Organic compounds -- part of the class 532-570 series – Organic compounds – Phosphorus esters
Reexamination Certificate
2002-08-08
2004-03-02
Davis, Brian (Department: 1621)
Organic compounds -- part of the class 532-570 series
Organic compounds
Phosphorus esters
C558S175000, C564S300000, C564S301000
Reexamination Certificate
active
06700007
ABSTRACT:
The present invention relates to a process for preparing &agr;,&bgr;,&bgr;-trisubstituted hydroxylamines, referred to hereinbelow as alkoxyamines, obtained from nitroxides, which can be used in particular as radical-polymerization initiators. The use of alkoxyamines such as those derived from (2,2,6,6-tetramethylpiperidyl)-N-oxide (TEMPO) in the preparation of macromolecules has given rise to many publications.
Thus, Hawker C. J. et al. (Macromolecules 1996, 29, pages 5245-5254) showed that the use of TEMPO-based alkoxyamines such as (2′,2′,6′,6′-tetra-methyl-1′-piperidyloxy)methylbenzene as initiators for the radical-mediated polymerization of styrene made it possible to control the polymerization and to gain access to well-defined polymers with low polydispersity indices, and they found that the polymerization rates were substantially equivalent to the rates obtained when they used conventional initiators such as AIBN or benzoyl peroxide in the presence of TEMPO.
Alkoxyamines can be prepared according to methods known in the literature. The most common method involves the coupling of a carbon radical with a nitroxide radical.
If an alkoxyamine is denoted by:
Y
1
, Y
2
, Y
3
, Y
4
, Y
5
, Y
6
, Z being defined later, the carbon radical Z
•
can be generated by various methods described in the literature: decomposition of an azo compound, abstraction of a hydrogen atom from a suitable substrate, addition of a radical to an olefin. The radical Z
•
can also be generated from an organometallic compound such as an organomagnesium reagent Z-MgX as described by Hawker C. J. et al. in Macromolecules 1996, 29, 5245-5254 or from a halo derivative Z-X in the presence of an organometallic system such as CuX/bipyridine (X=Cl or Br) according to a reaction of ATRA (Atom Transfer Radical Addition) type as described by Dorota Greszta et al. in Macromolecules 1996, 29, 7661-7670.
One of the methods most commonly used for preparing alkoxyamines (I) is the method involving the ATRA reaction.
This method consists in transferring an atom or a group of atoms onto another molecule in the presence of a CuX/bipyridine organometallic system, in solvent medium, according to the scheme:
In the organometallic system, X preferably represents a bromine, chlorine or iodine atom.
The procedure generally used consists in dissolving the organometallic system such as CuBr/bipyridine in an organic solvent, preferably an aromatic solvent such as benzene or toluene, and then in introducing the compound ZX and the nitroxide (II) into the solution.
This approach has the major drawback of requiring long reaction times, that are unacceptable for an industrial preparation of alkoxyamines, or of using a large excess of one of the reagents.
In addition, the removal of the residual metal from the products obtained is difficult, requiring expensive purification operations such as passing the products through a column of silica.
Thus, in international patent application WO 98/40415, for example, Matyjaszewski K. et al. obtain 1-(2,2,6,6-tetramethylpiperidyloxy)-1-phenylethane in a yield of 69% after purification by column chromatography, by reacting TEMPO and (1-bromoethyl)benzene in a TEMPO/(1-bromoethyl)benzene molar ratio of 2 (i.e. a molar excess of TEMPO equal to 100%) for 2 hours at 90° C., in the presence of an organometallic system [4,4′-bis(5-nonyl)-2,2′-bipyridine/Cu(OTf)
2
/Cu
0
].
A process has now been found for preparing alkoxyamines of formula:
the said process consisting in reacting the said nitroxide (II) with a halocarbon compound ZX in which X represents a chlorine, bromine or iodine atom, in the presence of an organometallic system MA
n
(L)
y
(III) in which:
M represents a transition metal with an oxidation state n such that it can participate in a redox reaction with the transferable atom or group,
A represents a halogen atom, a carboxylate group or a triflate group,
L represents a ligand for the metal M,
y is equal to 1, 2 or 3,
n is equal to 1, or 2, according to the scheme:
the said process being characterized in that the procedure is carried out in a biphasic medium comprising at least one ionic liquid and an organic solvent which is immiscible with the said ionic liquid.
