Visible-Light-Induced Direct Csp2-H Radical Trifluoroethylation of Coumarins with 1,1,1-Trifluoro-2-iodoethane (CF3CH2I)

Radical alkylation of acrylamides with peroxides to access mono/dialkylated fused N-heterocycles

A simple mono/dialkylation of acrylamide derivatives was achieved, affording diverse mono/dialkylated benzo[4,5]imidazo[2,1-a]isoquinolines or polycyclic coumarins with good substrate scope. This system used common peroxides as alkylating reagents. Meanwhile, a series of scaled-up reactions and mechanistic explorations well demonstrated the application and reaction process of this cascade system.

Review and Theoretical Analysis of Fluorinated Radicals in Direct CAr-H Functionalization of (Hetero)arenes

We highlight key contributions in the field of direct radical CAr- H (hetero)aromatic functionalization involving fluorinated radicals. A compilation of Functional Group Transfer Reagents and their diverse activation mechanisms leading to the release of radicals are discussed. The substrate scope for each radical is analyzed and classified into three categories according to the electronic properties of the substrates. Density functional theory computational analysis provides insights into the chemical reactivity of several fluorinated radicals through their electrophilicity and nucleophilicity parameters. Theoretical analysis of their reduction potentials also highlights the remarkable correlation between electrophilicity and oxidizing ability. It is also established that highly fluorinated radicals (e.g. ⋅OCF3) are capable of engaging in single-electron transfer (SET) processes rather than radical addition, which is in good agreement with experimental literature data. A reactivity scale, based on activation barrier of addition of these radicals to benzene is also elaborated using the high accuracy DLPNO-(U)CCSD(T) method.

Visible Light-Induced Cross-Dehydrocoupling of 3-Cyanocoumarins with Unactivated Aliphatic Aldehydes Enables Access to 4-Acylated Coumarins

We report visible light-induced cross-dehydrocoupling of 3-cyanocoumarins with unactivated aliphatic aldehydes for the direct synthesis of 4-acylated coumarins. Inexpensive and readily available (n-Bu)₄NBr was used as a precursor of the hydrogen atom transfer (HAT) catalyst and [Ir(ppy)₂(dtbbpy)PF₆] as a photocatalyst. A variety of aldehydes including linear, branched, cyclic, and α,β-unsaturated aliphatic aldehydes were suitable for this reaction yielding the desired acylated coumarin derivatives in 41-98% yields. This method provides a mild, atom-economical, and environmentally friendly synthetic route for the direct acylation of 3-cyanocoumarins. This is the first example so far of C-4 aliphatic acylation of coumarins.

Copper-assisted trifluoromethylthiolation/radical cascade cyclization of alkynes to construct SCF3-containing dioxodibenzothiazepines

A mild and efficient Cu-assisted trifluoromethylthiolation/radical cascade cyclization of alkynes with readily available and stable AgSCF₃ as the trifluoromethylthiolating reagent has been disclosed. This transformation provides an opportunity to construct a series of potential medicinally valuable trifluoromethylthio-substituted dioxodibenzothiazepines with wide functional group compatibility. This protocol opens up a new avenue for the construction of useful trifluoromethylthiolated seven-membered N-heterocycles.

TFA-Promoted Intermolecular Friedel-Crafts Alkylation of Arenes with 2,2,2-Trifluoroethylaryl Sulfoxides

The classical Pummerer rearrangement of 2,2,2-trifluoroethylaryl sulfoxide with trifluoracetic anhydride (TFAA) affords the S , O -acetal efficiently. In the presence of trifluoracetic acid (TFA) as the co-solvent, the S , O -acetal can regenerate reactive thionium intermediate of Pummerer rearrangement. When employing arenes as nucleophiles, this strategy produces corresponding 1-thiyl-2,2,2-trifluoroethyl arenes with excellent yields under metal-free conditions.

Copper(II)-Catalyzed Direct C-H Trifluoroethylation of Heteroarenes

Trifluoroethyl (CH₂CF₃) is an important functional group in many pharmaceutical and agrochemical compounds. Herein, we report an efficient method for the copper-catalyzed direct trifluoroethylation of heteroarenes. The reaction exhibited good compatibility to various substrates, and the desired products were obtained in good yields. Preliminary mechanistic investigations indicate the trifluoroethyl radical is involved in the catalytic circle. Moreover, the late-stage modification of bioactive molecules further confirmed the practical applications of this method.

Copper-promoted difunctionalization of unactivated alkenes with silanes

An efficient copper-catalyzed cascade difunctionalization of N-allyl anilines toward the synthesis of silylated indolines using commercially available silanes has been reported. This strategy provides a new avenue for the synthesis of a diverse array of indolines in reasonable yields. Preliminary mechanistic investigations indicate that the reaction probably proceeds via a radical pathway with unactivated alkenes as radical acceptors and simple silanes as radical precursors. This protocol is distinguished by its atom economy, broad substrate scope and readily available starting materials.

Metal-Free Alkylation of Quinoxalinones with Aryl Alkyl ketones

The first metal-free method for alkylation of quinoxalinones using cheap and stable aryl alkyl ketones as nucleophilic alkylation reagents is reported. This strategy greatly broadens the application channels of aryl...

Visible-Light-Induced Radical Difluoromethylation/Cyclization of Unactivated Alkenes: Access to CF2H-Substituted Quinazolinones

A mild and efficient visible-light-induced radical difluoromethylation/cyclization of unactivated alkenes toward the synthesis of substituted quinazolinones with easily accessible difluoromethyltriphenylphosphonium bromide has been developed. The transformation has the advantages of wide functional group compatibility, a broad substrate scope, and operational simplicity. The benign protocol offers a facile access to pharmaceutically valuable difluoromethylated polycyclic quinazolinones.

Z-Selective Pd-catalyzed 2,2,2-trifluoroethylation of acrylamides at room temperature

A straightforward 2,2,2-trifluoroethylation of acrylamides by Pd-catalyzed C-H bond activation was reported by using a fluorinated hypervalent iodine reagent as a coupling partner. At room temperature, this additive-free approach allowed the synthesis of Z-2,2,2-trifluoroethylated acrylamides (19 examples, up to 73% yield) in a stereoselective manner. Under these mild reaction conditions, the methodology turned out to be functional group tolerant and mechanistic studies gave us a better understanding of the transformation.

Photoredox-catalyzed 2,2,2-trifluoroethylation and 2,2-difluoroethylation of alkenes with concomitant introduction of a quinoxalin-2(1H)-one moiety

A photoredox-catalyzed three-component radical cascade reaction of alkenes, quinoxalin-2(1H)-ones, and ICH2CF3/ICH2CF2H is developed.