Photocatalytic Hydro Tri/Difluoromethylation of Alkenes with Bench Stable Tri/Difluoromethylating Reagents

1,3-Hydro-di/monofluoromethylation of N,N'-Cyclic Azomethine Imines with HCF2SO2Na/H2CFSO2Na via Photocatalytic Radical Addition

The radical 1,3-hydro-di/monofluoromethylation of N,N'-cyclic azomethine imines with HCF2SO2Na/H2CFSO2Na via photoredox catalysis is described. This reaction exhibits broad functional group compatibility, providing the desired products in good yields. However, CF3SO2Na failed to produce the trifluoromethyl product. DFT calculations revealed that the transition state activation energy for radical trifluoromethylation was significantly higher and the isotropic charge repulsion makes it difficult for the CF3 radical to transfer electrons.

Visible-Light-Triggered Difluoroacetylation/Cyclization of Chromone-Tethered Alkenes Enabling Synthesis of Tetrahydroxanthones

Hydroxanthones have attracted considerable attention due to their significance in organic and biological chemistry, yet their synthesis remains a great challenge. In this study, a series of chromone-tethered alkenes are designed, and a radical cyclization reaction of these chromone derivatives has been achieved under photoredox conditions. The reaction uses bromodifluoroacetamides or bromodifluoroacetates as coupling partners, affording a broad range of functionalized tetrahydroxanthone products with up to 85% yields. The reaction is triggered via the generation of difluoroacetate radicals or alkene radical cations with fac-Ir(ppy)3 or 2,3,5,6-tetrakis(carbazol-9-yl)-1,4-dicyanobenzene as a photocatalyst. This approach offers access to various tetrahydroxanthone derivatives from readily available starting materials and enriches the research content of heteroarene-tethered alkenes.

Photocatalytic Cyclization Cascades by Radical Relay toward Pyrrolo[1,2-a]indoles: Synthesis, Mechanism, and Application

A photocatalytic annulation cascade of unactivated N-alkene-linked indoles with Langlois' reagent by a radical relay is developed at room temperature under blue LED irradiation. The reaction afforded a series of tri/difluoromethylated pyrrolo[1,2-a]indoles in moderate to good yields. The DFT study suggests that the reaction is ascribed to a rhodamine 6G-induced cyclization cascade involving vinyl addition-radical relay and hydrogen-atom-abstraction (HAA) processes, and interestingly, pyrrolo[1,2-a]indoles are applied as fluorescent dyes into the fluorescence spectrum and live-cell imaging. This paper represents an initial example on photocatalytic cyclization cascades by radical relay and the HAA process.