Preparation method for 2,3-dichloro-4-hydroxyaniline

Abstract

The present invention discloses a preparation method for 2,3-dichloro-4-hydroxyaniline. The method comprises the following steps: adding reaction materials 2,3-dichloro-4-phenylazo phenol and a reducing agent to an aqueous solution of sodium hydroxide; reacting at 50-100 DEC C for 2-12 hours; after completion of the reaction, cooling to room temperature; adjusting the pH to 7; then, extracting with ethyl acetate; next, drying over anhydrous sodium sulfate; then, rotationally distilling off the solvent and recrystallizing toluene; and finally, baking to obtain the 2,3-dichloro-4-hydroxyaniline. The reducing agent is selected from one of hydrazine hydrate and sodium hydrosulfite. According to the preparation method disclosed by the present invention, a catalytic reduction method of using hydrogen / metal under a pressurized condition is avoided. It is not required to use expensive and flammable Raney nickel or other metal catalysts, and use any auxiliary. Operations are simple, a yield can be more than 95%, and reaction costs are low, so that the method of the present invention is suitable for large scale industrial production.

Description

technical field

[0001] The invention belongs to the technical field of crop protection agents, and in particular relates to a preparation method of a key intermediate 2,3-dichloro-4-hydroxyaniline. Background technique

[0002] Amide fungicides have been successfully developed and used since 1966, and this type of crop protection agent has been used as a fungicide for nearly 50 years. Fenhexamid is a new systemic and protective amide fungicide developed by Bayer Corporation of Japan, which was officially launched in 1999. Fenhexamid and its derivative fungicides have safe and beneficial toxicological data for crops, and good ecological effects, so they become ideal integrated pest management drugs.

[0003] 2,3-dichloro-4-hydroxyaniline is the key intermediate of fenhexamid and its derivatives crop fungicides, and its synthesis method has been reported and protected by Bayer Corporation of Japan, that is, the substituted aryl azo compound As a raw material, the target comp...

Examples

Embodiment 1

[0044] Preparation of 2,3-dichloro-4-hydroxyaniline by reduction of hydrazine hydrate / sodium hydroxide solution system

[0045] In a 100 ml two-necked flask equipped with a stirring bar and a reflux condenser, add 8.0 grams (0.03 moles) of raw material 2,3-dichloro-4-phenylazophenol, dissolve in 30 ml of 40% sodium hydroxide solution 15.0 g (0.3 mol) of hydrazine hydrate was slowly added. After the dropwise addition was completed, the mixture was heated to 90° C. for 10 hours under stirring. After the reaction, the dilute hydrochloric acid solution was neutralized to pH=7, extracted three times with ethyl acetate, the combined organic phase was dried with anhydrous sodium sulfate, the solvent was evaporated by a rotary evaporator, 20 ml of toluene was recrystallized, and the product was obtained by drying after filtration: 5.08 g of pale pink crystals, yield 95%.

[0046] Figure 1~3 shows the 2,3-dichloro-4-hydroxyaniline 1 HNMR characterization spectrum, 13 CNMR charact...

Embodiment 2

[0048] Preparation of 2,3-dichloro-4-hydroxyaniline by reduction of hydrazine hydrate / ethanol and sodium hydroxide solution system

[0049] In a 100 ml two-necked flask equipped with a stirring bar and a reflux condenser, add 8.0 g (0.03 moles) of raw material 2,3-dichloro-4-phenylazophenol, dissolve in 20 ml of ethanol and 20 ml of 40% To the sodium hydroxide mixed solution, 19.0 g (0.36 mol) of hydrazine hydrate was slowly added. After the dropwise addition was completed, the mixture was heated to 80° C. for 10 hours under stirring. After the reaction, the dilute hydrochloric acid solution was neutralized to pH=7, extracted three times with ethyl acetate, the combined organic phase was dried with anhydrous sodium sulfate, the solvent was evaporated by a rotary evaporator, 20 ml of toluene was recrystallized, and the product was obtained by drying after filtration: 5.13 g of light pink crystals, yield 96%.

