Semicarbazone synthesis method

Abstract

The synthesis process of semicarbazone includes the following steps: 1. reaction of hydrazine hydrate and urea at 90-100 deg.c and regulating the pH value of the reacted liquid with concentrated hydrochloric acid to 3-4; and 2. adding aldehyde and ionic liquid to the reacted liquid, reflux reaction, cooling and filtering to obtain the destination compound. The synthesis process is superior in that the ionic liquid has less trend of volatilization, combustion and explosion, excellent dissolving property on both organic and inorganic matters, and easy recovering, and the reaction in homogeneous phase condition is easy to operate and high in yield; that the condensation may be microwave heated for shortened reaction time, raised yield, high product purity and low power consumption; and that the condensation may be ultrasonically promoted.

Description

(1) Technical field [0001] The invention relates to a method for synthesizing a semicarbazone. (2) Background technology [0002] The semicarbazone produced by the reaction of aldehyde and semicarbazide is an important fine chemical intermediate, which is mainly used in the synthesis of furantidine, an antibacterial drug for urinary tract infection. [0003] Taking the synthesis of benzaldehyde semicarbazone as an example, there are currently three synthetic routes. Method 1: react hydrazine hydrate and urea to obtain semicarbazide, then use concentrated hydrochloric acid to precipitate and separate to obtain semicarbazide hydrochloride, and condense semicarbazide hydrochloride with benzaldehyde or diethyl benzylidene malonate to obtain benzaldehyde amino urea. A large number of bubbles are generated during the reflux stage of the condensation reaction, which often causes the material to overflow and adhere to the wall of the vessel, which brings difficulties to the operat...

AI Technical Summary

Problems solved by technology

Among the above three methods, the semicarbazide hydrochloride prepared by method one has a relatively large solubility in water, and can only be obtained by evaporation and concentration, which has high energy consumption, low yield, high raw material cost, and due to excessive hydration Hydrazine is discharged along with the waste liquid and causes serious environmental pollution

Method 2: Trimethylsilyl isocyanate, one of the raw materials, relies on imports, and the production cost is high, which has a great impact on large-scale industrial production

The raw material nitrourea used in method three must be self-made, and it is easy to explode, which is very unfavorable to the operation and protection. The by-product nitrous oxide will be oxidized into toxic gases such as nitrogen dioxide when it meets air, causing air pollution.

[0004] Due to the relatively backward manufacturing process and low equipment level of most domestic chemical enterprises, the production of many products is still using the production process of foreign countries in the 1960s and 1970s. , High production costs, the "three wastes" in the production process have caused serious damage to the ecological environment, and even directly harmed human health, and the "three wastes" in the chemical industry have become one of the main sources of pollution

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