JPS5978143A - Oxidation of phenol to p-benzoquinone - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION The oxidation of phenol to p-benzoquinone with oxygen in the presence of a copper ion catalyst is known in the art, and such a process is disclosed in US Pat. No. 3,987,068. In that patent, the oxidation is carried out using a complex formed from a copper catalyst and a solvent in a nitrile solvent, the operating conditions being a temperature of about 0 to 100°C, an oxygen partial pressure of about 7 to 200 (preferably 14 to 100) atm. It is said that US patent 3
As noted in No. 987,068, the yield of quinone product increases with increasing oxygen partial pressure, and data therein show that oxygen partial pressures above about 100 atm decrease the p- appears to be required to achieve conversion to benzoquinone. Such oxygen pressures are too high to be useful in economical commercial processes because they require specialized equipment with high capital costs.

US Patent No. 387.0731 is concerned with the oxidation of phenol to benzoquinone in the presence of a copper salt as a catalyst, where it improves the catalytic activity of anionic liquids such as thiocyanates, cyanates, cyanide and halogen ions in the catalyst system. In such reactions, solvents such as water are disclosed, and other polar solvents that are soluble or miscible with water can also be used. Such solvents are exemplified by the following species: amides, alcohols and sulfoxides. It is also stated that any of the various solvents can be used alone or in any proportion with water.

Our U.S. Application No. 284,893, filed July 20, 1981, has been abandoned and its pending application No. 4239
No. 84, filed in the United States on September 27, 1982, in which we describe the copper-catalyzed oxidation of phenol to p-benzoquinone in a nitrile solvent and the molar ratio of base to copper catalyst. It is fully disclosed that significant improvements are achieved by using divalent copper catalysts promoted with alkali metal bases such that the ratio is not greater than 2.0. The use of water in the reaction system at about 10% by volume or less further improves the reaction in increasing selectivity.

Our U.S. Patent Application No. 33, filed January 18, 1982
No. 9965, a copper-catalyzed process for the oxidation of phenol to p-benzoquinone was significantly improved;
It has been disclosed that the oxidation of phenol can be efficiently quenched in conventional solvent systems, allowing the operation to be carried out at lower commercially useful pressures, while also achieving improved product selectivity. 2) modified by IJ in the presence of a monovalent copper ion catalyst (for example, Ou) in a solvent.

In the present invention, another technique has been discovered to improve the copper-catalyzed process for the oxidation of phenol to p-benzoquinones or substituted benzoquinones, allowing operation at higher reaction rates and product selectivities. Ta. Such an object according to the invention is to carry out the oxidation of phenol in a nitroalkane as a solvent with an alkali metal phenoxide and a secondary or tertiary
This is achieved by carrying out in the presence of a copper ion catalyst promoted with a base selected from lower alkyl amines.

According to the present invention, phenols and substituted phenols are converted to the corresponding p-benzoquinones and substituted p-benzoquinones as illustrated in the following reactions.

In the formula, R, '+' R2, R3' and R4 are the same or different, and are hydrogen, halo or cyano, alkyl or alkoxy having 1 to about 12 carbon atoms, phenyl, naphthyl, phenylalkyl, 7 to about 1 carbon atoms of alkylphenyl, phenoxy, or phenalfoxy
6, and R1 and R2 or R5 and R4 may together form an aliphatic, aryl or heterocycle. Specific R groups include chloro, cyano, methyl, ethyl, propyl, butyl, isobutyl, tert-butyl, pentyl, p-tolyl, 'I', 7-nityl, methoxy, t-butoxy, phenoxy, p-methylphenoxy, etc. Contains.

Preferred phenols useful in this method are phenol, 0
-chlorophenol, 0-talesol, m-cresol, 2,5- and 2,6-di-t-butylphenol, 2
-t-7' tylphenol, 2.6=dimethylphenol, and 1-naphthol. R1 and R2 or Rs
and R4 taken together, the raw p-benzoquinone is derived from naphthalene, quinoline, isoquinoline, chroman (dihydrobenzopyran), indole, and the like.

In carrying out the process of the invention, conventional temperature conditions and -valent or divalent copper catalysts can be used. Preferred are copper halides, preferably copper chloride, but nitrates can also be used, and mixtures of such salts can also be used. The molar ratio of catalyst to phenolic reactant varies widely, from about 50:1 to 1:1;
Preferably the level is about 15:1 to 5°1. Base promoters include alkali metal phenoxides (e.g. sodium, potassium, lithium and cesium phenoxides) and secondary
or tertiary lower argyl amines (e.g. 0, to C
4 alkylamine) such as dimethylamine, diethylamine (DIA), dibutylamine, trimethylamine,
Selected from the group consisting of tripropylamine, triethylamine (TEA), and the like.

The amount of promoter is not critical. A suitable amount is about 0.1 to 1.9 moles of promoter per mole of catalyst, preferably about 1=1. As mentioned above, the reaction is carried out at moderate pressures, generally between about 100 and about 500 pslg (D rdJ C'1
Oxygen partial pressure of 03-3 to 15'i, preferably about 20
Between 0 and 400 psig (14.06~28.1+
It can be carried out with Mixtures of oxygen and nitrogen, air alone or oxygen alone can be used, but mixtures of oxygen and nitrogen, such as air, can be used as the oxygenating medium.

As indicated, the solvents used in the method are a, -a.

Nitroalkanes (preferably C1-C,) may be nitromethane, nitroethane, and nitropropane isomers. Nitromethane is the preferred mfK.

The following examples are provided to further illustrate the invention.

Example 1 5 vrl! containing 0.55 mmol catalyst and 0.55 mmol base. A solution of 16 mmol phenol in nitromethane was prepared at an initial total pressure of 750 pBig
(stirred in a magnetically stirred mini-autoclave under 2.73-/&A and oxidized with a mixture of 40% (customer foot) oxygen and 60 g nitrogen for a period of 3 hours. Parameters of the reaction and the obtained The results are shown in Table 1 below.Substantially improved conversion rod and/or selectivity was achieved.

Table I Experimental Effect of Base on Reaction Rate and Selectivity of Copper-catalyzed TS Oxidation of Phenol Catalyst Base Solvent Conversion (%)
Selectivity ($) 8 0urI! DICAOH3No2
62 35 Examples 2-7 Experiments carried out substantially as in Example 1, but with the substitution of the substituted phenols of Table 1 below, good selectivity, conversion and/or yield to the corresponding substituted benzoquinones was achieved. It was done.

Table ■

Claims (1)

[Scope of Claims] 1. Phenol or substituted phenol is used as a hydride solvent in a C1-06 nitroalkane, and the catalyst is an alkali metal phenoxylate and a secondary or tertiary lower alkyl amine. An improved method for carrying out the reaction by promoting the catalyst with a base selected from the group. 2. The method of item 1, wherein the solvent is nitromethane. 3. The method of item 2, wherein the accelerator is lithium phenoxide. 4.7: The method of item 1, where T-/- is alkylphenol. 5. The method according to item 4, wherein the alkylphenol is O-cresol or Ham-cresol. 6. The method of item 4, wherein the alkylphenol is dimethylphenol. 7. The method of item 4, wherein the alkylphenol is di-tert-butylphenol. 8. The method of item 4, wherein the alkylphenol is o-t-butylphenol.