Reaction of polyfluoroalkyl chlorosulfites with benzyl alcohols

Full text of DOI:10.1134/S1070363207100258

ISSN 1070-3632, Russian Journal of General Chemistry, 2007, Vol. 77, No. 10, pp. 1813 1814.
Pleiades Publishing, Ltd., 2007.
Original Russian Text A.I. Rakhimov, R.V. Fisechko, 2007, published in Zhurnal Obshchei Khimii, 2007, Vol. 77, No. 10, pp. 1750 1751.
LETTERS
TO THE EDITOR
Reaction of Polyfluoroalkyl Chlorosulfites with Benzyl Alcohols
A. I. Rakhimov and R. V. Fisechko
Volgograd State Technical University,
pr. Lenina 28, Volgograd, 400131 Russia
e-mail: organic@vstu.ru
Received June 5, 2007
DOI: 10.1134/S1070363207100258
It was earlier shown that the reaction of poly-
HF C
fluoroalkyl chlorosulfites with aliphatic alcohols (for
example, propan-1-ol) involves substitution of the
chlorosulfite group and formation of the correspond-
ing ethers in up to 50% yields [1, 2]. We now found
that the reaction of polyfluoroalkyl chlorosulfites with
benzyl alcohols, catalyzed by DMF, involves substitu-
tion of the chlorosulfite group and provides polyfluo-
roalkyl benzyl ethers:
2
0
.140
CF2
H
(3)
H0.110
C
0.0055
CH
2
0.500
O
0.380
O
(
1)
H3C
1
.441
0
H
.252
0
.277
S
O
N
C
0.401
O
(2)
OH
Cl
0.398
+
H(CF CF ) CH OS(O)Cl
2 2 n 2
H C
3
H
R
IX
DMF
CH OCH (CF CF ) H
2 2 2 2 n
SO2, HCl
1
energies (23.5 kcal mol ) are close to each other,
indicating reasonability of the proposed reaction
mechanism.
R
n = 1, 2, R = H: n = 1 (I), n = 2 (II); p-Cl: n = 1 (III),
n = 2 (IV); p-CH O: n = 1 (V), n = 2 (VI); m-NO : n = 1
1
The H NMR spectrum of the prepared complex
3
2
(
VII), n = 2 (VIII).
was recorded at 30 C (Table 2). Changes in the
proton chemical shifts of the CH group in polyfluo-
2
The yield of polyfluoroalkyl benzyl ethers achieves
3 90%, depending on the substituents in the benzene
6
Table 1. Physicochemical properties of newly synthesized
ring. Ethers I VIII are labile colorless liquids (the
meta-nitro derivative is slightly colored yellow) with
densities higher than unity (Table 1).
polyfluoroalkyl benzyl ethers
Comp.
no.
Yield,
%
bp,
C
2
0
20
d
n
D
4
(3 mm Hg)
The structure of six-membered complex IX formed
by the reaction of polyfluoroalkyl chlorosulfites with
the DMF benzyl alcohol associate at 30 C was
studied by ab initio quantum-chemical calculations
with the 3-21G basis set (from H to Ar) [3].
I
II
85
83
90
85
70
63
90
84
120
125
130
135
110
116
130
140
1.5065
1.6382
1.4025
1.5002
1.2856
1.3643
1.3570
1.5002
1.3580
1.3730
1.4580
1.4100
1.4440
1.3995
1.4760
1.4310
III
IV
V
VI
VII
VIII
The formation of compound IX leads to an energy
1
gain of 2.8764 kcal mol , and its cleavage and
formation of the reaction products is a barrier stage
with an energy of 25.341 kcal mol . It is important to
1
note that the calculated and experimental activation
1813

1814
RAKHIMOV, FISECHKO
Table 2. 1H NMR spectrum of complex IX
Chemical shifts , ppm, and spin spin coupling constants J, Hz
Compound
HCF2
O CH CF2
Ph
HO
J
2
J
J
IX
5.611 t.t
5.907 t.t
53.1
3.995 t
15.3
13.2
12.0
12.3
7.16 m
7.15 m
4.209 s
3
.9
3.532 t
4.802 t
4.515 t
Polyfluoroalkyl
chlorosulfite
Benzyl alcohol
52.5
3.9
3.92 s
Table 3. Influence of substituents in the aromatic ring on the rate of the reaction polyfluoroalkyl chlorosulfites with
benzyl alcohols
p-Methoxybenzyl
p-Chlorobenzyl
m-Nitrobenzyl
Parameter
k 10 , mol l 1 s 1
Benzyl alcohol
alcohol
alcohol
alcohol
3
25 C
0.08
0.25
0.38
23.5
0.05
0.21
0.32
0.102
0.29
0.402
21.40
0.10
0.305
0.410
21.05
30 C
5 C
3
Ea, kcal mol 1
28.61
roalkyl chlorosulfites and the OH group in the alcohol,
which both are directly involved in complex forma-
tion were analyzed.
cohols). Electron-donor substitutes in the alcohol
benzene ring (for example, para-methoxybenzyl al-
cohol) significantly reduce the reaction rate compared
to the unsubstituted benzyl alcohol.
Table 2 shows that the chemical shift of the poly-
fluoroalkyl chlorosulfite CH group connected with
the oxygen atom bearing a significant negative charge
2
Thus, the nucleophilic substitution of the poly-
fluoroalkyl chlorosulfite group by the benzyloxy
group proceeded via a six-membered cyclic inter-
mediate and provides a promising synthetic approach
to polyfluoroalkyl benzyl ethers.
[qO(2) 0.380] is shifted downfield. The same effect
is observed for the alcohol OH proton which interacts
with the negatively charged chlorine atom (qCl
0
.398).
REFERENCES
We also revealed the influence of the substituents
in the benzene ring on the rate constant of the sub-
1
. Rakhimov, A.I., Nalesnaya, A.V, and Vostrikova, O.V.,
Zh. Obshch. Khim., 2004, vol. 74, no. 4, p. 693.
stitution of the chlorosulfite group by PhCH O within
2
a certain temperature range. The resulting data are
presented in Table 3.
2. Rakhimov, A.I., Nalesnaya, A.V, and Vostrikova, O.V.,
Zh. Prikl. Khim., 2004, vol. 77, no. 9, p. 1573.
Table 3 shows that alcohols with electron-acceptor
substituents in the aromatic ring are the most reac-
tivite (meta-nitrobenzyl and para-chlorobenzyl al-
3. Shmidt, M.V., Baladridge, K.K., and Boatz, J.A.,
J. Comput. Chem., 1993, vol. 14, p. 1347.
RUSSIAN JOURNAL OF GENERAL CHEMISTRY Vol. 77 No. 10 2007