JPH02164843A - Synthesis of naphthalenecarboxylic acids - Google Patents

Abstract

PURPOSE:To produce the subject compound useful as an intermediate for chemicals in improved yield under mild condition while suppressing the by- production of acetoxy compound by reacting naphthalene with oxygen and carbon monoxide in the presence of a palladium catalyst and acetic acid. CONSTITUTION:The objective compound is produced by reacting naphthalene or methylnaphthalene with oxygen and carbon monoxide using palladium and/or a palladium compound as a catalyst in the presence of acetic acid and/or trifluoroacetic acid. The reaction solvent is e.g. methylcyclohexane, methyl isobutyl ketone, etc., or the above acetic acid and/or trifluoroacetic acid may be used as the solvent. The oxidative regeneration agent for the by-produced Pc(O) is preferably an oxygen complex of a complex of formula Mm.Xn.Le (M is Cu, Ti, V, etc.; X is halogen, etc.) capable of forming an oxygen complex.

Description

[Detailed Description of the Invention] (Industrial Application Field) - The present invention relates to a method for synthesizing naphthalenecarboxylic acids,
In particular, the present invention relates to a method for synthesizing naphthalenecarboxylic acids by reacting naphthalene or methylnaphthalene with carbon monoxide using a palladium catalyst.

(Prior Art) Naphthalenecarboxylic acids are important as intermediates for various chemicals, and in particular, 2,6-dicarboxynaphthalene is a raw material for polyethylene-2,6-nacclate (PEN). PEN has superior mechanical strength and thermal stability compared to conventional polyethylene terephthalate (PET).
It is attracting attention as a material for long-duration 3mm video film, etc.

By the way, in order to synthesize 2-methyl-6-naphthoic acid, which can be easily converted into 2,6-dicarboxynaphthalene, in a laboratory, the following complicated steps are required. For example, first, β-methylnaphthalene and acetyl chloride are reacted in a nitrobenzene solution using aluminum chloride as a catalyst at 5°C for 2 hours to synthesize 2-methyl-6-acetoxynaphthalene. Next, wash this solution with water,
Separate the aqueous and oil phases. After distilling off nitrobenzene from the oil phase, the residue is distilled under reduced pressure and recrystallized in ligroin solvent. The crystals are filtered and the groin is distilled off from the mother liquor to obtain 2-methyl-6-acetoxynaphthalene. Furthermore, sodium hypochlorite was added to this 2-methyl 6-acetoxynaphthalene to adjust the pH to 11, and the temperature was raised to 80°C.
After reacting for 2 hours, filter. Add hydrochloric acid to the filtrate,
Strain the precipitate that forms. Next, this precipitate is dissolved in acetic acid, filtered while hot, and further washed with water and dried to obtain 2
-Methyl-6-naphthoic acid is obtained.

However, not only 2.6 units, but also 2.1 units, 2.4 units
Monoliths, 2,5-bodies, 2.7-bodies, and 28-bodies also occur as by-products.

On the other hand, carbon monoxide (
Until now, no method has been known for selectively synthesizing 2-methyl-6-naphthoic acid by reacting it in the coexistence of Co.

Note that an interesting method has been reported in which naphthoic acid or naphthoic anhydride is synthesized by reacting naphthalene in the presence of CO as a similar reaction.
ganometallic Chem, 256
(1983) C35-C36 and J, Chem, S.
oc,,Chem,Commun,, (1982)
132-133), this method uses palladium acetate, t-butyl peroxide and allyl chloride,
latm, 75°C, 24 to 72 h, or using palladium acetate and 1,2-dibromoethane.
The synthesis method is different from the synthesis method of the present invention because it is carried out under conditions of 5 atm, 100° C., and 120 hours.

There is also a method of synthesizing naphthoic acid by reacting naphthalene and CO using Pd (OAc)2 in the coexistence of oxygen in an acetic acid solvent.
The yield is 8% in hours.

On the other hand, a method has been reported in which naphthoic acid methyl ester is synthesized from naphthalene and CO by carrying out carbonylation and esterification reactions in one step in a methanol solvent using PdCl2 as a catalyst.

In this reaction, the yield is 60% at 200° C., CO pressure of 5 Qatm, and reaction time of 10 hours.

(Problems to be Solved by the Invention) What is particularly important in aromatic reactions is the introduction of a specific reaction substrate into a specific position, that is, regioselectivity. For naphthoic acid, it is particularly desirable to have a high selectivity for β-naphthoic acid, but conventional methods have a low selectivity of 20-80%. Furthermore, although it is naturally necessary to have a high yield, it is difficult to activate aromatic C-H bonds under mild conditions, and the current yield of β-naphthoic acid is 2-8%
(Coof-1-1Oat low, Coofte reaction temperature 20
It is necessary to set the temperature strictly to 0°C, and even in that case, the yield is 60%.

