Method for preparing perfluoro-oxaziridines

A process for preparing perfluoro-oxyaziridines of formula: ##STR1## where R.sub.x is F, a C.sub.1 -C.sub.10 perfluoroalkyl group or a --NR.sup.f.sub.2 group in which R.sup.f is a C.sub.1 -C.sub.10 perfluoroalkyl group, R.sub.y is F or a C.sub.1 -C.sub.10 perfluoroalkyl group and R.sub.z is a C.sub.1 -C.sub.10 perfluoroalkyl group. The process consists in reacting the corresponding perfluoroimine with an aromatic peroxyacid having a benzenic nucleus, in an aprotic solvent, at a temperature ranging from -50.degree. to +100.degree. C.

The present invention relates to a process for preparing 
perfluoro-oxyaziridines. 
The simplest perfluoro-oxyaziridine is perfluoro-2-azapropane oxide: 
##STR2## 
A process for preparing this compound has been described by Falardeau and 
DesMarteau in J. Am. Chem. Soc., 98, 3529 (1976). It comprises adding 
trifluoromethyl hydroperoxide CF.sub.3 OOH to the corresponding imine 
CF.sub.3 N.dbd.CF.sub.2 and subsequently converting the resulting 
hydroperoxide to oxyaziridine through NaF. 
This process exhibits several drawbacks, which are mainly due to 
hydroperoxide CF.sub.3 OOH used as an oxidant, which is potentially 
explosive and is preparable only by means of a complex multistep process. 
The same process described by Falardeau and DesMarteau has been utilized by 
Zheng and DesMarteau (J. Org. Chem., 48, 4844 (1983)) for preparing 
oxyaziridines of formula: 
##STR3## 
from the corresponding imines. By means of this process, however, it is 
not possible to prepare oxyaziridines substituted, on the carbon atom, by 
perfluoroalkyl groups. 
Another method for preparing perfluoro-oxyaziridines is described in U.S. 
Pat. No. 4,287,128, where a perhaloalkyl imine is reacted with gaseous 
chlorine in the presence of a carbonate or bicarbonate of an alkali or 
alkaline-earth metal. The presence of water traces is necessary to 
catalyze the reaction. This fact represents a drawback as both the 
starting imines and the obtained oxyaziridines hydrolize easily, in 
particular when they are non-substituted. By consequence, said method 
cannot be used for preparing perfluoro-2-azapropene oxide. 
U.S. Pat. No. 4,874,875 describes another process for synthesizing 
perfluoro-oxyaziridines. It consists in reacting a perfluoroimine with 
H.sub.2 O.sub.2, in the presence of a base, in an aprotic polar solvent. 
Owing to the presence of the water deriving from H.sub.2 O.sub.2, neither 
this process can be utilized for preparing perfluoro-2-azapropene oxide. 
Thus, for preparing said first member of the class of 
perfluoro-oxyaziridines, only the complicated method disclosed by 
Falardeau and DesMarteau is utilizable, which is affected with the 
above-described drawbacks. 
The Applicant has now surprisingly found that the perfluoro-oxyaziridines 
can be prepared by reacting the corresponding perfluoro-imines with an 
aromatic peroxyacid in an aprotic solvent; in particular, the process is 
utilizable for preparing, with good yields, perfluoro-oxyaziridines 
non-substituted on the carbon atom, such as perfluoro-2-azapropene oxide. 
Thus, an object of the present invention is a process for preparing 
perfluoro-oxyaziridines of formula: 
##STR4## 
wherein: R.sub.x is F, a perfluoroalkyl group having 1 to 10 carbon atoms 
or a --NR.sup.f 2 group in which R.sup.f is a perfluoroalkyl group having 
1 to 10 carbon atoms, 
R.sub.y is F or a perfluoroalkyl group having 1 to 10 carbon atoms, 
R.sub.z is a perfluoroalkyl group having 1 to 10 carbon atoms. 
The process consists in reacting a perfluoro-imine of formula: 
##STR5## 
where R.sub.x, R.sub.y and R.sub.z are the same as defined hereinbefore, 
with an aromatic peroxyacid of formula: 
##STR6## 
where X is H or an electron-attractor substituent, in an aprotic solvent, 
at a temperature ranging from -50.degree. to +100.degree. C. 
The starting perfluoro-imines are known compounds and are preparable 
according to the methods described, for example, in "Organic Fluorine 
Chemistry" by W. A. Sheppard and C. M. Sharts, W. A. Benjamin Inc. (1969) 
and in Inorg. Chem., 14, 1223 (1975) by K. E. Peterman and J. M. Shreeve. 
