Abstract
The regiospecific synthesis of 1H-pyrazole derivatives has been accomplished through the 1,3-dipolar cycloaddition of aryldiazoalkane to but-3-en-2-one. A convenient and inexpensive ultrasound-assisted preparation of cyclopropenes in good yields has been realized. The effect of solvent, ultrasonic power, frequency, reaction time and temperature of cyclopropenation were studied and the order of yield indicates ultrasound, 25 KHz > Ultrasound, 40 KHz > conventional synthesis method.