Process for preparing aromatic or heteroaromatic sulfur compound

Details Process for preparing aromatic or heteroaromatic sulfur compound Process for preparing aromatic or heteroaromatic sulfur compound

1996-07-24

1998-04-21

Ivy, C. Warren

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

Organic compounds

Sulfur containing

568 62, C07C31906

Patent

active

057419337

DESCRIPTION:

BRIEF SUMMARY
This application is a 371 of PCT/JP95/02315 which is now published as WO 96/16034 on May 30, 1996.


FIELD OF THE INVENTION

The present invention relates to a novel process for preparing an aromatic or heteroaromatic thiol or an aromatic or heteroaromatic disulfide and a novel process for preparing an aromatic or heteroaromatic halogenated methyl sulfide which is useful as the starting material for said thiol or disulfide. The aromatic or heteroaromatic thiol and disulfide are useful compounds which are used for various purposes as in pharmaceutical compositions, agricultural compositions, functional materials or the like.


BACKGROUND ART

Various processes have been known for preparing an aromatic or heteroaromatic thiol or disulfide. Among them, the conventional processes for preparing an aromatic or heteroaromatic thiol by bond cleavage in alkyl sulfide are classified into the following three processes: thiolate in hexamethylphosphoric triamide (abbreviation HMPA) used as a solvent ##STR1## (B) Process comprising reacting an aromatic alkyl sulfide with metal sodium in liquid ammonia ##STR2## (C) Process comprising oxidizing an aromatic methyl sulfide with perbenzoic acid, reacting the oxide with trifluoroacetic acid, and causing triethylamine to act on the reaction mixture ##STR3##
However, these conventional processes pose the following drawbacks when commercially conducted.
The process (A) is defective in that the HMPA used as a solvent is not easily available and expensive and that the sodium mercaptide used as a reagent is difficult to handle in a nonaqueous system. Further problematic is the disposal of dialkyl sulfide produced as a by-product.
The process (B) is industrially difficult to carry out because of high risks involved in handling, use of an expensive metal sodium and low-yield production. The process (C) requires a number of reaction procedures and necessitates the use of an expensive, highly dangerous reaction reagent such as perbenzoic acid, trifluoroacetic acid, etc.
As described above, none of the conventional processes for preparing an aromatic or heteroaromatic thiol by bond cleavage in alkyl sulfide are satisfactory from the viewpoint of industrial application.


DISCLOSURE OF THE INVENTION

An object of the present invention is to provide a process for preparing an aromatic or heteroaromatic thiol at a commercially low cost and with ease.
Another object of the invention is to provide a process for preparing an aromatic or heteroaromatic disulfide at a commercially low cost and with ease.
The present inventors conducted extensive research on the reaction for bond cleavage in alkyl sulfide to overcome the drawbacks of said known processes and to provide processes for preparing aromatic or heteroaromatic thiol and disulfide at commercially low costs and with ease.
The inventors' research found that the aromatic or heteroaromatic halogenated methyl sulfide represented by the formula (1) can be easily hydrolyzed to give the corresponding aromatic or heteroaromatic thiol represented by the formula (2) in a high yield. The finding led to the completion of the present invention. Stated more specifically, the first invention is directed to a process for preparing an aromatic or heteroaromatic thiol represented by the formula (2), the process comprising hydrolyzing an aromatic or heteroaromatic halogenated methyl sulfide represented by the formula (1) as shown below: ##STR4## wherein Ar is an aromatic or heteroaromatic ring which has no substituent or which has an optional substituent or substituents, X is a halogen atom, m is an integer of 1 to 3 and n is 1 or 2.
Since thiol can be easily converted to disulfide by oxidation, the corresponding disulfide can be produced by executing an oxidation step subsequent to the above-mentioned reaction step. The second invention is directed to a process for preparing an aromatic or heteroaromatic disulfide represented by the formula (3), the process comprising the steps of hydrolyzing an aromatic or heteroaromatic halogenated methyl sulfide represe

REFERENCES:
patent: 4868336 (1989-09-01), Presnall
Testaferri et al., "A Convenient Synthesis of Aromatic Thiols from Unactivated Aryl Halids," Tetrahedron Letters, 21:3099 (1980). Elimination-Substitution Competition with Methoxide and Methanethiolate Ions in Hexamethylphosphoric Triamide," Synthesis, p. 478 (Jun. 1982).
Ferretti, "1,2,-Dimercaptobenzene," Org. Synth. Coll., 5:419 (1973).
Adams et al., "Thioethers. III. Preparation of Aromatic Di- and Tri-mercapto Compounds by Dealkylation of Aryl Aklyl Thioethers," J. Am. Chem. Soc., 81:4939 (1959).
Young et al., "The Methyl Group as a Protecting Group for Arylthiols: A Mild and Efficient Method for the Conversion of Methyl Acryl Sulfides to Arylthiols," Tetrahedron Letters, 25:1753 (1984).

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