Rhodium‐Catalyzed Regioselective C7‐Olefination of Indazoles Using an N‐Amide Directing Group

Abstract

A rhodium-catalyzed regioselective C-H olefination of indazole is described. This protocol relies on the use of an efficient and removable N,N-diisopropylcarbamoyl directing group, which offers facile access to C7-olefinated indazoles with high regioselectivity, ample substrate scope and broad functional group tolerance.

Direct Catalytic Functionalization of Indazole Derivatives

“…In this transformation, the desired C-7 alkenyl 1H-indazole ( . [117] Electron-donating, as well as electron-withdrawing substituents at different positions of indazoles were well tolerated by this reaction. Different kinds of acrylates, vinylphenylsulfone, substituted styrene etc were easily acted as olefin coupling partners for this reaction.…”

Rhodium‐Catalyzed C(sp2)‐ or C(sp3)−H Bond Functionalization Assisted by Removable Directing Groups

“…[234] Despite the high electron density of the indazole ring, selective product formation was observed and the presence of an N-amide was found to be essential for the success of the reaction. [234] Despite the high electron density of the indazole ring, selective product formation was observed and the presence of an N-amide was found to be essential for the success of the reaction.…”

“…The[ RhCp*Cl 2 ] 2 -catalyzed C7 À Ha lkenylation of indazoles with alkenes,a ided by the presence of an N-amide directing group was reported (Scheme 62). [234] Despite the high electron density of the indazole ring, selective product formation was observed and the presence of an N-amide was found to be essential for the success of the reaction. Thelarge functional group tolerance contributes to the importance of these findings.T omore clearly demonstrate the utility of the alkenylation reaction, the N,N-diisopropylcarbamoyl directing group was removed smoothly by treatment with an aqueous 50 %s olution of NaOH in ethanol to provide the desired indazole derivative 205 in high yield (Scheme 63).…”

Oxidative Alkenylation of Fused Bicyclic Heterocycles

“…Very recently, in another interesting development of C-H alkenylation, Pan and co-workers [91] reported rhodium-catalyzed regioselective C7-olefination of (1H)-indazole using a N-carbamate directing group. Thus, the N,N-dimethylcarbamoyl (1H)indazole 105 and methyl acrylate were connected using [RhCp*Cl 2 ] 2 as catalyst in the presence of AgSbF 6 and AgOAc in tBuOH at 70°C for 48 h. The desired C7-alkenylated product 106 was isolated in 90 % yield (Scheme 43).…”