Reaction of perfluorocarbonyl chlorides with ethyl- and phenylmagnesium bromides

Article abstract of DOI:10.1007/s11176-005-0380-1

The structure of the products formed by the reactions of perfluoroadipoyl and perfluorocyclo-hexanedicarbonyl difluorides with ethyl- and phenylmagnesium bromides depends on the nature of the radical in the organomagnesium compound. 2005 Pleiades Publishing, Inc.

Full text of DOI:10.1007/s11176-005-0380-1

Russian Journal of General Chemistry, Vol. 75, No. 7, 2005, pp. 1136 1138. Translated from Zhurnal Obshchei Khimii, Vol. 75, No. 7, 2005,
pp. 1199 1201.
Original Russian Text Copyright
2005 by V. Chapurkin, Litinskii, Leont’eva, S. Chapurkin.
Reaction of Perfluorocarbonyl Chlorides
with Ethyl- and Phenylmagnesium Bromides
V. V. Chapurkin, A. O. Litinskii, O. S. Leont’eva, and S. V. Chapurkin
Volgograd State Technical University, Volgograd, Russia
Received March 23, 2004
Abstract The structure of the products formed by the reactions of perfluoroadipoyl and perfluorocyclo-
hexanedicarbonyl difluorides with ethyl- and phenylmagnesium bromides depends on the nature of the radical
in the organomagnesium compound.
Polyfluorinated diketones are applied as extractants,
monomers, biologically active compounds, and syn-
thetic intermediates [1]. Polyfluorinated ketones have
been prepared by organomagnesium synthesis [2 4],
but reactions of perfluorocarbonyl fluorides with
Grignard reagents have scarcely been reported.
pound IIIb to 15% with compound IIIa, whereas in
going from the perfluroalkyl- to perfluorocyclohexyl-
containing difluoride, the reaction yield decreases
from 62% with compound IIIb to 21% with com-
pound IIId. The properties of the synthesized com-
pounds are presented in the table.
Here we present the synthesis of polyfluorinated
diketones by the reactions of perfluoroadipoyl and
perfluorocyclohexanedicarbonyl difluorides with ethyl-
and phenylmagnesium bromides.
With excess Grignard reagent, as well as at tempe-
ratures above 15 C, reactions leading to tertiary
alcohols take place. The formation of tertiary alcohols
in reactions of organometallic compounds with per-
fluorocarboxylic acid derivatives is explained [5] by
the fact that increased temperature induce reaction of
the resulting carbonyl compounds with new molecules
of the Grignard reagent. Bulky radicals prevent forma-
tion of tertiary alcohols. Therefore, no tertiary al-
cohols were detected by GLC in the reaction of per-
fluorocyclohexanedicarbonyl difluoride with phenyl-
magnesium bromide.
FC(O)RFC(O)F + 2RMgBr
I
II
RC(O)RFC(O)R RRC(OH)RFC(OH)RR
IV
III
+ 2MgBrF
RF = (CF2)4, C6F10; R = Et, Ph.
To gain insight into the mechanism of the reaction
in hand, we calculated its elementary stages by
MNDO PM3 [6 8] with full geometry optimization.
As model compounds we chose methylmagnesium
bromide and perfluoroacetyl fluoride (see scheme).
According to the calculations, first an adduct of
The yield of the diketones is much dependent on
the structure of both the starting difluoride and the
radical in the organomagnesium reagent. On replace-
ment of phenyl by ethyl in the Grignard reagent the
yield of the diketone decreases from 62% with com-
CF3
CF3
CF3
H3C
1.22
C
H3C
H3C
1.35
C
C
1.38
1.40
1.35
CF3
O
135
F
CH3MgBr + O=C
F
O
111
1.80
O
1.84
F
100
2.41
1.81
128.8
Mg
1.77
Mg
1.89
122.7
Br
Mg
1.89
1.9
Br
F
130
Br
A
B
C
1070-3632/05/7507-1136 2005 Pleiades Publishing, Inc.

