A novel photochemical rearrangement of diarylethenes bearing oxazole and benzene derivatives as aryl moieties that results in the formation of polyaromatic systems was investigated. The mechanism of the transformation includes photocyclization, sequential [1,9] and [1,3]-hydrogen shifts, as well as a lateral oxazole ring-opening process. It was shown that this reaction can be an effective synthetically preparative method for the preparation of naphthalene (polyaromatic) derivatives.

Due to the great value of amino alcohols, new methods for their synthesis are in high demand. Abundant aliphatic alcohols represent the ideal feedstock for the method development toward this important motif. To date, transition-metal-catalyzed approaches for the directed remote amination of alcohols have been well established. Yet, they have certain disadvantages such as the use of expensive catalysts and limited scope. Very recently, transition-metal-free visible-light-induced radical approaches have emerged as new powerful tools for directed remote amination of alcohols. Relying on 1,5-HAT reactivity, these methods are limited to βor δ-amination only. Herein, we report a novel transition-metal-and visible-light-free room-temperature radical approach for remote β-, γ-, and δ-C(sp 3)-N bond formation in aliphatic alcohols using mild basic conditions and readily available diazonium salt reagents.

The photochemical rearrangement of dihetarylethenes is a powerful tool for the benzannulation of heterocycles, providing a wide scope of benzannulated heterocycles and N-, S-, C-, and O-substituents in the newly formed benzene ring.

The effect of the size of the ethene bridge on the structural and spectral properties of photochromic diarylethenes, which remains a poorly understood phenomenon, was studied as applied to diarylethenes containing unsymmetrical (cyclohexenone and cyclopentenone) and symmetrical (cyclohexene and cyclopentene) ethene bridges. Thiophene, oxazole, and imidazole derivatives were used as aryl moieties. An increase in the size of the ethene bridge in the cycloalkenone series was found to be accompanied by a hypsochromic shift of the absorption maximum of the photoinduced form, whereas no difference was found for cycloalkenes. A detailed analysis of the NMR spectra (including 2D experiments) revealed previously unknown effects associated with the existence of an intramolecular hydrogen bond (CH···N) between the six-membered ethene bridge and the azole substituents. The NMR experimental data obtained were confirmed by DFT quantum chemical calculations and X-ray analysis. It was found that an intramolecular hydrogen bond favors an increase of the quantum yield of the photocyclization reaction.

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A new efficient method was developed for the synthesis of triaryl-substituted cyclohexenones and salicylates. The method is based on the Robinson annulation of readily available keto esters and chalcones, followed by the aromatization of the cyclohexenone moiety. The aromatization can be accomplished either by reaction with bromine in boiling chloroform or bromination with copper(II) bromide in ethanol followed by treatment with pyridine or 1,8-diazabicyclo[5.4.0]undec-7ene (DBU). The new synthetic method was also implemented in a onepot protocol, which in some cases resulted in higher yields of the final product compared to those obtained in the stepwise synthesis.

The synthesis of arylamines from renewable resources under mild reaction conditions is highly desired for the sustainability of the chemical industry, where the production of hazardous waste is a prime concern. However, to date, there are very few tools in chemists’ toolboxes that are able to produce arylamines in a sustainable manner. Herein, a robust one‐pot approach for constructing bio‐based arylamines via a combined photooxidative dearomatization‐rearomatization strategy is presented. The developed methodology enables the synthesis of structurally complex amines in moderate‐to‐good isolated yields using biomass‐derived phenols, natural α‐amino acids, and naphthols under remarkably mild reaction conditions. For the photooxygenation of phenols, a novel chrysazine‐based catalyst system was introduced, demonstrating its efficiency for the synthesis of natural products – hallerone, rengyolone, and the pharmaceutically relevant prodrug DHED.

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