Indeno-Annulation of o -Formyl-Ynones, o -Bis-Ynones, and p -Bis- o -Formyl-Ynones with Dimethyl Acetone-1,3-Dicarboxylate: One Flask Cascade Synthesis of Functionally Endowed 9-Fluorenols and Indeno[1,2- b ]fluorenols.

A mild, scalable, one-pot access to multifunctional 9-fluorenols from o -formyl-ynones and o -bis-ynones on reaction with dimethylacetone-1,3-dicarboxyate through tandem Michael addition-Aldol condensation cascade has been conceptualized and executed. The scope and utility of this synthetic approach have been further amplified for one-pot entry into functionally enhanced, higher order fluorenols like pentacyclic indeno[1,2- b ]fluorene-6,12-diols and further to indeno[1,2- b ]fluorene-6,12-diones through the implementation of "double indeno-annulation" tactic on p -bis- o -formyl ynones and dimethylacetone-1,3-dicarboxylate. Besides several green attributes, the current approach is also compatible with the emerging time and energy economy features and is a swift gateway to build complexity.