1,3-Dipolar Cycloaddition of Benzofuranone Derivatives and Azomethine Ylides Promoted by Simple Functional Ionic Liquids: Direct Access to Highly Substituted Pyrrolidine and Spirocyclic Benzofuranone

A concise update on the synthetic transformation of aurones via asymmetric cycloaddition, annulation, and Michael/Mannich reactions

This review provides a comprehensive overview of the significance of aurone cores in organic chemistry, highlighting their crucial role as synthetic intermediates. With their innate electrophilic reactivity and convenient accessibility, aurone cores play a vital role in catalysing the development of novel methodologies and facilitating the creation of intricate compounds. The objective of this review is to present a current and insightful compilation that summarizes the progress in aurone synthetic transformations, focusing on diverse cycloaddition ([3 + 2], [4 + 2], [4 + 3], [10 + 2]) and annulation reactions.

Diastereoselective synthesis of chroman bearing spirobenzofuranone scaffolds via oxa-Michael/1,6-conjugated addition of para-quinone methides with benzofuranone-type olefins

A simple and convenient cyclization of ortho-hydroxyphenyl-substituted para-quinone methides with benzofuran-2-one type active olefins via oxa-Michael/1,6-conjugated addition has been developed, which afforded an easy access to enriched functionalized chroman-spirobenzofuran-2-one scaffolds with good to excellent yields (up to 90%) and diastereoselectivities (up to >19 : 1 dr). This reaction provided an efficient method for constructing desired spirocyclic compounds combining both well-known heterocyclic pharmacophores chroman and benzofuran-2-one.

Highly diastereoselective synthesis of spirocyclic compounds combining both well-known heterocyclic pharmacophores chroman and benzofuran-2-one.

Asymmetric syntheses of spiro[benzofuro-cyclopenta[1,2-b]indole-indoline] scaffolds via consecutive cyclization

An efficient method to construct enantioenriched spiro[benzofuro-cyclopenta[1,2-b]indole-indoline] scaffolds via consecutive cyclization is described here. The new scaffolds possess five successive chiral stereogenic centers and two spiroheterocycles. A range of highly enantioenriched scaffolds has been obtained with up to 93% yield, 99% ee and >19 : 1 d.r. catalyzed by Brønsted acid catalysts.

An easy and practical approach to access multifunctional cylcopentadiene- and cyclopentene-spirooxindoles via [3 + 2] annulation

A highly regioselective [3 + 2] annulation of Morita-Baylis-Hillman (MBH) carbonates of isatin with aurone/thioaurone is developed. Spiroheterocycles such as spirooxindole cyclopentadiene and spirooxindole fused hydroxy cyclopentene derivatives are constructed in one pot by exploring the reactivity of Lewis bases. Combined experimental and density functional theory (DFT) calculations offered an insight into the reaction mechanism.