Sustainable Cascades to Difluoroalkylated Polycyclic Imidazoles

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

An efficient and mild protocol for the visible light-induced radical cascade difluoromethylation/cyclization of imidazoles with unactivated alkenes using easily accessible and bench-stable difluoromethyltriphenylphosphonium bromide as the precursor of the -CF2H group has been developed to afford CF2H-substituted polycyclic imidazoles in moderate to good yields. This strategy, along with the construction of Csp3-CF2H/C-C bonds, is distinguished by mild conditions, no requirement of additives, simple operation, and wide substrate scope. In addition, the mechanistic experiments have indicated that the difluoromethyl radical pathway is essential for the methodology.

Photochemically induced chloromethylation/cyclization of benzimidazole derivatives with CCl4/CHCl3

Herein, it is reported that a series of trichloromethyl/dichloromethyl substituted benzimidazole derivatives have been synthesized by dechlorination of CCl4/CHCl3 to form polychloromethyl radicals and cyclization with an unactivated olefin under a purple LED lamp. The protocol features a wide substrate scope, high atom economy, and excellent regioselectivity, and is easy to scale up.

Metal-free polychloromethylation/cyclization of unactivated alkenes towards ring-fused tricyclic indolones and benzoimidazoles

Polychloromethylative cyclization of N-alkenyl indoles was developed under metal-free conditions to afford tricyclic pyridoindolones and pyrroloindolones in moderate to good yields. In the reaction, commercially available CHCl3 and CH2Cl2 were employed as tri- and dichloromethyl radical sources. Moreover, tri- and dichloromethylated polycyclic benzoimidazoles can also be obtained under standard conditions.

Synthesis of Trifluoromethylated γ-Lactams through Radical Cascades of N-Cyano Alkenes with CF3SO2Na

We report herein a facile strategy to synthesize trifluoromethylated γ-lactams through trifluoromethylcarbonylation of N-cyano alkenes using readily available CF₃SO₂Na as the CF₃ radical source. A range of trifluoromethyl-containing γ-lactams was obtained in good yields. This transition-metal-free protocol is demonstrated with mild conditions, broad substrate scope, good functional group tolerance, convenient reagents, and an easy-to-handle operating system.

Visible-Light Photosynthesis of CHF2 /CClF2 /CBrF2 -Substituted Ring-fused Quinazolinones in Dimethyl Carbonate

With eco-friendly and sustainable CO₂ -derived dimethyl carbonate as the sole solvent, the visible-light-induced cascade radical reactions have been established as a green and efficient tool for constructing various CHF₂ /CClF₂ /CBrF₂ -substituted ring-fused quinazolinones.

Copper-Catalyzed Direct Cycloaddition of Imidazoles and Alkenes to Trifluoromethylated Tricyclic Imidazoles

We reported herein a copper-catalyzed trifluoromethylarylated cycloaddition of imidazoles and olefins using CF₃SO₂Cl as the radical source to synthesize highly functionalized tricyclic imidazoles. This procedure exhibits a wide range of substrate scope with 25%-93% isolated yields (36 examples). Mechanistic studies were carried out to support a free trifluoromethyl radical pathway.