US2191062A - Ortho- and para-nitrophenyl-trifluoromethyl-sulphoxides, oxidation products thereof, and prodcess of preparing the same - Google Patents

Description

Patented Feb. 20, 1940.

UNITED STATES PATENT OFFICE ORTHO AND PARA. NITROPHENYL TRI- FLUOROMETHYL-SULPHOXIDES, OXIDA- TION PRODUCTS THEREOF, AND PROC- ESS 0F PREPARING THE SAME No Drawing. Application October 5, 1938, Serial No. 238,474. In Germany October 5, 1937 5 Claims.

The present invention relates to orthoand paranitrophenyl trifluoromethyl sulphoxides, oxidation products thereof and to a process of preparing the same; more particularly, it relates to compounds of the following general formula:

XOF

SOg.CF

Consequently, the nitration of this compound also occurs only in meta-position, as expected. Orthoand para-nitrophenyl trifiuoromethylsulphones cannot be obtained in this manner.

We have found that orthoand para-nitroderivatives of trifluoromethyl-phenyl-sulphones are obtainable by causing nitric acid to act in the presence of sulphuric acid upon the t'rifluoromethyl-phenyl-sulphides obtainable as described in U. S. Patent No. 2,108,606 and oxidizing the nitrophenyl-trifluoromethyl-sulphoxides so obtained. Since the trifluoromethyl-phenyl-sulphides, under the said conditions, are first oxidized to form the trifluoromethyl-phenyl sulphoxides and the latter are then nitrated in the second phase to the nitrophenyl-trifluoromethylsulphoxides, there may also be used as parent material for the manufacture of the orthoand paranitrophenyl-trifluoromethyl-sulphones the trifluoromethyl-phenyl-sulphoxides, obtainable in a manner similar to that described in Chemisches Centralblatt, 1927 (1), page 1821, by causing nitric acid to act upon trlfiuoromethyl-phenyl sulphides. The nitro-group enters always in orthoor para-position to the SO.CF3-group.

It is surprising that the action of nitric acid in the presence of sulphuric acid upon the trifluoromethyl-phenyl-sulphides or trifluoromethyl-phenyl-sulphoxidesis so smooth and uniform, since by the action of nitric acid upon parabromothio-anisol and thio-anisol only the corresponding sulphoxides have been obtained, but no nitrated sulphoxides (cf. Chemisches Centralblatt, 1927 (1), page 1822).

The simultaneous oxidation and nitration of the trifluoromethyl-phenyl-sulphides or the nitration of the trifluoromethyl-phenyl-sulphoxides by means of nitric acid in the presence of sulphuric acid occurs very smoothly, and the nitrophenyl-trifluoromethyl-sulphoxides are obtained with very good yields. They may easily be oxidized with the usual oxidizing agents to form the corresponding nitrophenyl trifluoromethyl sulphones which are valuable parent materials, for instance, for the manufacture of dyestufls or pharmaceutical products.

The following examples serve to illustrate the invention, but they are not intended to limit it thereto; the parts are by weight unless otherwise stated:

1. 25 parts of 2,4-dichlorophenyl-l-trifluoromethyl-sulphide are caused to run, while stirring, into '75 parts by volume of a mixture consisting of about 30 per cent. of pure nitric acid and about 70 per cent. of sulphuric acid monohydrate and heated on the steam bath at about C. to C. Stirring is continued for a short time at 70 C. to C. and the Whole is then poured on ice. The 2,4-dichloro-fi-nitrophenyl- 1-trifluoromethyl-sulphoxide of the formula QiN Cl which has separated is filtered with suction and washed. It is obtained with a nearly quantitative yield in the form of a feebly yellow powder. By recrystallization, for instance, from trichlorethylene, beautiful crystals are obtained which melt at 100 C.

31 parts of Z/i-dichloro-(i-nitrophenyl-l-trifluoromethyl-sulphoxide are dissolved in 100 to 150 parts by volume of glacial acetic acid. Into this solution there are introduced by portions at about C., while stirring, about 10 parts of chromic anhydride. When the introduction is, finished, the whole is heated for to 1 hour at 70 C. to 80 C. and then diluted with water. The 2,4-dich1oro6-nitrophenyl-l-trifiuoromethyl-sulphone of the formula IS OzCFz which has separated is filtered with suction. After recrystallization, for instance, from benzine, it is obtained-in the form of yellow crystals melting at 76 C. The yield obtained is nearly quantitative.

