This book is a comprehensive exploration of topics in chemistry, offering insights into various aspects of heterocycles, sustainable synthesis, and advanced characterization techniques. It is organized into four chapters, each dedicated to a specific facet of heterocyclic compounds. It provides an extensive overview of heterocycles, with a particular emphasis on annelated azoles and their relevance in the field of science. It introduces innovative strategies for the synthesis of functionalized annelated azoles, emphasizing their efficiency and positive environmental impact. The book's structure is designed to make the content accessible and engaging for readers, aligning with the principles of sustainable and theoretical chemistry. It not only provides valuable insights into the latest developments in the field but also emphasizes the importance of sustainability and process intensification in chemical research. Overall, this book serves as a source of inspiration for those interested in the forefront of chemistry, offering a blend of theoretical knowledge and practical applications.