Method for preparing aromatic diphenyl thioethers

Details Method for preparing aromatic diphenyl thioethers Method for preparing aromatic diphenyl thioethers

2001-08-27

2003-07-22

Vollano, Jean F. (Department: 1621)

Organic compounds -- part of the class 532-570 series

Organic compounds

Sulfur containing

C568S058000, C546S294000

Reexamination Certificate

active

06596905

ABSTRACT:

This application is an application under 35 U.S.C. Section 371 of International Application Number PCT/FR99/03273 filed on Dec. 23, 1999.
The present invention relates to a process for preparing biphenyl type aromatic thioethers.
More precisely, the invention relates to the preparation of an aromatic compound comprising a concatenation of at least two phenyl groups at least one of which carries a thioether group.
More particularly, the invention relates to the preparation of 4-chloro-4′-thiomethyldiphenyether.
When a functional group is to be introduced into a biphenyl type molecule, there is a problem with introducing a functional group into only one of the benzene rings.
The present invention aims to provide a process that consists of introducing at least one thioether group into one of the phenyl groups.
It has now been discovered, and this forms the subject matter of the present invention, a process for preparing a biphenyl type aromatic thioether, characterized in that a diazonium salt of a biphenyl type aromatic compound is reacted with a disulphide type sulphur-containing compound in an aqueous medium in the presence of an effective quantity of a coupling catalyst.
The term “biphenyl type aromatic thioether” means a concatenation of two phenyl groups connected together wherein at least one of the benzene rings carries a thioether function.
In a preferred variation of the process of the invention, the thioether is prepared using a process that associates preparation of the diazonium salt from the corresponding aromatic amine then, without separation, carrying out the reaction with the sulphur-containing compound.
In accordance with the process of the invention, a biphenyl type aromatic amine can be used as the starting compound; in a first step, it is transformed into a diazonium salt.
The term “biphenyl type aromatic amine” means a concatenation of two phenyl groups connected together wherein at least one of the benzene rings carries an amine function.
The starting aromatic amine can be represented by the following general formula (1):
in which formula (I):
R
1
represents a hydrogen atom or a substituent R;
Z represents:
a covalent bond;
an alkylene or alkylidene group containing 1 to 4 carbon atoms, preferably a methylene or isopropylidene group;
a group B which may be one of the following atoms or groups:
—O—, —CO—, —COO—, —OCOO—
—S—, —SO—, —SO
2
—,
 in which formulae, R
2
represents a hydrogen atom or an alkyl group containing 1 to 6 carbon atoms, or a phenyl group.
In formula (I), one or both benzene rings can be substituted, meaning that in the biphenyl type starting substrate, at least one of the 5 hydrogen atoms of the aromatic ring can be replaced by an atom other than a hydrogen atom. In particular, it can be a halogen atom, carbon, oxygen or nitrogen.
Group R
1
represents a hydrogen atom or any other group R.
Group R can have any nature provided that it does not interfere with the diazotisation reaction.
Non-limiting examples of substituents that can be cited are given below:
a linear or branched alkyl group, preferably containing 1 to 6 carbon atoms, more preferably 1 to 4 carbon atoms;
a linear or branched alkenyl group preferably containing 2 to 6 carbon atoms, more preferably 2 to 4 carbon atoms;
a linear or branched halogenoalkyl group preferably containing 1 to 4 carbon atoms, and 1 to 9 halogen atoms;
a cycloalkyl group containing 3 to 7 carbon atoms, preferably a cyclohexyl group;
a phenyl group;
a hydroxyl group;
a NO
2
group;
a R
3
—O— alkoxy group or R
3
—S— thioether group where R
3
represents a linear or branched alkyl group containing 1 to 6 carbon atoms, preferably 1 to 4 carbon atoms, or a phenyl group;
a —N—(R
2
)
2
group where groups R
2
, which may be identical or different, represent a hydrogen atom, a linear or branched alkyl group containing 1 to 6 carbon atoms, preferably 1 to 4 carbon atoms, or a phenyl group;
