Free Radical-Promoted Monochloroalkylarylation of Alkenes with Chloralkanes

Electrochemically-Driven 1,4-Aryl Migration via Radical Fluoromethylation of N-Allylbenzamides: a Straightforward Access to Functionalized β-Arylethylamines

An electrochemical radical Truce Smiles rearrangement of N-allylbenzamides is documented herein. The selective 1,4-aryl migration was triggered by the radical fluoromethylation of the alkene providing a direct route to fluoro derivatives of the highly privileged β-arylethylamine pharmacophore. This practical transformation utilizes readily available starting materials and employs an electrical current to drive the oxidative process under mild reaction conditions. It accommodates a variety of migratory aryl groups with different electronic properties and substitution patterns. Careful selection of the protecting group on the nitrogen atom of the N-allylbenzamide is crucial to outcompete the undesired 6-endo cyclization and achieve high level of selectivity towards the 1,4-aryl migration. DFT calculations support the reaction mechanism and unveil the origin of selectivity between the two competitive pathways.

Photocatalytic Proton-Coupled Electron Transfer Enabled Radical Cyclization for Isoquinoline-1,3-diones Synthesis

Radical cyclization has been demonstrated to be an efficient method to access functionalized heterocycles from easily accessible raw materials. Described herein is the development of a photocatalytic proton-coupled electron transfer (PCET) strategy for the synthesis of isoquinoline-1,3-diones using readily prepared naphthalimide (NI)-based organic photocatalysts. The process features free metal-complex photocatalysts, acids, and mild reaction conditions. This mild radical cyclization protocol has a broad substrate scope and can be effectively applied to a variety of medicinally relevant substrates. Furthermore, control experiments were conducted to elucidate the mechanism of this visible light-induced methodology.

Metal-free radical bicyclization/chloroalkylarylation of 1,6-enynes with chloroalkanes

Free radical initiated bicyclization of 1,6-enynes with chloralkanes, is achieved via selective activation of the C(sp3)-H bond of the chloralkane, resulting in diverse polychlorinated/chlorinated polyheterocycles. Two kinds of transformations and a scaled-up experiment were performed to test the synthetic importance of the organic chlorides. Finally, a range of radical inhibition operations and radical clock tests were explored to support the reaction process.

Nitro-Spirocyclization of Biaryl Ynones with tert-Butyl Nitrite: Access to NO2-Substituted Spiro[5,5]trienones

A metal/peroxide-free involved simple cascade 6-exo-trig spirocyclization of tert-butyl nitrite with biaryl ynones has been finished, which resulted in various NO₂-modified spiro[5,5]trienones with good regioselectivity/yields. A variety of scaled-up experiments, reduction/epoxidation operations, and mechanistic studies were performed to verify the merits and spirocyclization process of this radical system. Finally, the structure of the spirocycles was confirmed by single-crystal X-ray diffraction.

Free Radical Promoted Trifluoromethylthiolation of Alkynes to Access SCF3-Containing Dibenzazepines or Dioxodibenzothiazepines

Persulfate-promoted radical cascade trifluoromethylthiolation of aryl acetylenes with AgSCF₃ provides a simple reaction system for the synthesis of SCF₃-substituted dibenzazepines or dioxodibenzothiazepines with good Z/E selectivity. The single-crystal X-ray diffraction data confirms the structures of the final products. A series of scaled-up experiments, further transformations, and radical inhibition experiments were operated in the reaction system.

Metal-free polychloromethyl radical-initiated cyclization of unactivated N-allylindoles towards pyrrolo[1,2-a]indoles

A metal-free polychloromethyl radical-initiated cyclization of unactivated alkenes was developed using CH₂Cl₂ and CHCl₃ as the di- and trichloromethyl radical sources. Variously substituted N-allyl-indoles were successfully transformed into the corresponding C2-(di- and trichloromethyl) pyrrolo[1,2-a]indoles in moderate to good yields. This reaction has a broad substrate scope and good functional group tolerance. Dibromomethylated products can also be obtained using CH₂Br₂ under standard conditions.

Selective polychloromethylation and halogenation of alkynes with polyhaloalkanes

We disclosed a selective polychloromethylation and halogenation reaction of alkynes via a radical addition/spirocyclization cascade sequence, in which applying polyhaloalkanes as the precursor of polyhalomethyl and halogen radical. Across this...

C-centered radical-initiated cyclization by directed C(sp3)–H oxidative functionalization

C(sp3)–H functionalization is attracting constant attention. This review emphasizes C-centered radicals initiated cyclization strategies by directed C(sp3)–H oxidative functionalization since 2012.