Organocatalytic Vinylogous Michael Addition/Cyclization Cascade of 2‐Alkylidene Indane‐1,3‐diones with Enals: A Regio‐ and Stereocontrolled Diversity‐Oriented Route to Indane‐1,3‐dione Derivatives

Abstract

A substrate‐dependent, regio‐ and stereo‐controlled diversity‐oriented organocatalytic vinylogous Michael addition/cyclization cascade of 2‐alkylidene indane‐1,3‐diones with enals, using secondary amines as the catalyst have been developed. These present methodologies allow the synthesis of spiroindane‐1,3‐diones, tetrahydrofluoren‐9‐one derivatives, and benzofused oxabicyclo[3.3.1]nonanes in a highly selective manner. Plausible catalytic pathways for the formation of these biologically interesting compounds were proposed. Density functional theory (DFT) calculations have clarified and supported the mechanisms how the organocatalyst is able to activate the enals and 2‐hydroxycinnamaldehydes, directing the C‐C bond forming with the vinylogous dienolates and enabling the synthesis of these interesting indane‐1,3‐diones derivatives.

Asymmetric (3 + 3) and (4 + 2) Annulation Reactions of 2,3-Dioxopyrrolidines with 3-Alkylidene Oxindoles to Construct Diverse Chiral Heterocyclic Frameworks

“…In continuation of our ongoing research toward the development of (asymmetric) organocatalytic annulation using vinylogous nucleophiles, 19 we envisioned that the electrophilic properties of 2,3-dioxopyrrolidines could serve as a bis-electrophile for [3 + 3] annulation reaction if a vinylogous nucleophile could be identified as a 3C bis-nucleophile.…”

Rapid Construction of Polycyclic Skeletons via Brønsted-Base-Catalyzed Annulations of Ethylidene 1,3-Indenediones and Vinyl 1,2-Diketones

“…For instance, oxabicyclo[3.2.1]­octane, spiro[4.5]­decane, and branched triquinane are three types of key components in a myriad of natural products or bioactive molecules, but the concise construction of these skeletons is still challenging, especially starting from the same set of substrates. On the other hand, the use of ethylidene 1,3-indenediones (EIDs) as the versatile building blocks in organic synthesis has recently attracted the focus of the academic community . Mainly three reaction modes have been disclosed: the first one is vinylogous type nucleophilic addition (Scheme a, eq 1), and the second type is the annulation with reagents having both electrophilic and nucleophilic properties to form bicyclic products (Scheme a, eq 2) .…”