5ꢀAroylmethylpyrazoles and their hydrazones
Russ.Chem.Bull., Int.Ed., Vol. 55, No. 5, May, 2006
901
Difluoroboron chelate of 5ꢀdimethylaminoꢀ1ꢀ(4ꢀmethoxyꢀ
phenyl)pentꢀ4ꢀeneꢀ1,3ꢀdione (3c). The yield was 91%, m.p.
222—223 °C. Found (%): C, 56.95; H, 5.49; N, 4.80.
C14H16BF2NO3. Calculated (%): C, 56.98; H, 5.47; N, 4.75.
MS, m/z (Irel (%)): 295 [M]+ (91), 251 [M – NMe2]+ (81).
1H NMR (CDCl3), δ: 3.00, 3.24 (both s, 3 H each, N—Me);
3.87 (s, 3 H, OMe); 5.03, 8.05 (both d, 1 H each, CH=, J =
12.2 Hz); 6.06 (s, 1 H, CH=); 6.93, 7.91 (both d, 2 H each, Ar,
J = 8.8 Hz). IR, ν/cm–1: 1652, 1588, 1504.
was filtered off and recrystallized from little amount of ethyl
acetate to give aroylmethylpyrazoles 9, 10, and 11a,b.
1ꢀ(Benzoimidazolꢀ2ꢀyl)ꢀ5ꢀphenacylpyrazole (9). The yield
was 47%, m.p. 180—181 °C. Found (%): C, 71.18; H, 4.98;
N, 18.72. C18H14N4O. Calculated (%): C, 71.51; H, 4.67;
N, 18.53. MS, m/z (Irel (%)): 302 [M]+ (46), 274 (12). 1H NMR
(DMSOꢀd6), δ: 5.06 (s, 2 H, CH2); 6.54 (s, 1 H, H(4) pyraz.);
7.85—7.09 (m, 8 H, Ph, H(3) pyraz.); 8.02 (d, 2 H, oꢀPh, J =
7.3 Hz); 12.92 (s, 1 H, NH). IR, ν/cm–1: 3360, 3140, 2912,
1700, 1632, 1592, 1568, 1556.
Difluoroboron chelate of 5ꢀdimethylaminoꢀ1ꢀ(4ꢀmethoxyꢀ
phenyl)hexꢀ4ꢀeneꢀ1,3ꢀdione (4c). The yield was 87%, m.p.
253—254 °C. Found (%): C, 58.25; H, 5.93; N, 4.55.
1ꢀ(Benzothiazolꢀ2ꢀyl)ꢀ5ꢀphenacylpyrazole (10). The yield was
45%, m.p. 188—189 °C. Found (%): C, 67.18; H, 4.15; N, 13.13.
C
15H18BF2NO3. Calculated (%): C, 58.28; H, 5.87; N, 4.53.
C18H13N3OS. Calculated (%): C, 67.69; H, 4.10; N, 13.16. MS,
MS, m/z (Irel (%)): 309 [M]+ (22), 265 [M – NMe2]+ (26).
1H NMR (DMSOꢀd6), δ: 2.58 (s, 3 H, Me); 3.19, 3.21 (both s,
3 H each, N—Me); 3.82 (s, 3 H, OMe); 5.27, 6.38 (both s,
1 H each, CH=); 7.05, 7.80 (both d, 2 H each, Ar, J = 8.8 Hz).
IR, ν/cm–1: 1616, 1570, 1508.
m/z (Irel (%)): 319 [M]+ (18). 1H NMR (DMSOꢀd6), δ: 5.04 (s,
2 H, CH2); 6.43 (s, 1 H, H(4) pyraz.); 7.05 (m, 1 H, H(3)
pyraz.); 8.09—7.32 (m, 9 H, Ar). 13C NMR (DMSOꢀd6), δ: 37.3
(CH2); 112.3, 121.5, 122.7, 124.9, 126.5, 128.1, 128.7, 132.2,
133.1, 137.0, 139.2, 143.0, 150.5, 160.6, 195.3 (C=O). IR,
ν/cm–1: 3096, 2920, 1676, 1600, 1568, 1540.
