JPH1045715A - Production of 2,3,3-trimethyl-4,5-benzindolenine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To simply obtain the subject compound useful as a synthetic intermediate for cyanine dyes used for recording membrane of diagnostics and electric materials as a functional dye in a high yield by carrying out a reaction under mild conditions by using an inexpensive raw material. SOLUTION: Methylisopropyl ketone-β-naphtylhydrazone represented by formula II is reacted with a mineral acid (e.g. hydrochloric acid) in water or a water soluble organic solvent, preferably at 50-60 deg.C and the reacted solution is neutralized with an alkali (e.g. sodium hydroxide) and the deposited crystals are filtered to extremely efficiently provide the objective 2,3,3-trimethyl-4,5- benzindolenin represented by formula I. An amount of the mineral acid used in the reaction is preferably 1-3 equivalent based on the compound of formula II.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

TECHNICAL FIELD The present invention relates to a 2,3,3-trimethyl-4,5- useful as a functional dye, which is useful as an intermediate for synthesizing a cyanine dye used in a recording film of a diagnostic agent or an electronic material.
The present invention relates to a method for producing benzindolenin.

[0002]

2. Description of the Related Art As a method for producing 2,3,3-trimethyl-4,5-benzindolenin, conventionally, methyl isopropyl ketone and β-naphthyl hydrazine are condensed to give methyl isopropyl ketone-β-naphthyl hydrazone. And a method of heating using oxalic acid, zinc chloride or the like as an acid catalyst is known (Zangerle, Monatsh. Chem., 31, (1910) 12).
8, Plancher et al., Gazz.Chim.Ital., 55, (1925) 5
Five).

[0003]

However, in the conventional method, the reaction conditions are severe, the post-treatment operation is complicated, and the waste liquid treatment requires a great deal of cost. Had many problems. Therefore, development of an industrially advantageous production method has been desired.

[0004]

Means for Solving the Problems Under such circumstances, the present inventors have conducted intensive studies and found that methyl isopropyl ketone-β-naphthylhydrazone was produced under mild conditions.
It has been found that the above compound can be synthesized industrially advantageously by using an inexpensive mineral acid such as hydrochloric acid, and the present invention has been completed.

[0005] The production method of the present invention is represented by the following reaction formula.

[0006]

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That is, the present invention is characterized in that a mineral acid is reacted with methyl isopropyl ketone-β-naphthyl hydrazone in water or a water-soluble organic solvent, and characterized in that it is characterized in that it is reacted with 2,3,3-trimethyl-4,5-benzindone. It is intended to provide a method for producing renin.

[0008]

BEST MODE FOR CARRYING OUT THE INVENTION The mineral acid used in the present invention includes hydrochloric acid, sulfuric acid, nitric acid, phosphoric acid, etc.
Particularly, hydrochloric acid is preferable. The amount of the mineral acid used is 0.1 to 0.1 parts of methyl isopropyl ketone-β-naphthylhydrazone.
Equivalent or more, especially 1-3 equivalent is preferable.

The reaction solvent used in the present invention is water or a water-soluble organic solvent, but may be any solvent capable of dissolving or suspending methyl isopropyl ketone-β-naphthylhydrazone. Specifically, water, a primary class having 1 to 6 carbon atoms,
Secondary and tertiary alcohols, acetone, acetonitrile, tetrahydrofuran, dioxane, dimethylformamide, dimethylsulfoxide and the like can be mentioned, and these can be used alone or in combination of two or more.
Of these, lower alcohols, particularly methanol, ethanol, 1-propanol, 2-propanol and the like are preferred.

[0010] The reaction temperature may be any of room temperature to reflux temperature, and the higher the temperature, the faster the reaction proceeds. However, considering the generation of impurities and the reaction time, it is preferably about 50 to 60 ° C.

By this reaction, 2,3,3-trimethyl-4,5-benzindolenine is produced almost quantitatively, and this reaction solution is neutralized with an alkali such as sodium hydroxide, potassium hydroxide or calcium hydroxide. The crystals precipitate when they are combined, and the crystals are filtered to obtain the desired 2,3,3-trimethyl-4,5-benzindolenin. When a solvent that does not precipitate crystals is used, the solvent may be distilled off and then neutralized with an alkali.

[0012]

EXAMPLES The present invention will be described in more detail with reference to the following Examples, but it should not be construed that the invention is limited thereto.

Reference Example 35 g of β-naphthylhydrazine was dissolved in toluene, and 19 g of methyl isopropyl ketone was gradually added. After the addition, toluene was distilled off to obtain 50 g of methyl isopropyl ketone-β-naphthylhydrazone.

Example 1 50 g of methyl isopropyl ketone-β-naphthyl hydrazone
Was dissolved in 2-propanol. 45 ml of concentrated hydrochloric acid was added and reacted at 60 ° C. for 15 hours. After distilling off 2-propanol,
Neutralized with sodium hydroxide, and the precipitated crystals were collected by filtration and 2,3,3-
38 g of trimethyl-4,5-benzindolenin were obtained. Yield 8
2.2%, mp 115.5-116.0 ° C.

EXAMPLE 2 50 g of methyl isopropyl ketone-β-naphthyl hydrazone
Was dissolved by adding methanol. Add 90 ml of 6N hydrochloric acid,
The reaction was performed at 60 ° C. for 18 hours. Neutralized with sodium hydroxide, and the precipitated crystals were collected by filtration to obtain 2,3,3-trimethyl-4,5-benzindolenin (30 g). Yield 64.9%, mp 115.2-115.8 ° C.

Example 3 Methyl isopropyl ketone-β-naphthyl hydrazone 50 g
Was suspended in water, 45 ml of concentrated hydrochloric acid was added, and the mixture was reacted at 50 ° C. for 24 hours. Neutralize with sodium hydroxide, filter the precipitated crystals,
45 g of 3,3-trimethyl-4,5-benzindolenin were obtained.
Yield 97.3%, mp 115.0-116.0 ° C.

EXAMPLE 4 50 g of methyl isopropyl ketone-β-naphthylhydrazone
Was dissolved by adding methanol. 9 ml of concentrated sulfuric acid was added, and the mixture was reacted under reflux for 10 hours. After distilling off methanol, neutralize with sodium hydroxide and collect the precipitated crystals by filtration.
40 g of -4,5-benzindolenin were obtained. Yield 86.5%, mp 115.4-116.0 ° C.

Example 5 50 g of methyl isopropyl ketone-β-naphthylhydrazone
Was dissolved in 2-propanol. 12 ml of concentrated sulfuric acid was added and reacted at 60 ° C. for 15 hours. After the solvent was distilled off, the residue was neutralized with sodium hydroxide, and the precipitated crystals were collected by filtration.
37 g of -4,5-benzindolenin were obtained. Yield 80.0%, mp 115.5-116.0 ° C.

[0019]

As described above, according to the method of the present invention, 2,3,3-
Trimethyl-4,5-benzindolenin is obtained in a high yield, and the desired product can be isolated by a simple treatment. This is an extremely efficient and industrially advantageous production method.

 ────────────────────────────────────────────────── ─── Continuing on the front page (72) Inventor Tetsuji Sudo 4-115 Matsuo, Matsuo-mura, Iwate-gun, Iwate Pref.

Claims (1)

[Claims] 1. A process for producing 2,3,3-trimethyl-4,5-benzindolenin, which comprises reacting methyl isopropyl ketone-β-naphthyl hydrazone with a mineral acid in water or a water-soluble organic solvent. Method.