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

Recursive anion-mediated activation of -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 -ynone moieties. Repeating the recursive anion engagement with the 1-indenones unfolded access to a functionally embellished cyclopenta[]inden-8(2)-one core and its spiroannulated analogues either directly or stepwise through tandem 1,6-Michael-type addition-6π electrocyclization and an oxidation sequence.