D.N. Bazhin et al. / Journal of Fluorine Chemistry 186 (2016) 28–32
31
Table 2
J = 288 Hz), 128.80, 135.68, 136.25, 142.48, 153.64, 183.95 ppm.
MS (EI) m/z 250.87 [M-H2O]+.
Scope of carbonylcyanides 4 via detrifluoroacetylation of compounds 3.
Entry
1
Starting
compound
R
Reaction
Yield of 4b,
%
conditionsa
3.5. 1-(2,4-Dimethylphenyl)-4,4,4-trifluoro-3,3-dihydroxy-2-
(hydroxyimino)butan-1-one (3d)
3a
Ac2O
AcOH
85
79
1H NMR (500 MHz, DMSO-d6):
Me), 7.14 (m, 2H, Ph), 7.66 (m,1H, Ph), 7.78 (s, 2H, 2 OH),11.70 (s,1H,
NOH) ppm. 19F NMR (470 MHz, DMSO-d6):
= À81.8 (s, CF3) ppm.
13C NMR (125 MHz, DMSO-d6):
= 21.01, 21.28, 91.49 (q, CF3,
d= 2.33 (s, 3H, Me), 2.49 (s, 3H,
d
2
3b
Ac2O
AcOH
55
44
d
J = 32 Hz), 122.67 (q, J = 289 Hz), 126.52, 131.40, 132.40, 132.44,
133.31, 138.92, 142.96, 155.12 ppm. MS (EI) m/z 272.94 [M-H2O]+.
3.6. 1,1,1,5,5,5-Hexafluoro-4,4-dihydroxy-3-(hydroxyimino)pentan-2-
one (3e)
3
4
3c
Ac2O
AcOH
76
63
1H NMR (500 MHz, DMSO-d6):
d= 8.45 (s, 2H, 2 OH), 12.95 (s,
1H, NOH) ppm. 19F NMR (470 MHz, DMSO-d6):
d
= À82.7 (s, CF3),
À77.2 (s, CF3) ppm. MS (EI) m/z 236.86 [M-H2O]+.
3d
Ac2O
AcOH
81
75
3.7. Ethyl 4,4,4-trifluoro-3,3-dihydroxy-2-(hydroxyimino)butanoate
(3f)
1H NMR (500 MHz, DMSO-d6):
(q, 2H, CH2, J = 7 Hz), 7.85 (s, 2H, 2 OH), 12.08 (s, 1H, NOH) ppm. 19
F
d= 1.22 (t, 3H, Me, J = 7 Hz), 4.20
5
6
7
3e
CF3
OEt
Ac2O
AcOH
Ac2O
AcOH
Ac2O
AcOH
0
0
48
42
78
71
NMR (470 MHz, DMSO-d6):
d
= À82.3 (s, CF3) ppm. MS (EI) m/z
3f
212.93 [M-H2O]+.
3g (+2g)
3.8. 4,4,4-Trifluoro-1-(furan-2-yl)-3,3-dihydroxy-2-(hydroxyimino)
butan-1-one (3g)
1H NMR (500 MHz, DMSO-d6):
Ar), 7.84 (s, 2H, 2 OH), 8.04 (m, 1H, Ar), 11.95 (s, 1H, NOH) ppm. 19
NMR (470 MHz, DMSO-d6):
= À82.0 (s, CF3) ppm.
d= 6.75 (m, 1H, Ar), 7.34 (m, 1H,
8
3h (+2h)
Ac2O
AcOH
79
72
F
d
3.9. 4,4,4-Trifluoro-1-(furan-2-yl)-2-(hydroxyimino)butan-1,3-dione
(2g)
a
Reaction conditions: 3a–h (20 mmol), acidic reagent (20 mmol), CHCl3, reflux.
Yields of isolated products.
b
1H NMR (500 MHz, DMSO-d6):
Ar), 8.17 (m, 1H, Ar), 14.52 (s, 1H, NOH) ppm. 19F NMR (470 MHz,
DMSO-d6):
= À71.6 (s, CF3) ppm.
d= 6.83 (m, 1H, Ar), 7.58 (m, 1H,
d
OAc
N
3.10. 4,4,4-Trifluoro-3,3-dihydroxy-2-(hydroxyimino)-1-(pyridin-4-
yl)butan-1-one (3h)
i
F3C
R
OH
O
N
N
HO OH
R
O
1H NMR (500 MHz, DMSO-d6):
2 OH), 8.86 (m, 2H, Ar), 12.13 (s, 1H, NOH) ppm. 19F NMR (470 MHz,
DMSO-d6):
= À82.1 (s, CF3) ppm.
d= 7.75 (m, 2H, Ar), 8.07 (s, 2H,
F3C
R
A
H
O+
O
HO OH
d
ii
N
H
4a-d,f-h, 42-85%
3a-h
F3C
R
3.11. 4,4,4-Trifluoro-2-(hydroxyimino)-1-(pyridin-4-yl)butan-1,3-
dione (2h)
HO OH
O
B
1H NMR (500 MHz, DMSO-d6):
Ar), 14.66 (s, 1H, NOH) ppm. 19F NMR (470 MHz, DMSO-d6):
= À71.6 (s, CF3) ppm.
d= 7.78 (m, 2H, Ar), 8.92 (m, 2H,
i : Ac2O (1 eq), CHCl3, reflux; ii: AcOH (1 eq), CHCl3, reflux.
d
Scheme 2. Detrifluoroacetylation of 4,4,4-trifluoro-3,3-dihydroxy-2-(hydroxyi-
mino)butan-1-ones.
3.12. Acyl nitriles 4 (general procedure)
Compound 3 (20 mmol) and Ac2O (20 mmol) in 20 ml of CHCl3
was refluxed for 1 h. Then 25 mL of water was added to quench the
reaction. Organic layer was washed with brine and dried over
anhydrous MgSO4. After removal of the solvent under reduced
pressure the residue was purified by column chromatography on
silica gel (eluent CHCl3/hexane = 3:1). Spectral data (1H NMR
spectra) and physico-chemical properties (mp or bp) were in
accordance with the literature [7].
3.4. 4,4,4-Trifluoro-3,3-dihydroxy-2-(hydroxyimino)-1-(thien-2-yl)
butan-1-one (3c)
1H NMR (500 MHz, DMSO-d6):
d= 7.28 (m, 1H, Ar), 7.77 (m, 1H,
Ar), 7.89 (s, 2H, 2 OH), 8.07 (m, 1H, Ar), 11.95 (s, 1H, NOH) ppm. 19
F
NMR (470 MHz, DMSO-d6):
(125 MHz, DMSO-d6):
d
= À81.9 (s, CF3) ppm. 13C NMR
d
= 91.49 (q, CF3, J = 32 Hz), 122.62 (q,