A new cascade halosulfonylation of 1,7-enynes toward 3,4-dihydroquinolin-2(1H)-ones via sulfonyl radical-triggered addition/6-exo-dig cyclization

Double SO2 Insertion into 1,7-Diynes Leading to Functionalized Naphtho[1,2-c]thiophene 2,2-dioxides

A novel metal-free double SO₂ insertion/multicomponent bicyclization cascade of benzene-linked 1,7-diynes has been established by treatment with aryldiazonium tetrafluoroborates and DABCO-bis(sulfur dioxide) under redox-neutral conditions, providing a range of dual sulfone-containing naphtho[1,2-c]thiophene 2,2-dioxides with generally high stereoselectivity. The reaction pathway is proposed to proceed through the sequence of arylsulfonyl-radical-induced 6-exo-dig/5-endo-trig bicyclization, H-abstraction, and diazotization.

Visible-light-induced methylsulfonylation/bicyclization of C(sp3)-tethered 1,7-enynes using a DMSO/H2O system

A visible light photocatalytic methylsulfonylation/bicyclization of C(sp³)-tethered 1,7-enynes has been established using a dimethyl sulfoxide (DMSO)/H₂O system as the methylsulfonyl source.

Iodine promoted iodosulfonylation of alkynes with sulfonyl hydrazides in an aqueous medium: highly stereoselective synthesis of (E)-β-iodo vinylsulfones

An efficient, molecular iodine-promoted MCR of alkynes and sulfonyl hydrazide for the synthesis of (E)-β-iodo vinylsulfone derivatives has been developed.

Recent advances in radical transformations of internal alkynes

This review highlights the recent progress in the radical transformation of internal alkynes and focuses on the reaction mechanisms by carbon/heteroatom-centered triggered additions, and offers a comprehensive overview on the existing procedures and employed methodologies.

Stereoselective synthesis of sulfonated 1-indenones via radical-triggered multi-component cyclization of β-alkynyl propenones

New radical-triggered multi-component cyclizations of β-alkynyl propenones have been developed, leading to 50 examples of sulfonated 1-indenones with generally good yields and high levels of stereoselectivity.

Metal-free deoxygenative sulfonylation of quinoline N-oxides with sodium sulfinates via a dual radical coupling process

The first example of a metal- and reductant-free deoxygenative sulfonylation of quinoline N-oxides with sodium sulfinates via a dual radical coupling process is reported.

Sulfonylative and Azidosulfonylative Cyclizations by Visible-Light-Photosensitization of Sulfonyl Azides in THF

The generation of sulfonyl radicals from sulfonyl azides using visible light and a photoactive iridium complex in THF is described. This process was used to promote sulfonylative and azidosulfonylative cyclizations of enynes to give several classes of highly functionalized heterocycles. The use of THF as the solvent is critical for successful reactions. The proposed mechanism of radical initiation involves the photosensitized formation of a triplet sulfonyl nitrene, which abstracts a hydrogen atom from THF to give a tetrahydrofuran-2-yl radical, which then reacts with the sulfonyl azide to generate the sulfonyl radical.

Photoredox-catalyzed procedure for carbamoyl radical generation: 3,4-dihydroquinolin-2-one and quinolin-2-one synthesis

A reductive approach for carbamoyl radical generation from N-hydroxyphthalimido oxamides under photoredox catalysis is outlined. This strategy was applied to the synthesis of 3,4-dihydroquinolin-2-ones via the intermolecular addition/cyclization of carbamoyl radicals with electron deficient olefins in a mild, redox-neutral manner. Under a general set of reaction conditions, diversely substituted 3,4-dihydroquinolin-2-ones, including spirocyclic systems can be prepared. By using chlorine-substituted olefins, aromatic quinolin-2-ones can also be accessed.

MnO2 -Promoted Oxidative Radical Sulfonylation of Haloalkynes with Sulfonyl Hydrazides: C(sp)-S Bond Formation towards Alkynyl Sulfones

A catalyst-free oxidative radical sulfonylation of haloalkynes with sulfonyl hydrazides is reported. It represents an example of C(sp)-S bond formation using sulfonyl hydrazides as sulfonyl radical sources. Various alkynyl sulfones were synthesized in moderate to good yields. Having MnO₂ as the oxidant is very critical for this transformation. Remarkably, the self-coupling reaction of haloalkynes through C(sp)-C(sp) bond formation is significantly inhibited under the standard reaction conditions.

Sustainable Difluoroalkylation Cyclization Cascades of 1,8-Enynes

We reported a visible-light-induced difluoroalkylation and cyclization cascade reaction of 1,8-enynes with broad substrate scopes in up to 92% isolated yields. This method provides a sustainable and efficient access to the synthesis of difluoroalkylated tetracyclic compounds under mild conditions.

Oxidative bicyclization of N-tethered 1,7-enynes toward polycyclic 3,4-dihydroquinolin-2(1H)-ones via site-selective decarboxylative C(sp3)–H functionalization

A new Ag-catalyzed oxidative bicyclization of N-tethered 1,7-enynes with alkylcarboxylic acids for forming 41 examples of polycyclic 3,4-dihydroquinolin-2(1H)-ones has been established using readily accessible K₂S₂O₈ as an oxidant.

A method for accessing sulfanylfurans from homopropargylic alcohols and sulfonyl hydrazides

A sulfenylation/cyclization reaction has been developed for the synthesis of sulfanylfurans in the presence of iodine.

Radical cascade cyclization of 1,n-enynes and diynes for the synthesis of carbocycles and heterocycles

This review highlights recent advances in radical cascade cyclization of 1,n-enynes and diynes for the construction of carbo- and heterocycles.

Metal-free benzannulation of 1,7-diynes towards unexpected 1-aroyl-2-naphthaldehydes and their application in fused aza-heterocyclic synthesis

A novel I₂-mediated benzannulation of 1,7-diyne-involved 1,4-oxo-migration was established, providing unexpected 1-aroyl-2-naphthaldehydes. The resulting 1-aroyl-2-naphthaldehydes were successfully applied in the synthesis of polycyclic isoindoles.

Diastereoselective building up polycyclic tetrahydrofurans via tandem annulation of 1,n-enynes with aliphatic acids

A silver-catalyzed tandem annulation of aniline-linked 1,7-enynes with aliphatic acids has been reported. These synergistic tandem annulations allowed for the straightforward and efficient synthesis of various highly diastereoselective polycyclic tetrahydrofurans.

Facile synthesis of benzo[b]thiophenes via metal-free radical-triggered intramolecular C–S bond formation

A facile method for the synthesis of benzo[b]thiophenes with good to excellent yields via metal-free intramolecular C–S bond formation has been developed by utilizing I₂ as a catalyst and O₂ from air as an oxidant (20 examples).

Construction of Polycyclic γ-Lactams and Related Heterocycles via Electron Catalysis

Cascade radical cyclization of 1,6-enynes for the construction of biologically important polycyclic γ-lactams and related heterocycles is reported. In these radical cascade processes, three new C–C bonds are formed and transition metals are not required to run these sequences. The mild reaction conditions, broad substrate scope, and the importance of the heterocyclic products render the approach valuable.