The Rh(III)‐catalyzed ortho‐C−H bond functionalization of 2‐aryl indazoles with β‐ketosulfoxonium ylides has been developed for the synthesis of 6‐arylindazolo[2,3‐a]quinoline derivatives in good to excellent yields with a broad substrate scope and good functional group tolerance. The reaction proceeds through a sequential ortho‐alkylation followed by cyclodehydration. The combination of 5 mol% of Cp*Rh(III) and 40 mol% AgSbF6 was found to be effective for this conversion.
An oxidative annulation of 2-arylindazoles with cyclic enoneshas was developed using Rh(III)/Cu(OAc) 2 catalytic system for the first time to produce 3,4-dihydroindazolo[2,3-f] phenanthridin-1(2H)-one derivatives in good yields with high selectivity. When AgSbF 6 was used instead of Cu(OAc) 2 , the corresponding uncyclized products, 3-(2-(2H-indazol-2-yl) phenyl)cyclohexan-1-one scaffolds were formed exclusively. The reaction proceeds through a sequential conjugate addition of ortho-C-H bond of aryl group followed by an oxidative annulation of indazole ring to generate fused polycyclic scaffolds.
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