Synthesis and Utilization of 1H-Indazole N-Oxides in the Production of C3-Functionalized 1H-Indazoles

Abstract

The medicinal importance, natural rarity, and challenges associated with the synthesis of C3-functionalized 1H-indazoles have propelled the development of novel and practical 1H-indazole N-oxides for the production of diverse arrays of C3-functionalized 1H-indazoles. Utilizing 1H-indazole N-oxides has demonstrated remarkable efficacy in selectively introducing diverse functional groups, including amino (–NHAr), chloro (–Cl), hydroxy (–OH), sulfonyl (–SO2Ar), aromatic (–Ar), olefin, alkyl, and N-formyl (–NRCHO) groups, to indazole pharmacophore molecules. This review aims to offer a concise overview of synthetic approaches and practical applications of 1H-indazole N-oxides, including recent studies conducted by the authors. Transformative reactions involving 1H-indazole N-oxides not only offer strategies for synthesizing C3-functionalized 1H-indazoles but also hold significant potential in medicinal chemistry.