JPH0742264B2 - Process for producing unsaturated carboxylic acid isocyanatoethyl ester - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION Industrial Field of the Invention The present invention relates to general formula (I) useful as various synthetic intermediates. (Wherein R and R'represent a hydrogen atom or a lower alkyl group) and relates to an economically advantageous process for producing an unsaturated carboxylic acid β-isocyanatoethyl ester.

(Prior Art and Problems to be Solved by the Invention) The compound represented by the general formula (I) of the present invention is useful as various synthetic intermediates, and one of them is noted as a bifunctional monomer. It is a promising compound as an intermediate for synthesis such as β-isocyanatoethyl acrylate or methacrylate.

Isocyanatoalkyl esters of unsaturated carboxylic acids have hitherto been carried out by room temperature phosgenation of 2-alkenyl-2-oxazolines (JP-A-54-5921, JP-B-59-24).
977), and 2-alkenyl-2-oxazoline, which is the starting material, has been conventionally produced by using a relatively expensive chemical in a multi-step method, and the yield thereof was low (Angebadhemie 78 Vol. 113. page). In recent years, an improved method for increasing the yield has been proposed (Japanese Patent Publication No. 59-2497).
7), it is still a multi-step process, and since it includes a process with a relatively low conversion rate, it is a complicated method including the raw material recovery process.

Since the process of deriving 2-alkenyl-2-oxazoline to alkenyl-2-isocyanatoalkyl ester, which is the target product, is an excellent process that is extremely energy-saving and safe, it can be guided to the target product by a known excellent method. Uru 2
Finding an -oxazoline derivative is a key point for industrial production of unsaturated carboxylic acid-2-isocyanatoalkyl ester.

One of the reasons why the conventional method of synthesizing 2-alkenyl-2-oxazoline depends on the circumvented method and is complicated is because the target compound (and the starting material and the intermediate each contain an active double bond). This is because the reagents having active hydrogen such as hydrogen chloride, amine, etc. used in the conventional method are not used.

(Means for Solving Problems) The present inventor believes that 2-alkyl-2-oxazoline in which an unsaturated bond is protected should be synthesized by a conventional method, and if the protecting group is a phosgenation reaction. The present invention has been completed by searching for an economical protecting group which satisfies the requirements, based on the guiding principle that a alkenyl-2-isocyanatoalkyl ester production method can be rationalized if it can be eliminated depending on the conditions.

That is, the present invention has the general formula (II) (Wherein R and R'represent a hydrogen atom or a lower alkyl group, and X represents a chlorine or bromine atom), and the 2-oxazoline compound is reacted with phosgene under alkaline conditions. Formula (I) (In the formula, R and R'are the same as above.) The present invention is intended to provide a method for producing an unsaturated carboxylic acid β-isocyanatoethyl ester.

In the method of the present invention, the general formula (I
The compound I) is generally prepared from 2-bromoalkylnitrile, which is easily obtained from unsaturated nitrile, and is reacted with chlorohydrin in the presence of anhydrous hydrogen chloride to obtain an amidine compound, which is further treated with a tertiary amine. It can be produced by a method of ring-closing by treatment with a strong base as described above or a method of reacting 2-bromoalkylnitrile with ethanolamine in the presence of a small amount of a catalyst. However, in the former method, anhydrous conditions are required in a series of steps, and the yield of the second step is not necessarily good. Moreover, since it is relatively difficult to obtain chlorohydrin in an anhydrous state, the latter method is preferable in practice.

The lower alkyl group of the general formulas (I and II) is methyl,
Examples include ethyl and propyl groups.

The reaction of the 2-oxazoline compound of the general formula (II) with phosgene is carried out in the reaction liquid of a two-phase system of water and an organic solvent in the presence of a phase transfer catalyst.

The phase transfer catalyst used here is, for example, tetraalkylammonium halide, trialkylarylammonium halide, tetraalkylphosphonium halide, trialkylarylphosphonium halide, or the like, as long as it is usually used in synthetic organic chemistry. There is no limit.

The organic solvent is not particularly limited in principle as long as it is stable under the reaction conditions and phase-separates from water, but from a practical point of view, for example, methylene chloride, chloroform,
Typical examples include chlorinated carbon hydrogen such as chlorobenzene, aromatic hydrocarbons such as benzene, toluene and xylene, and oxygen-containing compounds such as ethyl acetate, butyl acetate, dioxane and tetrahydrofuran.

