Recent Developments in the Photochemical Reactions of N-Heterocyclic Compounds

The adoption of clean and renewable light sources is becoming increasingly prevalent in organic synthesis due to their welfare, workability and economic benefits. In recent times, photo-redox catalysis has emerged as a valuable tool in organic transformations owing to its environmentally friendly nature and utilization of abundant resources. Since harmful or polluting reagents are not needed for the organic photochemical reactions, these reactions provide insights into sustainable processes and green chemistry. N-Heterocyclic compounds (NHC's) constitute fundamental structural motifs in numerous organic compounds and are widely encountered in natural products and pharmaceuticals with diverse biological activities. Consequently, investigations into the synthesis and modification of these NHC's such as indole, carbazole, benzimidazole, quinoline, isoquinoline and pyridine hold particular significance for chemists and pharmacologists. This review provides an overview of the impact of photocatalysis on synthesis of NHC's and their modification from 2019 to 2024. These transformations are achieved through the utilization of both metal photocatalysts (e. g., Ir, Pd, Co, Gd etc.) and non-metallic photocatalysts (e. g., Eosin-Y, 4CzIPN, Mes-Acr+ClO4- etc.), or even without the necessity of photocatalysts. It is anticipated that this review will serve as a valuable resource for researchers delving into the promising realm of photocatalyzed transformations.