CN102816120A - Technology for synthesizing 2-(1-hydroxyethyl) benzimidazole - Google Patents

Abstract

The invention discloses a synthesis process of 2-(1-hydroxyethyl)benzimidazole, which belongs to the field of organic synthesis. In this method, o-phenylenediamine and L-lactic acid are condensed in an aqueous solution of hydrochloric acid. After the reaction, the temperature is lowered, and the pH of the reaction system is adjusted to weak alkalinity. After filtration and drying, 2-(1-hydroxyethyl)benzene is obtained. And the crude product of imidazole. The synthesis method has mild reaction conditions, safe production, high and stable yield; the consumption of acid and alkali is reduced, the production cost is reduced, and the environmental pollution is lightened. Very beneficial to industrialized production.

Description

Synthetic process of 2-(1-hydroxyethyl)benzimidazole

technical field

The invention relates to a synthesis process of 2-(1-hydroxyethyl) benzimidazole and belongs to the field of organic synthesis.

Background technique

Benzimidazoles are broad-spectrum systemic fungicides with strong activity. Due to the emergence of this type of fungicide, the development of fungicides has reached a new stage, and new systemic fungicides have emerged, such as thiabendazole, which has epoch-making significance in the history of fungicides. 2-(1-Hydroxyethyl)benzimidazole is an intermediate in the process of producing the fungicide thiabendazole. The synthesis method of the fungicide intermediate is briefly mentioned in the existing literature, but there is no literature report on the optimized process for the synthesis of 2-(1-hydroxyethyl)benzimidazole.

Contents of the invention

The object of the present invention is to provide a safe and reliable, low production cost, high yield and less environmental pollution 2-(1-hydroxyethyl) benzimidazole synthesis optimization process.

In order to realize the purpose of the present invention, the technical solution of the present invention is: add o-phenylenediamine, L-lactic acid and hydrochloric acid in the reactor, stir and heat to carry out condensation reaction, after the reaction finishes, cool down, adjust its pH value to weak base property, filtered and dried to obtain the crude product of 2-(1-hydroxyethyl)benzimidazole, which can be recrystallized to obtain 2-(1-hydroxyethyl)benzimidazole with a content of about 98% crystals. The molar ratio of L-lactic acid/o-phenylenediamine is 1.0~1.8:1, the molar ratio of hydrochloric acid/o-phenylenediamine is 1.0~1.8:1, the reaction time is 2~6 hours, and the temperature of the synthesis reaction is 93~ 105°C.

The reaction scheme of the present invention is as follows:

The following conditions are preferred: the ratio of moles of L-lactic acid/moles of o-phenylenediamine is 1.2:1, the ratio of moles of hydrochloric acid/moles of o-phenylenediamine is 1.2:1, the reaction time is 4 hours, and the reaction temperature is 102°C .

In the synthetic technique described in the present invention, hydrochloric acid has played the effect of two aspects in this technique: the one, the reaction of hydrochloric acid and o-phenylenediamine forms the salt soluble in water, has prevented o-phenylenediamine from being oxidized, and simultaneously makes The reaction of o-phenylenediamine and L-lactic acid can be carried out in a homogeneous solution; on the other hand, hydrochloric acid acts as a catalyst during the condensation reaction. The mass fraction of hydrochloric acid solution added in the synthesis process of the present invention is 20%.

The invention has the advantages of mild reaction conditions, safe production, high and stable yield, reduced acid and alkali consumption, reduced production cost, reduced environmental pollution, and is very beneficial to industrialized production.

Detailed ways

In order to illustrate the present invention better, give examples as follows:

Example 1

The reaction was carried out in a three-necked flask, which was connected to a condenser and passed through water for reflux, a thermometer was inserted to display the temperature, stirred by an electric stirrer, and the three-necked flask was placed in an oil bath for heating. The mass fraction of the added hydrochloric acid is 20%, and the molar number of the added hydrochloric acid is 1.6 times of the molar number of o-phenylenediamine. The reaction temperature is 102°C, and the reaction time is 4h. Experiments were carried out with the molar ratios of L-lactic acid and o-phenylenediamine molar ratios being 1.0:1, 1.2:1, 1.4:1, 1.6:1, and 1.8:1.

After the reaction, the temperature was lowered and the pH value was adjusted between 8 and 9 with an aqueous solution of sodium hydroxide, and the crude product was obtained after filtration and drying. The crude product was taken for analysis and detection, and the yields based on o-phenylenediamine were calculated, and the results were: 0.821, 0.909, 0.900, 0.892, and 0.885, respectively. It can be seen that with the increase of the amount of L-lactic acid, the yield first increases and then decreases. When the molar number of L-lactic acid is 1.2 times that of o-phenylenediamine, the maximum yield is 90.9%. In the experiment, it was found through analysis that with the increase of the amount of L-lactic acid, the content of 2-(1-hydroxyethyl)benzimidazole in the crude product obtained by the reaction gradually decreased. Therefore, the consumption of L-lactic acid is too large, not only the yield is slightly reduced, but also the content of the target product in the crude product is also reduced, and the cost is also increased. Therefore, the ratio of the number of moles of L-lactic acid to the number of moles of o-phenylenediamine is preferably 1.2.

