Aryne insertion into α-cyanocarbonyl compounds: direct introduction of carbonyl and cyanomethyl moieties into the aromatic skeletons

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.

Synthesis of 2-(Cyanomethyl)benzoic Esters via Carbon-Carbon Bond Cleavage of Indanones

A novel synthesis of 2-(cyanomethyl)benzoic esters from indanone derivatives has been established. This reaction proceeds via a deprotonation of alcohols with a chemical base, followed by a nucleophilic addition to indanones and Beckmann fragmentation. In addition, this reaction could also work under electrochemical conditions, and no external chemical bases were needed. This mild method offers a novel strategy for the late-stage functionalization of various natural alcohols.

Acylalkylation of Arynes Generated from o-Iodoaryl Triflates with Hydrosilanes and Cesium Fluoride

An efficient method to generate aryne intermediates from o-iodoaryl triflates triggered by triethylsilane and cesium fluoride is disclosed. This method realized the acylalkylation of arynes using easily available o-iodoaryl triflate-type precursors, which was difficult when using conventional nucleophilic activators. A wide range of (hetero)arenes including various fused benzothiazoles were successfully synthesized from o-iodoaryl triflates by virtue of their good accessibility and divergent transformations of aryne intermediates.

An efficient synthesis of 4-phenoxy-quinazoline, 2-phenoxy-quinoxaline, and 2-phenoxy-pyridine derivatives using aryne chemistry

Herein we report the mild and efficient synthesis of 4-phenoxyquinazoline, 2-phenoxyquinoxaline, and 2-phenoxypyridine derivatives from the starting materials viz. quinazolin-4(3H)-one, quinoxalin-2(1H)-one, and pyridin-2(1H)-one and aryne generated in situ from 2-(trimethylsilyl)phenyl trifluoromethanesulfonate and cesium fluoride. This synthetic methodology gives a new environmentally benign way for the preparation of several unnatural series of 4-phenoxyquinazoline, 2-phenoxyquinoxaline and 2-phenoxypyridine compounds with high yields and broad substrate scope.

Efficient synthesis of 4-phenoxyquinazoline, 2-phenoxyquinoxaline, 2-phenoxypyridine derivatives were generated of aryne from 2-(trimethylsilyl)phenyltrifluoromethanesulfonate with cesium fluoride.

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.

A cascade process for the synthesis of ortho-formyl allyl aryl ethers and 2H-chromen-2-ol derivatives from arynes via trapping of o-quinone methide with an activated alkene

A transition-metal free synthetic strategy for the direct synthesis of ortho-formyl substituted allyl aryl ethers and 2H-chromen-2-ol derivatives via a cascade three-component coupling of arynes, activated alkene and N,N-dimethylformamide.

Sequential σ-Bond Insertion/Benzannulation Involving Arynes: Selective Synthesis of Polysubstituted Naphthalenes

An interesting σ-bond insertion/benzannulation reaction for the synthesis of polysubstituted naphthalene derivatives has been developed from readily accessible ketones, arynes, and alkynoates. This practical and transition-metal-free method provides a novel route to diverse naphthalenes through a substrate-controlled rearrangement reaction with the cleavage of C-C bonds.

[Multi-component Reactions Based on Formal [2+2] Reaction of Benzyne with Formamide]

Arynes, such as benzyne, are highly strained and kinetically unstable intermediates that have been widely employed in organic synthesis. In particular, since the initial report regarding the in situ generation of arynes under neutral conditions from ortho-(trimethylsilyl)aryl triflates and fluoride ions in 1983, numerous nucleophilic additions to arynes have been utilized in the synthesis of carbocycles, heterocycles, and multi-substituted arenes. Recently, we reported the insertion of arynes into the π-bond in formamides, as well as related cascade reactions. First, we synthesized salicylaldehydes and aminophenols via the insertion of arynes into the C=O bond of sterically less hindered N,N-dimethylformamide (DMF). Notably, computational studies revealed the generation of unstable benzoxetene and ortho-quinone methide as reactive intermediates. We also studied multi-component coupling reactions leading to 2H-chromenes, coumarins, and xanthen-1-ones under mild conditions through the stepwise release of the strain energy in arynes. Furthermore, we studied the synthesis of O-heterocycles such as dihydrobenzofuran, benzofuran, and 4H-chromene as an application of our method. In this review, we will describe these studies in detail.

Synthesis of ortho-haloaminoarenes by aryne insertion of nitrogen-halide bonds

A rapid and general access to ortho-haloaminoarenes has been developed by aryne insertion into N-chloramine, N-bromoamine, and N-iodoamine bonds via two complementary protocols harnessing fluoride-promoted 1,2-elimination of ortho-trimethylsilyl aryltriflates. Typically, electron-deficient N-chloramines effectively react with aryne intermediates generated at elevated temperature with CsF, while less stable N-haloamines are found more efficient under milder, TBAF-mediated aryne formation at room temperature. Both protocols demonstrate a good level of regioselectivity and functional group tolerance. Efforts to elucidate the mechanism of N-X insertion are also discussed. The practical value of this transformation is highlighted by rapid synthesis of novel analogues of the antipsychotic cariprazine.

Transition-metal-free α-arylation of β-keto amides via an interrupted insertion reaction of arynes

Direct α-arylation reactions of secondary β-keto amides with arynes, generated by fluoride-induced elimination of ortho-silyl aryltriflates, are described. The transformation proceeds via an interrupted insertion reaction of arynes and leads to densely functionalized aromatic compounds exhibiting a chiral 'all carbon' quaternary center under transition-metal-free conditions. An organocatalytic asymmetric version of the reaction also proved possible, affording the proof of concept that arynes can be involved in enantioselective transformations.