PIDA‐Mediated Intramolecular N‐N Bond Formation to Access 2‐Aminoindazoles and 2,2′‐Biindazoles**

Abstract

A synthesis of 2‐aminoindazole and 2,2′‐biindazole derivatives from corresponding hydrazones using phenyliodine(III) diacetate (PIDA) as oxidant is reported at ambient temperature. This oxidative intramolecular cyclization reaction proceeds through the formation of the N−N bond. This protocol is metal‐free, operationally simple, has a short reaction time, and proceeds in ethyl acetate (preferred green solvent). Indazole core moieties are well established for their biological activity similarly 2‐aminoindazoles may also possess biological significance. A plausible reaction pathway has been reported based on a few control experiments.

Applications of Phenyliodine(III)diacetate in C−H Functionalization and Hetero‐Hetero Bond Formations: A Septennial Update

“…Ynamides (241) can be easily converted into CF 3 S-substituted oxazolidine-2,4-diones (243) with a quaternary carbon centre through a PIDA-mediated trifluoromethylthiolation/ oxidative cyclization with the Shen reagent (242) and this was disclosed by He and co-workers(Scheme 84). [164] The optimized reaction parameters are: Shen'sreagent (1.5 equiv. ), PIDA (2 equiv.)…”

Applications of phenyliodine(III) diacetate in heterocyclic ringformations: An updatefrom 2015 to date

“…Additionally, they are utilized as a reliable bioisosteric substitute for other heterocyclic assemblies like benzimidazole and indoles. Yadav and co-workers reported that at room temperature, 2-aminoindazole and 2,2 0 -biindazole derivatives were produced utilizing hydrazones and PIDA as an oxidant (Scheme 35) [55]. The N-N bond is formed as this oxidative intramolecular cyclization event developed.…”