Reactions of difluoroboron chelates 3a—c and 4c with phenylꢀ
hydrazine (general procedure). A mixture of chelate 3a—c or 4c
(1 mmol) and phenylhydrazine (2 mmol) was refluxed in pyriꢀ
dine (15 mL) for 4—5 h. The solvent was removed, chloroform
was added, and the mixture was filtered through a thin layer of
silica gel and concentrated. Recrystallization from benzene gave
pyrazoles 5a—c and 6 as white or creamꢀcolored powders.
1ꢀPhenylꢀ5ꢀ[2ꢀphenylꢀ2ꢀ(phenylhydrazono)ethyl]pyrazole
(5a). The yield was 67%, m.p. 177—178 °C. Found (%): C, 78.24;
H, 5.65; N, 16.18. C23H20N4. Calculated (%): C, 78.38; H, 5.72;
N, 15.90. MS, m/z (Irel (%)): 352 [M]+ (100), 260 [M – HNPh]+
(85). 1H NMR (DMSOꢀd6), δ: 4.22 (s, 2 H, CH2); 5.96 (d, 1 H,
H(4) pyraz., J = 1.2 Hz); 6.80 (br.s, 1 H, H(3) pyraz.); 7.68—7.15
(m, 15 H, Ar); 9.62 (s, 1 H, NH). IR, ν/cm–1: 3260, 3052, 1600,
1584, 1560.
3ꢀMethylꢀ1ꢀphenylꢀ5ꢀ[2ꢀphenylꢀ2ꢀ(phenylhydrazoꢀ
no)ethyl]pyrazole (6). The yield was 32%, m.p. 160—161 °C.
Found (%): C, 78.56; H, 6.22; N, 15.46. C24H22N4. Calcuꢀ
lated (%): C, 78.66; H, 6.05; N, 15.29. MS, m/z (Irel (%)):
366 [M]+ (28), 274 [M – HNPh]+ (35). 1H NMR (DMSOꢀd6),
δ: 2.08 (s, 3 H, Me); 4.18 (s, 2 H, CH2); 5.73 (s, 1 H,
H(4) pyraz.), 7.67—7.15 (m, 15 H, Ar); 9.69 (s, 1 H, NH). IR,
ν/cm–1: 3276, 3052, 1604, 1588, 1548.
1ꢀ(Benzothiazolꢀ2ꢀyl)ꢀ3ꢀmethylꢀ5ꢀphenacylpyrazole (11a).
The yield was 32%, m.p. 182—183 °C. Found (%): C, 67.97;
H, 4.74; N, 12.56. C19H15N3OS. Calculated (%): C, 68.45;
H, 4.53; N, 12.60. MS, m/z (Irel (%)): 333 [M]+ (48), 187 (22).
1H NMR (DMSOꢀd6), δ: 2.29 (s, 3 H, Me); 5.00 (s, 2 H, CH2);
6.45 (s, 1 H, H(4) pyraz.); 8.09—7.04 (m, 9 H, Ar). IR, ν/cm–1
:
3024, 2916, 1696, 1604, 1580, 1540.
1ꢀ(Benzothiazolꢀ2ꢀyl)ꢀ5ꢀ(4ꢀchlorobenzoyl)methylꢀ3ꢀmethylꢀ
pyrazole (11b). The yield was 41%, m.p. 175—176 °C. Found (%):
C, 61.88; H, 3.95; N, 11.53. C19H14ClN3OS. Calculated (%):
C, 62.04; H, 3.84; N, 11.42. MS, m/z (Irel (%)): 367 [M]+ (52),
1
187 (17). H NMR (DMSOꢀd6), δ: 2.29 (s, 3 H, Me); 4.96 (s,
2 H, CH2); 6.44 (s, 1 H, H(4) pyraz.); 7.04 (m, 1 H, Ar); 7.30
(m, 2 H, Ar); 7.67 (d, 2 H, Ar, J = 8.5 Hz); 7.97 (m, 1 H, Ar);
8.08 (d, 2 H, Ar, J = 8.5 Hz). IR, ν/cm–1: 3026, 2924, 1684,
1604, 1580, 1540.
