Room-Temperature Cascade Electrophilic Addition/Cyclization/Oxidation Reactions: Divergent Selective Synthesis of Brominated 2H-Chromenes, 2H-Chromen-2-ols and 2H-Chromen-2-ones

The room temperature metal-free cascade electrophilic addition/cyclization/oxidation reactions of (3-phenoxyprop-1-yn-1-yl)benzenes to divergently synthesize various brominated benzopyran derivatives (3-bromo-2H-chromenes, 3-bromo-2H-chromen-2-ols and 3-bromo coumarins) by tuning the amount of Br2 and H2O have been developed. The method exhibited high selectivity, mild reaction conditions, broad substrate scope, high efficiency, and the applicability for derivatization of the brominated products. The importance of the strategies provides a great advantage for selective synthesis of brominated benzopyran derivatives.

Synthesis of Benzodioxepinones and Benzoxazepinones via Tandem Oxidation and Iodolactonization of 2-O/N-tethered Alkenyl Benzaldehyde Mediated by CuI/TBHP

An efficient methodology for the synthesis of halogenated benzodioxepinones and benzoxazecinones has been developed via tandem oxidation and iodolactonization reaction of 2-O/N-tethered alkenyl benzaldehydes mediated by CuI and tertiarybutylhydro-peroxide in acetonitrile at 70 °C in moderate to good yields. The reaction involves initial oxidation of aldehyde to acid followed by iodolactonization. Terminal propargyl ether resulted in a mixture of mono- and diiodido-3-methylene-1,4-dioxepin-5-ones. The post-synthetic modification of the reaction products leads to the formation of corresponding thiocyanate, azide, thioether, and triazole derivatives.

Pd-Catalyzed Alkyne and Aryne Annulations: Synthesis and Photophysical Properties of π-Extended Coumarins

A Pd-catalyzed alkyne and aryne annulation strategy via C-H activation has been implemented for the synthesis of π-extended coumarins. This synthetic strategy provides a wide range of π-extended coumarins in moderate to good yields with good functional group compatibility. Photophysical properties of the synthesized π-extended coumarins have been evaluated, and some of them show interesting fluorescent properties. Three of the synthesized coumarins have been unambiguously established by a single-crystal XRD study.

Diverse Synthesis of Triarylselenonium Salts and o-(Alkoxy)aryl Aryl Selanes via Insertion of Benzyne into the Se═O Bond

An insertion of benzyne into the Se═O bond has been realized. In this reaction, two types of compounds containing selenium could be synthesized from different substrates. When diaryl selenium oxides were used, triarylselenonium salts were furnished, while o-(alkoxy)phenyl phenyl selanes could be produced from aryl alkyl selenium oxides.

Recent Advances in Construction of C(sp2)–O Bonds via Aryne Participated Multicomponent Coupling Reactions

Aryne chemistry is a powerful synthetic technique that forms new bonds to aromatic rings. The recent resurgence of aryne-based multicomponent coupling strategies has led to an influx of methodologies for the mild synthesis of arene derivatives. In particular, these innovative discoveries broaden and streamline approaches toward phenol ether motifs, which are a prevalent structural component across a broad range of chemistry related research fields. Herein, this review aims to provide a comprehensive overview of the recent progress in the construction of C(sp2)–O bonds via aryne-induced multicomponent reactions. Special attention has been paid to reaction design and mechanistic pathways.

1 Introduction

2 Insertion-Based MCRs

3 Nucleophilic-Addition-Based MCRs

4 Cycloaddition-Based MCRs

5 Summary

One-pot synthesis of 3-substituted-3-hydroxyindolin-2-ones: three component coupling of N-protected isatin, aryne precursor and 1,3-cyclodione under metal-free conditions

A transition-metal free synthetic strategy for the direct synthesis of 3-substituted-3-hydroxy-indolin-2-ones via three component coupling of N-protected isatin, aryne precursor, and 1,3-cyclodione.

o-Quinone Methides and o-Quinone Sulfides via Arynes: Synthesis of Ortho-Disubstituted Arenes and Heterocycles

In recent decades, o-quinone methides and o-quinone sulfides have been extensively highlighted as reactive intermediates for the synthesis of diversely functionalized ortho-disubstituted arenes and heterocycles. Additionally, ortho-disubstituted arenes offer a constructive path for the synthesis of fused carbocycles, heterocycles, natural products, and drug candidates. In the lieu of that, this Synopsis highlights a comprehensive overview on the potential applications of in situ generated o-quinone methides and o-quinone sulfides for one-pot synthesis of ortho-disubstituted arenes and heterocycles via arynes.

Direct synthesis of ortho-methylthio allyl and vinyl ethers via three component reaction of aryne, activated alkene and DMSO

A transition-metal free synthetic strategy for the direct synthesis of ortho-methylthio allyl and vinyl ethers via cascade three-component coupling of aryne, activated alkene and DMSO.

Synthesis of 6-substituted indoloquinazolinones from arynes and 2-acyl-4-quinazolinones: a transition-metal free C–N and C–C bond formation strategy

A versatile transition-metal free synthetic strategy has been developed for the direct synthesis of 6-substituted indoloquinazolinones from 2-acyl-4-quinazolinones and aryne precursors. This cascade strategy proceeds via successive C–N and C–C bond formation in a single reaction vessel.

Mild, Modular, and Convergent Synthesis of Helical Naphtho[2,1-c]chromenes via a Multistep Cyclization/Aromatization Cascade Sequence

Tetracyclic 6H-naphtho[2,1-c]chromenes are expeditiously synthesized through a BF₃·OEt₂-mediated, three-step cascade reaction, creating new central pyran and aromatic rings. The cascade involves the addition of phenol-derived alkynyl substrates to BF₃-activated aldehydes followed by alkyne-Prins cyclization, Friedel-Crafts reaction, and final elimination. Aliphatic and electron-deficient aromatic aldehydes afford the products in 50-74% isolated yields, but benzaldehyde and tolualdehyde resulted in lower yields. X-ray analysis of a p-bromophenyl derivative (5aA) shows the two aromatic moieties are twisted by 28° to create a helical backbone.

Aryne insertion into the PO bond: one-pot synthesis of quaternary phosphonium triflates

A novel transition-metal free synthetic strategy for the direct synthesis of quaternary phosphonium triflates via insertion of aryne into phosphine oxide.

Transition-metal free C(sp2)–C(sp2) bond formation: arylation of 4-aminocoumarins using arynes as an aryl source

A mild, efficient and transition-metal free synthetic strategy has been developed for the α-arylation of 4-aminocoumarins using arynes as an aryl source. This synthetic strategy proceeds via C(sp²)–C(sp²) bond formation between 4-aminocoumarins and aryne precursors in a single step in the absence of a metal-catalyst.