Catalyst-Free Halogenation of α-Diazocarbonyl Compounds with N-Halosuccinimides: Synthesis of 3-Halooxindoles or Vinyl Halides

HNTf2-Catalyzed Formal [3 + 2] Cycloaddition of Vinyldiazoacetates to Indole-Substituted Diazo Compounds and Their Conversion to Carbazoles

Triflimide catalysis of the [3 + 2]-cycloaddition of 3-indolymethanols with vinyldiazoacetates provides general access to β-tetrahydrocyclopenta[b]indol-substituted α-diazoesters. Initiated by addition of the in situ generated vinylogous iminium electrophile from 3-indolymethanol to the vinylogous position of the vinyldiazo compound and completed by intramolecular cyclization from the vinyldiazonium ion intermediate, this transformation occurs in good yields and excellent diastereoselectivity with a broad substrate scope under mild conditions. The resulting α-diazoesters undergo Rh2(OAc)4-catalyzed substrate-dependent 1,2-migration to form multisubstituted carbazoles in high yields.

Indium-Catalyzed Formal Carbon-Halogen Bond Insertion: Synthesis of α-Halo-α,α-disubstituted Esters from Benzylic Halides and Diazo Esters

One-carbon-unit insertion into carbon-halogen (C-X) bonds accompanied by the formation of a new C-X bond and carbon-chain elongation is a powerful synthetic method of complex organohalides. Herein, we developed an indium trihalide catalyzed formal insertion of diazo esters into a C-X (X = Cl, Br, I) bond. In the present system, the reactions of α-aryl diazo esters with benzylic chlorides, bromides, and iodides yielded α-chloro, α-bromo, and α-iodo esters, respectively.

gem-Difunctionalization of α-diazoarylketones with diaryldiselenides and N-halosuccinimides: facile synthesis of α-halo-α-arylseleno ketones

An efficient synthesis of α-halo-α-arylseleno ketones has been developed via gem-difunctionalization of α-diazoarylketones with diaryldiselenides and N-halosuccinimides. With this multicomponent approach, a series of α-halo-α-arylseleno ketones were accessed in excellent yields and chemoselectivities under mild conditions. This transformation is proposed to proceed via the key intermediate arylselenenyl halide that generated from diaryldiselenides/N-halosuccinimides, followed by addition with α-diazoarylketones to give the desired gem-difunctionalization products.

Desaturation via Redox-Neutral Hydrogen Transfer Process: Synthesis of 2-Allyl Anilines, Mechanism and Applications

An unprecedented desaturation method via redox-neutral hydrogen transfer process has been disclosed under mild conditions for the selective formation of terminal alkene with alkyl diazo compounds and aza-o-QMs. The control experiments and DFT calculations suggest that the visible light was introduced as a key parameter to enhance the reactivity via a radical process in the formation of closed-shell cyclopropane intermediate, followed by a ring opening and redox-neutral hydrogen transfer process to give the desaturated product. The high regioselectivity in this transformation is enabled by the internal amino species as an ancillary group (AG) in the final olefin formation step. This method provides a missing link in the expeditious preparation of synthetically useful 2-allyl anilines with broad substrate generality. Further applications of these generated products in N-heterocycle construction, including 5- and 6-membered rings with structural diversity, have been tactfully explored, which highlight the potential in methodology development and drug discovery.

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Highly site and regioselective synthesis enabled by ancillary group

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Desaturation via redox-neutral inert hydrogen transfer process

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Missing link in the synthesis of 2-allyl anilines with board substrate scope

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Methodology development and diversity synthesis based on 2-allyl anilines

Site Selectivity in Pd-Catalyzed Reactions of α-Diazo-α-(methoxycarbonyl)acetamides: Effects of Catalysts and Substrate Substitution in the Synthesis of Oxindoles and β-Lactams

The Pd-catalyzed intramolecular carbene C–H insertion of α-diazo-α-(methoxycarbonyl)acetamides to prepare oxindoles as well as β-lactams was studied. In order to identify what factors influence the selectivity of the processes, we explored how the reactions are affected by the catalyst type, using two oxidation states of Pd and a variety of ligands. It was found that, in the synthesis of oxindoles, ((IMes)Pd(NQ))₂ can be used as an alternative to Pd₂(dba)₃ to catalyze the carbene C_Arsp²–H insertion, although it was less versatile. On the other hand, it was demonstrated that the Csp³–H insertion leading to β-lactams can be effectively promoted by both Pd(0) and Pd(II) catalysts, the latter being most efficient. Insight into the reaction mechanisms involved in these transformations was provided by DFT calculations.

Thermally induced N–S bond insertion reaction of diazo compounds with N-sulfenylsuccinimides: synthesis of sulfides and mechanism studies

A metal-free gem-functionalization reaction of diazo compounds via a formal N–S bond insertion process under mild conditions is presented.

TfOH-Catalyzed Reaction between 3-Diazoindolin-2-imines and Electron-Rich Arenes: Access to 3-Aryl-2-aminoindoles

TfOH-catalyzed reactions between 3-diazoindolin-2-imines and electron-rich arenes were disclosed. These metal-free reactions furnished 3-aryl-2-aminoindoles in moderate to excellent yields with the tolerance of a broad range of functional groups.

Silver-catalyzed geminal aminofluorination of diazoketones with anilines and N-fluorobenzenesulphonimide

A silver-catalyzed three-component reaction of diazoketones, anilines and NFSI is developed. The reaction provides a new method for gem-aminofluorination of acceptor diazo compounds with aniline as the nitrogen source and NFSI as the fluorine source.

Synthesis of oxindole from acetanilide via Ir(iii)-catalyzed C–H carbenoid functionalization

The Ir(iii)-catalyzed intermolecular C–H annulations of acetanilide with diazotized Meldrum's acid furnished the oxindole derivative. Brief synthetic applications of the synthesized oxindole were also demonstrated.

Palladium-catalysed intramolecular carbenoid insertion of α-diazo-α-(methoxycarbonyl)acetanilides for oxindole synthesis

A novel, selective palladium-catalysed carbenoid C(aryl)–H insertion of α-diazo-α-(methoxycarbonyl)acetanilides leading to oxindoles is described.

Transition-Metal-Free Fluoroarylation of Diazoacetamides: A Complementary Approach to 3-Fluorooxindoles

An efficient transition-metal-free fluoroarylation reaction of N-aryl diazoacetamides with NFSI (N-fluorobenzenesulfonimide) is described. This reaction directly provides 3-fluorooxindole derivatives in yields of 67-93% with high selectivity via a carbene-free process under mild reaction conditions.

NBS-mediated dinitrogen extrusion of diazoacetamides under catalyst-free conditions: practical access to 3-bromooxindole derivatives

A synthetically useful reaction via NBS-mediated dinitrogen extrusion of N-aryl diazoacetamides under catalyst-free conditions is disclosed, which gives the 3-bromooxindoles in high to excellent yields with high selectivity via a non carbene process.