Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
1~7~il8
The reaction of ketones and aldehydes with hexafluoro-
propene-oxide (HFP0) at 100 to 300 C is disclosed by United
States Patent specification 3,450,716. This reaction leads to
perfluoro pyruvic acid fluoride or its cyclic dimer, the perfluoro-
4-oxo-2,5-dimethyl-2-fluorocarbonyl-1,3-dioxolane.
This cyclic compound can be used - in accordance with
United States Patent 3,450,716 - as soil disinfectant and insecticide
and as well as a valuable intermediate product. Said compound may
be hydrolyzed e.g. to perfluoro pyruvic acid which is also a suit-
able insecticidal agent.
However, according to this known process the one-step-
synthesis of perfluorinated dioxolane calls for a reaction under
elevated pressure.
Therefore, object of the present invention had to be
finding a process for preparing perfluoro-4-oxo-2,5-dimethyl-
fluorocarbonyl-1,3-dioxolane which would not include the disadvan-
tages of the known process, especially which would be feasible under
normal pressure and at low temperatures.
A process has now been found for preparing perfluoro-4-
oxo-2,5-dimethyl-2-fluorocarbonyl-1,3-dioxolane from hexafluoro
propene epoxide which comprises reacting at temperatures from -50
to ~20 C hexafluoro propene oxide with an N-formylated second-
dary amine, removing non-reacted hexafluoropropene oxide and
isolating perfluorinated dioxolane from the reaction pro-
ducts.
If dimethyl formamide is used as N-formylated secondary
amine, the process according to the invention may be described
by the following reaction scheme: -
- 2 -
: . . : , ,
:
: . - ': ~ : .
: . ' ;
76~8 HOE 7 6 / 1 113
O F
2 (CH3 ) 2l~-C + 2 E~FPO 3 2 2
\H O~CF3
0~
CF3
II
This reaction scheme reveals -that 2 moles of a fluorine-
containing tertiary amine are formed lor 1 mole of desired
perfluorinated dioxolane (PODF).
An excess of HFPO may be easily removed after completion
of the reaction by distilling off or blowing off with inert
gas. The easiest way to isolate PODF is a fractional distilla-
tion. However, it is also possible to separate the reaction
batch in two liquid phases by addition of a perfluorinated
solvent, e.g. of a perfluorinated ether or ketone having a
boiling point of preferably higher than 200 C. The phase essen-
tially consisting of perfluorinated solvent practically contains
but the desired PODF (I) without the simultaneously formed
fluorine-containing tertiary amine(II). Subsequently it is
easy to separate PODF by distillation from the solvent added.
The process according to the invention may also be carried
out in the presence of an inert solvent. Particulary well
suitable for that purpose are aprotic polar solvents, especial-
ly ethers such as diethylene glycol dimethyl ether or tetra-
ethylene glycol dimethyl ether; there may also be used nitriles
such as acetonitrile or propionitrile. The quantity of the
solvent is not critical, preferably are used from 0.15 to 1.0
.
. ~ - . , - , ........... : ... . . . ... .. .
- : : .: . , : . : -, ~ .
- . . ~ : - -.. ,. , , ... : ,
HOE 76/~ 113
376~8
parts by volume of solvent per part by volume of N-formylated
secondary an1ine.
HFPO mây be used as such or also in admixture with hexa-
fluoropropene (HFP). The quantity at which HFPO is used is
not critical, preference is given, however, to the use of
equimolar quantities calculated on the N-formylated secondary
amine, or of a slight excess, e.g. of 10 mole %. If HFPO is
present in an excess, this excess quantity is distilled off
upon work-up of the reaction mixture and may be used for
further subsequent reactions. If HFPO is present at a defi-
cient rate, part of the N-formylated secondary amine is not
reacted and remains in the residue left upon work-up. This
non-reacted quantity of N-formylated amine may also be used
for further reaction batches.
