JPS6228769B2 - - Google Patents

Description

[Detailed description of the invention]

Prenyl halides are extremely important substances as synthetic intermediates because various compounds having an isoprene skeleton can be synthesized by subjecting them to a dehydrochlorination reaction with ketones or by other methods. The present invention relates to a novel method for stabilizing such prenyl halides. The decomposition of prenyl halides is accelerated by contact with metals such as iron, copper, or by the presence or interaction of air (oxygen) and water. The decomposition products are hydrogen halide and isoprene, and prenyl halide becomes acidic due to the hydrogen halide. Further, once decomposition occurs, subsequent decomposition proceeds rapidly, and isomerization and an increase in polymerized products occur together with this, and the purity of prenyl halide decreases rapidly. In addition, halogenated prenyl has the property of being in equilibrium with a tertiary structure in which a halogen is added to the tertiary position of the carbon chain, as shown by the following formula, and purified high-purity halogenated prenyl is As the decomposition progresses, the composition quickly reaches an equilibrium composition.
For example, in prenyl chloride, the equilibrium composition at room temperature of 3-chloro-3-methyl-1-butene on the right side of the above formula and 1-chloro-3-methyl-2-butene on the left side is 1 for the former and 9 for the latter. When high-purity 1-chloro-3-methyl-2-butene purified by distillation is left to stand, it quickly assumes an equilibrium composition and its purity decreases. Therefore, when synthesizing various compounds having an isoprene skeleton, the use of such impure prenyl halides causes disadvantages such as a decrease in yield and an increase in impurities. Therefore, it is necessary to use a stabilizer to suppress the decomposition of the prenyl halide and to maintain the prenyl halide at a high purity. Conventionally, many types of stabilizers for halogenated hydrocarbon solvents have been proposed, but such stabilizers have been unsatisfactory for extremely unstable prenyl halides. The present inventors studied the stabilizing effects of various substances in order to stabilize prenyl halides, and found that it is effective to add an N/N-diarylamine compound. invention has been achieved. The present invention involves stabilizing prenyl halide obtained by reacting isoprene with hydrogen halide or concentrated hydrogen halide during distillation purification, or distilling prenyl halide obtained in this manner. It is particularly effective in stabilizing high purity products after treatment. However, it is not necessarily limited to this. The addition amount of N/N-diarylamine compounds (hereinafter simply referred to as diarylamine) as a stabilizer is 0.01 to prenyl halide.
-10% by weight, particularly preferably in the range of 0.05-2% by weight. The high purity prenyl halide to which diarylamine was added maintained its purity for a surprisingly long time, and wasomerization, decomposition, etc. were suppressed. Prenyl halide is an important starting material for the synthesis of methylheptenone and dehydrolinalool, and methylheptenone was synthesized using prenyl halide to which diarylamine was added, and then dehydrolinalool was synthesized from this prenyl halide. As a result, diarylamine did not affect these synthetic reactions at all. In the present invention, prenyl halides are prenyl chloride, prenyl bromide and prenyl iodide. Particularly suitable N·N-diarylamine compounds in the present invention include diphenylamine, phenyl-α-naphthylamine, and phenyl-α-naphthylamine.
β-naphthylamine, N・N′-di-α-naphthyl-p-phenylenediamine, N・N′-di-β
-naphthyl-p-phenylenediamine, N.
It is one type or a mixture of two or more types selected from the group such as N'-diphenyl-p-phenylenediamine, but is not necessarily limited thereto. Furthermore, the present invention does not preclude the use of diarylamine in combination with other substances considered to be effective for stabilization. As mentioned above, the diarylamine may be added after purifying the prenyl halide by distillation, but it is more advantageous to charge it into the prenyl halide receiver before distillation and then carry out the distillation. be. Alternatively, it may be added to the reaction completed solution of prenyl halide synthesis, but the stabilizing effect will be more pronounced if the diarylamine is added after drying using a dehydrating agent and then stored. Furthermore, storage in an inert gas atmosphere in conjunction with the addition of diarylamine further enhances the stabilizing effect. As is clear from the above explanation, the method of the present invention
This is an excellent method because the stability of the crude prenyl halide after the completion of the reaction or the high purity prenyl halide purified by distillation can be maintained for a long period of time. EXAMPLES The present invention will be specifically explained below using Examples and Comparative Examples, but the present invention is not limited to these Examples. Examples 1 to 5 and Comparative Examples 1 to 5 100 g of prenyl chloride with predetermined amounts of various stabilizers shown in Table 1 added to a 200 ml eggplant-shaped flask equipped with a reflux condenser was provided and maintained at a temperature of 80°C. It was immersed in an oil bath and heated for 5 hours. After heating, cool and remove free hydrogen chloride generated by decomposition with 0.1N NaOCH ₃ (methanol to benzene solution).
It was titrated with Note that the prenyl chloride used was dried. From the results in Table 1, N.
Since prenyl chloride to which N'-diarylamine was added had less free hydrogen chloride, it was clear that the decomposition of prenyl chloride was suppressed.

【table】

[Table] * The amount of free hydrochloric acid after heating is calculated based on the amount of free hydrochloric acid in the raw material.
Value divided by the amount of hydrochloric acid Example 6 Crude prenyl chloride synthesized by reacting isoprene with hydrogen chloride was neutralized and dried, and after distillation, prenyl chloride with a purity of 95.2% was obtained. The obtained prenyl chloride
Add 0.1% by weight phenylnaphthylamine,
Stored in amber bottles under argon atmosphere. The purity after standing for one month was 94.8%, with almost no decomposition, isomerization, polymerization, etc. observed. In addition,
Without the addition of phenylnaphthylamine, the purity decreased to 82.5% in one week.

Claims (1)

[Scope of Claims] 1. A method for stabilizing halogenated prenyl, which comprises adding an N·N-diarylamine compound to halogenated prenyl. 2 The N/N-diarylamine compound is diphenylamine, phenyl-α-naphthylamine,
Phenyl-β-naphthylamine, N・N'-di-
α-naphthyl-p-phenylenediamine, N.
Claims 1. At least one member selected from the group of N'-di-β-naphthyl-p-phenylenediamine and N.N'-diphenyl-p-phenylenediamine. The method described in Section 1. 3. The method according to claim 1 or 2, wherein the amount of the N·N-diarylamine compound added is 0.01 to 10% by weight.