Recent Advances in the Light-assisted Synthesis of Ring Junction Nitrogen Heterocycles

Nitrogen ring junction heterocycles play a crucial role in synthetic organic chemistry due to their remarkable activity. The fused nitrogen ring junction compounds are abundant in nature; they have excellent biological activity and are used against various health issues. To make selective nitrogen ring junction products from the nitrogen ring junction heterocycles, expensive chemicals and catalysts, like expensive transition metal complexes and metal composites, are required. To neglect the drawbacks of conventional synthesis methods like long reaction times, by-product formation, lower selectivity, and low yields, an alternative of nonconventional light-mediated techniques can be opted for. The light source uses a radical mechanism that reduces by-product formation, provides a regio-selective product, increases yield, decreases reaction time, is cost-effective, and does not require special catalysts or chemicals. There are a variety of light sources, viz., UV, visible, IR, laser, and X-ray. The UV, visible light, white, green, and blue LED light sources are widely used in the photochemical method. This review emphasizes the light-mediated synthesis of nitrogen-ring junction heterocyclic compounds.