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VOL’EVA et al.
plicated by side reactions, and the target ketal formed
triple mixtures with water and actone boiling in a wide
temperature range and inseparable by rectification into
individual components. The extraction with ethyl ether
with salting-out by NaCl provided no more than 15% of
ketal V containing up to 7% of acetone. Obviously the
main difficulty for the isolation of ketal V consists in the
close boiling points of ketal V, water, and various azeo-
tropic mixtures. The success in the synthesis of ketal V
by the transketalization of ketal I may be ascribed to the
absence of water in this process.
of acetone, 1 g of TsOH·2H O, 25 ml of benzene was
boiled for 20 h at constant stirring using a Soxhlet ap-
paratus filled with 20 g of molecular sieves. The catalyst
2
was neutralized with 1 g of Ca(OH) , the precipitate was
2
filtered off, acetone and benzene were distilled off from
the filtrate, the residue was distilled in a vacuum. Yield
1
9.3 g (~70%), bp 99–101°С (5 mm Hg) [2]. Н NMR
spectrum, δ, ppm: 1.34, 1.40 s (3Н, СН ), 2.50 t (1Н, ОН,
3
J 5.5 Hz), 3.55, 3.65 d.d (2Н, СН ОН, J 12.0, J 6.1, J
2
5.5 Hz), 3.72, 3.98 d.d (2Н, СН , J 8.3, J 6.8 Hz), 4.18
2
m (1Н, СН).
The mechanism of a latent transketalization is appar-
ently involved in the other successful synthesis of ketal V
by acetone condensation with ethylene glycole with the
use of dimethyldichlorosilane as dehydrating agent [3].
Most probably actually no free water is formed in this
process. The reaction proceeds in two stages including
the intermediate formation of siladioxacyclane VI and
its transketalization with acetone.
b. A mixture of 9.2 g (0.1 mol) of glycerol, 7 g (0.12
mol) of acetone, 10.2 g (0.1 mol) of Ac O was boiled
2
for 3 h at stirring. The reaction mixture was distilled
at atmospheric pressure (till 115°С), then at 5 mm Hg.
We obtained 12.6 g of reaction product of bp 99–103°С
1
(5 mm Hg), according the data of Н, NMR spectroscopy
it was a mixture of ketals I and IV in the ratio ~9:1. Ketal
IV was obtained by acylating ketal I with Aс O.
2
c. A mixture of 9.2 g (0.1 mol) of glycerol, 7 g
(0.12 mol) of acetone, 1 g of amberlyst, 10 g of ethanol
was boiled for 5 h at stirring in a flask equipped with a
column packed with 20 g of molecular sieves and a re-
flux condenser. The catalyst was filtered off, acetone
and ethanol were distilled off, the residue was distilled
in a vacuum. We obtained 12.5 g (95%) of ketal I, bp
+
(CH ) SiCl
3 2 2
OH OH
CH3
Si
(
CH ) CO
3
2
O
O
V
+
_HCl
O
Si
n
CH3
H C CH3
3
VI
9
9–100°С (5 mm Hg) [2].
The formation of intermediates like siladioxacyclane
VI is possible at the chemisorption on active Si-centers
of heterogeneous silicon-containing catalysts (zeolites,
4-Hydroxymethyl-2-methyl-2-ethyl-1,3-dioxolane
(II). A mixture of 13.2 g (0.1 mol) of ketal I, 8 g
(0.12 mol) of methyl ethyl ketone, and 1 g of amberlyst
was stirred for 20 min at ≤56°С distilling off acetone.
The catalyst was filtered off, the filtrate was distilled in
molecular sieves, SiO , etc.) used in ketal syntheses [4].
2
The transketalization of the adsorbed intermediates with
ketone also does not result in free water liberation.
a vacuum. Yield 12.9 g (88%), bp 90–91°С (6 mm Hg)
1
[
5]. Н NMR spectrum, δ, ppm: 0.93, 0.95 t (3Н, СН ,
3
EXPERIMENTAL
J 8.0 Hz), 1.32, 1.37 s (3Н, СН ), 1.65, 1.70 q (2Н, СН ,
3 2
J 8.0 Hz), 2.08 s (1Н, ОН), 3.60, 3.73 m (2Н, СН ОН),
2
In the study were used commercially available
glycerol, ethylene glycol, ethanol, acetone, methyl ethyl
ketone, cyclohexanone of the “chemically pure” grade,
amberlyst 15 dry, molecular sieves 4 A, dried to a con-
stant weight at 180°С, capacity for water ~15 wt%. The
analysis of reaction mixtures was carried out by TLC on
Silufol UV-254 plates in the system hexane–ether, 1 : 1,
and by Н NMR spectroscopy. Н NMR spectra were
registered on a spectrometer BrukerAvance 500 in CDCl3,
internal reference TMS.
3.75, 4.04 d.d (2Н, СН , J 12.0, 8.0 Hz), 4.20, 4.27 m
(1Н, СН).
2
4
-Hydroxymethyl-2,2-pentamethylene-1,3-dioxo-
lane (III). Amixture of 13.2 g (0.1 mol) of ketal I, 11.8 g
0.12 mol) of cyclohexanone, and 1 g of amberlyst was
(
stirred for 20 min at ≤56°С distilling off acetone. The
catalyst was filtered off, the reaction product was distilled
in a vacuum. Yield 15.5 g (90%), bp 121–123°С (5 mm
1
1
1
Hg). Н NMR spectrum, δ, ppm: 1.40–1.66 m (10Н,
С Н ), 2.01 t (1Н, ОН, J 5.7 Hz), 3.58, 3.73 m (2Н,
6
10
4
-Hydroxymethyl-2,2-dimethyl-1,3-dioxolane (I).
СН ОН), 4.03, 4.05 d.d (2Н, СН , J 8.2, 6.6 Hz), 4.24,
2
2
а.Amixture of 9.2 g (0.1 mol) of glycerol, 23 g (0.4 mol)
4.26 m (1Н, СН). Found, %: С 62.98; H 9.56. C H O .
9
16
3
RUSSIAN JOURNAL OF ORGANIC CHEMISTRY Vol. 48 No. 5 2012