Recursive Anion-Triggered Tandem Reactions of ortho-Bis-ynones: Tunable Synthesis of 1‑Indenones and Cyclopenta[a]inden-8(2H)‑ones

Recursive anion-mediated activation of o-bis-ynones sets off a Michael addition–aldol reaction–dehydrative rearrangement cascade, leading to the one-pot synthesis of 1-indenones via orthogonal interplay between the two ortho-ynone moieties. Repeating the recursive anion engagement with the 1-indenones unfolded access to a functionally embellished cyclopenta­[a]­inden-8­(2H)-one core and its spiroannulated analogues either directly or stepwise through tandem 1,6-Michael-type addition–6π electrocyclization and an in situ oxidation sequence.