An Organocatalytic Approach to the Synthesis of Six-Membered Heterocycles

Abstract

"""In the last few years, the new era of organocatalysis opened up an effective and efficient way to high yielding metal free, enantio- and diastereoselective reactions leading to six-membered heterocycles. This review provides an overview of the current achievements in the organocatalytic synthesis of these crucial building blocks. Ranging from hetero-Diels-Alder to cycloadditions, from one step cyclizations to cascade reactions, recent results offer new powerful tools to obtain six membered heterocycles with facile procedures in high yields and stereoselection, often leading to many new stereogenic centres in a single reaction. The total syntheses of natural products having heterocyclic ring formation as crucial stage, are also reported. When available, alternative supported organocatalysts have been examined""

Synthesis of Benzofuran-2-One Derivatives and Evaluation of Their Antioxidant Capacity by Comparing DPPH Assay and Cyclic Voltammetry

“…Such a distinguishing scaffold not only is found in key intermediates towards the synthesis of biologically active molecules [ 22 , 23 ], but occurs also as a common feature of many natural medicinal products, among which the antioxidant species play a critical role [ 24 , 25 , 26 , 27 ]. Indeed, the 3 H -benzofuran-2-ones, or 2-coumaranones, are a significant class of heterocyclic molecules highly widespread in nature, consisting of a benzene fused with a furan-2-one ring [ 27 , 28 , 29 , 30 ]. For example, the 3,3-disubstitued 2-coumaronone scaffold is a prominent structural motif in many natural compounds, such as in yuccaol A–E, isolated from Yucca Schidigera , which have exhibited antioxidant, radical scavenging, and inflammatory properties, as well as inducible NO synthase (iNOS) expression and platelet aggregation inhibition [ 31 , 32 , 33 , 34 , 35 ].…”

Asymmetric Hetero-Diels–Alder Reaction of Danishefsky’s Dienes with α-Carbonyl Esters Catalyzed by an Indium(III)–PyBox Complex

“…The asymmetric hetero-Diels–Alder (HDA) cycloaddition of Danishefsky type dienes with aldehydes is an attractive and well-investigated reaction in organic synthesis . Since the enantioenriched oxygen-containing heterocycles generated by this reaction are versatile building blocks for the syntheses of numerous biologically active compounds, the development of chiral catalysts for this asymmetrical HDA reaction is of great synthetic importance.…”