Embodiment 3

[0051] Preparation of 2,3-Dichloro-4-Hydroxyaniline by Reduction of Sodium Sodium Hydroxide / Sodium Hydroxide Solution System

[0052] In a 100 ml two-necked flask equipped with a stirring bar and a reflux condenser, add 8.0 grams (0.03 moles) of raw material 2,3-dichloro-4-phenylazophenol, dissolve in 20 ml of 40% sodium hydroxide solution , heated to 85°C under stirring, added 20 grams (0.12 moles) of sodium hydrosulfide in small portions, and kept the temperature to continue the reaction for 3 hours. After the reaction, the dilute hydrochloric acid solution was neutralized to pH=7, extracted three times with ethyl acetate, the combined organic phase was dried with anhydrous sodium sulfate, the solvent was evaporated by a rotary evaporator, 20 ml of toluene was recrystallized, and the product was obtained by drying after filtration: 5.28 g of pale pink crystals, yield 98%.

technical field

[0001] The invention belongs to the technical field of crop protection agents, and in particular relates to a preparation method of a key intermediate 2,3-dichloro-4-hydroxyaniline. Background technique

[0002] Amide fungicides have been successfully developed and used since 1966, and this type of crop protection agent has been used as a fungicide for nearly 50 years. Fenhexamid is a new systemic and protective amide fungicide developed by Bayer Corporation of Japan, which was officially launched in 1999. Fenhexamid and its derivative fungicides have safe and beneficial toxicological data for crops, and good ecological effects, so they become ideal integrated pest management drugs.

[0003] 2,3-dichloro-4-hydroxyaniline is the key intermediate of fenhexamid and its derivatives crop fungicides, and its synthesis method has been reported and protected by Bayer Corporation of Japan, that is, the substituted aryl azo compound As a raw material, the target comp...

Examples

Embodiment 1

[0044] Preparation of 2,3-dichloro-4-hydroxyaniline by reduction of hydrazine hydrate / sodium hydroxide solution system

[0045] In a 100 ml two-necked flask equipped with a stirring bar and a reflux condenser, add 8.0 grams (0.03 moles) of raw material 2,3-dichloro-4-phenylazophenol, dissolve in 30 ml of 40% sodium hydroxide solution 15.0 g (0.3 mol) of hydrazine hydrate was slowly added. After the dropwise addition was completed, the mixture was heated to 90° C. for 10 hours under stirring. After the reaction, the dilute hydrochloric acid solution was neutralized to pH=7, extracted three times with ethyl acetate, the combined organic phase was dried with anhydrous sodium sulfate, the solvent was evaporated by a rotary evaporator, 20 ml of toluene was recrystallized, and the product was obtained by drying after filtration: 5.08 g of pale pink crystals, yield 95%.

[0046] Figure 1~3 shows the 2,3-dichloro-4-hydroxyaniline 1 HNMR characterization spectrum, 13 CNMR charact...

Embodiment 2

[0048] Preparation of 2,3-dichloro-4-hydroxyaniline by reduction of hydrazine hydrate / ethanol and sodium hydroxide solution system

[0049] In a 100 ml two-necked flask equipped with a stirring bar and a reflux condenser, add 8.0 g (0.03 moles) of raw material 2,3-dichloro-4-phenylazophenol, dissolve in 20 ml of ethanol and 20 ml of 40% To the sodium hydroxide mixed solution, 19.0 g (0.36 mol) of hydrazine hydrate was slowly added. After the dropwise addition was completed, the mixture was heated to 80° C. for 10 hours under stirring. After the reaction, the dilute hydrochloric acid solution was neutralized to pH=7, extracted three times with ethyl acetate, the combined organic phase was dried with anhydrous sodium sulfate, the solvent was evaporated by a rotary evaporator, 20 ml of toluene was recrystallized, and the product was obtained by drying after filtration: 5.13 g of light pink crystals, yield 96%.

Embodiment 3

[0051] Preparation of 2,3-Dichloro-4-Hydroxyaniline by Reduction of Sodium Sodium Hydroxide / Sodium Hydroxide Solution System

[0052] In a 100 ml two-necked flask equipped with a stirring bar and a reflux condenser, add 8.0 grams (0.03 moles) of raw material 2,3-dichloro-4-phenylazophenol, dissolve in 20 ml of 40% sodium hydroxide solution , heated to 85°C under stirring, added 20 grams (0.12 moles) of sodium hydrosulfide in small portions, and kept the temperature to continue the reaction for 3 hours. After the reaction, the dilute hydrochloric acid solution was neutralized to pH=7, extracted three times with ethyl acetate, the combined organic phase was dried with anhydrous sodium sulfate, the solvent was evaporated by a rotary evaporator, 20 ml of toluene was recrystallized, and the product was obtained by drying after filtration: 5.28 g of pale pink crystals, yield 98%.

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