JPH1112258A - Production of 3-aryldihydro-1,3-benzoxazine compound - Google Patents

Abstract

PROBLEM TO BE SOLVED: To produce the subject compound in high yield by allowing a secondary or tertiary amine, or a basic nitrogen-containing heterocyclic compound to coexist when a phenol compound is reacted with formalin and an aromatic primary amine in an organic solvent. SOLUTION: A solution obtained by mixing an aromatic primary amine (e. g. aniline, 4-chloroaniline, toluidine and naphthylamine) with an organic solvent such as dioxane is gradually added to formalin in the coexistence of a secondary or tertiary aliphatic amine (e.g. dipropylamine and triethylamine) or a basic nitrogen-containing heterocyclic compound (e.g. pyridine, imidazole, piperidine and morpholine) at a temperature of <=10 deg.C, and further the solution obtained by mixing a phenol compound e.g. a compound of formula I [(n) is 1-4; R2 is O, CH2 or the like]} with the organic solvent such as dioxane is added to the resultant mixture at the room temperature. The obtained mixture is heated and refluxed for 5-6 hr to provide the objective compound of formula II (R1 is an aryl; R2 is a 1-4C organic group) in the method for producing 3- aryldihydro-1,3benzoxazine compound.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a method for producing a 3-aryldihydro-1,3-benzoxazine compound which is useful as a thermosetting compound which generates very few volatile components during a curing reaction.

[0002]

2. Description of the Related Art A phenolic compound is reacted with formalin and an aromatic primary amine to form a 3-aryldihydro-
A method for synthesizing a 1,3-benzoxazine compound is already known. According to JP-A-49-47378, an acidic or alkaline substance is used as a catalyst for forming an oxazine ring. Only discloses the use of caustic potash or caustic soda.

[0003]

In using a dihydro-1,3-benzoxazine compound as a molding material, a substituent at the 3-position is required to further improve mechanical properties, electrical properties and flame retardancy. Various derivatives having a methyl group, a cyclohexyl group, a phenyl group, etc. introduced therein have been developed. However, the 3-aryldihydro-1,3-benzoxazine compound having an aromatic substituent at the 3-position is caused by the fact that the basicity of the starting aromatic amine is weakened by conjugation with the aromatic ring and the nucleophilicity is reduced. Therefore, it was difficult to form an oxazine ring with a high yield.

[0004]

Means for Solving the Problems In order to solve such problems, the present inventors have conducted intensive studies, and as a result, even when a weakly reactive aromatic primary amine is used as a raw material, the basic reactivity is further reduced. The inventors have found that an oxazine ring can be formed in good yield by coexisting a strong secondary or tertiary aliphatic amine and a basic nitrogen-containing heterocyclic compound, and have completed the present invention.

That is, the present invention relates to 3-
For the production of the aryldihydro-1,3-benzoxazine compound, 1 mol of a phenol compound in an organic solvent is added.
When reacting with at least 2 mol of formalin and 1 mol of aromatic primary amine with respect to one phenolic hydroxyl group, a secondary aliphatic amine, a tertiary aliphatic amine or a basic nitrogen-containing heterocyclic compound is present. To a method characterized by the following.

[0006]

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[0007]

DESCRIPTION OF THE PREFERRED EMBODIMENTS In carrying out the method of the present invention, the ratio of the secondary aliphatic amine is 0.5 to 10% by mole relative to 1 mole of the phenol compound, and the tertiary aliphatic amine and the base are used. The nitrogen-containing heterocyclic compound is a phenol compound 1
It should be added in a proportion of 0.5 to 100% mol per mol. If the amount of these compounds with respect to the phenolic compound falls below this range, the desired catalytic effect cannot be obtained, and even if the compound is added beyond this range, the yield of the desired product will not change. Side reaction with formalin occurs, and the yield of the target product decreases.

In carrying out the method of the present invention, formalin is co-existed with an organic solvent such as dioxane in the presence of a secondary aliphatic amine, a tertiary aliphatic amine or a basic nitrogen-containing heterocyclic compound, and an aromatic amine is added thereto. A solution in which an organic solvent such as dioxane is mixed is gradually added at a temperature of 10 ° C. or lower, then a solution in which a phenol compound is mixed in an organic solvent such as dioxane is added at room temperature, and the mixture is heated and refluxed for 5 to 6 hours. After completion of the reaction, the solvent of the reaction mixture is distilled off under reduced pressure, the residue is converted into an ether solution, and the mixture is washed with an aqueous sodium hydroxide solution, an aqueous hydrochloric acid solution and water. Is obtained. If further purification is required, it can be purified by a conventional method such as column chromatography.

