DE1915385A1 - Process for the preparation of o-benzoylbenzoic acid - Google Patents

Description

Process for the preparation of o-benzoyl-benzoic acid The invention relates to a process for the preparation of o-benzoylbenzoic acid by oxidation of indanes with nitric acid.

It is from Ullmann's Encyclopedia of Technical Chemistry, Volume 3, Page 660, it is known that phthalic anhydride and benzene can be used in the presence of aluminum chloride can convert in a Friedel-Crafts reaction to o-benzoylbenzoic acid. Disadvantageous in this process is the uneconomically high consumption of catalyst.

Also in the oxidation of 1-methyl-3-phenyl-indane with chromic acid o-benzoylbenzoic acid is formed, but only in unsatisfactory yield and in a mixture with a high proportion of by-products, e.g. B. o-Acetylbenzophenone (Journal of Organic Chemistry, Volume 19 (1954), pages 17 ff .; Journal of the American Chemical Society, Vol. 72 (1950), pp. 4918 ff.). This result can at least be explained partly from the influence of the oxidation medium on the o-benzoyl-benzoic acid formed. If o-benzoylbenzoic acid is oxidized under the conditions of this process, in this way, only 45% of the raw material is returned unreacted; the main part becomes thus destroyed by the oxidation medium (J. Am. Chem. Soc., loc. cit., page 4920). If you start from 1.1.3-trimethyl-3-phenylindane as the starting material, the oxidation process must be modified, but the modified process gives only moderate yields of o-benzoylbenzoic acid and a high proportion of o-acetylbenzophenone (reports of the German Chemical Society, Volume 90 (1957), pages 1208 ff.).

It has now been found that o-benzoylbenzoic acid is advantageously obtained by oxidation of indanes when indanes of the general formula are used in which R1, R2, R3 can be identical or different and each represent an alkyl radical, R1 and / or R3 can also each denote a hydrogen atom, oxidized with nitric acid at a temperature between 50 and 2500C.

If 1-methyl-3-phenyl-indane is used, the reaction can be represented by the following formulas: Compared to the known processes, the process according to the invention provides o-benzoylbenzoic acid in a simple and economical way in better yield and very high purity and without the formation of substantial amounts of o-acetylbenzophenone.

These beneficial results are in view of the state of the art Technique surprising, one would have missed it as a result of the use of nitric acid an additional, substantial proportion of nitrated compounds should be expected.

The indanes used as starting materials I can be obtained by dimerization of unsubstituted or substituted styrenes, e.g. B. according to the aforementioned Publications or in Rabjohn, Organic Syntheses, Collective Volume IV (John Wiley Inc., New York 1963), pages 665 ff.

Preferred indanes I are those whose formula R1, R2, R3 are the same or can be different and in each case an alkyl radical with 1 to 8, in particular Mean 1 to 4 carbon atoms, R1 and / or R3 in addition can also each denote a hydrogen atom. Suitable indanes I are, for. B. 1-methyl-, 1. 3-dimethyl-, 1.1. 3-trimethyl-, 1-propyl-, 1-isobutyl-3-phenylindane.

The reaction is carried out with nitric acid at a temperature between 50 and 2500C, preferably between 110 and 2300C.

You work without pressure or under pressure, z. B. at a pressure up to 100 at, in general at that which is established under the reaction conditions Pressure. The reaction can be carried out continuously or batchwise.

One sets the starting material I with nitric acid in stoichiometric Amount or in excess, preferably in a molar ratio of 1 mol of starting material-I to 3 to 30, in particular 3 to 20 mol of nitric acid. Generally used for the oxidation, aqueous nitric acid solutions of 2 to 50, preferably from 5 to 40? in particular from 5 to 30% by weight of nitric acid. The one for a certain Temperature optimal nitric acid concentration and amount of nitric acid is through Easy to set up preliminary tests.

The reaction can be carried out as follows: A mixture of starting material I and nitric acid of the above concentration are placed in a pressure vessel for approx. Maintained 1/4 to 2 hours at the reaction temperature and at the reaction pressure. Then the reaction mixture is cooled. The end product can be made from it in the usual way Way, e.g. B. isolated by filtration or decanting, usually will but the end product is processed further without separation.

