Heterocyclic compounds constitute the largest group of organic compounds playing a central role in Organic Chemistry. Heterocycles have a wide range of applications namely as pharmaceuticals, as agrochemicals, as veterinary products, as polymers, as dyestuffs and as pigments. They are used as antioxidants and as corrosion inhibitors, among other applications. Therefore, an impressive amount of research work on Heterocyclic Chemistry has been developed making the compilation of the more relevant contributions very important. The book Recent Research Developments in Heterocyclic Chemistry provides comprehensive reviews reporting the state of the art on selected topics. The book comprises chapters on the application of chiral aziridines in the design of biologically active compounds (Chapter 1), on the use of addition reactions to 2H-azirine imine bonds for the construction of nitrogen-containing heterocycles (Chapter 2) and an overview on recent developments in the synthesis of four- and three-membered ring heterocycles by radical cyclisations (Chapter 3). Contributions covering the use of pyrrole based catalysts in oxidation reactions with particular emphasis on metalloporphyrins catalysis (Chapter 4) and on the synthesis of heterocycle-fused C60 fullerenes (Chapter 5) are also included. In our days, the development of more sustainable methodologies in synthetic organic chemistry is a very important target. Chapter 6 offers an overview on the progress of more sustainable methodologies for the synthesis of N- and S-based heterocycles. This compilation focuses on solvent free transformations, fluororous tag approaches and the use of water, ionic liquids, fluorinated fluids and supercritical CO2 as solvents. The book also includes a chapter on the investigation of molecular structure and reactivity of selected families of heterocyclic compounds using matrix isolation infrared spectroscopy (Chapter 7). Illustrative examples of the application of the method to the study of thermally and photochemically induced conformational isomerization and tautomerization processes, ring-opening reactions and rearrangements are presented. The final chapter is focused on NMR techniques, an essential tool for structural characterization of heterocyclic compounds. The main 1H, 13C and 15N NMR features of three- to six-membered heterocyclic compounds and the application of several 1D and 2D NMR techniques in the structural elucidation of these compounds are discussed. What is offered to the readers is the result of the work and expertise of all the authors of each specific chapter. The editors are highly indebted for their availability and efforts to lay down their excellent pieces of work.