Synthesis of Indenopyrazole Frameworks via Cascade C–H Functionalization/[3 + 2] Dipolar Cycloaddition/Aromatization Rearrangement Reactions

The redox-neutral Ir(III)- or Ru(II)-catalyzed C-H couplings of azomethine imines with α,α-difluoromethylene alkynes have been realized, leading to the efficient synthesis of indenopyrazole frameworks via a tandem C-H functionalization/[3 + 2] dipolar cycloaddition/ring-opening aromatization rearrangement process, in which the generated fluoroallene species was involved as the dipolarophile via a selective β-F elimination process. Subsequent biological evaluation revealed that these synthesized indenopyrazoles could serve as interesting cytotoxic agents for further development.