2. At 70 C. to 80 0., 74 parts of 3,4-dichlorophenyl-1-trifluoromethyl-sulphide are run, while stirring, into 200 parts by volume of a mixture consisting of about'90 per cent of pure nitric acid and about 10 per cent of sulphuric acid monohydrate. Stirring is continued for 1 to 2 hours at 70 C. to 80 C. and the whole is then poured on ice. The 3,4-dichloro-6-nitrophenyl-l-trifiuoromethyl-sulphoxide which has separated is filtered with suction and washed. It is obtained with a very good yield in the form of a yellow powder and after recrystallization, for instance from alcohol, it forms yellow crystals, melting at 100 C. The compound is oxidized, as indicated in Example 1, to form the 3,4-dichloro-6-nitrophenyl-l-trifluoromethyl-sulphone, melting at 72 C. to 73 C.

3. In a mannerquite similar to that described in Example 1, there is obtained from 2-ohlorophenyl-1-trifluoromethyl-sulphide with a good yield the 2-chloro-4-nitrophenyl-l-trifluoromethyl-sulphoxide which melts at 51 C. and is transformed by oxidation into the corresponding sulphone melting at 46 C.

Instead of 2-chlorophenyl-l-trifiuoromethylsulphide there may also be used other halogensubstituted products of phenyltrifluoromethylsulphide, for instance, the metaor para-chloroderivative, mono-bromo-derivatives or the like.

4.. At 50 C. to C., 124 parts of 2,5-dichlorophenyl-ltriiluoromethyl-sulphide are run into 250 parts by volume of a mixture consisting of 90 per centof pure nitric acid and 10 per cent of sulphuric acid monohydrate. The product is worked up as described in Example 1. The 2,5- dichloro-i-nitrophenyll-trifluoromethyl-sulphoxide melts at 99 C. to 100 C. and the sulphone obtainable therefrom by oxidation with a nearly quantitative yield melts at 60 C. In this case too there may be used instead of 2,5-dichlorophenyl-1-trifiuoromethyl-sulphide the corresponding bromo-compound.

5. In a manner similar to that indicated in Example 1 or 2 there is obtained from 4-methylphenyl-l-trifluoromethyl-sulphide the ei-methyl- 2 nitrophenyl 1 trifluoromethyl sulphoxide which, after recrystallization, for instance, from benzine, form feebly yellow needles melting at 84 C. The 4-methyl-2nitrophenyl-l-trifluoroe methyl-sulphone obtainable therefrom by om'dation melts at 56 C.

6. 26.3 parts of 2,4-dichloro-phenyl-l-trifluoromethyl-sulphoxide melting at 60 C., are introduced at 10 C. to 15 C, while stirring, into 50 parts by volume of. a mixture of 90 per cent of pure nitric acid and 10 per cent of sulphuric acid monohydrate. Stirring is continued for about 2. to 3 hours at 10 C. to 15 C. and the whole is then poured on ice. The 2, l-dichloro- S-nitrophenyll-trir'fluoro-methyl-sulphoxide is" obtained with a quantitative yield. It is identical with the compound described in Example 1 and melts at 100 C.

Instead of the mixture of nitric acid and sulphuric acid mentioned in the examples there may, of course, also be used mixtures of these acids in all other proportions; furthermore, there may be used for the oxidation of the sulphoxides to the corresponding sulphones potassium permanganate, bichromate and sulphuric acid, permonosulphuric acid, or the like, instead of chromic acid.

We claim:

1. The process which comprises causing nitric acid to act in the presence of sulphuric acid at a temperature below 100 C. upon a compound of the following general formula:

XCF:

wherein X stands for one of the group consisting of S and SO, Y1 stands for a member of the group consisting of halogen and methyl and Y2 for a member of the group consisting of hydrogen and halogen, and oxidizing the nitrophenyl-trivfluoromethyl-sulphoxides thus obtained.

3. The compounds of the following general formula:

SIOCFa wherein the nitro-group stands in one of the positionsv ortho and para to the SOCFz group, Y1 stands. for a member ofjthe group consisting of halogen and methyl and Y2 for a member of the 5. The compound of the following formula: group consisting of hydrogen and halogen, being soor yellow-colored crystallized products. 3

4. The compound of the following formula:

S o OFa 5 I 01 0 forming, when recrystallized from benzine, feebly I 1 yellow needles melting at 84 C. 10

NO: WILLY SCHUMACHER. being a yellow-colored crystallized product which OTTO SCHERER' melts at 99 C. to 100 C. FRITZ Mfi'LLER.