Study On Reaction Of Synthesize Pyrazoles

The synthesis of heterocyclic compounds is a hot research topic in organic chemistry. As an important class of heterocyclic compounds, pyrazoles have attracted much attention in the fields of medicine and agricultural chemistry due to their broad biological activities. In this thesis, new pyrazoles synthesis approaches from hydrazonyl chlorides or hydrozones are reported. The results and details are described as below:1. A regioselective synthesis of 1,3,4,5-tetrasubstituted pyrazoles is established between 2-azidoacrylated and hydrazonyl chlorides in the presence of triethylamine. The yields are moderate to good except the reaction goes with hydrazonyl chlorides derived from alkyl aldehydes. Besides, we provide a possible [3+2]cycloaddition mechanism for this transformation.2. 5-Sulfonamidopyrazoles were efficiently synthesized in one pot from terminal alkynes, sulfonyl azides and hydrozones. The sequential reaction involves a copper-catalyzed three-component reaction, a Lewis acid catalyzed electrocyclic reaction and a dehydrogenation. In the first step, the intermediate ketenimine was trapped by hydrazone to form benzenesulfonamide. This reaction is mild, efficient, and suitable for varied substituted reagent. Then Zn(OTf)2 was used to catalyze the cyclization of benzenesulfonamide in the presence of di-tert-butyl peroxide (DTBP) and finally 5-sulfonamidopyrazoles were obtained.