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

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. Diversified oxepines fused with pyrazoles have been synthesized by simple base mediated alkylation followed by intra‐molecular cyclization strategy using 1‐alkyl/aryl‐5‐hydroxy‐1H‐pyrazole‐4‐carbaldehydes. When extended to thio version the same strategy gives pyrazolo thiophenes and 1H‐indazoles. This protocol paves the way for the synthesis of interesting biologically active molecules.