CH620190A5 - Process for the preparation of p-quinones - Google Patents

Description

The invention relates to a process for the preparation of p-quinones according to claims 1 and 8.

According to "Recueil des Travaux Chimiques des Pays-Bas", vol. 86, pp. 520-526 (1967), 2,6-dimethylphenol and 2,3,5,6-tetramethylphenol can be used to give the corresponding p-benzoquinones Oxidize oxygen in the presence of methanol or chloroform as solvent and N, N'-ethylene-bis- (salicylidiminato) cobalt (II) as a catalyst. However, the yields are unsatisfactory, by-products are formed by coupling the aryloxy radicals, and the rate of oxidation is also very slow.

Trimethyl-p-benzoquinone can be obtained in better yields and greater purity according to FR-PS 2 015 576 by oxidation of 2,3,6-trimethylphenol in the presence of N, N'-ethylene-bis- (salicylidene iminato) cobalt (II ) as a catalyst and a carboxamide as a solvent.

It has now been found that di-ortho-substituted p-benzoquinones can be obtained in very satisfactory yields if the oxidation is carried out in the presence of another cobalt catalyst.

The invention thus relates to the process for the production of p-quinones defined in claims 1 and 8, which is characterized in that the oxidation in the presence of a solvent and as a catalyst of an organic cobalt (II) coordination compound with a coordination number of 4 and two imino ligands, the nitrogen atoms of which are bound to the cobalt (II) atom and to a 1,2-arylene radical.

Accordingly, the cobalt (II) coordination compound has the following structure:

\ /

CO y \

✓

> C = Ny 1

c-

N i

-c.

c <

3rd

620 190

Cobalt (II) coordination compounds of the general formula I are particularly suitable as catalysts for the process according to the invention

R -C - 0

- C - R "

Co

R2- C

- C = N

* 1 1

R C

N = C

I 1

- C - R

(I)

2nd

C R

<=>

in which R \ R2 and R3 are each a hydrogen atom or an aliphatic radical or R2 and R3 together with the carbon atoms to which they are attached form an aromatic ring. This aromatic ring can optionally carry one or more substituents.

Particularly preferred catalysts are N, N'-arylene-bis (salicylideniminato) cobalt (II) compounds, in particular N, N'-o-phenylene-bis (salicylideniminato) cobalt (II).

The phenols used as starting compounds in the process according to the invention are derived from benzene or from hydrocarbons with two or more condensed rings, one of which is benzene.

“Inert substituents” are substituents that remain intact during the process according to the invention. Preferred inert substituents are hydrocarbon radicals and hydrocarbon radicals substituted by a hydroxyl group. Excellent results are obtained with hydrocarbon residues.

Examples of phenols used as starting compounds are 2,6-dimethylphenol, 2,3,6-trimethylphenol, 2,3,5,6-tetramethylphenol, 2,6-dimethylhydroquinone, 2-methyl-1-naphthol, 2,3 -Dimethyl-l-naphthol, 2,8-dimethyl-l-naphthol, 8-hydroxy-7-methyl-l, 2,3,4-tetrahydronaphthalene, 9-anthranol, 2-methyl-l-anthranol, 2,3 -Dimethyl-l-anthranol and phenols in which one or more methyl groups are replaced by ethyl, propyl, isopropyl, n-butyl, sec-butyl, tert-butyl, phenyl, phenoxy or methoxy radicals are, e.g. B. 2,6-diethylphenol and 2-methoxy-2,6-dimethylphenol. Excellent results are obtained with 2,3,6-tri-methylphenol.

In the process according to the invention, the phenol used as the starting compound is, for. B. in an initial concentration of 100-1250 mmol, preferably 300-1000 mmol per liter of solvent.

The cobalt (II) coordination compounds are e.g. B. in an amount of 1-100 mmol, preferably 10-50 mmol per liter of solvent used.

Very satisfactory results are obtained if the process according to the invention is carried out at a temperature between 0 and 100 ° C., preferably 35-70 ° C.

The inventive method can in the presence of protic or preferably aprotic solvents

25th

be performed. Preferred solvents are N-Me-thyI-2-pyrrolidone, N, N-dimethylacetamide and in particular N, N-dimethylformamide.

Sulfolane, dimethyl sulfoxide and hexamethylphosphoric triamide are also suitable as solvents.

The p-chi-non produced in the process according to the invention can be isolated from the reaction mixture by any conventional process, e.g. B. by fractional distillation.

The p-chi-none produced in the process according to the invention can be used for many syntheses. Trimethyl-p-benzoquinone is a precursor of a-tocopherol, a compound with vitamin E activity.

