CH634841A5 - Process for the preparation of optionally substituted thioxanthones. - Google Patents

Abstract

Optionally substituted thioxanthones are prepared by reacting the corresponding o,o'-dihalogenobenzophenones with sulphur in an alkaline medium. The reaction is performed in a two-phase system in the presence of a phase transfer catalyst. The thioxanthones thus prepared may be used as, for example, photoinitiators.

Description

** WARNING ** Beginning of DESC field could overlap end of CLMS **.

PATENT CLAIMS 1. A process for the preparation of substituted or unsubstituted thioxanthones by reacting the corresponding o, o'-dihalogenobenzophenones in an alkaline medium in the presence of sulfur, characterized in that the reaction is carried out in a two-phase system in the presence of a phase transfer catalyst.

2. The method according to claim 1 for the preparation of compounds of the formula

wherein R1 and R2 independently of one another are hydrogen, alkyl (C1-C4), alkoxy (CrCu) or halogen, R3 independently of one another alkyl (C1-C4), R4 independently of one another denote alkyl (C1-C4) and n and m independently denote zero, 1, 2 or 3, by reaction of a compound of the formula

wherein R1, R2, R3, R4, n and m have the above meaning and Hal is halogen, in an alkaline medium in the presence of sulfur, in a two-phase system in the presence of a phase transfer catalyst.

3. The thioxanthones produced by the process of claims 1 and 2.

4. Use of the compounds prepared by the process of claims 1 and 2 as photoinitiators.

The present invention relates to a process for the preparation of substituted or unsubstituted thioxanthones by reacting the corresponding o, o'-dihalogenobenzophenones in an alkaline medium in the presence of sulfur, characterized in that the reaction is carried out in a two-phase system in the presence of a phase transfer catalyst.

The invention also relates to the thioxanthones produced in this way. In particular, the invention relates to a process for the preparation of compounds of the formula

wherein R1 and R2 independently of one another are hydrogen, alkyl (C1-C4), alkoxy (C1-Cl2) or halogen, R3 independently of one another alkyl (C1-C4), R4 independently of one another are alkyl (C1Cj and n and m independently of one another mean zero, 1, 2 or 3, by reacting a compound of the formula

wherein R1, R2, R3, R4, n and m have the above meaning and Hal means halogen in an alkaline medium in the presence of sulfur in a two-phase system in the presence of a phase transfer catalyst.

The process according to the invention is preferably used for the preparation of compounds of the formula

wherein R'1 alkyl (C1-C4), alkoxy (C1-C8) or halogen R'2 is hydrogen or halogen n 'is zero, 1 or 2, and m' is zero or 1, and R3 and R4 have the above meanings by adding a compound of the formula

wherein R'1, R'2, R'3, R'4, m ', n' and Hal have the above meaning, in an alkaline medium in the presence of sulfur in a two-phase system in the presence of a phase transfer catalyst.

Preference is given to preparing compounds of the formula

where R "1 is halogen, R'3 signifies methyl or ethyl and n "signifies zero or 1 by adding a compound of the formula

wherein R "1, R'3, n" and Hal have the above meaning, in an alkaline medium in the presence of sulfur in a two-phase system in the presence of a phase transfer catalyst.

In the above formulas, halogen is preferably chlorine or bromine, preferably chlorine.

R1 preferably denotes R'1, preferably alkoxy or halogen, preferably R "1, preferably chlorine.

R2 is preferably hydrogen, alkyl or halogen, preferably R'2, preferably hydrogen.

R3 is preferably R'3, preferably methyl, preferably in the 1- and / or 4-position R4 is preferably methyl or ethyl, preferably methyl, preferably in the 5- and / or 8-position.

n preferably denotes n ', preferably n ", preferably zero.

m preferably denotes zero, 1 or 2, preferably m ', preferably zero.

As alkyl, R1 preferably has 1 or 4 carbon atoms and is preferably methyl.

As alkyl, R2 preferably has 1 or 4 carbon atoms.

R2 as alkoxy preferably has 1-8, preferably 1-4, preferably 1 or 4 carbon atoms, preferably 1 carbon atom.

Hydroxides, carbonates, hydrocarbonates or alcoholates, for example, can be used as compounds with an alkaline reaction. Alkali or alkaline earth compounds in aqueous 30-50% strength solution and / or ammonia are preferably used, preferably alkali hydroxides, alkali carbonates and / or ammonia. Preferably sodium or potassium compounds, preferably sodium or potassium hydroxide.

At least as much sulfur and cation equivalents of the alkaline compound are used as is necessary for ring formation for the thioxanthone compound or for binding the released halogen of the compound of the formula (II). The compound of the formula (all) is prepared in a manner known per se by means of the Friedel-Craft reaction.

