Process for producing aromatic disulfides

Details Process for producing aromatic disulfides Process for producing aromatic disulfides

2001-04-04

2002-09-03

Vollano, Jean F. (Department: 1621)

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

Organic compounds

Sulfur containing

C568S024000

Reexamination Certificate

active

06444853

ABSTRACT:

This application is the national phase application of International Application PCT/JP99/04371 (not published in English) filed Aug. 12, 1999.
TECHNICAL FIELD
This invention relates to a process for the preparation of aromatic disulfides from aromatic thioethers, more specifically, to a process for the preparation of aromatic disulfides which comprises reacting aromatic thioether and halogen or precursor thereof.
BACKGROUND ART
Aromatic disulfides having an electrophilic group bonded to an aromatic ring, particularly aromatic disulfides represented by the general formula (II′):
wherein Y represents a monovalent electrophilic group which may be the same or different from each other; and
n is an integer of 1 to 5,
have been widely-used as intermediates of medicines and agricultural chemicals.
Aromatic disulfides having such a substituent can be usually produced by the oxidation of corresponding aromatic thiols. As a process for the preparation of said aromatic thiols, several processes have been proposed.
For example, there have been proposed a method of mercaptization of a polychlorinated benzene by sodium sulfide dissolved in liquid ammonia in an autoclave (Kogyo Kagaku Zasshi, vol. 70, pp. 114-118 (1967)); a method for the preparation of halogenated aromatic thiols by reacting sodium nitrite with an amino group-containing aromatic halide to obtain a diazonium salt, followed by reacting it with potassium O-ethyldithio-carbonate and treating the same with an alkali (Japanese Patent Publication No. 26100/1969); a method for the preparation of halogenated thiophenols by the reduction of 4-halobenzensulfinic acids in the presence of a mineral acid and zinc powder (Japanese Provisional Patent Publication No. 295968/1990), etc.
However, these methods are limited since high pressure reaction using liquid ammonia shall be carried out, they are dangerous since diazonium salts are formed, and require a specific apparatus for carrying out the reduction in the presence of a mineral acid, etc., and in either of these methods, yields are low and the purification of the desired product is difficult.
Moreover, in Japanese Provisional Patent Publication No. 143533/1996, a method for the preparation of aromatic thiols by the chlorination of a methyl group bonded to a sulfur atom of thioanisol with a chlorine gas and then hydrolysis of the resulting compound in the presence of a mineral acid has been disclosed. However, in this method, methyl mercaptane, which is volatile and stinking, must be used and complex steps to introduce chlorine gas are required for the chlorination of the methyl group.
Desired aromatic disulfides can be obtained by the oxidation and the dimerization of the aromatic thiols obtained by these methods with an oxidizing agent. However, according to these methods, multi-step reactions in which aromatic thiols are once obtained and then aromatic disulfides are formed by the dimerization reaction shall be carried out. Also, most of the aromatic thiols are sublimable so that the drying and the purification become complex and they have irritating property whereby they should be handled carefully. Accordingly, it is earnestly desired to obtain a process for. the preparation of aromatic disulfides without passing through aromatic thiols.
In Synthesis, June, 1993, pp. 573-574 (written by D. A. Dickman et al.), a method for the preparation of disulfides represented by the formula:
R′—S—S—R′
wherein R′ represents a phenyl group which is unsubstituted or substituted by a formyl group, a benzyl group or a n-butyl group,
by the reaction of a thioether represented by the formula:
R′—S—t—C
4
H
9
wherein R′ has the same meaning as defined above, with an acetic acid solution of hydrobromic acid in the presence of dimethylsulfoxide. However, according to this method, dimethylsulfide having remarkably bad smell is formed by the reaction of dimethylsulfoxide so that recovery of the same shall be carried out without dissipating it in air. Also, depending on the kind of R′, the reaction does not substantially proceed under the conditions disclosed therein and no desired compound can be obtained.
DISCLOSURE OF THE INVENTION
An object of this invention is to produce aromatic disulfides having an electrophilic group from aromatic thioether which can be relatively easily synthesized with a simple and easy method, with good purity and without generating byproducts handling of which are complicated.
The present inventors have earnestly studied to solve the above-mentioned problems, and as a result, they have found that the above objects can be accomplished by the reaction of an aromatic thioether having a hydrocarbyl group and a substituted aromatic ring with halogen such as bromine, and found that the same results can be obtained when hydrogen halide and hydrogen peroxide are used as precursors of said halogen to accomplish this invention.
That is, this invention relates to a process for the preparation of aromatic disulfides represented by the formula (II):
Y
n
—Ar—S—S—Ar—Y
n
  (II)
wherein Ar represents a hydrocarbon aromatic ring group;
Y represents a monovalent electrophilic group, and when n is 2 or more, a plural number of Y's may be the same or different from each other; and n is an integer of 1 to 12,
which comprises allowing
(A) an aromatic thioether represented by the formula (I):
Y
n
—Ar—S—R  (I)
wherein Y, Ar and n have the same meanings as defined above; and R represents a monovalent hydrocarbyl group selected from the group consisting of a monovalent tertiary hydrocarbyl group, and a benzyl group and a monovalent secondary hydrocarbyl group derived from a benzyl group;
to react with
(B) at least one of the following (1) to (4):
(1) bromine;
(2)(a) hydrogen bromide and (b) hydrogen peroxide;
(3)(c) chlorine, in the presence of a catalytic amount of iodine and/or hydrogen iodide;
(4)(d) hydrogen chloride and (b) hydrogen peroxide, in the presence of a catalytic amount of iodine and/or hydrogen iodide.
EMBODIMENTS FOR CARRYING OUT THE INVENTION
When the preparation process of this invention is shown by a chemical formula, it become as follows:
2Y
n
—Ar—S—R+X
2
→Y
n
—Ar—S—S—Ar—Y
n
+2RX
wherein X is a halogen atom, and Ar, R, Y and n have the same meanings as defined above.
(A) an aromatic thioether to be used in this invention is thioether derivatives having one —SR bonded to the carbon atom of the aromatic ring, and having at least one of Y.
Ar is a hydrocarbon aromatic group. As Ar, there may be mentioned an aromatic group such as benzene, biphenyl, terphenyl, naphthalene, anthracene, pyrene rings, etc. A benzene ring group is particularly preferred due to the reactivity with (B) and usefulness of the resulting disulfides.
Y is a monovalent electrophilic group which is bonded to a carbon atom of the aromatic ring group Ar, and introduced as a substituent into the aromatic disulfides which are objective products. According to the presence of Y. the reaction of (A) and (B) is promoted and a substitution reaction of a hydrogen atom on the aromatic ring with halogen can be restrained. As Y, there maybe typically mentioned halogenated, nitro, nitrile, sulfone, sulfamoyl or hydrocarbylsulfonyl groups. As the halogenated, there may be mentioned fluoro, chloro, bromo and iodo, and as the hydrocarbylsulfonyl group, there may be mentioned methylsulfonyl, phenylsulfonyl, p-toluylsulfonyl, etc. When a plural number of Y's exist, they may be the same or different from each other.
n is an integer of 1 to 12, and, for example, when Ar is a benzene ring group, it is an integer of 1 to 5, and when it is a terphenyl ring group, it is an integer of 1 to 12. With regard to the same Y's, the larger the n is, the easier the reaction of (A) and (B) proceeds.
R is a monovalent hydrocarbyl group within a specific range, which binds to a sulfur atom, and more specifically, it is selected from a monovalent tertiary hydrocarbyl group, and a benzyl group and a monovalent secondary hydrocarbyl group derived from the benzyl gr

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