JPS6112886A - Manufacture of phthalaldehyde acetal - 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 present invention relates to a novel electrochemical process for the preparation of phthalaldehyde acetals.

Phthalaldehyde acetals can be produced, for example, by reacting phthalaldehyde with an O-ester (J, 'Chem, Sac, Perkin n.
1975, p. 1656). The phthalaldehyde required as starting material is prepared, for example, from bis-(chloromethyl)-benzole and hexamethylenetetramine by the Thumelet method. It is obtained, for example, in moderate yields and with low environmental friendliness by the method described in Journal of the Chemical Society, 1950, pages 2141-2145. According to DE 31 08 790, a process is known for the preparation of phthalaldehyde acecure by reacting α, α, α', α'-tetrahalogenokidylol with an alkali alcoholade. A disadvantage of this synthesis method is the difficulty in obtaining tetrahalogenokidylol, which is produced as a mixture of quidylols with different degrees of halogenation with low selectivity during halogenation of quidylol.

The inventor Z has developed an alkoxymethylpenzole represented by the general formula 2ROH
(In these formulas, R has the meaning below) by electrolyzing at a current density of 0.1 to 20 A/dm2 and a temperature 5°C lower than the boiling temperature of the alkanol, to obtain the general formula It has now been found that phthalaldehyde acetals of the formula (R in the formula is an alkyl group having 1 to 4 carbon atoms) can be prepared with particular advantage. According to the process of the invention, the oxidation of dialdehydes is surprisingly achieved with high selectivity.

Examples of the alkoxymethylpenzole of formula (1) include the following. 1,2-11,3- or 1,4-
Bis-(methoxymethyl)-benzole, 1,2-11
, 6- or 1,4-bis-(ethoxymethyl)-benzole, 1,2-11,6- or 1,4-bis-(propoxymethyl)-benzole, 1,2-11,6- or 1,4-bis-(impropoxymethyl)-benzole and 1,2-11.3- or 1,4-bis(tert-butoxymethyl)-benzole. Examples of ROH alcohols are methanol, ethanol, glopanol and butanol.

The electrochemical oxidation according to the invention is carried out using an industrially common electrolytic cell. Particularly suitable are undivided flow-through containers. As electrolyte, preferably an alcoholic solution of bis-(alkoxymethyl)-benzole is used, which may contain auxiliary electrolytes to improve the electrical conductivity. Suitable auxiliary electrolytes are, for example, bases such as alkali alcoholides, neutral salts such as fluorides, tetrafluoroborates, sulfonates and sulfates or acids such as alkylsulfonic acids, alkanesulfonic acids and sulfuric acid. Preferably a neutral auxiliary electrolyte such as KF or KSO3C'6H,
or acidic auxiliary electrolytes such as H,, so4, CH35
Use o3H or C, H5SO3H. For example, the electrolyte has the following composition.

2-3.0]ii% Bis-(alkoxymethyl)-benzole 65-98% by weight Alkanol 0.1-5% by weight Auxiliary electrolyte In the electrolysis of the present invention, as an anode, for example, noble metals, metal oxides such as RuO2 and Pbo2 or Graphite is used. A particularly preferred anode material is graphite. As cathode material, for example steel, iron, nickel, lead or graphite is used. Current density is 0.1-2
0 A/d, m2, preferably 2-8 A,/
It is dm2. The temperature is preferably at least 5° C. lower than the boiling point of the alkanol used, as long as the electrolysis is carried out at normal pressure.

For example, -5 to +55℃, especially 10 to 50℃, 4 to 12
Electrolysis is carried out using F/Mol bis-(alkoxymethyl)-benzole. Preferably 7-10 F/M
Electrolysis is carried out using ol bis-(alkoxymethyl)-benzole so that most of the bis-(alkoxymethyl)-pen, sol reacts. Electrolysis can be carried out both discontinuously and continuously. ``Working up of the electrolytic effluent is preferably carried out by distillation. Unreacted alkanol can be returned to electrolysis without purification. No deactivation or corrosion of the electrodes is observed even after multiple reuses of the electrodes.

The phthalaldehyde acetals obtained by the process of the invention are intermediates for the production of dyes and optical clarifying agents, for example, and are also used in the synthesis of special polymers.