The reaction is carried out in a two-phase system, the organic starting compound, i.

the o, o'-dihalobenzophenone is predominantly in the organic phase, and the sulfur is predominantly in the aqueous or solid phase. The reaction takes place with the addition of phase transfer catalysts, so-called onium salts, preferably ammonium or phosphonium salts. Such onium salts are known per se, e.g. quaternary ammonium salts or quaternary phosphonium salts such as triethylbenzylammonium chloride, methyltricaprylammonium chloride, methyltrioctylammonium chloride or hexadecyltributylphosphonium bromide.

It is preferable to use quaternary compounds with larger cations such as tetrabutylammonium, tetradodecylammonium, tetrabutylphosphonium and others. The choice of the organic solvent, which is largely insoluble in water, is not critical. However, it should have sufficient solubility for the organic starting substance and for the onium compound. Preferred is a two-phase liquid-liquid system, e.g. Benzene / water, toluene / water and related systems.

The concentration of the onium salt is not critical.

Preferably 1 to 100 mol%, preferably 1 to 20 mol%, of the onium salt, calculated on the o, o'-dihalobenzophenone, are used.

The sulfide or hydrosulfide anion in the aqueous or in the solid phase is used in an equimolar amount, preferably in an excess of preferably at least 10-20 mol%, the concentration in the aqueous phase preferably being close to the saturation limit.

The thioxanthone compounds prepared in this way can be used for all known purposes, for example as photon initiators.

The thioxanthones produced according to the invention can be used in many ways. In particular, the invention also relates to the use of the thioxanthone compounds prepared according to the invention as photoinitiators.

example 14.3 g of 2,2 ', 5-trichlorobenzophenone, 40 ml of benzene, 3.2 g of sulfur, 20 g of 50% NaOH and 5.1 g of hexadecyl-tributylphosphonium bromide were stirred together at a bath temperature of 70 ° C. and under nitrogen During the reaction, 3.2 g of sulfur and 3 times each 1 g of hexadecyl-tributylphosphonium bromide were added. After a reaction time of 22 hours, the reaction mixture was cooled to room temperature. The deposited precipitate was filtered off after the addition of 20 ml of methanol. After washing with methanol and water 11 g of 2-chlorothioxanthone were obtained, mp = 1550 ° C.

The compounds listed in Table 1 are prepared in an analogous manner.

TABLE 1

No. Compound 0 1 CH3 s CH3 2 Qxctz CH3 0 3 CH3 tC tC l 01, 4, ssr o CH3 n 3 Clx C1 CH3 0 CH2 6 Cll3 0 H, C'SIQ 0 n Cl3 {Ct C1 CH3 0 9 W CmCH3 S c

Claims (4)

PATENT CLAIMS 1. A process for the preparation of substituted or unsubstituted thioxanthones by reacting the corresponding o, o'-dihalogenobenzophenones in an alkaline medium in the presence of sulfur, characterized in that the reaction is carried out in a two-phase system in the presence of a phase transfer catalyst. 2. The method according to claim 1 for the preparation of compounds of the formula wherein R1 and R2 independently of one another are hydrogen, alkyl (C1-C4), alkoxy (CrCu) or halogen, R3 independently of one another alkyl (C1-C4), R4 independently of one another denote alkyl (C1-C4) and n and m independently denote zero, 1, 2 or 3, by reaction of a compound of the formula wherein R1, R2, R3, R4, n and m have the above meaning and Hal is halogen, in an alkaline medium in the presence of sulfur, in a two-phase system in the presence of a phase transfer catalyst. 3. The thioxanthones produced by the process of claims 1 and 2. 4. Use of the compounds prepared by the process of claims 1 and 2 as photoinitiators. The present invention relates to a process for the preparation of substituted or unsubstituted thioxanthones by reacting the corresponding o, o'-dihalogenobenzophenones in an alkaline medium in the presence of sulfur, characterized in that the reaction is carried out in a two-phase system in the presence of a phase transfer catalyst. The invention also relates to the thioxanthones produced in this way. In particular, the invention relates to a process for the preparation of compounds of the formula wherein R1 and R2 independently of one another are hydrogen, alkyl (C1-C4), alkoxy (C1-Cl2) or halogen, R3 independently of one another alkyl (C1-C4), R4 independently of one another are alkyl (C1Cj and n and m independently of one another mean zero, 1, 2 or 3, by reacting a compound of the formula wherein R1, R2, R3, R4, n and m have the above meaning and Hal means halogen in an alkaline medium in the presence of sulfur in a two-phase system in the presence of a phase transfer catalyst. The process according to the invention is preferably used for the preparation of compounds of the formula wherein R'1 alkyl (C1-C4), alkoxy (C1-C8) or halogen R'2 is hydrogen or halogen n 'is zero, 1 or 2, and m' is zero or 1, and R3 and R4 have the above meanings by adding a compound of the formula wherein R'1, R'2, R'3, R'4, m ', n' and Hal have the above meaning, in an alkaline medium in the presence of sulfur in a two-phase system in the presence of a phase transfer catalyst. Preference is given to preparing compounds of the formula ** WARNING ** End of CLMS field could overlap beginning of DESC **.