Rh(Ⅲ)-Catalyzed Acylmethylated Of 2H-Indazole With Sulfoxonium Ylides

As a class of N-heterocycles.indazoles have been recognized as a ubiquitous scaffold due to their prevalence in natural products,pharmaceutics,and bioactive compounds.In addition,sulfoxonium ylides.as a useful organic synthon,have been utilized as alternative carbene sources to achieve a range of transformations due to their stability.In this thesis,an efficient Cp*Rh(Ⅲ)-catalyzed direct acylmethylation of 2H-indazoles with sulfoxonium ylides has been realized under air atmosphere via chelation-assisted strategy.The main research contents were shown as follows:Our initial investigation employed 2-phenyl-2H-indazole la and sulfoxonium ylides 2a as the model substrates.The reaction conditions were screened and the optimal conditions were as follows:2-phenyl-2H-indazoles la(0.2 mmol)and sulfoxonium ylides 2a(0.4 mmol)as the substrate,[Cp*RhCl2]2(3.7 mg,3 mol%)as the catalyst,AgSbF6(13.7 mg,20 mol%),PivOH(40.8 mg,0.4 mmol)and Zn(OAc)2(22.0 mg,60 mol%)as additives.DCE(2 mL)as the solvent,under air,stirred at 100℃ for 12 h.Under the optimal conditions,the substrate scope was extended to afford acylmethylation productes 3 or 4 is up to 88%yield with totally 42 examples(Scheme 1).This protocol enables a regioselective access to a variety of ortho-acylmethylated 2-phenylindazole derivatives in moderate to good yield,which has the advantages of broad substrate scope,good functional group tolerance,and operational convenience.The H/D exchange experiment reveals that a reversible cleavage of C-H bond might not be the determining step in this transformation.