Pranjal K. Baruah is a Professor at Gauhati University. He obtained his PhD from NCL, Pune, followed by postdoctoral research at UNC at Chapel Hill, USA, and as a Marie Curie Fellow at the University of Oxford, UK. His research spans catalysis, synthetic methodology, C–H functionalization, nanomaterials, medicinal chemistry, and sustainable technologies. He has supervised several PhD scholars and authored over 85 publications and many book chapters. Dr. Baruah serves on editorial boards of reputed journals and was ranked among the top 5% most-cited RSC journal authors in 2020. Pallabi Borah is an Assistant Professor in the Department of Chemistry at Assam Don Bosco University, Assam, India. Her research interests include heterocycle synthesis, green and sustainable chemistry, catalysis, and nanomaterials. Subhasish Roy is an Assistant Professor in the Department of Chemistry at Assam Don University, Assam, India. His research interests include cross-coupling reactions, heterocycle synthesis, nanoparticle synthesis, metal complex synthesis, C–H activation reactions, cycloaddition reactions, photocatalytic transformations, and the design of green catalysts for organic transformations.

• Preface• Importance of heterocycles in chemistry and biology• Role of photocatalysis in green and sustainable chemistry• Scope and objective of the bookSection I: Heterocyclic Compounds and Their Importance1. Importance of Heterocycles in Modern Applications2. Challenges in the Synthesis of HeterocyclesSection II: Introduction to Photocatalysis3. Overview of Photocatalysis in Organic Synthesis4. History and Principles of Light-driven Reactions in Organic Synthesis5. Photophysical and Photochemical Process of Heterocyclic Compounds6. Types of Photocatalysts: Application in Heterocycle Synthesis7. Mechanism of Photocatalysis8. Investigation of Photocatalytic Mechanism Through Computational and Spectroscopic ApproachesSection III: Photocatalytic Pathways for Heterocyclic Synthesis9. Radical and Ionic Pathways in Heterocyclic Formation10. Functionalization of Pre-existing Heterocycles Using Photoredox Catalysis11. Metal-catalyzed Annulation Reactions for the Construction of Heterocycles Using para-Quinone Methides12. Metal-free Photocatalyst for Heterocycle SynthesisSection IV: Photocatalytic Synthesis of Five- and Six-membered Heterocycles13. Photocatalytic Synthesis of Five-membered Heterocycles Containing One Hetero Atom14. Photocatalytic Synthesis of Six-membered Heterocycles Containing One Hetero Atom15. Photocatalytic Synthesis of Six-membered Heterocycles Containing More Than One Hetero AtomSection V: Photocatalytic Synthesis of Fused and Polycyclic Heterocycles16. Photocatalytic Synthesis of Fused N-heterocycles17. Photocatalytic Synthesis of O-fused Heterocycles18. Visible Light-promoted Photocatalytic C(sp2)-H Functionalization of CoumarinsSection VI: Sustainable aspects of photocatalysis19. Green Chemistry Principles in Photocatalyzed Synthesis of Heterocycles20. Photocatalysis for Energy Efficiency -Waste Management, Atom Economy, and Energy-efficient Technologies in Photocatalysis21. Photocatalysis in Chemical Engineering and Continuous Flow Technologies for Heterocycle Synthesis22. Photocatalytic Technologies for Sustainable Waste Management and Solar Energy ConversionSection VII: Conclusion23. Future Scope and Challenges: Scalability of Photocatalytic Reactions24. Compatibility of Photocatalyst with Diverse Substrates25. Challenges and Future Scope of Photocatalysis