Tunable Synthesis of Pyrazolo Oxepines, Pyrazolo Thiophenes and 1H‐Indazoles Using Alkylation, Aldol Condensation and Thermal Rearrangement

Abstract

Base‐mediated alkylation of 1‐alkyl/aryl‐5‐hydroxy/mercapto‐1H‐pyrazole‐4‐carbaldehydes with functionalized 3‐bromo‐prop‐1‐enes and 3‐bromo‐1‐(arylsulfonyl)propenes followed by intra‐molecular cyclization afforded regioselective pyrazolo oxepines, pyrazolo thiophenes, and 1H indazoles respectively, with good to excellent yields. This protocol paves the way for the development of syntheses of interesting biologically active scaffolds.