The purpose of this book is to provide academic and industrial chemists with significant advances in current chemical research in the area of biological active compounds. This book involves the synthesis of some new biological active phenothiazine derivatives having different heterocycles. The book is based on a study conducted on development of new methodology for synthesis of biological active phenothiazines. All structural transformations, reagents, experimental conditions, antimicrobial activities, as well as structural characterization have been explained in details. This book is meant for researchers who carry out their research in the field of medicinal chemistry