Furthermore, there is a problem in that oxidative regeneration of Pd (O), which is a by-product of reduction, hardly occurs with conventional oxidizing agents in acetic acid or trifluoroacetic acid solvents.

An object of the present invention is to synthesize naphthalenecarboxylic acids using naphthalene or methylnaphthalene as a raw material under mild conditions by reacting naphthalenes with carbon monoxide using a palladium catalyst.

(Means for Solving the Problems) The present invention provides a method for synthesizing carboxylic acids by reacting naphthalene or methylnaphthalene with carbon monoxide, in which a palladium compound is used as a catalyst and acetic acid and/or trifluoroacetic acid is synthesized. It is characterized in that the reaction is carried out in the coexistence of.

The naphthalenes used as raw materials in the present invention are naphthalene or methylnaphthalene. If 26-naphthalene dicarboxylic acid is the final objective, it is advantageous to use β-methylnaphthalene as the raw material.

In the present invention, oxygen is present together with CO, but
This oxygen can be used as molecular oxygen, that is, oxygen gas itself, or as a mixed gas obtained by diluting oxygen gas with a diluent inert to the reaction (for example, nitrogen, carbon dioxide, etc.), or air can also be used. .

The catalyst used in the present invention is a palladium compound, and by adding acetic acid and/or trifluoroacetic acid to it, carboxylic acids can be synthesized in high yield as detailed in the Examples.

The solvent used in the present invention is preferably one that can be easily separated from the produced carboxylic acids, lowers the viscosity of the catalyst solution, and promotes mass transfer, such as aliphatic alicyclic compounds, aromatic hydrocarbon compounds, etc. , at least one compound selected from the group consisting of oxygen-containing organic compounds, organic halogen compounds, nitrogen-containing compounds, organic phosphorous compounds, and nitriles; more specifically, methylcyclohexane, methyl isobutyl ketone, ethylene glycol, dioxane, At least one selected from various solvents such as ethylene carbonate, chlorobenzene, N-methylpyrrolidone, ethers such as ethylene glycol dibutyl ether, ethylene glycol monomethyl ether, and ethylene glycol monoethyl ether, and aliphatic hydrocarbon compounds such as kerosene. Mention may be made of one type of solvent or a mixture thereof. Note that acetic acid and/or trifluoroacetic acid can also be used as a solvent.

In the present invention, as an oxidation regenerant for pd (O) that is produced as a by-product, the general formula (Mm-Xn-
The oxygen complex of the complex represented by Lj, hydrogen peroxide (H2O
), tert-butyl hydroxy peroxide (t-
Bu○OH), henzoquinone, anthraquinone, and the like can be used, but the above-mentioned oxygen complexes are preferred, which allows the reaction to be carried out continuously.

In the general formula, M is Cu, Ag of group 1 of the periodic law, Ti, Zr of group
, Mo, , W, M n of group II, FC of group II, Co
Transition metals such as Cu (1), Ti (3
), V (3) are more preferred. Also, as X, c
e-, Br-, -1■- halogen, BF4-1p F
Anions such as -1CH3COO-1SO4- are preferred, and Cr-, Br-, and -1■- are more preferred. Ligands include nitriles, phosphoric acid derivatives such as triphenylphosphine oxyto, hexamethylphosporamide, mono-, di-, or triester formed from the reaction of phosphoric acid with methanol, ethanol, etc., and methyl phosphonic acid. dimethyl, methyl dimethylphosphinate, or phosphorous acid derivatives, di- or l-lyesters produced from the reaction of phosphorous acid with methanol, ethanol, etc., and phenylphosphonates, dimethylphosphinates, triethylphosphine, Preferred examples include organic phosphorus compounds such as triphenylphosphine, and particularly preferred are hexamethylphosphoramide (hmpa) and benzonitrile (P h CN).

Figures 1 and 2 show the results of a pd(O) regeneration experiment in acetic acid and trifluoroacetic acid solvents, respectively, using an oxygen complex as an oxidation regenerant and Cu(○AC)2 as a comparison. It is. The figure shows that pa (O) is successfully oxidized and regenerated by using an oxygen complex.

According to the present invention, since the reaction is carried out under mild conditions, side reactions can be suppressed and naphthoic acid or methylnaphthoic acids can be selectively synthesized.

(Examples) Next, the present invention will be explained in more detail using Examples, but the present invention is not limited to these Examples.

Example 1 6 Pd(OAc)2 was added to a volumetric flask with an internal volume of IIl.
7.3 g (O, 30 mol) and 914 g of CH3C0OH, 89.1 g of CuC1 and 125 g of hmpa
g Charged catalyst liquid 11 was prepared. To this, 42.7 g (O, 3M) of β-methylnaphthalene was added, and the solution was transferred to an autoclave and sealed. After that, it was heated to 80°C to absorb 0.2M oxygen, and then degassed and CO
was injected and pressurized with an initial CO pressure of 11 atm, and it was confirmed by liquid chromatography that 1.27 g of 2-methyl-6-naphthoic acid was produced in a reaction time of 2.5 hours. In addition, as by-products, 0.37 g and 0.0.
55g and 0.08g were produced. Furthermore, 0.85 g of a product obtained by coupling the raw material β-methylnaphthalene was produced.

