Oxygenation of α-Methylstyrene with Molecular Oxygen, Catalyzed by 10-Methylacridinium Ion via Photoinduced Electron Transfer

Abstract

Photooxygenation of R-methylstyrene with oxygen occurs efficiently in the presence of 10-methylacridinium perchlorate (AcrH + ClO 4 -) under visible light irradiation in oxygen-saturated acetonitrile (MeCN) to yield acetophenone as the main oxygenated product. No photoinduced oxygenation of R-methylstyrene occurs in the absence of AcrH + under otherwise the same experimental conditions. Little photodegradation of AcrH + occurs in the present photocatalytic system, which provides a clean method of photoinduced oxygenation reaction with molecular oxygen, alternate to the ene reaction of singlet oxygen. The photocatalytic oxygenation of R-methylstyrene with oxygen is shown to proceed via photoinduced electron transfer from R-methylstyrene to the singlet excited state of AcrH + ( 1 AcrH + *) on the basis of the fluorescence quenching of 1 AcrH + * by R-methylstyrene, the quantum yield determination, and the detection of radical intermediates by laser flash photolysis and ESR measurements.

Organic Photoredox Catalysis

“…282 Oxidative cleavage of α-methylstyrene under similar conditions was also studied. 327 Interestingly, Griesbeck and Cho 328 show that alkenes bearing allylic C−H bonds react to give the SchenckEne products under similar conditions, suggesting that Mes-AcrMe + is also capable of generating singlet oxygen. The authors provide an additional example of alkyne reactivity in this system in the cyclization of alkyne 74.1a,b to give tetrahydrofuran 74.2a,b (Scheme 74).…”

Aerobic C–C Bond Cleavage of Indoles by Visible‐Light Photoredox Catalysis with Ru(bpy)32+

“…HRMS was carried out on a LCMS-IT-TOF high resolution mass spectrometer. The structures of known compounds were confirmed by comparing the experimental 1 H NMR, 13 C NMR, and MS data with those values in the literature. Melting points were measured with a melting point instrument.…”

“…A radical‐radical cross‐coupling reaction then occurs to deliver superoxide intermediate C followed by an intramolecular nucleophilic addition reaction to give dioxetane intermediate D . Our isotope labeling studies indicate that the final product 2a is most likely formed by path a as well as path b (Scheme ) …”

“…A radical-radical cross-coupling reaction then occurs to deliver superoxide intermediate C fol-lowed by an intramolecular nucleophilic addition reaction to give dioxetane intermediate D. Our isotope labeling studies indicate that the final product 2a is most likely formed by path a as well as path b (Scheme 4). [13] Notably, the efficient gram-scale synthesis of 2a (1.37 g, 84 % yield) was achieved to demonstrate the robust nature of the mild photocatalysis at room temperature (Scheme 5a). The incorporation of two carbonyl groups into product 2a allows for further modifications through simple synthetic methods.…”

Selective aerobic oxidation of sulfides to sulfoxides catalyzed by coenzyme NAD+ models

“…1 NAD þ models have been successfully applied to selective oxygenation of a-methylstyrene, 2 benzyl alcohol, 3 p-xylene, 4 4,4 0 -dimethylbiphenyl, 5 tetraphenylethylene, 6 and 1,4-dihydropyridines 7 as effective catalysts. Owing to our interest in the reactions and mechanisms of coenzyme NAD þ /NADH models, 8 we envisioned that NAD þ models might be utilized in the oxidation of sulfides with O 2 .…”