The compound that can be made by the method of the invention is a valuable starting material for numerous syntheses (s0i e.g.

Ullmanns Encyklopadie der Technischen Chemie, Volume 3, pages 660 ff.). It is of particular importance as a starting material for the production of anthraquinone. The method according to the invention opens up an elegant way of producing Anthraquinone; starting from cheap styrene. It is advantageous to cyclize the o-Benzoyl-benzoic acid after removal of the nitric acid in the after the process of the invention resulting reaction mixture. The yield of o-benzoylbenzoic acid therefore results exactly from the yield of anthraquinone. By reacting with glycerine under reducing conditions (Annali di Chimica Applicata, Volume 22 (1932), pages 691 ff.) One obtains another starting material for dyes, benzanthrone.

The parts listed in the following examples are parts by weight.

EXAMPLE 1 6 parts of t-methyl-3-phenylindane are converted into an autoclave at 220.degree 94%) is oxidized with 47 parts of a nitric acid for 1 hour. After this The pressure in the autoclave is cooled down and the aqueous phase is decanted severed. The organic phase remaining in the autoclave is dissolved in dilute sodium hydroxide solution dissolved and the o-benzoylbenzoic acid precipitated by careful acidification with cooling Yield: 3 parts = 48.8% of theory.

Fp. After Umkrlst. from benzene / cyclohexane 125 - 126 ° C.

Example 2 The reaction with 70.5 parts of 20 is carried out analogously to Example 1 pointer nitric acid carried out.

Yield; 3.2 parts = 52% of theory. Example 3 Analogous to the example 2, the reaction is carried out at a temperature of 200 ° C. The received o-Benzoyl-benzoic acid is 100% strength in 40 parts of sulfuric acid for 1 hour Cyclized to anthraquinone at 1500C. By pouring into ice / water becomes the Anthraquinone precipitated, sucked off, heated in hot dilute sodium hydroxide solution, sucked off upd washed neutral with water.

Yield: 3.5 parts of anthraquinone (62% of theory).

Example 4 As in Example 1, the reaction is carried out at 160.degree.

Yield: 4.8 parts of o-benzoylbenzoic acid (78.2% of theory).

Example 5 As in Example 1, the reaction is carried out at 1700.degree.

Yield: 4.9 parts of o-benzoylbenzoic acid (79.8% of theory).

Example 6 2.7 parts of 1-methyl-3-phenyl-indane are placed in an autoclave (99%) at 2200C with 120 parts of nitric acid (5%) for 1 hour at 2200C oxidized. The work-up is carried out analogously to Example 1.

Yield: 1.8 parts of o-benzoylbenzoic acid (61.2% of theory).

Example 7 6 parts of 1,3.3-trimethyl-1-phenyl-indane are produced analogously to the example 1 oxidized with 80 parts of 30% nitric acid.

Yield: 4.1 parts of o-benzoylbenzoic acid (71.2% of theory).

Example 8 6 parts of 1-methyl-3-phenyl-indane are used in an autoclave (94%) oxidized with 56.5 parts of nitric acid (25%) for 1 hour at 1700C. the Work-up takes place as in Example 1.

Yield: 4.8 parts of o-benzoylbenzoic acid (78.2% of theory).

Example 9 6 parts of 1-methyl-3-phenyl-indane (94%) and 94 parts Nitric acid (40 sig) are in a stirred vessel for 4 hours at reflux temperature touched. After cooling, the aqueous phase is decanted off, followed by the mixture 40 parts of sulfuric acid 100 sig kept at 1500C for 1 hour. Analogously after work-up Example 2 gives 3.8 parts of anthraquinone (66% of theory).

Claims (1)

Claim Process for the preparation of o-benzoylbenzoic acid by oxidation of indanes, characterized in that indanes of the general formula in which R1, R2> R3 can be identical or different and each represent an alkyl radical, R1 and / or R3 can also each denote a hydrogen atom, oxidized with nitric acid at a temperature between 50 and 2500C.