JPH11140078A - Production of cyclic acetal - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for producing a cyclic acetal by which industrial practice can be performed without accompanying troublesome operations such as use of a toxic mercury salt or a large amount of copper chloride. SOLUTION: Olefins are brought into contact with a polyhydric alcohol, a nitrous acid ester or a nitrogen oxide in the liquid phase in the presence of a platinum group metal or its salt.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

TECHNICAL FIELD The present invention relates to a novel method for producing a cyclic acetal. Acetals can be hydrolyzed to give the corresponding aldehydes or ketones. For example, it is possible to synthesize a corresponding ketone, cyclohexanone, from a cyclic olefin, cyclohexene, via a cyclic acetal.
Thus, acetal has various industrial uses.

[0002]

2. Description of the Related Art As a method for producing a cyclic acetal from an olefin, a method of reacting cyclohexene and ethylene glycol in the presence of mercury and palladium to obtain 2,2-pentamethylene-1,3-dioxolan (Tetrahedron).
Lett., 1972 , 3595), but there is a problem that harmful mercury salts must be used. In addition, cyclohexene and ethylene glycol are reacted in 3 atm of oxygen in the presence of palladium chloride and copper chloride to give 2,2-pentamethylene.
Method for obtaining -1,3-dioxolane (J. Org.Chem., 34 , 3949 (19
69)), but there is a problem that a large amount of copper chloride must be used. As described above, the method for producing a cyclic acetal has the above problems, and has not reached a practical level.

[0003]

SUMMARY OF THE INVENTION The present invention provides a process for producing a cyclic acetal which can be carried out industrially without complicated operations such as using harmful mercury salts or a large amount of copper chloride. Things.

[0004]

Means for Solving the Problems The present inventors have conducted research for the purpose of overcoming the above problems and establishing a method for producing a cyclic acetal which can be applied industrially.
It has been found that a cyclic acetal can be produced at a surprisingly high reaction rate by bringing an olefin, a polyhydric alcohol, and a nitrite or a nitrogen oxide into liquid phase contact in the presence of a platinum group metal or a salt thereof. Was.

[0005]

BEST MODE FOR CARRYING OUT THE INVENTION Specific examples of olefins which are the raw materials of the present invention include aliphatic olefins having 2 to 20, preferably 2 to 12 carbon atoms, such as ethylene, propylene, butene and isobutene; acrylic acid, methacrylic acid Acid, crotonic acid or the like having a carboxyl group having 2 to 20 carbon atoms, preferably 2 to 12 carbon atoms
Aliphatic olefins and esters thereof; carbon atoms having a nitrile group such as acrylonitrile and methacrylonitrile
An aliphatic olefin having 2 to 20, preferably 2 to 12 carbon atoms such as cyclopentene, cyclohexene and cyclododecene;
To 20, preferably 5 to 12 alicyclic olefins; styrene and the like.

On the other hand, polyhydric alcohols include ethylene glycol, 1,2-propanediol, 1,3-propanediol, 1,4-butanediol, 2,3-butanediol, 1,6-
Aliphatic polyhydric alcohols having 2 or more hydroxyl groups and having 2 to 12 carbon atoms, such as hexanediol and glycerol (1,2,3-propanetriol), are used. These polyhydric alcohols may have a substituent such as an alkoxy group and a halogen atom that does not inhibit the reaction. The amount used is about 1 to 1000 times, preferably about 2 to 100 times the mol of the olefin.

As the nitrite, a polyhydric ester of the above-mentioned polyhydric alcohol and nitrous acid is used. For example,
Ethylene glycol, 1,2-propanediol, 1,3-propanediol, 1,4-butanediol, 2,3-butanediol, 1,6-hexanediol, glycerol (1,2,3-propanetriol), etc. And an ester of an aliphatic polyhydric alcohol having 2 to 12 carbon atoms with nitrous acid. Further, a monoester of a monohydric alcohol and nitrous acid may be used. For example, esters of an aliphatic monohydric alcohol having 1 to 12 carbon atoms such as methanol, ethanol, n-propanol, i-propanol, n-butanol, i-butanol and t-butanol with nitrous acid are used.

When the above-mentioned monoester of nitrite is used, the monoester of nitrite and the polyhydric alcohol can be transesterified in the reaction system to form a polyester of nitrite. These nitrites are preferably used in an amount of 0.01 wt% or more based on the starting polyhydric alcohol,
In particular, it is preferable to use 0.1 to 10 wt%. The nitrite may be charged in the reaction system in advance.

In the present invention, nitrogen oxides such as dinitrogen trioxide and nitrogen dioxide can be supplied in the polyhydric alcohol solution instead of the nitrite. The amount is 0.1-100
The molar amount is 0 times, preferably 2 to 100 times. When supplying by diluting with an inert gas, the concentration should be 1 to 1
It is preferably 00 vol%, especially 10 to 60 vol%. Also, nitrites such as sodium nitrite and potassium nitrite and hydrates thereof can be present in the reaction system as a nitrogen oxide source. The amount is 1-1000 for polyhydric alcohol
The molar amount is 2 times, preferably 2 to 100 times. Further, oxygen gas can be supplied to the reaction system as needed.