The examples illustrate the invention.

example 1

Through a mixture of 50 g of NN-dimethylformamide, 5 g of 2,3,6-trimethylphenol and 0.3 g of N, N'-o-phenylene-bis- (salicy-lideniminato) cobalt (II) is stirred vigorously and at a temperature of 60 ° C oxygen from atmospheric pressure passed at a rate of 15 normal liters per hour. The conversion of 2,3,6-trimethylphenol and the selectivity to trimethyl-p-benzoquinone are determined by gas-liquid chromatography in the crude mixture at different times after the start of the introduction of oxygen.

The percent selectivity of trimethyl-p-benzoquinone is defined as moles of p-quinone per 100 moles of converted phenol.

The table summarizes the results.

table

40

Reaction time,

Conversion,

Selectivity,

Minutes

percent

percent

20th

60

93

40

84

94

60

94

96

90

99

96

The reaction mixture contains a trace 2,3,3 ', 5,5', 6'-He-45 xamethyl-4,4'-biphenoquinone.

Example 2

A mixture of 50 g of NN-dimethylformamide, 5 g of 2,6-di-tert-butylphenol and 0.3 g of N, N'-o-phenylene-bis- (sali-50 cylideniminato) cobalt (II) with vigorous stirring and a temperature of 60 ° C oxygen from atmospheric pressure at a rate of 15 normal liters per hour. After stirring for 20 minutes, the reaction mixture is cooled to 0 ° C., whereby 0.6 g of 3,3 ', 5,5'-tetra-55 tert-butyl-4,4'-biphenoquinone precipitate (yield: 12%). The precipitate is filtered off. The filtrate is analyzed by gas-liquid chromatography, it contains 4.6 g of 2,6-di-tert-butyl-p-benzoquinone (yield: 86%).

Claims (10)

620 190 1 c— = -c R P (I) - R " in which R \ R2 and R3 each represent a hydrogen atom or an aliphatic radical or R2 and R3 form an aromatic ring with the carbon atoms to which they are attached, in particular N, N'-phenylene-bis- (salicylideniminato) cobalt ( II). 1. Process for the preparation of p-quinones with two inert ortho substituents with respect to one of the oxygen atoms, or two rings fused in the ortho position, or with one ortho substituent and one ring fused in the ortho position, by oxidation with molecular oxygen of a corresponding phenol with two inert ortho substituents or two rings fused in the ortho position, or with one ortho substituent and one in ortho -Position fused ring and an io hydrogen atom para to the hydroxyl group, characterized in that the oxidation in the presence of a solvent and as a catalyst of an organic cobalt (II) coordination compound with a coordination number of 4 and two imino ligands, the nitrogen atoms of 15 the cobalt (II) atom and are bonded to a 1,2-arylene radical. 2nd P R 20th 30th 35 40 in which R1, R2 and R3 are each a hydrogen atom or an aliphatic radical or R2 and R3 form an aromatic ring with the carbon atoms to which they are attached. 2. The method according to claim 1, characterized in that that a compound of the formula I is used as the cobalt (II) coordination compound, R - C - 0 O - C - R ~ R2- C Co '* \ C = N ix 1 C- N! -c = C - C - R (I) 2nd PATENT CLAIMS 3. The method according to claim 2, characterized in that one uses N, N'-pheny-bis- (salicylideniminato) cobalt (II) as the cobalt (II) coordination compound. 4th N N = c ! ! 4 and two imino ligands, the nitrogen atoms of which are bonded to the cobalt 65 (II) atom and to a 1,2-arylene radical. 4. The method according to any one of claims 1-3, characterized in that the phenol is used in an initial concentration of 300-1000 mmol per liter of solvent. 5. The method according to any one of claims 1-4, characterized in that the cobalt (II) coordination compound is used in an amount of 10-50 mmol per liter of solvent. 6. The method according to any one of claims 1-5, characterized in that the solvent used is N, N-dimethylformamide. 7. The method according to any one of claims 1-6, characterized in that one starts from 2,3,6-trimethylphenol. 8. Process for the preparation of p-quinones with two inert ortho substituents with respect to one of the oxygen atoms, or two rings fused in the ortho position, or with one ortho substituent and one ring fused in the ortho position, by oxidation with molecular oxygen of a corresponding phenol with two inert ortho substituents or two rings fused in the ortho position or with one ortho substituent and one in the ortho position Position condensed ring and a hydroxyl group para to the hydroxyl group, characterized in that the oxidation in the presence of a solvent and as a catalyst of an organic cobalt (II) coordination compound with a coordination number of 9. The method according to claim 8, characterized in 50 55 60 that a compound of the formula I is used as the cobalt (II) coordination compound, R - C - 0 R2- C O - C - R " Co ' 10. The method according to claim 8 or 9, characterized in that one uses the phenol in an initial concentration of 300-1000 mmol per liter of solvent and the cobalt (II) coordination compound in an amount of 10-50 mmol per liter of solvent, wherein the solvent is preferably N, N-dimethylformamide.