Though reaction temperatures above +20 C, e.g. up to
50 C, are possible, they bring about the risks of decomposi-
tion and lesser yield. Reaction temperatures below -50 C re-
duce considerably the reaction speeds.
The reaction products PODF and tert.fluorine-containing
amine may be separated by fractional distillation under normal
pressure. In order to avoid decomposition, fractionating is
most usefully carried out under reduced pressure so that the
head and sump temperatures - particularly prior to limination
of the fluorine -containing amine - will not exceed 20 C,
preferably 0 C. Moreover, it is useful to add to the distilla-
tion batch a HF binding agent, preferably an alcali fluoride
such as sodium fluoride or potassium fluoride; the fluoride
may be used at the rate of from 0 to 50, especially from 2 to
2~ 40, and particularly from 10 to 25 g per 100 g of distillation
-- 4 --
` ' ' ' ` "
`
, ` ' ' ' ,
. . '~ ~ '
' ' , ' ' ' ' ' '
ll0~_7~ 113
761 8
hatch.
The structure of the N-formylated secondary amine as it is
employed is not critical as such. However, the N-formyl com-
pound must not contain any active hydroqen, i.e. this compound
should be free from hydroxy groups, carboxy groups and sulfonic
acid groups. Especially good results are obtained, when the
free secondary amine , whereof the N-formyl compound is a deri-
vative, has a basic nature, especially pK values superior to
6, preferably superior to 7.
There may be used e.g. N-formyl compounds of a secondary
aliphatie or heteroeyclic amine having the general formula
\ N - C
R2 / \ H
.
wherein R1 and R2 may be identiGal or different and may re- -
present a straight-chained or branched alkyl radical having
from 1 to 13 earbon atoms or a eyeloalkyl radieal (with from
3 to - 8 earbon atoms). Preference is given to alkyl radicals
having from 1 to 4 earbon atoms and eyeloalkyl radieals having
5 and 6 earbon atoms. However, R1 and R2 may also form to-
gether a bivalent radieal, preferably a bivalent saturated ra-
dieal. In that ease the bivalent radical- combined with the
N-formyl group - is forming a heteroeyele with 5 to 7 members.
The bivalent radical may represent, for example, an alkylene
group with from 4 to 6 earbon atoms, e.g. a radieal
-CH2CH2CH(CH3)CH2CH2- or a polymethylene radieal with from 3
to 6 earbon atoms, e.g. a (CH2)4-radieal or (CH2)6-radieal.
... . ....... ... .... . . . . .
. - ..... ..... .. .... : .~ . i .. ,: . .. .. .. ..... ... . . .
.- -.. . . . ... ...... . ~ . .. . ... . . . ,.: , . .... ..
. . . ~ . - . .. . .. , , . : ........ ... . , . .. . , . : .
.:.: : , :-. :. . . ' : :
: .: . ~ : .
1~ 76~8 HOE 76/F 113
.
The alkylene groups may as well b~ interru~ted ~y hetero groups
(preferably by one hetero group). Such hetero groups include
e.g. oxygen = N-(C1-C4)-alky] or =~-CHO.
There may be used, for example, the N-formyl compound o~
heterocycles pyrrolidine, piperidine, hexamethylene imine,
morpholine, piperazine, N-methyl-piperazine, N-methy]-imidazoli-
- dine and oxazolidine. It is evident that stoichiometrically
the use of a compound with 2 N-formyl groups in the molecule
(example: N,N'-diformyl-piperazine) requires but half a mo]e per
mole of HFPO.
When using an N-formyl compound with a low molecular
weight (example: DMF) or with a relatively high molecular weight
(example:bis-tridecyl-amine) tert. fluorine-containing tert.a~ines
are formed as by-products, the boillng point of which differs
substantially from the boiling point of the desired compound.
This fact favors an easy distillative separation of the reaction
mixture. When an N-formyl compound is used which is a derivative
of a long-chain secondary allphatic amine, it may happen in
some cases, especially upon addition of a solvent, that ihe re-
action mixture decomposes spontaneously in two phases, one of
them essentially containing the desired PODF.