Example 2 CF3C instead of CH3C0OH in Example 1
When the same reaction was carried out except that 565 g of 0OH was charged, 1.88 g of 2-methyl-6 was produced in a reaction time of 2.5 hours.
- It was confirmed that naphthoic acid was produced. Also,
The methyl group remains as a by-product at the 2-position, and 5.7
Alternatively, 0.02 g, 0, 34 g, and 0.09 g of compounds containing a carboxyl group at the 8-position were produced, respectively.

By using CF3C0OH, 2-methyl-6
- Increased naphthoic acid yield and improved selectivity.

Example 3 In Example 2, 234 g of CF3C0oH.

A similar experiment was conducted except that 212 g of PhCN was used, and the results showed that in a reaction time of 2.5 hours, a compound containing a methyl group at the 2-position and a carboxyl group at the 5, 6, 7 or 8 position was 0.18 g. g, 1.98 g, 0,44
g and 0.11 g were produced.

A comparison with Example 2 shows that the yield is reduced by adding PhCN.

Example 4 In Example 3, PhCN was converted into acetonitrile (CH3C
A similar experiment was conducted except that N) was used, and the results showed that in a reaction time of 2.5 hours, compounds containing a methyl group at the 2-position and a carboxyl group at the 5-, 6-, 7-, or 8-positions showed a reaction time of 0.
03 g, 1.44 g, 0.56 g and 0.0
3 g was produced.

It can be seen that the yield is higher when PhCN is used as the nitrile.

Examples 5 to 11 In Example 1, 6.73 g (O
, 03 mol), but under the same reaction conditions, 2 g of Bi(NO3)3 was added as a cocatalyst, and pd
CH2CHCH2 (1!, t
Table 1 shows the results obtained by adding -BuOOH and the like.

Example 12 Pd (0.30g・a of Pd black instead of OAc>2)
When the same experiment as in Example 1 was conducted except that tm was used, the same results as in Example 1 were obtained.

Below margin *1: 400mo I eq, /Pd ('/,)! TW'1) a(O)lad Comparative Example 1 In Example 1, pd(OAc)2 was replaced with
When (acac)2 was used and acetylacetone was added instead of acetic acid, no carboxylic acids were produced at all.

(Effects of the Invention) According to the present invention, since an active palladium catalyst is used, the desired product 2-methyl-6 can be produced under mild conditions.
- Naphthoic acid can be selectively synthesized. Furthermore, by-product production of acetoxy compounds can be suppressed, and by using Cu(,7!·PhCN complex, etc.), it becomes possible to proceed with the reaction in a continuous manner.

[Brief explanation of the drawing]

Figures 1 and 2 show the oxygen complex and Cu as a comparison in acetic acid and trifluoroacetic acid solvents, respectively.
(OAc) 2 was added, and the time change in the amount of Pd (O) oxidation was measured with a spectrophotometer and compared.

Claims (4)

[Claims] (1) In a method of synthesizing carboxylic acids by reacting naphthalene or methylnaphthalene with oxygen and carbon monoxide, the reaction is performed in the presence of acetic acid and/or trifluoroacetic acid using palladium and/or a palladium compound as a catalyst. A method for synthesizing naphthalenecarboxylic acids, characterized by carrying out the following steps. (2) In claim 1, as an oxidation regenerant for Pd(O) produced as a by-product during the reaction, the general formula (Mm・X
n・Ll) (where M is a transition metal belonging to Group I, IV-VII or VIII of the Periodic Law, and X is Cl^-, Br^-, I^ −、BF_4＾−
, an anion selected from PF^- and SO_4^-,
A method for synthesizing naphthalene carboxylic acids, characterized in that the ligand L is an organic phosphorus compound or a nitrile, m and n are constants determined by the valence balance, and l is a coordination number. (3) In claim 1 or 2, together with acetic acid and/or trifluoroacetic acid as a solvent,
It is characterized by using at least one compound selected from the group consisting of aliphatic alicyclic compounds, aromatic hydrocarbon compounds, oxygen-containing organic compounds, organic halogen compounds, nitrogen-containing compounds, organic phosphorus compounds, and nitriles. Synthesis method of naphthalenecarboxylic acids. (4) In any one of claims 1 to 3, basic (electron-donating) compounds such as sulfolane, dimethylsulfolane, dimethylsulfoxide, dimethylformamide, etc., and or amines such as tri-n-butylamine A method for synthesizing naphthalenecarboxylic acids characterized by the coexistence of naphthalenecarboxylic acids.