Photochemistry is a tremendous research field offering many synthetic possibilities to chemists. Breakthroughs in this area have been notably driven by the implementation of new classes of photocatalysts. Within this context, Bodipy (Boron-dipyrromethene) dyes possess attractive chemical and physical features such as their modularity, strong absorption under visible light irradiation, good thermal and photochemical stabilities, and high fluorescence quantum yields. As such, this class of compounds has found widespread applications in functionalized materials, biology, medicine, or organic chemistry. From an organic-synthetic point of view, excited states of Bodipy dyes have been harnessed in electron and energy transfer reactions. This minireview collates the relevant literature on the applications of these catalysts in synthetic photochemistry and provides some perspectives of this research area.

A series of functionalized 6-alkoxy phenalenones was prepared through an unprecedented oxidative dealkylation of readily available phenalene precursors. The starting phenalenes were efficiently synthesized via an aminocatalyzed annulation/O-alkylation strategy starting from simple substrates. The spectroscopic properties of some phenalenones were investigated in different solvents. Introducing an alkoxy substituent at the 6-position onto the phenalenone framework results in a redshift of the absorption. The synthesized phenalenones exhibit low fluorescence quantum yields and the fluorescence decay was studied in different solvents highlighting the presence of several lifetimes. The singlet oxygen ( 1 O 2 ) photosensitizing propensity of some phenalenones was investigated and the results showed the striking importance of the phenalenone molecular structure in generating singlet oxygen with high yields. The ability of phenalenones to generate singlet oxygen was then harnessed in three photooxygenation  AUTHOR INFORMATION

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The quest for molecules able to trap, store, and release singlet oxygen is of utmost interest due to their applicability in various domains such as materials science and photomedicine. The aim of this study was to prepare and study a new family of singlet oxygen donors based on the 1,2‐dihydropyridine motif. The experiments demonstrated the influence of substituents and solvents on the photooxygenation rate constants. The process can be operated reversibly by thermolysis of the in situ formed endoperoxide leading to a release of singlet oxygen and formation of the parent 1,2‐dihydropyridine compound. A bifunctional structure based on a phenalenone photosensitizer covalently connected to a 1,2‐dihydropyridine module was synthesized via a multi‐step sequence. Upon irradiation with blue light, singlet oxygen was produced leading to the formation of the endoperoxide intermediate. In the dark cycle, the endoperoxide underwent cycloreversion reaction affording the parent 1,2‐dihydropyridine unit paving the way to a continuous production of singlet oxygen during the light/dark cycles.

Over the past decades, the advent of asymmetric organocatalysis has changed the way chemists think about creating or breaking chemical bonds, enabling new enantioselective strategies for functionalized molecules. The success of asymmetric organocatalysis is notably based on the existence of various activation modes, leading to countless transformations, and on the vast array of available chiral organic catalysts. Breakthroughs in this area have also been driven by selective functionalization of compounds with multiple activation sites such as cyclohexanone-derived dienones. These platforms can undergo diverse transformations such as Michael addition, Friedel-Crafts alkylation or Diels-Alder cycloaddition that offer new opportunities for reaching natural products and biologically relevant compounds. Amongst cyclohexanone-derived dienones, the 2,5-cyclohexadienone motif has received a great deal of attention due to its reactivity pattern and recently, (cross)-conjugated cyclohexanone-derived substrates have also been considered. In this review, we discuss the intermolecular functionalization of (cross)-conjugated cyclohexanone-derived compounds employing asymmetric organocatalysis.

A series of pyrroloquinolone photosensitizers bearing different halogen substituents (Cl, Br, I) on the heterocyclic framework was studied. These structures were readily prepared through a multi-step synthetic sequence involving an oxidative protocol as an important step to access the quinolone framework. Spectroscopic characterizations and computational investigations were carried out to study the dyes before and after the oxidative step. Interestingly, the fluorescence emission was significantly reduced upon oxidation. In spite of a low photostability under UV light, the pyrroloquinolone photosensitizers proved effective to produce singlet oxygen. Higher singlet oxygen quantum yields were obtained with photosensitizers bearing halogen atoms with a higher atomic number.