Sulfur Ylide Initiated [4 + 1]/[4 + 2] Annulation Reactions: A One-Pot Approach to Dibenzofuran Acrylate Derivatives

Direct Synthesis of α-Ketothioamide Derivatives through a One-Pot Reaction of Sulfur Ylides, Nitrosobenzenes, and Thioacetic Acid

A one-pot approach has been developed for the synthesis of α-ketothioamide derivatives from sulfur ylides, nitrosobenzenes, and thioacetic acid. This protocol is carried out under mild reaction conditions in generally moderate to excellent yields without any precious catalysts, affording the derivatives with structural diversity. Additionally, a possible mechanism for this chemical transformation is proposed.

Interrupted Corey-Chaykovsky Reaction of Tethered Bis-Enones to Access 2,3-Epoxy-hexahydrofluoren-9-ones

The Corey-Chaykovsky reaction is usually employed to synthesize cyclopropanes from activated olefins. We intercepted the intermediates prevailing during this transformation and diverted the process for the creation of intricate molecular motifs. We describe an unusual skeletal remodelling of tethered bis-enones to 2,3-epoxy-hexahydrofluoren-9-ones via an "interrupted Corey-Chaykovsky reaction". The strategy rationally merges the nucleophilic features of sulfur ylides with electronically biased olefins to achieve the regio- and stereoselective synthesis of several new classes of hydrofluorenones. We have demonstrated the synthetic utility of the products in accessing several highly functionalized molecules.

Recent advances in the synthesis of dibenzofurans

This review reports recent accesses to the dibenzofuran nucleus described in the literature since 2008. This article starts with synthesizing dibenzofurans by creating the C-O bond of the furan ring. In the following section, we evoke the formation of dibenzofurans by cyclizing diarylether derivatives. The last part of this update concerns the construction of dibenzofurans from benzofuran or phenol derivatives. Representative examples showing the scope of these processes illustrate new approaches and biological activities of dibenzofurans. Reaction mechanisms explaining certain dibenzofuran formation are described, as suggested by their authors.

Direct Access to 3-Thioether-Substituted Dihydrofuro[2,3-b]benzofurans via Tandem Reactions of Sulfur Ylides and 2-Nitrobenzofurans

The synthesis of 3-thioether-substituted dihydrofuro[2,3-b]benzofurans involving the [3 + 2] coupling of sulfur ylides with 2-nitrobenzofurans has been realized in moderate to good yields under mild conditions without any precious catalysts or additives. It is worth mentioning that the reutilization of the departed nitro-anion in the reaction process facilitates this new chemical transformation and presents a manner of high atom economy to provide products with a complex structure.

The chemistry of 2-hydroxy-β-nitrostyrenes: versatile intermediates in synthetic organic chemistry

The applications of 2-hydroxy-β-nitrostyrenes as efficient bifunctional intermediates in organic synthesis are investigated in this review. For this purpose, reactions of 2-hydroxy-β-nitrostyrenes with diverse molecules, including carbonyl compounds, 1,3-dicarbonyl compounds, α,β-unsaturated carbonyl compounds, hemiacetals, nitroalkenes, γ-butenolides, tetronic acid, azalactones, pyrazolones, enamines, malononitrile, methyleneindolinones, ylides, etc., were investigated to construct interesting biologically active scaffolds such as chromans, chromenes, coumarins, benzofurans and their fused and spiro rings, natural products, and other useful cyclic and acyclic compounds. The main focus is on the asymmetric synthesis of these compounds via cascade/domino/tandem reactions catalyzed by chiral organocatalysts. In this review, around 60 papers reported between the years 2000 and 2022 are presented.

Recent advances in the application of ylide-like species in [4+1]-annulation reactions: an update review

In this review, advances in [4+1]‐annulation reactions involving sulfonium, sulfoxonium and ammonium ylides, as well as diazo compounds and carbenes are summarized over the last 6 years. Newly emerged methods...

Water-Mediated Intramolecular Cyclization/Oxidation of α-Carbonyl Sulfur Ylides: Synthesis of Corey-Chaykovsky Reagent Type Heterocycles

A new class of Corey-Chaykovsky reagent type five-membered heterocycles with an oxosulfonium ylide moiety has been synthesized by the water-mediated intramolecular cyclization/oxidation of α-carbonyl sulfur ylides generated in situ from sulfonium salts under mild conditions.

Metal-free synthesis of quinoline-2,4-dicarboxylate derivatives using aryl amines and acetylenedicarboxylates through a pseudo three-component reaction

An efficient, useful and one-pot protocol for the synthesis of quinoline-2,4-dicarboxylate scaffolds is accomplished from aryl amines and dimethyl/diethyl acetylenedicarboxylates using 20 mol% molecular iodine as a catalyst in acetonitrile at 80 °C. In addition, the mechanistic explanation for the formation of the desired products is disclosed. The pivotal role of molecular iodine in the formation of the major products, diester quinoline derivatives, and the minor product, triesters, in two cases is described in the mechanism. The notable advantages of this method are non-involvement of a metal catalyst, avoiding of metal contamination in the final product as well as waste generation, use of a low cost and eco-friendly catalyst, ease of handling, high regioselectivity, shorter reaction time, the formation of one C-N and two C-C bonds and a broad substrate scope with good yields.

(2 + 1 + 1 + 1)-Annulation Reactions of Aryldiazonium Tetrafluoroborates with Sulfur Ylides to Polysubstituted Pyrazoles

Novel divergent domino annulation reactions of sulfur ylides with aryldiazonium tetrafluoroborates have been developed, affording various tetra- and trisubstituted pyrazole derivatives in moderate to good yields. Three molecules of sulfur ylides were applied as C1 synthon to construct the complex products with five new chemical bonds formed in these one-pot reactions.

A cascade double 1,4-addition/intramolecular annulation strategy for expeditious assembly of unsymmetrical dibenzofurans

Existing synthetic routes for accessing dibenzofuran core have intrinsic regioselectivity, limiting the substitution patterns available in heteropolycyclic arene products. Here we report a double 1,4-conjugate addition/intramolecular annulation cascade reaction between propargylamines and two equivalents of imidazolium methylides that allows efficient access of structurally versatile dibenzofurans. This transition metal-free protocol proceeds smoothly under bench-top air atmosphere and offers easy manipulation of substituents on the dibenzofuran core, and also provides good-to-excellent product yields with good functional group tolerance, particularly the -Br and -Cl groups which are often incompatible with existing metal-catalyzed C-C and/or C-O bond ring-forming processes. It is worth noting that ladder-type π-systems with all-arene quarternary carbon structure can be straightforwardly generated upon simple late-stage functionalization.

Efficiently diastereoselective synthesis of functionalized hydro-carbazoles by base-mediated tandem annulation of 1-(2-amino-aryl)prop-2-en-1-ones and sulfur ylide

The base-promoted [3 + 3]/[1 + 4] tandem reaction of tosyl-protected o-amino α,β-unsaturated ketones and crotonate-derived sulfur ylide is developed for efficiently diastereoselective synthesis of functionalized hydrocarbazoles.

Efficient access to fluorescent benzofuro[3,2-b]carbazoles via TFA-promoted cascade annulations of sulfur ylides, 2-hydroxy-β-nitrostyrenes and indoles

An efficient, TFA-promoted cascade annulation of sulfur ylides, 2-hydroxy-β-nitrostyrenes and indoles was established.