Synthesis and diversification of SuFEx-active 2H-indazoles from azobenzenes and ethenesulfonyl fluoride.

Abstract

A direct approach to SuFEx-active 2H-indazoles from azobenzenes and ethenesulfonyl fluoride was developed through Rh(iii)-catalyzed tandem C-H activation and annulation. The transformation provided a range of SO₂F-containing 2H-indazoles with good functional group tolerance while preserving the synthetically valuable sulfonyl fluoride functionality. The practicality of the method was demonstrated by gram-scale synthesis and subsequent SuFEx conjugation with representative biologically relevant molecules. This strategy provides efficient access to functionalized 2H-indazoles bearing a versatile SuFEx handle for further molecular diversification in medicinal chemistry and chemical biology.