The ultimate goal of organic synthetic chemistry is to design and synthesise more complex structures from simple molecules. Being a cheaper and more attractive alternative to precious metal catalysts, cobalt compounds are being extensively studied and used as catalysts in organic synthesis. The aim of the Doctoral Thesis is the development of novel methods for the synthesis of heterocycles using cobalt catalysis. The Doctoral Thesis has been prepared as a thematically united collection of scientific publications. It consists of a Summary, three scientific original publications, two review articles and one book chapter.