In the present invention, a platinum group metal such as palladium, platinum, rhodium, ruthenium or the like, or a halide, sulfate, nitrate or acetate thereof is used as the catalyst. Catalyst in the reaction raw material solution (including olefin, polyhydric alcohol, nitrite, solvent)
Preferably, it is present at a concentration of 0.001 to 10% by weight, particularly 0.1 to 5% by weight in terms of platinum group metal.

In practicing the present invention industrially,
In order to facilitate recovery of the catalyst or the product, and to prevent loss of the catalyst, the platinum group metal or a salt thereof is supported on a carrier such as activated carbon, silica gel, alumina, silica alumina, silicon carbide, magnesia, and molecular sieves. May be used.

The present invention can be carried out in the presence or absence of a solvent inert to the reaction. Suitable solvents include
For example, lower fatty acid esters such as ethyl acetate, propyl acetate and butyl acetate; aliphatic dicarboxylic acid diesters such as dimethyl oxalate, diethyl oxalate, dimethyl succinate, diethyl succinate and dimethyl adipate;
Carbonic acid esters; aromatic carboxylic acid esters; ethers such as tetrahydrofuran, 1,4-dioxane, 1,2-dimethoxyethane; acetonitrile, propionitrile,
Nitriles such as benzonitrile; aromatic hydrocarbons such as benzene, chlorobenzene, nitrobenzene, and toluene; aliphatic hydrocarbons such as hexane and heptane; alkyl sulfoxides such as dimethyl sulfoxide; Alkyl sulfones and the like. The amount of use is, for example, about 0 to 1000 times by volume, preferably about 10 to 100 times by volume of the olefin.

[0013] The reaction temperature in the present invention is in the range of 20 to 150 ° C, preferably 20 to 80 ° C. The reaction pressure is from normal pressure to pressurized, for example, from normal pressure to 200 kg / cm ² · G, preferably from normal pressure to 5 kg / cm ² · G.

The generated cyclic acetal is separated by a distillation operation or the like.

[0015]

The present invention will be specifically described below with reference to examples. The product yield was based on the charged olefin, and the selectivity was calculated based on the consumed olefin.

Example 1 A three-necked flask equipped with a gas inlet, a thermometer and a reflux condenser was charged with 15 ml of 1,2-dimethoxyethane, 10 g of ethylene glycol, 0.04 g of palladium chloride and 1 g of cyclohexene as solvents. The content was maintained at 60 ° C., and a mixed gas consisting of 26.7 vol% of nitric oxide, 33.3 vol% of air, and nitrogen was supplied from the gas inlet at a rate of 30 ml / min. For 2 hours. In addition,
The gas led out from the upper part of the reflux pipe was led to a trap (cooled with dry ice-methanol) containing 50 ml of methanol to collect unreacted raw materials and products. The reaction solution in the flask and the collected solution in the methanol trap were analyzed by gas chromatography. As a result, 2,2-pentamethylene-1,3-dioxolane was produced in a yield of 30%.

Comparative Example 1 In Example 1, 26.7 vol% of nitric oxide and 33.3 vol of air
%, And air instead of a mixed gas consisting of nitrogen, 30 ml / mi
The experiment was performed in the same manner as in Example 1, except that the solution was supplied at the speed of n. As a result, 2,2-pentamethylene-1,3-dioxolane was produced in a yield of 0.6%.

Example 2 A three-necked flask equipped with a gas inlet, a thermometer and a reflux condenser was charged with 15 ml of 1,2-dimethoxyethane, 10 g of ethylene glycol, 0.04 g of palladium chloride and 1 g of cyclohexene as solvents. The content was maintained at 60 ° C., and nitrogen gas containing 10 vol% methyl nitrite was supplied from the gas inlet at 30 ml / min. For 2 hours. The amount of gas discharged from the upper part of the reflux pipe is 50
The mixture was led to a trap (dry ice-methanol) to which ml of methanol had been added, and unreacted raw materials and products were collected. The reaction solution in the flask and the collected solution in the methanol trap were analyzed by gas chromatography. As a result, 2,2-pentamethylene-1,3-dioxolane was produced in a yield of 23% and cyclohexanone dimethyl acetal in a yield of 4%.

Example 3 An experiment was conducted in the same manner as in Example 1 except that the reaction temperature was changed to 40 ° C. and 0.05 g of palladium acetate was used instead of palladium chloride. as a result,
2,2-Pentamethylene-1,3-dioxolane was produced in a yield of 31%.

Examples 4 to 6 Experiments were carried out in the same manner as in Example 1 except that the type of the catalyst, the reaction temperature and the polyhydric alcohol were changed as shown in Table 1. The results are shown in Table 1.

[Table 1]

[0021]

According to the present invention, harmful mercury salts and a large amount of olefins, polyhydric alcohols, and nitrites or nitrogen oxides are brought into contact in the liquid phase in the presence of a platinum group metal or a salt thereof. It is possible to provide a very industrially advantageous production method for obtaining a cyclic acetal at a high reaction rate without complicated operations such as the use of copper chloride.

Claims (1)

[Claims] 1. A process for producing a cyclic acetal, comprising bringing an olefin, a polyhydric alcohol, and a nitrite or a nitrogen oxide into liquid phase contact in the presence of a platinum group metal or a salt thereof.