BOLTACHEVA et al.
884
with hexane. Yield 0.25 g (26%), white powder,
C10
O3
C9
mp 102–104°C. IR spectrum, ν, cm–1: 1154 m (C–F),
C11
O1
1198 s (C–F), 1253 s (C–F), 1274 m (C–F), 1723 s
C1
O4
1
(C=O), 3200–3416 br (OH). H NMR spectrum
O2
F2
3
C12
(CDCl3), δ, ppm: isomer 2a; 1.30 t (6H, CH3, J =
C5
C6
7.13 Hz), 4.01 s (2H, CH), 4.21–4.40 m (4H, CH2),1
C2
C3
3
4.64 br.s (2H, OH); isomer 2b: 1.35 t (6H, CH3, J =
F1
O7
7.12 Hz), 4.03–4.04 m (2H, CH), 4.21–4.40 m (4H,
CH2),1 4.64 br.s (2H, OH). 19F NMR spectrum
(CDCl3), δF, ppm: 78.02 s (2a), 81.00 s (2b) (CF3).
Found, %: C 37.29; H 3.53; F 29.40. C12H14F6O7.
Calculated, %: C 37.51; H 3.67; F 29.67.
C7
F6
C8
C4
F3
O5
O6
F4
F5
b. Potassium permanganate, 0.11 g (0.7 mmol), was
added in small portions with stirring to a solution of
0.65 g (2.7 mmol) of manganese(II) acetate tetrahy-
drate in 10 mL of acetic acid. The mixture was heated
for 15 min at 60–70°C, 1 g (5.3 mmol) of compound 1
was added with stirring, and the mixture was stirred for
4 h at 60–70°C and left to stand for 15 h at 18–20°C.
A 5-mL portion of acetic acid was distilled off, and
the residue was poured into water and extracted with
diethyl ether. The extract was evaporated, and the resi-
due was reprecipitated from diethyl ether with hexane.
Yield 0.24 g (25%), white powder, mp 102–104°C.
The spectral parameters were identical to those of
a sample obtained as described above in a.
Fig. 1. Structure of the molecule of diethyl (2S*3S*4S*5S*)-
2,5-dihydroxy-2,5-bis(trifluoromethyl)tetrahydrofuran-3,4-
dicarboxylate (2a) according to the X-ray diffraction data;
non-hydrogen atoms are shown as thermal vibration ellip-
soids with a probability of 50%.
gence factors: R1 = 0.1254, wR2 = 0.0794 (for all
independent reflections); R1 = 0.0406, wR2 = 0.0736
[for reflections with I > 2σ(I)]; goodness of fit S =
1.000; residual electron density peaks (max/min)
0.174/–0.123 ēÅ–3. The complete set of X-ray diffrac-
tion data was deposited to the Cambridge Crystallo-
graphic Data Centre (CCDC entry no. 1911465).
Thus, we have found a new reaction of lithium
4-ethoxy-1,1,1-trifluoro-4-oxobut-2-en-2-olate and
synthesized a new tetrahydrofuran derivative as a mix-
ture of two stereoisomers; the steric structure of the
major isomer (2S*3S*4S*5S*) has been determined by
X-ray analysis. It should be noted that fluorinated keto
ester lithium salts are accessible compounds; they can
be obtained in one step by condensation of fluoro-
carboxylic acid esters with ethyl acetate in the pres-
ence of lithium hydride as condensing agent [2].
1
The H and 19F NMR spectra were recorded on
a Bruker Avance-500 spectrometer using tetramethyl-
silane (1H) or C6F6 (19F) as internal standard. The IR
spectra of solid samples (diffuse reflectance) were
recorded in the range 400–4000 cm–1 on a Perkin
Elmer Spectrum One FT-IR instrument. The elemental
analyses were obtained with a Perkin Elmer PE 2400
analyzer.
The X-ray diffraction study was performed on
an Xcalibur 3 automated diffractometer with a CCD
detector according to standard procedure [Mo Kα radia-
tion, graphite monochromator, ω-scanning through
a step of 1°, temperature 295(2) K]. The structure was
solved by the direct method and was refined against F2
by the full-matrix least-squares method in anisotropic
approximation for all non-hydrogen atoms. Hydrogen
atoms linked to carbons were placed in geometrically
calculated positions, and the positions of NH and OH
hydrogens were refined independently in isotropic
approximation. All calculations were carried out using
SHELX software package [4].
Lithium 4-ethoxy-1,1,1-trifluoro-4-oxobut-2-en-2-
olate (1) was synthesized by condensation of ethyl
trifluoroacetate with ethyl acetate according to [2].
Manganese(III) acetate was prepared as described in
[3] (method a) or generated in situ (method b).
Diethyl 2,5-dihydroxy-2,5-bis(trifluoromethyl)-
tetrahydrofuran-3,4-dicarboxylate (2). a. Compound
1, 1 g (0.0053 mol), was added with stirring to a solu-
tion of 4.83 g (0.018 mol) of manganese(III) acetate
dihydrate in 10 mL of acetic acid. The mixture was
stirred for 4 h at 60–70°C and left to stand for 15 h at
18–20°C, the solvent was distilled off, and the oily
residue was subjected to chromatography using diethyl
ether as eluent. The eluate was evaporated, and the
residue was reprecipitated from methylene chloride
1
Signals of the CH2 groups of isomers 2a and 2b overlapped each
other and the OH signal.
RUSSIAN JOURNAL OF ORGANIC CHEMISTRY Vol. 55 No. 6 2019
Boltacheva
