
161.3
160.8
160.9
11.6
10.3
12.1
12.0
12.5
12.3
12.1
34.8
164.8, 61.1, 44.1, 13.9
136.4, 128.5, 128.4, 127.9, 45.96
136.1, 128.9, 125.5, 119.9
157.4, 128.7, 122.7, 114.2, 55.3
147.4, 147.2, 139.3, 120.7, 111.6
Vg
broadened singlets (overlapped in some cases) were
present at 5.64 8.20 ppm due to protons in the
amide group. Also, a singlet at 2.32 2.48 ppm
(5-CH3) and signals belonging to protons in the sub-
stituent on N1 were observed. The spectra were re-
corded from solutions in a 10:1 CDCl3 DMSO-d6
mixture, taking into account that pyrazolones V are
insoluble in CDCl3, while the spectral patterns ob-
tained from solutions in pure DMSO-d6 were con-
siderably impaired: the NH signal was broadened so
strongly that it merged into the baseline, signals from
the amide protons were also strongly broadened and
partially or completely overlapped by signals from
protons in the aromatic substituent on the nitrogen
RUSSIAN JOURNAL OF GENERAL CHEMISTRY Vol. 77 No. 12 2007

2160
YUSKOVETS et al.
atom, and the 5-Me singlet was generally obscured
by the quintet from residual protons in the solvent.
acid and stirred for 30 min, and the precipitate was
filtered off, washed with 200 ml of water, dried in air,
and recrystallized from benzene. It is advisable to use
a Soxhlet apparatus for crystallization. Yield 100 g
(69%), mp 198 200 C. The product sublimed ap-
preciably at the melting point.
The 13C NMR spectra of 2-substituted 5-methyl-3-
oxo-2,3-dihydro-1H-pyrazole-4-carboxamides Va Vg
in DMSO-d6 (Table 8) contained signals from the
methyl carbon atom ( 10.3 12.5 ppm), amide car-
C
bonyl group ( 158.5 162.1 ppm) and C3, C4, and C5
in the pyrazoCle ring (
142.6 150.0, 96.7 97.6,
N-Substituted 1-amino-6-methyluracils IIIa IIIj
(general procedure) (Table 1). A mixture of 1 g of
5-acetyl-4-hydroxy-2H-1,3-thiazine-2,6-dione (Ia) and
5.5 mmol of mono- or N,N-disubstituted hydrazine in
10 ml of dimethylformamide was kept for 15 min at
18 25 C and was then heated as quickly as possible
to the boiling point and maintained boiling until the
reaction was complete (0.5 1 h, TLC). Vigorous
evolution of carbonyl sulfide with a characteristic
odor was observed during the process, and the DMF
condensate usually had greenish-blue color. The
solvent was distilled off on a rotary evaporator, and
the residue was recrystallized from propan-2-ol.
164.7 167.5 ppm, respecCtively). Compound Va Vg
showed in the IR spectra (KBr) absorption bands
corresponding to stretching vibrations of the NH
1
(3025 3260 cm ) and C=O groups (1655 1670 and
1
1705 1715 cm ) (Table 7). Their UV spectra re-
corded from solutions in 96.5% ethanol (Table 7)
were characterized by the presence of two absorption
maxima at
260 262 and 207 208 nm.
EXPERIMENTAL
The mass spectra (electron impact, 70 eV) were
recorded on an MKh-1321 mass spectrometer. The
1H and 13C NMR spectra were measured on a Bruker
AM-500 instrument at 500 and 125 MHz, respectively,
from solutions in DMSO-d6 or CDCl3. The IR spectra
were recorded in KBr on an FSM 1201 spectrometer
with Fourier transform. The UV spectra of solutions
in 96.5% ethanol were obtained on an SF-2000 spec-
trophotometer (cell path length 1 cm). The progress
of reactions and the purity of products were monitored
by TLC using Sorbfil® plates. The melting points
were determined in capillaries and were not corrected.
The yields, melting points, and elemental analyses of
compounds IIIa IIIt and Va Vg are given in
Tables 1 and 5.
1-Acylamino-6-methyluracils IIIk IIIt (general
procedure) (Table 1). A mixture of 1 g of 5-acetyl-4-
hydroxy-2H-1,3-thiazine-2,6-dione (Ia) and 5.5 mmol
of the corresponding carboxylic acid hydrazide in
15 ml of dimethylformamide was heated under reflux
until the reaction was complete (0.5 1 h, TLC).
Vigorous evolution of carbonyl sulfide was observed
during the process. The solvent was distilled off on a
rotary evaporator, and the residue was recrystallized
from ethanol or propan-2-ol.
2-Substituted 5-methyl-3-oxo-2,3-dihydro-1H-
pyrazole-4-carboxamides Va Vg (general proce-
dure) (Table 5). A mixture of 1 g of 5-acetyl-4-hy-
droxy-2H-1,3-thiazine-2,6-dione (Ia), 5.34 mmol of
monosubstituted hydrazine, and 15 ml of propan-1-ol
was heated under reflux until the reaction was com-
plete (1 2 h, TLC). Vigorous evolution of carbonyl
sulfide was observed during the process. The solvent
was distilled off on a rotary evaporator, and the
residue was recrystallized from chloroform ethanol.
5-Acetyl-4-hydroxy-2H-1,3-thiazine-2,6-dione
(Ia). The synthesis was carried out in a 2000-ml
beaker. Dry malonic acid, 80 g, was mixed with
180 ml of acetic anhydride, and 400 ml of glacial
acetic acid was added under vigorous stirring. The
mixture was stirring until it became homogeneous (the
solution appreciable cooled down), and 85 g of dry
finely powdered potassium isothiocyanate was added
in one portion under stirring, maintaining the tem-
perature at 25 30 C (a slight heat evolution was ob-
served) by cooling with water. Immediately after ad-
dition of KSCN, the solution turned violet, and it then
changed to goldish yellow (in 15 20 min) and grad-
ually turned red. The mixture was stirred for 4 5 h at
room temperature, and the product began to abun-
dantly crystallize from the solution. The mixture was
stirred for 2 3 h more and was left to stand for 72 h at
20 C. The mixture was diluted with a mixture of
1000 ml of water and 200 ml of 35% hydrochloric
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