Cascade Radical Cyclization on Alkynyl Vinylogous Carbonates for the Divergent Synthesis of Tetrasubstituted Furans and Dihydrofurans

Abstract

A single alkynyl vinylogous carbonate was elaborated to tetrasubstituted furan or dihydrofuran via a cascade inter-intramolecular radical reaction by changing the radical being added. The strategy could be used in the synthesis of polycyclic heterocycles as well as bis-furan exhibiting atropisomerism. Installation of a new furan motif on the existing one was feasible by iteration. Stannyl dihydrofuran derivative was used in Stille coupling, whereas intramolecular Friedel–Crafts acylation on the furan gave furanonaphthol.

Iron‐Catalyzed Reductive Cyclization of Alkenyl Vinylogous Carbonates for Stereoselective Synthesis of Substituted Tetrahydrofurans, Tetrahydropyrans, and Chromans

“…[10,11] In continuation of our interest on using vinylogous carbonates in the synthesis of cyclic ethers, herein we describe systematic study on utilization of HAT radical cyclization to vinylogous carbonates for the stereoselective synthesis of densely substituted THFs, THPs and chromans. [12] Further, we also demonstrate that method is amenable for getting access to oxaspirocyclic as well as fused bi/tricyclic scaffolds.…”

Thiyl Radicals: Versatile Reactive Intermediates for Cyclization of Unsaturated Substrates

“…Research from Gharpure et al elaborates on the pyrrole synthesis previously developed by Dutta et al, but instead offers tetrasubstituted furans 297a – c from alkynyl vinylogous carbonates 296 ( Scheme 45 ) [ 121 ]. The authors note that substitution at the α-position of the alkynyl vinylogous carbonate affects diastereoselectivity of the cascade, and propose a mechanism in which the thiyl radical attacks the alkyne first.…”

Protecting Group-Dependent Synthesis of Densely Substituted Dihydropyrroles v/s Pyrroles via 5-Exo-trig Cascade Radical Cyclization to Alkynyl Vinylogous Carbamates

“…However, the synthesis of starting materials was lengthy in many of these cases and chemoselectivity too was a challenge. In continuation of our interest in the synthesis of heterocycles using the cascade radical cyclization, herein, we disclose an approach for the divergent synthesis of penta-substituted dihydropyrrole and pyrrole derivatives via cascade radical cyclization to vinylogous carbamate. We also demonstrate that this reaction can lead to the rapid assembly of an unprecedented heterocyclic framework having an adjacent furan, thiophene, and pyrrole.…”