K2CO3‐Promoted Pyrazoles Synthesis from 1,3‐Dipolar Cycloaddition of N‐Tosylhydrazones with Acetylene Gas

Abstract 1,3‐Dipolar cycloaddition of N ‐tosylhydrazones with acetylene gas on balloon was investigated. Bases and solvents were screened and K 2 CO 3 was verified to be an efficient base to promote this process. DMSO gave the better result in the reaction of N ‐tosylhydrazones derived from aldehyde, and NMP was a better suitable solvent in the reaction of ketone N ‐tosylhydrazones. And a series of pyrazoles were provided in mediate to good yields. This process was easy to handle and suitable to the industrial application.