1ꢀ(Benzothiazolꢀ2ꢀyl)ꢀ5ꢀ[2ꢀphenylꢀ2ꢀ(phenylhydrazoꢀ
no)ethyl]pyrazole (12). Two drops of glacial acetic acid were
added to a solution of aroylmethylpyrazole 10 (0.32 g, 1 mmol)
and phenylhydrazine (0.2 mL, 2 mmol) in ethyl acetate (10 mL).
The reaction mixture was refluxed for 10 min and cooled
to ~20 °C. The crystals that formed were filtered off and washed
with ether. The yield of compound 12 was 0.29 g (72%), m.p.
184—185 °C (from ethyl acetate). Found (%): C, 70.48; H, 4.61;
N, 16.93. C24H19N5S. Calculated (%): C, 70.39; H, 4.68;
N, 17.10. MS, m/z (Irel (%)): 409 [M]+ (49), 317 [M – HNPh]+
(15), 302 (45). 1H NMR (DMSOꢀd6), δ: 4.80 (s, 2 H, CH2);
6.04 (s, 1 H, H(4) pyraz.); 6.77 (br.s, 1 H, H(3) pyraz.);
8.12—7.15 (m, 14 H, Ar); 9.77 (s, 1 H, NH). IR, ν/cm–1: 3268,
3064, 3032, 1604.
5ꢀ[2ꢀ(4ꢀChlorophenyl)ꢀ2ꢀphenylhydrazono]ethylꢀ1ꢀphenylꢀ
pyrazole (5b). The yield was 60%, m.p. 188—189 °C. Found (%):
C, 71.55; H, 5.05; N, 14.61. C23H19ClN4. Calculated (%):
C, 71.40; H, 4.95; N, 14.48. MS, m/z (Irel (%)): 386 [M]+ (65),
294 [M – HNPh]+ (31). 1H NMR (DMSOꢀd6), δ: 4.24 (s, 2 H,
CH2); 5.92 (d, 1 H, H(4) pyraz., J = 1.2 Hz); 6.78 (br.s, 1 H,
H(3) pyraz.); 7.67—7.21 (m, 14 H, Ar); 9.78 (s, 1 H, NH). IR,
ν/cm–1: 3260, 3052, 1600, 1580, 1556.
5ꢀ[2ꢀ(4ꢀMethoxyphenyl)ꢀ2ꢀphenylhydrazono]ethylꢀ1ꢀphenylꢀ
pyrazole (5c). The yield was 36%, m.p. 171—172 °C. Found (%):
C, 75.28; H, 5.91; N, 14.73. C24H22N4O. Calculated (%):
C, 75.37; H, 5.80; N, 14.65. MS, m/z (Irel (%)): 382 [M]+ (75),
290 [M – HNPh]+ (20), 263 (25). 1H NMR (DMSOꢀd6), δ:
4.20 (s, 2 H, CH2); 5.90 (d, 1 H, H(4) pyraz., J = 1.2 Hz); 6.74
(br.s, 1 H, H(3) pyraz.); 7.67—6.82 (m, 14 H, Ar); 9.58 (s, 1 H,
NH). IR, ν/cm–1: 3256, 3004, 1600, 1540.
Reactions of difluoroboron chelates 3a and 4a,b with benzoꢀ
azolylhydrazines (general procedure). A mixture of chelate 3a or
4a,b (1 mmol) and a benzoazolylhydrazine (2.5 mmol) was reꢀ
fluxed in acetic acid for 3 h. The flaky precipitate that formed
Reactions of difluoroboron chelates 3a—c and 4a,c with hydrꢀ
azine hydrate (general procedure). A suspension of chelates 3a—c
or 4a,c (2 mmol) and hydrazine hydrate (1 mL) in 96% ethanol
(50 mL) was stirred for 3—5 days until the solution became
completely colorless. Then the solvent and the excess of hydrꢀ
azine hydrate were thoroughly removed in vacuo. The resulting
oil was diluted with water (50 mL) and the mixture was refluxed
for 4—5 h. The yellow precipitate that formed was filtered off
and recrystallized from considerable amount of ethanol or ethyl
acetate to give azines 15a—c and 16a,c.
1ꢀPhenylꢀ2ꢀ(pyrazolꢀ3ꢀyl)ethanone azine (15a). The yield
was 70%, m.p. 223—224 °C. Found (%): C, 71.37; H, 5.60;