Visible-Light-Mediated (<i>sp</i>³)Cα–H Functionalization of Ethers Enabled by Electron Donor–Acceptor Complex

A synthetically beneficial visible-light-mediated protocol has been disclosed to achieve C–H amination of readily available feedstocks cyclic and acyclic ethers. A rarely identified N-bromosuccinamide–tetrahydrofuran electron donor–acceptor complex served as an initiator to functionalize both α-diazoketones and dialkyl azodicarboxylates. This developed methodology gives an alternative and milder way to construct the C–N bond and can be explored for the formation of C–C bond to perform arylation and allylation reactions

Brønsted Acid-Catalyzed Transfer Hydrogenation of Imines and Alkenes Using Cyclohexa-1,4-dienes as Dihydrogen Surrogates

Cyclohexa-1,4-dienes are introduced to Brønsted acid-catalyzed transfer hydrogenation as an alternative to the widely used Hantzsch dihydropyridines. While these hydrocarbon-based dihydrogen surrogates do offer little advantage over established protocols in imine reduction as well as reductive amination, their use enables the previously unprecedented transfer hydrogenation of structurally and electronically unbiased 1,1-di- and trisubstituted alkenes. The mild procedure requires 5.0 mol % of Tf₂NH, but the less acidic sulfonic acids TfOH and TsOH work equally well

C(sp³)–C(sp³) Radical-Cross-Coupling Reaction via Photoexcitation

The photoexcitation of 4-alkyl-1,4-dihydropyridines (alkyl-DHPs) in the presence of a base triggers the single-electron-transfer-mediated desulfonative radical-cross-coupling (RCC) reaction without the need for any metal or photocatalyst. 4-Alkyl-substituted 1,4-DHPs as the electron donor (reductant) and alkyl sulfones as the electron acceptor (oxidant) are chosen strategically as the two best-matched modular radical precursors for the construction of C(sp3)–C(sp3) bonds. Ultraviolet light-emitting diodes (365 nm) have proven to be adequate for inducing single-electron transfer between two radical precursors in the excited state. Following this designed strategy, a diverse collection of primary, secondary, and tertiary persistent alkyl radicals from both radical precursors have been used to forge C(sp3)–C(sp3) bonds. This blueprint features good functional group compatibility, a broad scope, and detailed mechanistic investigation

Photoinduced Diverse Reactivity of Diazo Compounds with Nitrosoarenes

A diverse reactivity of diazo compounds with nitrosoarene in an oxygen-transfer process and a formal [2 + 2] cycloaddition is reported. Nitosoarene has been exploited as a mild oxygen source to oxidize an in situ generated carbene intermediate under visible-light irradiation. UV-light-mediated in situ generated ketenes react with nitosoarenes to deliver oxazetidine derivatives. These operationally simple processes exemplify a transition-metal-free and catalyst-free protocol to give structurally diverse α-ketoesters or oxazetidines

C(sp³)–C(sp³) Radical-Cross-Coupling Reaction via Photoexcitation

The photoexcitation of 4-alkyl-1,4-dihydropyridines (alkyl-DHPs) in the presence of a base triggers the single-electron-transfer-mediated desulfonative radical-cross-coupling (RCC) reaction without the need for any metal or photocatalyst. 4-Alkyl-substituted 1,4-DHPs as the electron donor (reductant) and alkyl sulfones as the electron acceptor (oxidant) are chosen strategically as the two best-matched modular radical precursors for the construction of C(sp3)–C(sp3) bonds. Ultraviolet light-emitting diodes (365 nm) have proven to be adequate for inducing single-electron transfer between two radical precursors in the excited state. Following this designed strategy, a diverse collection of primary, secondary, and tertiary persistent alkyl radicals from both radical precursors have been used to forge C(sp3)–C(sp3) bonds. This blueprint features good functional group compatibility, a broad scope, and detailed mechanistic investigation

Photoinduced Diverse Reactivity of Diazo Compounds with Nitrosoarenes

A diverse reactivity of diazo compounds with nitrosoarene in an oxygen-transfer process and a formal [2 + 2] cycloaddition is reported. Nitosoarene has been exploited as a mild oxygen source to oxidize an in situ generated carbene intermediate under visible-light irradiation. UV-light-mediated in situ generated ketenes react with nitosoarenes to deliver oxazetidine derivatives. These operationally simple processes exemplify a transition-metal-free and catalyst-free protocol to give structurally diverse α-ketoesters or oxazetidines

Copper-Catalyzed Regioselective Remote C–H Bond Chalcogenation of Aromatic Amine Derivatives without Using Any Large Template

A mild and convenient strategy has been developed for the para-selective chalcogenation of anilide scaffolds via C–H bond functionalization. This methodology employs one of the most earth-abundant and inexpensive Cu(II) catalysts and a commercially available simple aryl chalcogen source without any complex directing template, exogenous ligand, acid/base, oxidant, or other additives. The key feature of this methodology is an impressive regioselectivity along with a wide range of functional group tolerance with good to excellent yields under aerobic conditions

Copper-Catalyzed Regioselective Remote C–H Bond Chalcogenation of Aromatic Amine Derivatives without Using Any Large Template

A mild and convenient strategy has been developed for the para-selective chalcogenation of anilide scaffolds via C–H bond functionalization. This methodology employs one of the most earth-abundant and inexpensive Cu(II) catalysts and a commercially available simple aryl chalcogen source without any complex directing template, exogenous ligand, acid/base, oxidant, or other additives. The key feature of this methodology is an impressive regioselectivity along with a wide range of functional group tolerance with good to excellent yields under aerobic conditions

Transition-Metal-Free Regioselective Intermolecular Hydroamination of Conjugated 1,3-Dienes with Heterocyclic Amines

The unique property of hexafluoroisopropanol (HFIP) enables the regioselective hydroamination of 1,3-dienes with nitrogen heterocycles in a Markovnikov manner in the presence of catalytic Brønsted acid. This transition-metal-free intermolecular hydroamination protocol is achieved under mild reaction conditions. The aggregation by HFIP and Brønsted acid helps to activate the terminal double bond regioselectively. Following the protonation of diene, the C–N bond formation is accomplished upon the involvement of heterocyclic amines

In-Catalyzed Transfer Hydrogenation and Regioselective Hydrogen–Deuterium Addition to the Olefins

A unique and valuable methodology is developed for the hydrogenation of aromatic as well as aliphatic 1,1-di- and trisubstituted alkenes. In the presence of catalytic InBr3, readily available 1,3-benzodioxole and residual H2O present in the reaction mixture are utilized as a hydrogen gas surrogate and proved to be a practical source of deuterium incorporation into the olefins on either side by varying the source of the starting deuterated 1,3-benzodioxole or D2O. Experimental studies show the transfer of hydride from 1,3-benzodioxole to the carbocationic intermediate generated from the protonation of alkenes by the H2O–InBr3 adduct remains the critical step