In particular for CF.sub.2 .dbd.N--CF.sub.3 it is possible to utilize the 
process described by Barr and Haszeldine in J. Chem. Soc., 1881 (1955). 
The R.sub.x, R.sub.y and R.sub.z groups have preferably from 1 to 8 carbon 
atoms. The R.sup.f group has preferably from 1 to 3 carbon atoms. 
As regards the aromatic peroxyacids of formula (III), substituent X can be 
in ortho, meta or para position with respect to the peroxycarboxylic group 
and it is preferably selected from F, Cl, --NO.sub.2, --COOR and 
--CONR.sub.2, where R is H or an alkyl group preferably having from 1 to 5 
carbon atoms. 
Examples of aromatic peroxyacids utilizable in the process of the present 
invention are: m-chloroperoxybenzoic acid, p-nitroperoxybenzoic acid, 
p-methoxycarboxy-peroxybenzoic acid, monoperoxyphthalic acid. Particularly 
preferred is m-chloroperoxybenzoic acid. 
As already mentioned, the reaction is conducted in an aprotic solvent. It 
is possible to utilize any solvent of this type compatible with the 
peroxyacid and with the perfluoro-imine. Utilizable are, for example, 
nitriles (such as acetonitrile and benzonitrile), ethers (such as 
diethylether, dioxane, tetrahydrofuran, 2-methoxyethylether), chlorinated 
hydrocarbons (such as dichloromethane, terachloromethane, chloroform, 
mono-chloroethane) or mixtures thereof. 
Acetonitrile and dichloromethane are preferred. 
Preferably, the solvent and the peracid are thoroughly anhydrified prior to 
the reaction in order to avoid the hydrolysis of the starting amine and of 
the oxyaziridine. This procedure is particularly recommended when 
oxyaziridines non-substituted on the carbon atom, such as 
perfluoro-2-azapropene oxide, are to be prepared. 
Conventional techniques are utilizable to this purpose. For example, the 
solvent can be distilled in the presence of an anhydrifying agent (for 
example P.sub.2 O.sub.5, CaCl.sub.2, MgSO.sub.4, etc.), while the 
peroxyacid can be kept in contact with any anhydrifying agent which is 
compatible with the peroxyacid itself. Suitable for this purpose are, for 
example, the common molecular sieves. 
The reaction temperature ranges from -50.degree. to +100.degree. C., 
preferably from -50.degree. to +50.degree. C. 
The peroxyacid/imine molar ratio is generally in the range of from 1:1 to 
10:1, preferably from 1:1 to 2:1. 
The reaction time is not a critical parameter and is a function of the 
selected reaction temperature. Generally, the reaction is concluded in a 
time ranging from 10 minutes to 24 hours. 
The perfluoro-oxyaziridines preparable by the process of the present 
invention are utilized for the synthesis of polymers or copolymers 
characterized by a high chemical inertia and by a high thermal stability, 
such as the perfluoroaminoether polymers described in patent application 
EP-338,585. 
The perfluoro-oxyaziridines can be utilized also in the preparation of 
nitrons. Furthermore, they form complexes with the ions of transition 
metals, which act as catalysts for the photopolymerization of ethylene 
monomers.

The following examples are given for illustrative purposes and are by no 
way to be considered as a limitation of the scope of the present 
invention. 
EXAMPLE 1 
Preparation of 
##STR7## 
Into a Pyrex.RTM.50 ml flask there were introduced, inside a dry-box, 2.0 g 
(7.0 mmols) of m-chloro-peroxybenzoic acid (MCPBA), a commercial product 
of Aldrich Co., containing 75-80% of MCPBA, the remaining portion being 
m-chloro-benzoic acid. 
The MCPBA was dissolved in 25 ml of CH.sub.2 Cl.sub.2 (commercial product 
of Aldrich), previously distilled on P.sub.2 O.sub.5. The solution was 
maintained in contact with molecular sieves (Fisher M-564, type 3A, 8-12 
mesh) for 50 minutes, at room temperature. The solution was then 
transferred into another 50 ml flask equipped with a magnetic stirrer. 
The flask was cooled with liquid nitrogen (-196.degree. C.) and evacuated. 
By means of a Pyrex.RTM. vacuum line, 0.4 g (3.0 mmols) of 
perfluoro-2-azapropene CF.sub.2 .dbd.N--CF.sub.3 were condensed in the 
flask. 
The flask was introduced into a water-ice bath. The reaction mixture was 
stirred for 15 minutes at 0.degree. C. 
