Photocatalytic Mechanisms of Organic Thermally Activated Delayed Fluorescence Compounds.

Reverse intersystem crossing (RISC) has become possible by minimizing the energy gap between the first excited singlet (S) and triplet state (T), which facilitates the thermally activated delayed fluorescence (TADF). Due to the small singlet-triplet energy gap, the S and T states exhibit comparable redox reactivity, leading organic TADF compounds to be potent photocatalysts. Here, we report such TADF compounds with multiple donor units designed as an efficient photocatalyst for the direct C(sp)-H carbamoylation of saturated aza-heterocycles.

Exploring Solvent Polarity-Dependent Photocatalysis Mechanism of Organic Photoredox Catalysts.

Organic dyads with intramolecular charge-transfer (ICT) character are emerging as viable and more sustainable photocatalysts than metal-based complexes. Herein, a carbazole- and naphthalimide-based organic dyad () was designed as an efficient organic photocatalyst for the direct C(sp)-H carbamoylation of saturated aza-heterocycles. Aiming at understanding the effect of environment, especially the solvent polarity on photocatalysis performance, the excited-state dynamics of in different polar solvents were studied by femtosecond (fs) and nanosecond (ns) time-resolved transient absorption (TA) spectroscopy.

Organic photoredox catalyzed dealkylation/acylation of tertiary amines to access amides.

A mild metal-free C-N bond activation strategy for the direct conversion of inert tertiary amines with acyl chlorides into tertiary amides organic photoredox catalysis is presented. In this protocol, a novel organic photocatalyst (Cz-NI-Ph) that showed excellent catalytic performance during C-N bond cleavage is developed. Moreover, this reaction features green and mild conditions, broad substrate scope, and readily available raw materials.

Organic photoredox catalytic amino-heteroarylation of unactivated olefins to access distal amino ketones.

Here we describe a metal-free amino-heteroarylation of unactivated olefins organic photoredox catalysis, providing a concise and efficient approach for the rapid synthesis of various δ (β, ε)-amino ketones under mild conditions. This protocol demonstrates that the new photocatalyst Cz-NI developed by our group has an excellent photoredox catalytic performance. Finally, a series of mechanistic experiments and DFT calculations indicate that this transformation undergoes a photoredox catalytic sequential radical addition/functional group migration process.

Organic photoredox catalytic α-C(sp)-H phosphorylation of saturated -heterocycles.

A metal-free C(sp)-H phosphorylation of saturated -heterocycles the merger of organic photoredox and Brønsted acid catalyses was established under mild conditions. This protocol provided straightforward and economic access to a variety of valuable α-phosphoryl cyclic amines by using commercially available diarylphosphine oxide reagents. In addition, the D-A fluorescent molecule DCQ was used for the first time as a photocatalyst and exhibited an excellent photoredox catalytic efficiency in this transformation.

Dehydrogenation/(3+2) Cycloaddition of Saturated Aza-Heterocycles via Merging Organic Photoredox and Lewis Acid Catalysis.

Herein, we report a photoinduced dehydrogenation/(3+2) cycloaddition reaction by merging organic photoredox and Lewis acid catalysis, providing a straightforward and efficient approach for directly installing a benzofuran skeleton on the saturated aza-heterocycles. In this protocol, we also describe a novel organic photocatalyst (-Bu-DCQ) with the advantages of a wider redox potential, easy synthesis, and a low price. Furthermore, the stepwise activation mechanism of dual C(sp)-H bonds was demonstrated by a series of experimental and computational studies.

Metal-Free α-C(sp)-H Aroylation of Amines via a Photoredox Catalytic Radical-Radical Cross-Coupling Process.

Here we describe an unprecedented metal-free C(sp)-H aroylation of amines via visible-light photoredox catalysis, which provides a straightforward route for the construction of a useful α-amino aryl ketone skeleton. Additionally, a number of selected products exhibit good biological activity for protecting PC12 cell damage, which shows that this skeleton has the potential to become a new neuroprotective agent. Finally, a series of mechanism experiments indicate that this transformation undergoes a photoredox catalytic radical-radical cross-coupling pathway.