REACTION OF PERFLUOROCARBONYL CHLORIDES
1137
1
Constants, yields, melting and boiling points, IR and H NMR spectra, and elemental analyses of fluorinated diketones
RC(O)RFC(O)R
IR spectrum,
Found, %
H
Calculated, %
1
, cm
1H NMR spectrum,
, ppm
d240
n2D0
Formula
C=O OH
C
F
C
H
F
IIIa 15 64 (5) 1.4332 1.3671 1750 3365 1.02 t (3H, Me), 37.46 3.24 48.01 C10H10F8O2 38.22 3.18 48.41
2.93 q (2H, CH2),
4.48 m (1H, CH),
12.90 s (1H, OH)
IIIb 62 42 43
1760
7.43 8.15m (5H, 52.15 2.48 36.90 C18H10F8O2 52.68 2.44 37.07
C6H5)
IIIc 16 85 (7) 1.5483 1.3602 1765 3380 1.12 t (3H, CH3), 37.72 2.79 50.12 C12H10F10O2 38.30 2.66 50.53
2.95 q (2H, CH2),
4.52 m (1H, CH),
13.10 s (1H, OH)
IIId 21 155
1770
7.69 8.14 m (5H, 49.83 2.16 39.81 C20H10F10O2 50.85 2.12 40.25
C6H5)
156
CH3MgBr adds to perfluorinated acyl fluoride. The
energy of adduct formation is 10 kJ mol , and its
bonyl difluorides, bromobenzene, and bromoethane
were commercial products. Ether was distilled over
P2O5 and handled over sodium. Ethyl- and phenyl-
megnesium bromides were prepared by the procedure
in [5].
1
the most stable structure comprises a four-membered
ring A with C F, C O, and Mg O bonds lying in the
same plane. Further on structure A undergoes rear-
rangement via transition state1 B with a barrier (activa-
1
Fluorinated diketones (general procedure). A
solution of 0.02 mol of alkyl- or arylmagnesium
bromide in 20 ml of absolute ether was added drop-
wise to a solution of 0.002 mol of perfluorocarbonyl
difluoride in 25 ml of the same solvent cooled to
15 C. The reaction mixture was allowed to stand for
1 h at 15 to 10 C, after which it was let to warm to
room temperature. After standing for an additional 3
h, the mixture was refluxed for 0.5 h and then treated
with 10% HCl. Organic compounds were extracted
with ether, and the extract was washed with 1%
potassium carbonate to neutral washings and dried
tion energy) of about 30 kJ mol into complex C (see
figure). The geometric parameters of all the mentioned
structures are given in the scheme. As seen from
the scheme, structure A converts into complex C via
synchronous stretching of the C F and O Mg bonds.
EXPERIMENTAL
The IR spectra were obtained on a Specord IR-75
spectrophotometer (NaCl prysm, 4000?600 cm 1) in
thin films for liquids and mulls in mineral oil for
solids. The NMR spectra were obtained on a Bruker-
300 spectrometer (300 MHz), internal standards TMS
and DMSO-d6.
B
Gas chromatography was performed on an LKhM-
8MD chromatograph using columns (3 3000 mm)
packed with 10% SKTFT on Chromosorb-W.
30
40
CF3
F
10
A
CH3MgBr + O=C
C
24
Perfluoroadipoyl and perfluorocyclohexanedicar-
Energy diagram of the reaction of perfluoroacetyl
fluoride with methylmagnesium bromide as given by the
quantum-chemical calculations (activation energies are
1
Transition state was found by automatic search for the cor-
responding node point on the potential energy surface as
a function of all geometric parameters.
1
in kJ mol ).
RUSSIAN JOURNAL OF GENERAL CHEMISTRY Vol. 75 No. 7 2005

1138
CHAPURKIN et al.
with calcium chloride. The solvent was removed, and
liquid reaction products were purified by repeated
vacuum distillations and solid, by recrystallization
from chloroform.
Chem., 1984, vol. 26, no. 3, p. 341.
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nomarenko, V.A., Izv. Akad. Nauk SSSR, Ser. Khim.,
1988, no. 5, p. 1163.
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RUSSIAN JOURNAL OF GENERAL CHEMISTRY Vol. 75 No. 7 2005