Preparation method of benzotriazole (BTA)

Benzotriazole (BTA)

[Structural formula]

[Physical and chemical properties] Benzotriazole, also known as benzotriazole , benzotriazole , benzotriazole, and triazine, is a colorless to light brown crystalline powder, melting point 90～95℃, boiling point 201～204℃(2kPa), sublimation at 98～100℃

[Preparation]

(1) Ortho-phenylenediamine atmospheric pressure method

First dissolve o-phenylenediamine in acetic acid aqueous solution, and prepare about 40% sodium nitrite aqueous solution; the two solutions are pre-cooled to 1～5℃, then mixed and reacted, kept in an ice bath, and then quickly heated to 80℃ The ring is closed to generate benzotriazole.

At present, most domestic manufacturers adopt this method

China's Du Bin et al.

Joseph used the method of dropping sodium nitrite aqueous solution.

The reaction mixture was extracted with hexanol, polyethylene glycol 200 was added to the extract, and the hexanol was recovered by distillation under reduced pressure, and then under a pressure of 266.

The former West German Rochat replaced sodium nitrite with potassium nitrite.

American Chan et al.

(2) o-phenylenediamine high pressure method

The o-phenylenediamine high pressure method was invented by American John

Since the diazonium ring-closing reaction does not involve acid, it reduces the chance of diazo coupling to produce dark-colored tars, thereby increasing the yield of the product, and at the same time making the purification of the product easier

Chinese researchers have achieved success in the synthesis of benzotriazole by a pressurized one-step method

(3) Benzoxazolone method

The benzimidazolone and sodium nitrite aqueous solution were reacted at 190°C under high pressure for 75 minutes, acidified, washed with water, and dried to obtain the product with a yield of 85.

(4) o-nitrophenylhydrazine method

O-Nitrophenylhydrazine is reacted in a mixed aqueous solution of ammonia, isopropanol and hexanediol for 1.

(5) o-nitrochlorobenzene method

Firstly, HBTA is directly synthesized from o-nitrochlorobenzene and hydrazine hydrate, and then BTA is generated by deoxygenation and hydrogenation.

①Synthesis of 1-hydroxybenzotriazole (HBTA) In a 250mL three-necked flask, equipped with a stirrer, reflux condenser and thermometer, put in 15.

② HBTA reduction HBTA can be converted into BTA by iron powder and hydrochloric acid reduction:

In a 250mL three-necked flask, equipped with a stirrer, thermometer, dropping funnel and reflux condenser, placed in a water bath for heating
.
Put in 5g (100%) of HBTA and 1.
4g of reduced iron powder, then inject 25mL of water, then keep it in a boiling water bath for 1h, and then add about 25mL of dilute hydrochloric acid made of 80mL of water and 21mL of 37% hydrochloric acid
.
After 1h, add 1.
4g iron powder and 25mL dilute acid at the same time (within 1h), and repeat the addition of iron powder and hydrochloric acid 4 times
.
Add 1.
4g of iron powder and 25mL of dilute hydrochloric acid each time, and reflux and keep the reaction for 1h after dripping
.
Strain the remaining iron powder while it is hot
.
The filtrate was concentrated to about half of the original solution
.
After cooling, add an appropriate amount of NaOH solution to neutralize to a pH of about 4
.
Then add an appropriate amount of NaCl to saturate, and extract with 80 mL of ethyl acetate for 4 times
.
The BTA is transferred to the organic phase, and the product BTA is obtained after the solvent is recovered by distillation
.
If the product has a darker color, it can be recrystallized, then dissolved in boiling water and decolorized, and white needle-like crystals can be obtained with a yield of 90%
.