Example 1 Electrolytic synthesis of terephkurdialdehyde tetramethyl acecool: Apparatus: Undivided flow-through cell with 9 graphite electrodes Anode: Graphite electrolyte: 263 g of 1,4-bis-(methoxymethyl)-benzole Sulfuric acid 13.2g Methanol 2370g Cathode: Graphite! Solution: Current density for 1,4-his-(methoxymethyl)-benzole 8.6 F/Mol '' 5 A/d7712 Temperature: 22~
25° C. In the electrolysis under the above conditions, the electrolytic solution is passed through a heat exchanger and passed into the cell at a flow rate of 20017. After completion of electrolysis, the electrolysis effluent is neutralized with sodium methylate. Then methanol was distilled off at normal pressure and 65-75°C,
The precipitated salts are separated by pressure nusoche at 60-70°C. The residue was heated to 12oC and 6 mbar.

Rectify with In this case, 1,4-bis-(methoxyme f/
5.5 g of l/)-hensol and 222.2 g of terephthaldialdehyde-tetramethyl acetal are obtained. From this 98.7% conversion of 1,4-bis-(methoxymethyl)-benzole, 62.1% yield of terephthaldialdehyde-tetramethyl acetal and 6
A selectivity of 2.9% is calculated. The recovered 1,4-bis-methoxymethyl)-benzole can be used again for electrolysis.

Example 2 Electrosynthesis of terephthalic dialdehyde-tetramethyl acetal: Apparatus: Undivided flow cell with 9 graphite electrodes Anode: Graphite electrolyte: 145 g of 1,4-bis-(methoxymethyl)-benzole Penzole sulfone Potassium acid 2° methanol 2570g Cathode: Graphite! Solution: Current density with L4-bis-(methoxymethyl)-benzole 8.5 F/Mol: 3.5 A
/ d7n2 temperature: 26-25° C. In electrolysis under the above conditions, the electrolyte is pumped into the cell via a heat exchanger at a flow rate of 20017 hours. When the electrolytic effluent is worked up as in Example 1 but without the addition of sodium methylate, 1,4-bis-(
Methoxymethy/l/) - hair 7"-l 0.4 g and terephthaldialdehyde-tetramethyl acetal 1
58.2. ! 9 is obtained. From this, 1,4-bis-(
methoxymethyl) ~ 99.7% conversion rate of penzole,
Terephthaldialdehyde-tetramethyl acetal 8
A yield of 0.1% and a selectivity of 80.4% are calculated.

The recovered methanol and potassium penzole sulfonate can be reused for electrolysis.

Example 6 Electrosynthesis of 0-phthaldialdehyde-tetramethyl acetal: Equipment Undivided flow cell anode with 29 graphite electrodes Graphite electrolyte = 263 g of 1,2-bis-(methoxymethyl)-benzole Penzole Potassium sulfonate 2° methanol 2370 g Cathode: Graphite electrolysis: 1,2-bis-(methoxymethyl)-benzole 8.5 F/Mol Current density: 3.6 A
/'d7IL2 Temperature=28-60° C. In electrolysis under the above conditions, the electrolyte is pumped into the cell via a heat exchanger at a flow rate of 2 oom/hour. After the completion of electrolysis, methanol is extracted from the electrolytic effluent at normal pressure and 65 to 80 ml.
Distill at °C. The resulting potassium lerbenzole sulfonate was separated using a pressurized Nutsche, and the filtrate was heated at 100 to 120°C.
and fractionated at 5 mbar. In this case, 3.8 g of 1,2-bis-(methoxymethyl)-benzole and 230.6 g of O-phthaldialdehyde-tetramethylacecool. ! i
' is obtained. From this, 98.6% conversion of 1,2-bis-(methoxymethyl)-benzole, 64.3% yield of 0-phthaldialdehyde-tetramethylacecool and 65.6% selectivity are obtained. Calculated. The recovered potassium penzole sulfonate and methanol can be reused for electrolysis.

Claims (1)

[Claims] 1. The alkoxymethylbenzole represented by the general formula ▲ There are numerical formulas, chemical formulas, tables, etc. ▼ II is expressed by the formula ROH
(In these formulas, R has the meaning given below) in the presence of an alkanol, at a current density of 0.1 to 20 A/dm^2 and at a temperature below 5°C lower than the boiling temperature of the alkanol. A method for producing phthalaldehyde acetal represented by the general formula ▲ There are numerical formulas, chemical formulas, tables, etc. ▼ I (R in the formula means an alkyl group having 1 to 4 carbon atoms). 2. The method according to claim 1, characterized in that the electrolysis is carried out in an undivided flow tank. 3. Bis-(alkoxymethyl)-benzole 2-30
2. Process according to claim 1, characterized in that an electrolyte is used with a composition of 65-98% by weight of alkanol and 0.1-5% by weight of auxiliary electrolyte. 4. KF, KSO_3C_6H_5 as auxiliary electrolytes,
H_2SO_4, CH_3SO_3H or C_6H_5
2. Process according to claim 1, characterized in that SO_3H is used.