Chemistry: electrical and wave energy – Processes and products – Processes of treating materials by wave energy
Reexamination Certificate
2000-08-24
2003-01-14
Wong, Edna (Department: 1741)
Chemistry: electrical and wave energy
Processes and products
Processes of treating materials by wave energy
C568S056000
Reexamination Certificate
active
06506286
ABSTRACT:
The present invention relates to a perfluoroalkylation technique and especially a reactant, a compound and a process for the perfluoroalkylation of a nucleophile, and to the derivatives thus obtained. It relates more particularly to the use of the homolytic scission of certain chalcogen esters with relatively heavy chalcogens, that is to say of an atomic rank at least equal to that of sulphur.
Thus, the field of the invention is that of the synthesis of compounds which are perhaloalkylated and/or acylated:
either by grafting of perhaloalkyl and/or acyl radicals on to substrates, at least partially organic and of various kinds, the said radicals being supplied by perhaloalkylating and/or acylating agents,
or by direct autotransformation of perhaloalkylating agents.
The present invention also relates to a process for obtaining perhalogenated, in particular perhaloalkylated and/or acylated compounds and to perhaloalkylated and/or acylated thioethers.
The halogen considered more precisely but without any limitation being implied is fluorine, because of the great interest which exists in employing it as a substituent in many industrial products such as colorants, polymers and pharmaceutical and agrochemical compounds. It is well known, in fact, that fluorine is an inducer of lipophilicity in biologically active molecules.
Moreover its electronegativity and its relatively small size are positive factors in relation to:
the absorption of light by colorants,
the stability, solubility and mechanical and electrical properties of polymers,
and the biological properties of certain pharmaceutical and/or agrochemical molecules.
Bearing in mind the scientific and technical interest of the trifluoromethyl substituent, especially in the pharmaceutical and the agrochemical fields, many methods of trifluoromethylation have already been proposed.
Among these, direct trifluoromethylation according to an electrophilic, nucleophilic and/or radical mechanism is that most worthy of interest from the technical and industrial standpoint.
Techniques for trifluoromethylation by a radical have the advantage of often making it possible to operate in very mild conditions.
To be sure, using this route, the perfluoroalkylation with the aid of perfluoroalkyl iodides such as CF
3
I is known. These compounds react with various substrates thermally, under irradiation or in the presence of a catalytic quantity of a radical initiator such as benzoyl peroxide or azobisisobutyronitrile (AIBN). Perfluoroalkyl iodides are costly products and rarely available on an industrial scale.
Moreover, the reactions involved are liable to give rise, as by-products, to iodine-containing products known to be toxic, of the CF
3
—CH
2
—CH
2
—I type.
Derivatives of perfluoroalkanesulphonic acids which are also suitable for a radical route are themselves also costly and still rarely available on an industrial scale.
Nitrosotrifluoromethane derivatives can also be employed, but suffer from the disadvantage of being toxic and hazardous to synthesize.
Perfluoroalkanoic acids and their derivatives, such as trifluoroacetic acid, could possibly have been employed as perhaloalkylating agents. It has been found, however, that they are difficult to convert into the .CF
3
radical. The electrochemical oxidation used for this purpose requires, in fact, very high voltages and large excesses of this reactant. The industrial feasibility of the process involving these compounds is therefore not established.
Trifluoromethanethiol (CF
3
SH) and trifluoromethanesulphenyl chloride CF
3
SCl are known as being reactive agents for trifluoromethylthiolation. However, they have the disadvantage of being gaseous and highly toxic.
In practice, the most common trifluoromethylating agent is bromotrifluoromethane (CF
3
Br). This industrial product is employed as a fire-extinguishing agent, especially in aircraft and computer rooms. It is at present one of the largest sources of trifluoromethyl radicals.
CF
3
Br can be reduced monoelectronically to give .CF
3
, a radical capable of being trapped, either by nucleophilic substrates, reducing agents and initiators, such as thiolates, thiophenates, selenophenates, stabilized carbanions or enamines, or by a reducing agent of the SO
2
−
. type.
