Aziridination via Nitrogen-Atom Transfer to Olefins from Photoexcited Azoxy-Triazenes.

Herein, we report that readily accessible azoxy-triazenes can serve as nitrogen atom sources under visible light excitation for the phthalimido-protected aziridination of alkenes. This approach eliminates the need for external oxidants, precious transition metals, and photocatalysts, marking a departure from conventional methods. The versatility of this transformation extends to the selective aziridination of both activated and unactivated multisubstituted alkenes of varying electronic profiles. Notably, this process avoids the formation of competing C-H insertion products. The described protocol is operationally simple, scalable, and adaptable to photoflow conditions. Mechanistic studies support the idea that the photofragmentation of azoxy-triazenes results in the generation of a free singlet nitrene. Furthermore, a mild photoredox-catalyzed N-N cleavage of the protecting group to furnish the free aziridines is reported. Our findings contribute to the advancement of sustainable and practical methodologies for the synthesis of nitrogen-containing compounds, showcasing the potential for broader applications in synthetic chemistry.

Photoinduced Nitroarenes as Versatile Anaerobic Oxidants for Accessing Carbonyl and Imine Derivatives.

Herein, we report a protocol for the anaerobic oxidation of alcohols, amines, aldehydes, and imines promoted by photoexcited nitroarenes. Mechanistic studies support the idea that photoexcited nitroarenes undergo double hydrogen atom transfer (HAT) steps with alcohols and amines to provide the respective ketone and imine products. In the presence of aldehydes and imines, successive HAT and oxygen atom transfer (OAT) events occur to yield carboxylic acids and amides, respectively. This transformation is amenable to a continuous-photoflow setup, which led to reduced reaction times.

Singlet Oxygen's Potential Role as a Nonoxidative Facilitator of Disulfide S-S Bond Rotation†.

The role of singlet oxygen potentially mediating increased conformational flexibility of a disulfide was investigated. Density functional theory (DFT) calculations indicate that the singlet oxygenation of 1,2-dimethyldisulfane produces a peroxy intermediate. This intermediate adopts a structure with a longer S-S bond distance and a more planar torsional angle θ (C-S-S-C) compared with the nonoxygenated 1,2-dimethyldisulfane. The lengthened S-S bond enables a facile rotation about the torsional angle in the semicircle region 0° < θ < 210°, that is ~5 kcal mol-1 lower in energy than the disulfane. The peroxy intermediate bears nO → σS-S and nO → σ*S-S interactions that stabilize the S-O bond but destabilize the S-S bond, which contrasts with stabilizing nS → σ*S-S hyperconjugative effects in the disulfane S-S bond. Subsequent departure of O2 from the disulfane peroxy intermediate is reminiscent of peroxy intermediates which also expel O2 , yet facilitate cis-trans isomerizations of stilbenes, hexadienes, cyanines, and carotenes. "Non-oxidative" 1 O2 interactions with a variety of bond types are currently underappreciated. We hope to raise awareness of how these interactions can help elucidate the origins of molecular twisting.

How Tryptophan Oxidation Arises by "Dark" Photoreactions from Chemiexcited Triplet Acetone.

Dioxetane intermediates readily decompose to chemiluminescent triplet carbonyls, giving rise to what has been paradoxically called photochemistry in the dark. In this issue of Photochemistry and Photobiology, Bechara et al. report on mechanistic advances in such a reaction. With the use of horseradish peroxidase for isobutyraldehyde-derived triplet acetone, light emission from acetone and singlet oxygen can be quenched. The experiments reveal that the reaction depends on oxygen and the amino acid. The analysis reveals that free tryptophan is a target of this form of "carbonyl stress," with the efficient formation of mono-, bi- and tricyclic compounds (N-formylkynurenine, indoline, 1λ2 -indole and 3H-indoles).

Diffuse large B-cell lymphoma of the maxillary sinus.

We report the case of a 25-year-old man with a history of recent facial trauma who presented with a mildly painful swelling of the left maxilla and nasal obstruction. The patient was initially diagnosed with left maxillary sinus osteomyelitis secondary to undiagnosed and untreated left maxillary sinus fractures. However, further evaluation revealed that the patient had diffuse large B-cell lymphoma.