Photocatalyst-free visible-light triggered amination of benzo[c][1,2,5]thiadiazole: direct C-N bond formation from C(sp2)-H bond

Photocatalytic Oxidative C(sp3)-H/N-H Cross-Dehydrogenative Coupling of Tertiary Anilines with Amides/Imides: Synthesis of N-Mannich Bases

A photocatalytic method for the synthesis of N-Mannich bases has been developed through the C(sp3)-H/N-H cross-dehydrogenative coupling of N,N-dimethylanilines with amides/imides. This process utilizes 2,4,6-triphenylpyrylium tetrafluoroborate (TPT) as the photocatalyst and is conducted at ambient temperature and atmospheric air. Various N,N-dimethylanilines and the aromatic, heteroaromatic and aliphatic (cyclic) amides, as well as imides were successfully employed, yielding moderate to good results. Preliminary mechanistic and isotope-labeling studies indicate that the reaction likely proceeds via a single electron transfer pathway and involves an α-aminoalkyl radical intermediate.

Harnessing light without photocatalysts: advances in photocatalyst-free C-N bond formation

The present feature article focuses on recent developments in the realm of photocatalyst-free C-N bond formations, highlighting the innovative approaches that leverage light without relying on traditional photocatalysts. Exploring alternative methodologies underscores the advancements in synthetic strategies, enabling efficient and sustainable C-N bond formation reactions. The abstracted review emphasizes the significant progress made in this field, shedding light on the potential for novel and environmentally friendly pathways for chemical synthesis.

Unusual Regioselective C-H Difluoroalkylation of Heteroarenes under Photoredox Catalysis

We disclose a new general strategy for the site-selective difluoroalkylation of nonprefunctionalized heteroarenes, such as quinoxaline at the C-8 position, and benzothiadiazole, benzoxadiazole, and benzothiazole at the C-4 position via consecutive organophotoredox-catalyzed radical-radical cross-coupling and base-assisted hydrogen abstraction reactions. The current methodology represents a site-selective direct difluoroalkylative strategy to allow broad functional group tolerance and a wide substrate scope in good to excellent yields. Careful experimental investigations and detailed DFT calculations revealed the exact site-selectivity of the heteroarenes and a possible mechanistic pathway.

Direct C-H Alkylation of Benzothiadiazoles via Organic Photoredox Catalysis

2,1,3-Benzothiadiazole is widely used as a privileged scaffold in pharmaceuticals and organic functional materials. Nonetheless, many current methods for the functionalization of 2,1,3-benzothiadiazole rely on preactivation, transition metal catalysts/promoters, or an elevated reaction temperature. Herein we disclose a transition-metal-free visible-light-induced photocatalytic method for the direct C-H alkylation of 2,1,3-benzothiadiazole using readily accessible carboxylic acid derivatives, i.e., N-hydroxyphthalimide esters (NHPEs), as alkylating reagents under room temperature. This mild and scalable method is highlighted by the late-stage installation of the benzothiadiazole scaffold in drugs and natural products.