There is no strict limitation on the amount of phosgene or catalyst used, but in order to carry out the reaction effectively, the former is at least 1 mol ratio or more, preferably 1.
5 to 3 molar ratio, and the latter is based on the raw material
0.1 to 5% by weight, preferably 0.5 to 1% by weight is suitable.

If the reaction temperature is too high, the production of by-products increases, so it is usually desirable to carry out the reaction at 10 ° C or lower.

According to the method of the present invention, formation of a β-isocyanatoethyl ester group by ring closure of the oxazoline ring of the compound of the general formula (II) and formation of a β-isocyanatoethyl ester group with a carbon atom at the α-position to the carbonyl group and an adjacent carbon atom The formation of a double bond between them simultaneously occurs, and the desired compound of general formula (I) is obtained in one step. In addition, since the hydrogen halide desorbed here is recovered as an aqueous solution from the reaction solution, an economically extremely advantageous method is provided, such as easy separation from the target product.

Hereinafter, representative examples of the method of the present invention will be shown and described in more detail. However, these are representative examples for the purpose of illustration, and the method of the present invention is not limited to these. Needless to say.

Example 1 18 g of β-bromoisobutyronitrile was dissolved in 50 g of chlorobenzene and heated to 120 ° C. under a nitrogen stream. 8 g of ethanolamine was added dropwise over 1 hour at such a rate that the gas generated was not violent. Then, the reaction temperature was raised to 130 ° C. and the reaction was performed for 10 hours with stirring. 0.2 mmH after distilling off the solvent
Distill under reduced pressure of g and distill at 90-98 ° C.
20.8 g of-(2-bromoethyl) -2-oxazoline was obtained. Yield 90.3% 100 g of 2 (2-bromoethyl) -2-oxazoline
Dissolve in 0.1 ml of methylene chloride and add 0.1 g of phenothiazine, 12 g of caustic soda, 0.5 g of trimethylbenzylammonium hydroxide in 100 ml of water solution,
And 150 ml of methylene in which 17.5 g of phosgene was dissolved at the same time, the water layer did not become acidic and the temperature in the reactor was 5 ° C.
Was added dropwise at a rate not exceeding 1.5 hours. Kakimaze was continued at a temperature of 5 ° C. or lower for 30 minutes after completion of dropping.

Remove the methylene chloride layer, dry with anhydrous sodium carbonate, distill off the solvent, and then vacuum distill to 46-47 / 0.4mmHg.
13.8 g of 2-isocyanatoethyl methacrylate of was obtained.

Example 2 21 g of β-bromoacrylonitrile was dissolved in 150 ml of xylene and heated under reflux in a nitrogen stream. To this, 10 g of ethanolamine was added dropwise over 1.5 hours. Further, heating and refluxing were continued for 3 hours under the same conditions. 0.1mmH after distilling off xylene
Distillation was performed under vacuum of g to obtain 21.4 g of a fraction at 64-68 ° C.

The above fraction was dissolved in 150 ml of methylene chloride and 0.2 g of phenothiazine was added. A solution obtained by dissolving 10 g of caustic soda and 0.45 g of trimethylbenzylammonium chloride in 100 ml of water and 100 ml of a methylene chloride solution containing 20 g of phosgene at the same time keep the aqueous layer alkaline, and
The temperature was dropped at a rate not exceeding 10 ° C over 2 hours. After the dropping was completed, the oysters were left standing for 1 hour. The methylene chloride layer was washed 3 times with water, dried over sodium sulfate and evaporated under normal pressure to remove the solvent, followed by vacuum distillation at 80 ° -90 ° C / 14m.
mHg acrylic acid-2-isocyanatoethyl ester 13.
I got 7g. The yield was 62.3% based on β-bromoacrylonitrile, and a small amount of high boiling by-products was observed.

Claims (1)

[Claims] 1. A general formula (In the formula, R and R'represent a hydrogen atom or a lower alkyl group, and X represents a chlorine or bromine atom.) A 2-oxazoline compound represented by the formula is reacted with phosgene under alkaline conditions. (In the formula, R and R ′ are the same as above.) A method for producing an unsaturated carboxylic acid β-isocyanatoethyl ester.