Rhodium(III)-Catalyzed Oxidative Annulation of Ketoximes with Sulfonamide: A Direct Approach to Indazoles

Abstract

A rhodium(III)-catalyzed intermolecular C−H amination of ketoxime and iodobenzene diacetate-enabled N− N bond formation in the synthesis of indazoles has been developed. A variety of functional groups were well tolerated, providing the corresponding products in moderate to good yields. Moreover, the nitro-substituted ketoximes are well compatible in this reaction, leading to the corresponding products in moderate to good yields.

Synthesis of triphenylpyridines via an oxidative cyclization reaction using Sr-doped LaCoO3 perovskite as a recyclable heterogeneous catalyst

“…The three precursors used to synthesize the strontium-doped lanthanum cobaltite perovskite catalyst, including La(NO 3 ) 3 , Sr(NO 3 ) 2 , and Co(NO 3 ) 2 , also exhibited low catalytic activity, forming the expected product in 2%, 39%, and 4% yields, respectively. In a second series of experiments, several heterogeneous catalysts were utilized for the reaction (entries [11][12][13][14][15][16][17][18]. Cu(BDC), a copper-organic framework, was active for the reaction, producing the product in 70% yield.…”

“…Subsequently, the condensation of the intermediate (12) with a second molecule of the ketoxime (7) produces the intermediate (13) and releases NH 2 OAc. Tautomerization of intermediate (13) affords intermediate (14), followed by the intramolecular cyclization of intermediate (14), generating intermediate (15). Finally, the dehydration of intermediate (15) produces 2,4,6-triphenylpyridine (16).…”

“…[10][11][12] Certainly, ketoximes have recently gained signicant interest as valuable building blocks for numerous important organic structures. [13][14][15][16][17] Perovskites have attracted extensive interest from researchers worldwide owing to their signicant physicochemical properties, such as redox behavior, superconductivity, ferroelectricity, magnetoresistance, and ionic conductivity. [18][19][20] Perovskites are mixed oxides, generally existing in the form of ABO 3 , where A represents an alkali, alkaline or lanthanide metal, and B stands for a transition metal.…”

Transition‐Metal‐Catalyzed Syntheses of Indazoles

“…Very recently Huang, Shi, Zhao, and co-workers have reported the synthesis of 2H-indazole by Rh(III)-catalyzed oxidative coupling between ketoximes and sulphonamides employing a combination of iodobenzene diacetate as the oxidant (Scheme 44). [48] Mechanistically, the reaction consists of Rh(III)-catalyzed intermolecular CÀ H bond amination of ketoxime, and iodobenzene-diacetate enabled NÀ N bond formation. The CÀ H bond amination was completed before the NÀ N bond formation as clear from the controlled experiments.…”

A Palladium-Catalyzed 4CzIPN-Mediated Decarboxylative Acylation Reaction of O-Methyl Ketoximes with α-Keto Acids under Visible Light

“…Inspired by these results, it was speculated that the indispensable oxidants such as excessive persulfate or silver salts may be replaced by using a photocatalyst with light, which would open a new, highly efficient pathway for decarboxylative reactions. Recently, our group presented several examples of oxime ether-directed selective C–H functionalization [ 13 , 14 , 15 ]. It is envisioned that when acetophenone oxime ether is employed as the substrate and benzoylformic acid as the source of benzoyl, the use of a photocatalyst under light may achieve direct ortho-selective benzoylation with a palladium catalyst.…”