The process according to the invention consists in carrying out the following steps:
a) a metal salt MA
n
, optionally a metal X with an oxidation state zero, a ligand L, at least one ionic liquid, an organic solvent, the halo carbon compound ZX and the nitroxide (II) are mixed, with stirring, in a ZX
itroxide (II) molar ratio ranging from 1 to 1.5, and preferably close to 1;
b) the reaction medium is kept stirring at a temperature of between 20° C. and 90° C., and preferably at a temperature ranging from 20° C. to 35° C., until the nitroxide (II) has completely disappeared; and then
c) the stirring is stopped, the mixture is separated by decantation, the organic phase is recovered and optionally washed with water, and then
d) the alkoxyamine (I) is isolated from the organic phase by evaporating the organic solvent under reduced pressure, and
e) optionally, the ionic liquid phase is recycled at least once with regeneration of the active species of the metal M(M
n
).
According to the present invention, the number of recyclings of the ionic liquid phase is not limiting. Preferably, the ionic liquid phase will be recycled a number of times ranging from 1 to 10.
According to the present invention, the expression ionic liquids refers to organic salts which are liquid at reaction temperatures.
By way of illustration of organic salts which can be used according to the present invention, mention will be made of ammonium, pyridinium, imidazolium, triazolium, guanidinium, phosphonium or sulphonium salts. The anion may be, inter alia, a halide such as Cl
−
, Br
−
, I
−
, a tin halide such as SnCl
3
−
, a germanium halide such as GeCl
3
−
, a gallium halide such as GaCl
3
−
, an aluminium halide such as AlCl
4
−
, Al
2
Cl
7
−
, Al
3
Cl
10
−
, a transition metal halide such as CuCl
2
−
, a boron, antimony or phosphorus fluoride such as BF
4
−
, SbF
6
−
or PF
6
−
, a carboxylate such as CF
3
CO
2
−
, a sulphonate such as CF
3
SO
3
−
or FSO
3
−
, an amide such as (CF
3
SO
2
)
2
N
−
, a tetralkyl or tetraaryl boride such as B(C
6
F
5
)
4
−
. The cation and the anion of the salt or of the mixture of salts will be appropriately chosen in order to have a liquid at the reaction temperature. Optionally, the ionic liquid may contain water. According to the present invention, use will be preferably made of N,N′-dialkylimidazolium salts. By way of example of such salts, mention will be made of:
1-butyl-3-methylimidazolium chloride,
1-propyl-3-methylimidazolium chloride,
1propyl-3-methylimidazolium bromide.
The organic solvent is chosen so as to have a biphasic system with the ionic liquid(s). Preferably, the organic solvent will be chosen from aliphatic or aromatic hydrocarbons, or alternatively from ethers. Toluene will be most particularly used.
According to the present invention, M preferably represents Cu(I), Fe(II), Ni(II), and most particularly Cu(I).
The active species of the metal M, hereinbelow M
n
, is generated from a metal salt, preferably a metal halide M
n
X
n
. It may also be generated in situ according to a redox reaction of the type:
n
M
n+1
X
n+1
+M
0
⇄n+
1M
n
X
n
in which the
M
of the metal M represents the oxidation state of the said metal, M
0
represents the metal M with the oxidation state zero and n=1 or 2.
Overall, the M
n
/RX ratio should be at least equal to 1. The preferred metal halide is CuBr.
Preferably, A represents a halogen such as Cl or Br, a carboxylate group such as acetate or a triflate group and X represents a chlorine atom or a bromine atom.
According to the present invention, the ligand L which co-ordinates with the metal M may contain one or more nitrogen, phosphorus, oxygen or sulphur atoms
Couturier Jean-Luc
Guerret Olivier
Atofina
Davis Brian
Millen White Zelano & Branigan P.C.
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