Representative secondary and tertiary aliphatic amines used in carrying out the method of the present invention include dipropylamine, dibutylamine, diamylamine, dicyclohexylamine, triethylamine, tripropylamine and 8-diazabicyclo [5,4,0]
And undec-7-ene. Further, typical basic nitrogen-containing heterocyclic compounds include pyridine, imidazole, piperidine, morpholine and the like.

A typical phenol compound used in the practice of the method of the present invention is represented by the following formula.

[0011]

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[0012]

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Typical aromatic primary amines used in the practice of the present invention are aniline, 4-chloroaniline, toluidine, naphthylamine and 2-aminothiazole, and the organic solvents used in the reaction include dioxane, tetrahydrofuran. Dimethylformamide, acetonitrile, dimethylsulfoxide, 1,3-dimethylimidazolidinone, and the like.

[0014]

The present invention will be specifically described below with reference to examples and comparative examples.

Example 1 Triethylamine 0.02 was added to a solution of 0.2 mol of 37% formalin and 30 ml of dioxane.
1 mol was added, and a solution composed of 0.1 mol of aniline and 20 ml of dioxane was added dropwise while maintaining the internal temperature at 10 ° C. or lower. After completion of the dropwise addition, the mixture was stirred at the same temperature for several minutes, then a solution composed of 0.05 mol of bisphenol A and 50 ml of dioxane was added, and the mixture was heated under reflux for 6 hours. The yield of the reaction solution by high performance liquid chromatography was 68%. The reaction mixture was evaporated to dryness under reduced pressure, the dried matter was dissolved in 100 ml of ether, washed with an aqueous solution of sodium hydroxide, an aqueous solution of hydrochloric acid, and water.
There was obtained 0.03 mol (13.8 g, yield 60 mol%) of bis (3,4-dihydro-3-phenyl-1,3-benzoxazine) propane.

Example 2 The reaction was carried out under the same conditions as in Example 1 except that the amount of triethylamine in Example 1 was changed to 0.001 mol. As a result, the yield by high performance liquid chromatography after the reaction was 60%. Met.

Example 3 Instead of triethylamine in Example 1, 1,8-diazabicyclo [5,4,0]
The reaction was carried out under the same conditions as in Example 1 using 0.005 mol of undec-7-ene. As a result, the yield of the reaction solution by high performance liquid chromatography was 57%.

Example 4 In place of triethylamine in Example 1, 0.005 mol of diamylamine was used.
As a result of carrying out the reaction under the same conditions as in Example 1, the yield of the reaction solution by high performance liquid chromatography was 62.5%.

Example 5 A reaction was carried out under the same conditions as in Example 1 except that 0.005 mol of pyridine was used in place of triethylamine in Example 1. As a result, the yield of the reaction solution by high performance liquid chromatography was 52. 0.5%.

Example 6 The reaction was carried out under the same conditions as in Example 1 except that the amount of 1,8-diazabicyclo [5,4,0] undec-7-ene in Example 3 was changed to 0.001 mol. As a result, the yield of the reaction solution by high performance liquid chromatography was 69%.

Comparative Example A reaction was carried out under the same conditions as in Example 1 without adding triethylamine in Example 1, and the yield of the reaction solution by high performance liquid chromatography was 39%. The reaction mixture was treated in the same manner as in Example 1 to give 2,2-bis (3,4-dihydro-3-
Phenyl-1,3-benzoxazine) propane 0.0
13 mol (6.0 g, yield 26 mol%) was obtained.

[0022]

According to the present invention, a 3-aryldihydro-1,3-benzoxazine compound can be synthesized in good yield by reacting a phenol compound, formalin and an aromatic primary amine in an organic solvent. It is extremely useful as an industrial production method.

Claims (2)

[Claims] 1. A process for reacting a phenol compound, formalin and an aromatic primary amine in an organic solvent to produce a 3-aryldihydro-1,3-benzoxazine compound represented by the following general formula: A process for producing a 3-aryldihydro-1,3-benzoxazine compound, which comprises a tertiary aliphatic amine, a tertiary aliphatic amine or a basic nitrogen-containing heterocyclic compound. Embedded image 2. The method for producing a 3-aryldihydro-1,3-benzoxazine compound according to claim 1, wherein dioxane is used as the organic solvent.