2H-Pyran-2-ones have received considerable attention during last two decades due to their synthetic potential as a valuable synthon in Organic Chemistry. Pyran ring system is widely present in animal and plant kingdom and possesses diverse pharmacological activities. Our group is working in the field of Synthetic Heterocyclic Chemistry from decades. We have exploited 2H-Pyran-2-ones for the synthesis of novel heterocycles. In this book I am giving a review on 2H-Pyran-2-ones and synthetic routes for the construction of Pyridines, Pyrimidines, Pyrazoles,Thiophenes, Thienopyrans and some novel class of Annelated Polycyclic Arenes and Heteroarenes from them. Hope the book will benefit both the students and young researchers.