Fast α‐oxyamination of stable enolates, silyl enol ethers, and in situ deprotonated dialkyl 2‐oxoalkane phosphonates and diphenyl‐2‐oxoalkyl phosphine oxides was performed in the presence of [Ru(bpy)3]2+ (bpy = 2,2′‐bipyridyl) as a photocatalyst, 2,2,6,6‐tetramethylpiperidine nitroxide (TEMPO), and visible light. The key step was the light‐induced one‐electron oxidation of TEMPO into the 2,2,6,6‐tetramethylpiperidine‐1‐oxoammonium ion, which was nucleophilically attacked to yield α‐functionalized carbonyl compounds. The reaction time was significantly reduced by the use of the microreactor flow technique.

Coumarin-functionalized cellulose sheets were chemically modified using a visible light catalyzed "Photo-Meerwein" arylation. Use of a photomask to pattern the surface resulted in directly visible images.

Visible light along with 1 mol % eosin Y catalyzes the direct C-H bond arylation of heteroarenes with aryl diazonium salts by a photoredox process. We have investigated the scope of the reaction for several aryl diazonium salts and heteroarenes. The general and easy procedure provides a transition-metal-free alternative for the formation of aryl-heteroaryl bonds.

Teaching old dogs new tricks: Visible light photoredox catalysis improves the classic Meerwein arylation protocol significantly and allows the light-controlled arylation of alkenes, alkynes and enones by diazonium salts.

A novel UV-A-light absorbing N-heterocyclic carbene precursor imidazolium salt 2 was synthesized by reaction of 1,4-bis(pyren-1-yl)-1,4-diazadiene 1 with paraformaldehyde in the presence of chlorotrimethylsilane. The title compound was characterized by 1H-NMR, 13C-NMR, 2D-NMR, mass spectrometry, IR and UV/VIS spectroscopy.