a —NH—CO—R
2
group where R
2
has the meaning given above;
a carboxyl group or R
2
—O—CO— derivative, where group R
2
has the meaning given above;
an acyloxy or aroyloxy group R
3
—CO—O—, where group R
3
has the meaning given above;
a B(OR
3
)
2
group, where group R
3
has the meaning given above;
a halogen atom, preferably a fluorine atom;
a CF
3
group;
two groups R can together form an alkylenedioxy group containing 1 to 4 atoms in the alkylene group, preferably a methylenedioxy or ethylenedioxy group.
Preferred groups R that can be cited are a halogen atom, preferably a fluorine, chlorine or bromine atom or a halogenoalkyl group, preferably perfluoroalkyl; a hydroxyl group; an alkyl or alkoxy group containing 1 to 6 carbon atoms, preferably 1 to 4 carbon atoms; an amino group or an amino group substituted with one or two alkyl groups containing 1 to 6 carbon atoms, preferably 1 to 4 carbon atoms.
Preferred compounds are those with formula (I) where R
1
represents a fluorine atom or a chlorine atom and Z represents an oxygen atom.
In accordance with the process of the invention, in a first step the diazonium salt of the biphenyl type aromatic amine preferably with formula (I) is prepared.
To this end, to transform the amino group into a diazonium group, the starting substrate is reacted with an acid. While it is possible to use an acid such as sulphuric acid, it is preferable to use a hydrogen acid to put the amine group into the halohydrate salt form.
Thus, the starting substrate preferably with formula (I) is preferably reacted with hydrochloric acid or hydrobromic acid.
The quantity of acid used is such that the mole ratio between the number of H
+
ions and the number of moles of substrate is in the range 2.0 to 2.5, preferably in the range 2.0 to 2.2.
In the next step, the diazonium salt is prepared by reacting the biphenyl type aromatic amine in the halohydrate form with a diazotisation reactant that is any source of NO+.
Thus it is possible to start from nitrogen dioxide NO
2
, nitrogen trioxide N
2
O
3
, nitrogen tetroxide N
2
O
4
, nitric oxide NO associated with an oxidising agent such as nitric acid, nitrogen dioxide or oxygen. When the reactant is a gas under the reaction conditions, it is bubbled into the mediun.
It is also possible to use a nitrous acid, a nitrosyl sulphide or a nitrose or a nitrous salt, preferably an alkali metal salt, more preferably a sodium salt.
It is also possible to use alkyl nitrites, more particularly those with formula (II):
R
a
—ONO  (II)
in which formula (II), R
a
represents a linear or branched alkyl group containing 1 to 12 carbon atoms, preferably 1 to 4 carbon atoms.
Advantageously, sodium nitrite is used.
The quantity of diazotisation reactant used can vary widely. When it is expressed as the mole ratio of the aromatic aminel diazotisation reactant defined as NO
+
, it is at least equal to the stoichiometric quantity but preferably, it is used in an excess of up to 120% of the stoichiometric quantity, preferably in the range 100% to 120%.
Regarding the concentration of the aromatic amine substrate in the reaction medium, it is preferably in the range 0.5 to 2.5 mol/l, more preferably about 1 mol/l.
The amine halohydrate is prepared by simply mixing the starting amine and the acid.
The reaction is advantageously carried out at a temperature in the range 50° C. to 100° C.
The diazotisation reactant is then added, preferably slowly in fractions or continuously.
Regarding the temperature of the diazotisation reaction, this is generally a low temperature, advantageously in the range −10° C. to 20° C., preferably in the range 0° C. to 10° C.
In the process of the invention, the sulphur-containing compound is reacted with the diazonium salt obtained, which preferably has the following formula (III):
in which formula (III):
X represents a halogen atom X, preferably a chlorine or bromine atom, a HSO
4
−
group or a SO
4
=
group;
R
1
and Z have the meanings given above;
n equals 1 or 2.
The sulphur-containing compound used preferably has the following formula (IV):
R
4
—S—S—R
5
  (IV)
in said formula (IV):
R

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