DMSO as a C1 Source for [2+2+1] Pyrazole Ring Construction via Metal-Free Annulation with Enaminones and Hydrazines

A cascade reaction between enaminones, hydrazines, and dimethyl sulfoxide (DMSO) for the synthesis of 1,4-disubstituted pyrazoles catalyzed by molecular iodine in the presence of Selectfluor has been realized. DMSO plays a dual role as the C-1 source and the reaction medium. In addition, the synthesis of 1,3,4-trisubstituted pyrazoles using aldehydes as alternative C-1 building blocks has also been achieved.

Automated summary

The synthesis of 1,4-disubstituted pyrazoles was successfully achieved through a cascade reaction between enaminones, hydrazines, and DMSO catalyzed by molecular iodine in the presence of Selectfluor. DMSO played a dual role as the C-1 source and the reaction medium, and the synthesis of 1,3,4-trisubstituted pyrazoles using aldehydes as alternative C-1 building blocks was also accomplished.