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

Abstract

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.

Synthesis of Pyridin-2(1H)-imines via the Transformation of Conjugated Ynones

“…Indeed, conjugated ynones have gained great attention because of their wide application in organic synthesis. For example, it can undergo 1,4- or 1,2-nucleophilic addition (Scheme a), , [2 + 2] cycloaddition, [3 + 2] 1,3-dipolar cycloaddition, Diels–Alder-type cycloaddition (Scheme b), aldol reactions (Scheme c), and cyclization . However, these reactivity and synthetic applications of ynones were focused on the transformation of mono- or dual-functional groups, while the total transfunctionalization of conjugated ynones, such as the simultaneous addition reaction of the triple bond, transfunctionalization of the carbonyl group, and C–C cleavage of the alkyl carbonyl group, has not been well developed (Scheme d).…”