By way of example of a conversion, according to the abovementioned technique, of disulphide substrates giving rise to trifluoromethylated alkyls or aryl sulphides, reference will be made to the paper by Clavel et al.:
Phosphorus, Sulfur
&
Silicon
, 1991, vol. 59, p. 129-132. The paper by Wakselman et al.,
J. Chem. Soc., Chem. Commun
., 1984, p. 793-794, gives an illustration of the trifluoromethylation of thiophenols with the aid of CF
3
Br.
Alternatively, .CF
3
can be generated with the aid of an oxidizing agent of the tert-butyl hydroperoxide (t-BuOOH) type and of sodium trifluoromethanesulphinate (CF
3
SO
2
Na), itself obtained from bromotrifluoromethane and sodium dithionite. In these conditions disulphides are converted to trifluoromethyl thioethers (RSCF
3
) (cf. Clavel & al.:
Phosphorus, Sulfur
&
Silicon
, 1991, vol. 59, pages 169-172), aromatic compounds are trifluoromethylated (cf. Langlois & al.:
Tetrahedron Letters
, 1991, vol. 32, No. 51, p. 7525-7528) and enol esters produce trifluoromethyl ketones (cf. Langlois & al.:
Tetrahedron Letters
, 1992, vol. 33, No. 10, p. 1291-1294).
The problem related to these known techniques employing bromotrifluoromethane as source of .CF
3
has to do with the difficulty of handling this gas. What is more, it is a product which is bound to be prohibited by the international regulations dealing with the environment, because of its presumed harmful effects on the environment, especially because of the greenhouse effect which it allegedly produces, and hypothetical effects on the ozone layer.
This will therefore give rise to a considerable demand for radical trifluoromethylating agents which are convenient to use, nontoxic, easily available and inexpensive.
Thus, one of the objectives of the present invention is to provide a process for obtaining perhalogenated, in particular perhaloalkylated and/or acylated, compounds in which advantageous substitutes for bromotrifluoromethane are used.
Another aim of the present invention is to provide a reactant of the above type which allows a perfluoro radical to be grafted on to an electrophile.
Another aim of the present invention is to provide compounds which are capable of being employed for the above reactants and/or in the above process.
Another aim of the present invention is to provide derivatives which are capable of being obtained by the reactants and process of the above type.
The Applicant Company has succeeded in developing such a reactant, which is characterized in that it comprises, for successive or simultaneous addition:
a compound of formula (I):
R
f
—M(X)(Z)
n
—Y—R;
with R denoting a carbon-containing radical, advantageously of at most 15 preferably 10 carbon atoms, preferably chosen from alkyls, aryls, acyls, thioacyls [such as the hydrocarbyl-chalcogenylacyls (and especially carbonyls) (the preferred chalcogens here are sulphur and oxygen), especially aryloxyacyls, alkoxyacyls and in particular aryloxycarbonyls, alkoxycarbonyls and aryloxythiocarbonyls, alkoxythiocarbonyls or their homologues when the oxygens are completely or partially replaced with sulphur];
with R
f
, advantageously exhibiting at most 20 carbon atoms, preferably at most 15 carbon atoms,
denoting a radical of formula (II):
[R
2
—(C
)
p
—][R
1
—(C
)
m
]CF—
where R
1
and R
2
, which are similar or different, denote a light halogen atom, fluorine or chlorine, preferably fluorine, a carbon-containing radical
where m is zero or an integer chosen-within the closed interval from 0 to 12, advantageously at most equal to 8 and preferably at most equal to 6;
where p is zero or an integer chosen within the closed interval from 0 to 12, advantageously at most equal to 6, preferably at most equal to 4;
where
s, which are similar or different, denote perhalogenated, advantageou
Forat Gerard
Langlois Bernard
Roques Nicolas
Tordeux Marc
Wakselman Claude
Rhodia Chimie
Wong Edna
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