Through vacuum distillation there were recovered 0.24 g (1.6 mmols) of 
perfluoro-2-azapropene oxide (yield: 53%). 
The oxyaziridine was identified by comparing the IR and .sup.19 F-NMR 
spectra with the data of the literature. 
EXAMPLE 2 
Preparation of 
##STR8## 
5.4 g (25.0 mmols) of MCPBA (commercial product as in example 1) were 
introduced, inside a dry-box, into a 50 ml flask. 
The MCPBA was dissolved in 30 ml of CH.sub.3 CN (commercial product 
manufactured by Aldrich). The solution was maintained in contact with 
molecular sieves for 40 minutes at room temperature. Then it was 
transferred into another 50 ml flask equipped with a magnetic stirrer, and 
it was cooled to +10.degree. C. 
10.0 g (23.0 mmols) of CF.sub.3 (CF.sub.2).sub.2 
--CF.dbd.N--(CF.sub.2).sub.3 CF.sub.3 were added. The reaction mixture was 
maintained under stirring at +10.degree. C. for 5 minutes, was allowed to 
heat up to room temperature in 10 minutes and then was diluted with 70 ml 
of CH.sub.3 CN so as to dissolve the precipitate which had formed during 
the reaction. 
The product so obtained was separated by means of a separatory funnel, 
anhydrified on CaCl.sub.2 for 1 hour and then distilled. 8.2 g (18.3 
mmols) of pure oxyaziridine (yield: 79%), which was characterized through 
the IR, .sup.19 F-NMR and mass spectra, were recovered. 
EXAMPLE 3 
Preparation of 
##STR9## 
5.0 g (22.0 mmols) of MCPBA, dissolved in 25 ml of CH.sub.3 CN, were 
reacted with 8.0 g (15.0 mmols) of a 1:1 isomeric mixture of the 
perfluoro-imines of formula: CF.sub.3 (CF.sub.2).sub.3 
--CF.dbd.N--(CF.sub.2).sub.4 CF.sub.3 and CF.sub.3 CF.sub.2 CF 
(CF.sub.3)--CF.dbd.N--(CF.sub.2).sub.4 CF.sub.3. 
Following the same procedure described in example 2, 6.5 g (11.8 mmols) of 
pure oxyaziridine (yield: 79%) were obtained. The boiling point was 
68.degree.-70.degree. C./135 mm Hg. 
On the basis of the IR and .sup.19 F-NMR spectra and of the 
gaschromatographic data, the obtained product resulted to consist of a 1:1 
mixture of the two isomers of formula: 
##STR10## 
EXAMPLE 4 
Preparation of 
##STR11## 
3.5 g (15.3 mmols) of MCPBA, dissolved in 25 ml of CH.sub.3 CN, were 
reacted with 3.5 g (12.4 mmols) of CF.sub.3 --CF.dbd.N--CF(CF.sub.3).sub.2 
according to the same procedure illustrated in example 2. 
There were obtained 1.4 g (4.9 mmols) of pure oxyaziridine (yield: 39%). 
The product was characterized through the IR, .sup.19 F-NMR and mass 
spectra. 
EXAMPLE 5 
Preparation of 
##STR12## 
4.0 g (17.4 mmols) of MCPBA, dissolved in 25 ml of CH.sub.3 CN, were 
reacted with 6.0 g (9.5 mmols) of: CF.sub.3 (CF.sub.2).sub.4 
--CF.dbd.N--(CF.sub.2).sub.5 CF.sub.3, following the same procedure as is 
described in example 2. 
4.3 g (6.6 mmols) of pure oxyaziridine were obtained (yield: 70%). 
The product was identified through the IR and .sup.19 F-NMR spectra. 
EXAMPLE 6 
Preparation of 
##STR13## 
1.0 g (4.4 mmols) of MCPBA was dissolved in 10 ml of CH.sub.3 CN and 
maintained in contact with molecular sieves for 45 minutes, at room 
temperature. The solution was transferred into a 50 ml flask equipped with 
a magnetic stirrer. The flask was cooled with liquid nitrogen 
(-196.degree. C.) and then it was evacuated. 
Into the flask there were condensed, by means of a Pyrex.RTM. vacuum line, 
0.8 g (3.0 mmols) of (CF.sub.3).sub.2 N--CF.dbd.N--CF.sub.3. The reaction 
mixture was heated to room temperature in 10 minutes, then it was stirred 
for 15 minutes at that temperature. Through vacuum distillation there were 
obtained 0.5 g (1.82 mmols) of pure oxyaziridine (yield: 61%). 
The product was identified by comparing the IR and .sup.19 F-NMR spectra 
with the data of the literature.