John A. Joule 
Heterocyclic Chemistry, 3rd Edition [PDF ebook] 

Covering the fundamentals of heterocyclic reactivity and synthesis, this book teaches the subject in a way that is understandable to graduate students. Recognizing the level at which heterocyclic chemistry is often taught, the authors have included advanced material that make it appropriate for postgraduate courses. The text discusses the chemical reactivity and synthesis of particular heterocyclic systems. Exercises and solutions help students understand and apply the principles. Original references are included throughout, as well as many review references.