The Handbook is a compilation of 99 articles on diverse reagents and catalysts that describe the synthesis of heteroarenes, the building blocks of a wide range of chemicals used in pharma and chemical industries. Articles are selected from the e-EROS database and edited to make sure that it includes only the material relevant to the topic of the book and focus on the synthetic aspects. This makes the articles very focused on the needs of readers wanting information on specific syntheses of specific heteroarenes. In addition, the chemistry of each “parent heteroarene” is also included to ensure that the reader rapidly finds important information. The Handbook is a part of the Handbook of Reagents for Organic Chemistry series, aiming at collecting articles on a particular theme that individual researchers in academia or industry can use on a daily basis.