We have described a practical and convenient procedure for the synthesis of 1,3,5-triaryl-2-pyrazolines in sodium acetate-acetic acid aqueous solution at room temperature under ultrasound irradiation.
Pyrazoline derivatives have been studied extensively because of their ready accessibility diverse chemical reactivity and variety of industrial applications. Variously substituted 2-pyrazolines can be effectively utilized as antimicrobial, anticonvulsant, cardiovascular, anti-inflammatory and antidepressant agent6-10. In additional pyrazolines have played a crucial role in organic synthesis11-12.
Table 2: Antibacterial activity of synthesized compounds (3a-g)
In view of interesting properties associated with 2-pyrozoline in the present investigation we report synthesis of some N-substituted 2-pyrozolines using microwave irradiation 16-17
ChemSynthesis - Chemical Database
Copper complexes of 1-formyl-2-pyrazolines were prepared by the reaction of 1-formyl-2-pyrazolines with copper chloride and nitrate with methanol. The structures of copper complexes 1a–3a have been established by elemental analysis, FT-IR, UV and thermogravimetric analysis. These compounds were tested against HM1:IMSS strain of Entamoeba histolytica by the microdilution method. Complexes 2a and 3a are more active than other complexes.
Synthesis of N -Heterocycles - Organic Chemistry Portal
The effect of the reaction conditions on the reaction of chalcones and phenylhydrazine hydrochloride under ultrasound irradiation was summarized in Table . When the molar ratio of chalcones(1):phenylhydrazine hydrochloride(2) was 1:1, the yield of 1,3,5-triphenylpyrazoline obtained was 76% (Table , Entry a). By increasing the molar ratio to 1:2, and 1:3 the yields of 3a increased to 82% and 89% respectively (Table , Entry b, c). The results showed that changing the molar ratio of 1:2 had a significant effect on the yield, and the optimum molar ratio of chalcone: phenylhydrazine was 1:3. The important discovery was that in the present of sodium acetate in acetate acid aqueous the yield of pyrazolines can be increased, it may be that sodium acetate is in favor of release of phenylhydrazine from phenylhydrazine hydrochloride. When the molar amount of sodium acetate increased from 0.15 to 0.2 and 0.3, the yield of pyrazoline decreased from 96% to 95% and 92% respectively (Table , Entry d, e, f). So the reaction conditions we chose were: the molar ratio of chalcone: phenylhydrazine: sodium acetate was 1:3:0.15.
Pyridine synthesis - Organic chemistry
In order to verify the effect of ultrasound irradiation, in the absence of ultrasound, we have performed the reaction of chalcone with phenylhydrazine hydrochloride by refluxing at 108°C for 4 h. The yield of pyrazoline was 76% (Table , Entry i). While under ultrasound irradiation, the reaction can be completed within 2 h in 96% yield at room temperature (Table , Entry d). It was clear that the ultrasound could accelerate the reaction of chalcone and phenylhydrazine hydrochloride.
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We also monitored the effect of different irradiation frequencies on the reaction. When the frequency was 25 kHz, the yield of pyrazoline was 96% (Table , Entry d) within 2 h. Under 40 kHz and 59 kHz irradiation, the yield of pyrazoline was 90% and 85% respectively (Table , Entry g, h). It seems that the lower frequency of ultrasound irradiation can improve the yield of pyrazoline. It is possible that as the ultrasonic frequency is increased, the production of cavitation in liquids decreases.