Abbreviations employed in the text:
HFP hexafluoropropene
HFPO hexafluoropropene-oxide
DMF dimethylformamide
PODF perfluoro-4-oxo-2,5-dimethyl-2-fluorocarbonyl-1,3-dioxo-
lane
Bp. Boiling point
29 The following Examples illustrate the present invention:
- 6 -
- : .. . , :. . , , . : - ~ - , . . .
. .. ,, .. : . . . .- . . . .
.. . . - . ~. . ~.... ,.. , .. . . -
.' ' . ' ~ ' ' . ' . . : '
l:[C)E 7 6 /F 1 1 3
~37618
E X A M P L E 1:
~ _ _ _ _ _ _
Perf]uoro-4-o~o-2,5-dimeihyl-2-fluorocarbon 1-1,3-dioxolane and
..... _ . . Y .~
, ~ -dirluo~otrimethylamine
216 g of ~ME~ (2,96 mole) are introduced into a three-necked
flask equipped with agitator, thermometer, intense cooling device
and gas inlet pipe, and subsequently at temperatures from -20 C
to -10 C and at a supply rate of 2S l per hour there are intro-
duced 850 g of a mixture of HFPO and HFP (weight ratio 60:40) -
corresponding to 3.07 mole of epoxide. This operation is follow-
ed by a 6 hours' period of agitation at -15 C to-10 C. The
temperature is then allowed to rise to +15 C to +20 C, while
319 g of a gaseous mix-ture of HFP and HFPO (weight ratio 70:30)
escape. The residue is distilled in vacuo (up to +40 C/70 mm).
In two coollng traps one set up behind the other (CH2Cl2/CO2)
there are obtained 579 g of a product mixture of (I) and (II)
leaving a residue of 34 g of non-reacted DMF. By distillation
over KF there are obtained 246 g of (II) ~bp 48 to 52 C) and
145 g of (I) (bp. 70 to 72 C~. -
The structure of (I) and (II) are confirmed by IR and NMR
spectroscopy and analyses.
E X A M P I E 2:
The apparatus of Example 1 is charged with 48.5 g (0.5 mole)
of N-formyl-pyrrolidine and 60 ml of tetraethylene glycol-di-
methyl ether. At a temperature from -30 C there are introduced
150 g of a mixture of HFPO/HFP (weight ratio 80/20). Agitation
is continued for two hours at this same temperature. Subsequent-
ly the temperature is allowed to rise to ambient temperature. -
Non-reacted HFPO and dissolved HFP escape and are collected
29 in a cooling trap. The remaining residue decomposes in two phases.
_ 7
,..... . , , ; ,, ,' ' ., :
.- - , . , , - : :
. , , .- ': ' . ' :, .. : .. . '. - - ' -' . . ' ' :
HOE 75~F 1 l 3
` 1J~)~76:~8
The heavier phase is distilled to provide 45 g of the desired
dioxolane (bp. 70 to 72 C.'
E X A M P L E 3:
150 g of 80 % hexafluoropropene epoxide are added at -25 C
to a solution of 27.5 g of N-formyl morpholine (0.5 mole) in
50 ml of tetraethylene glycol dimethyl ether. At this same teiTI~
- perature agitation is continued for 16 hours. The temperature
is then allowed to rise to +20 C, while non-reacted epo~ide
escapes and is recollected in a cooling trap. The two phases
which had been formed upon reaction, are separated and the low-
boiling parts of the upper phase are condensed in a cooling
trap at 25 C and 1 mm Hg. The thus obtained material is distil-
led together with the separated lower phase (72 g).
The result are 55 g (76.4 %) of the compound mentioned in the
title (of Example 1) having a boiling point of 70 - 72 C.
The distillation of the residue of the upper phase yields
22 g of N-difluoromethyl morpholine (bp. 25 - 27 C/3 mm) and
50 g of tetraglyme.
-- 8 --
~. ~ ' ' '. :
,