Example 2

The reaction was carried out in a three-necked flask, which was connected to a condenser and passed through water for reflux, a thermometer was inserted to display the temperature, stirred by an electric stirrer, and the three-necked flask was placed in an oil bath for heating. When reacting and feeding, the mass fraction of the added hydrochloric acid solution was 20%. In the experiment, under the condition that the ratio of the moles of L-lactic acid to the moles of o-phenylenediamine is 1.2, the reaction temperature is 102°C, and the reaction time is 4h, the moles of hydrochloric acid are 1.0, 1.2, 1.4, 1.6, 1.8 times to experiment.

After the reaction, the temperature was lowered and the pH value was adjusted between 8 and 9 with an aqueous solution of sodium hydroxide, and the crude product was obtained after filtration and drying. The crude product was taken for analysis and detection, and the yields based on o-phenylenediamine were calculated, and the results were: 0.503, 0.941, 0.917, 0.909, and 0.879, respectively. It can be seen that, with the increase of hydrochloric acid consumption, the yield of the product increases first and then decreases. When the mole number of hydrochloric acid/o-phenylenediamine mole number is 1.2, the yield of product reaches maximum, 94.1%. Along with the increase of hydrochloric acid consumption, the yield of product reduces, and cost increases instead. Therefore, the molar ratio of hydrochloric acid to o-phenylenediamine is 1.2 as the optimal condition.

Example 3

The reaction was carried out in a three-necked flask, which was connected to a condenser and passed through water for reflux, a thermometer was inserted to display the temperature, stirred by an electric stirrer, and the three-necked flask was placed in an oil bath for heating. When reacting and feeding, the mass fraction of the added hydrochloric acid solution was 20%. The ratio of moles of L-lactic acid/moles of o-phenylenediamine was 1.2, the ratio of moles of hydrochloric acid/moles of o-phenylenediamine was 1.2, and the reaction temperature was 102°C. Experiments were carried out when the reaction time was 2h, 3h, 4h, 5h and 6h.

After the reaction, the temperature was lowered and the pH value was adjusted between 8 and 9 with an aqueous solution of sodium hydroxide, and the crude product was obtained after filtration and drying. The crude product was taken for analysis and detection, and the yields based on o-phenylenediamine were calculated, and the results were: 0.833, 0.918, 0.941, 0.949, and 0.956, respectively. It can be seen from the analysis results that as the reaction time increases, the yield of the target product 2-(1-hydroxyethyl)benzimidazole also increases gradually. Although the yield was still increasing after 4h, the amount of increase was small. From the viewpoint of production, the longer the reaction time, the higher the cost, and after 4 hours of reaction, the yield of the product based on o-phenylenediamine has reached 94.1%. Therefore the preferred reaction time is 4h.

Example 4

The reaction was carried out in a three-necked flask, which was connected to a condenser and passed through water for reflux, a thermometer was inserted to display the temperature, stirred by an electric stirrer, and the three-necked flask was placed in an oil bath for heating. When reacting and feeding, the mass fraction of the added hydrochloric acid solution was 20%. The ratio of moles of L-lactic acid/moles of o-phenylenediamine is 1.2, the ratio of moles of hydrochloric acid/moles of o-phenylenediamine is 1.2, and the reaction time is 4 hours, select 93°C, 96°C, 99°C, Experiments were carried out at 102°C and 105°C.

After the reaction, the temperature was lowered and the pH value was adjusted between 8 and 9 with an aqueous solution of sodium hydroxide, and the crude product was obtained after filtration and drying. The crude product was taken for analysis and detection, and the yields based on o-phenylenediamine were calculated, and the results were: 0.868, 0.887, 0.923, 0.941, and 0.935, respectively. From the above experimental results, it can be seen that with the increase of temperature, the yield of the product first increases and then decreases. At a temperature of 102°C, the yield was maximum. Therefore, the reaction temperature is preferably 102°C.

Example 5

The present invention produces 2-(1-hydroxyethyl)benzimidazole under optimal conditions: the molar ratio of L-lactic acid/o-phenylenediamine moles is 1.2, and the molar ratio of hydrochloric acid/o-phenylenediamine moles is 1.2, the reaction time is 4 hours, and the reaction temperature is 102°C; under these optimal conditions, the production is safe and stable, the cost is low, and the yield based on o-phenylenediamine can reach 94.1%. the

Claims (3)

1. 2-(1-hydroxyethyl) benzoglyoxaline synthesis technique is characterized in that: O-Phenylene Diamine, L-lactic acid and hydrochloric acid are added in the reactor drum, and stirring heating is carried out condensation reaction; After reaction finishes; Cooling is regulated its pH value to weakly alkaline, filtration, drying; Can obtain the thick product of 2-(1-hydroxyethyl) benzoglyoxaline, obtain 2-(1-hydroxyethyl) benzoglyoxaline crystal through recrystallization.

2. 2-according to claim 1 (1-hydroxyethyl) benzoglyoxaline synthesis technique; It is characterized in that: the ratio of L-lactic acid/O-Phenylene Diamine mole number is 1.0 ~ 1.8:1; The ratio of hydrochloric acid/O-Phenylene Diamine mole number is 1.0 ~ 1.8:1, and in 2 ~ 6 hours reaction times, the temperature of building-up reactions is 93 ~ 105 ℃.

3. 2-according to claim 2 (1-hydroxyethyl) benzoglyoxaline synthesis technique; It is characterized in that: optimum condition is: L-lactic acid mole number/O-Phenylene Diamine mole number proportioning is 1.2:1; Hydrochloric acid mole number/O-Phenylene Diamine mole number proportioning is 1.2:1; Reaction times is 4h, and temperature of reaction is 102 ℃.