88
V.I. Saloutin, S.G. Perevalov / Journal of Fluorine Chemistry 96 (1999) 87±93
(2H, q, CH2, J 7.1 Hz); 7.18 (1H, t, CH, JH±F 1.6 Hz);
13.53 (1H, w.s., NH) ppm. 19F NMR (CDCl3) ꢀ: 166.81
(2F, m, meta-); 154.95 (1F, t, para-, J3±4 20.7 Hz);
141.77 (2F, d-d, ortho-, J2±3 20.5; J2±5 6.3 Hz)
ppm. IR (cm 1): 3260, 3130, 3100 (NH); 1695 (C=O, ester);
1560, 1530 (C=C, NH); 980 (CF). Analysis: Found: C,
46.69; H, 2.19; F, 31.47; N, 9.30%. Calc. for C12H7F5N2O2:
C, 47.07; H, 2.30; F, 31.07; N, 9.15%.
stirred at room temperature for 6 h, and then stored for 2
days. The solvent was removed and the residue was
extracted with hot (70±808C) hexane (4 Â 10 ml). The
extract was concentrated, and the residue was re¯uxed with
a mixture of acetic acid (6 ml) and conc. HCl (3 ml). The
solvent was removed to a 5 ml volume and the mixture was
diluted with 50 ml of water. The resulting precipitate was
collected by ®ltration, washed with water to give 0.35 g
(25%) of 4 (m.p. 158±159.58C). 1H NMR (CD3COCD3) ꢀ:
7.28(1H,t,CH,JH±F 1.6 Hz)ppm.19FNMR(CD3COCD3)
2.2.2. Method B
A mixture of compound 1b (1.37 g, 2 mmol) and
N2H4Á2HCl (0.45 g, 4.3 mmol) in 50 ml of MeOH was
stirred at room temperature for 4 h and then re¯uxed for
1 h. The reaction mixture was cooled, diluted with 200 ml of
water. The precipitate was collected by ®ltration, recrys-
tallized twice from a chloroform±hexane mixture to give
0.60 g (49%) of 2. The physicochemical data were identical
to those listed above.
ꢀ: 161.44 (2F, m, meta-); 150.66 (1F, t-t, para-, J3±4
20.7; J2±4 3.7 Hz); 138.03 (2F, m, ortho-) ppm. IR
(cm 1): 3470 (OH), 1715 (C=O, acid), 1655, 1580
(C=C), 1260 (COOH), 1000 (CF). Analysis: Found: C,
42.74; H, 0.62; F, 33.81; N, 4.92%. Calc. for C10H2F5NO3
: C, 43.07; H, 0.72; F, 34.03; N, 5.02%.
2.4.2. Method B
A mixture of compound 1b (1.37 g, 2 mmol) and
NH2OHÁHCl (0.35 g, 5 mmol) in 20 ml of MeOH was
re¯uxed for 8 h, cooled, and then 30 ml of aqueous HCl
(5%) was added to the mixture, stirred at room temperature
for 1 h. The resulting mixture was extracted with CHCl3
(3 Â 20 ml). The chloroform layer was evaporated to dry-
ness. The residue was eÂtracted with hot (70±808C) heptane
(4 Â 10 ml). The heptane extract was evaporated to dryness
and resulting residue was hydrolyzed as described above in
method A to give 0.34 g (30.5%) of 4. The physicochemical
data were identical to those listed in method A.
2.2.3. Method C
A powder of compound 1b (1.37 g, 2 mmol) was added
into a cold mixture of N2H4Á2HCl (0.42 g, 4 mmol) and
NaOH (0.16 g, 4 mmol) in 30 ml of EtOH. The reaction
mixture was stirred at room temperature for 4 h and at 708C
for 1 h and then was cooled, diluted with 60 ml of water. The
precipitate was collected, recrystallized twice from a
chloroform±hexane mixture to give 0.58 g (47%) of 2.
The physicochemical data were identical to those listed
in method A.
2.3. Synthesis of 1-phenyl-5-pentafluorophenyl-3-
ethoxycarbonylpyrazole (3)
2.5. Synthesis of 3-pentafluorobenzoylmethylenepiperazin-
2-one (5)
A mixture of compound 1a (1.55 g, 5 mmol) and phe-
nylhydrazine (0.65 g, 6.6 mmol) in 25 ml of MeOH was
stirred at room temperature for 6 h, and then allowed to
stand overnight. The solvent was removed almost to dry-
ness. 40 ml of hexane was added to the residue, then this
mixture was heated to a boiling. The solvent was removed to
one-third of original volume. The residue was cooled and
the precipitate was collected and recrystallized from hexane
to give 0.29 g (15%) of 3 (m.p. 88±908C). 1H NMR (CDCl3)
ꢀ: 1.41 (3H, t, CH3, J 7.2 Hz); 4.45 (2H, q, CH2, J
7.2 Hz); 7.14 (1H, s, CH); 7.35 (5H, m, C6H5) ppm. 19F
NMR (CDCl3) ꢀ: 161.53 (2F, m, meta-); 151.53 (1F, t-t,
para-, J3±4 20.7; J2±4 2.2 Hz); 138.75 (2F, m, ortho-)
ppm. IR (cm 1): 1735 (C=O, ester); 1650, 1595, 1500
(C=N, C=C); 990 (CF). Analysis: Found: C, 56.49; H,
3.07; F, 25.05; N, 7.44%. Calc. for C18H11F5N2O2 : C,
56.55; H, 2.90; F, 24.85; N, 7.33%.
A solution of 1,2-ethylenediamine (1.5 g, 25 mmol) in
10 ml of MeOH was added to a solution of compound 1a
(1.55 g, 5 mmol) in 10 ml of acetic acid under cooling. The
mixture was stirred at room temperature for 6 h, and stored
for 2 days. The precipitate was collected by ®ltration,
washed with water (3 Â 10 ml), dried. The dry precipitate
was dissolved in 20 ml of conc. HCl. The solution was
®ltered rapidly, and ®ltrate was diluted with 40 ml of water.
The resulting precipitate was collected by ®ltration, washed
with water (4 Â 10 ml), and dried at 1108C to give 0.66 g
(43%) of 5 (m.p. > 2708C; subl. ꢀ2408C). 1H NMR (DMF-
D7) ꢀ: 3.64 (4H, w.s., 2 CH2); 6.04 (1H, t, CH, JH±
1.6 Hz); 8.59 (1H, w.s., NH,); 10.7 (1H, w.s., NH)
F
ppm. 19F NMR (DMF-D7) ꢀ: 162.05 (2F, m, meta-);
154.56 (1F, t-t, para-, J3±4 20.7; J2±4 1.7 Hz);
143.00 (2F, m, ortho-) ppm. IR (cm 1): 3360, 3290,
3200, 3120 (NH); 1690 (C=O, amide); 1600 (C=O, ketone);
1540, 1510 (C=C, NH); 1020, 980 (CF). Analysis: Found:
C, 47.36; H, 2.23; F, 31.24; N, 9.04%. Calc. for
C12H7F5N2O2: C, 47.07; H, 2.30; F, 31.07; N, 9.15%.
Analogously, 0.40 g (26%) of 5 was obtained from
5 mmol of 1a in a mixture with 10 ml of MeCO2H and
10 ml of MeCN at room temperatures for 3 weeks.
2.4. Synthesis of 5-pentafluorophenyl-3-carboxyisoxazole
(4)
2.4.1. Method A
A mixture of compound 1a (1.55 g, 5 mmol) and
NH2OHÁHCl (0.42 g, 6 mmol) in 25 ml of MeOH was