Abstract : The work done during this thesis has focused on three different themes. First among them is the nucleophilic reactivity of hydrazones, whose study was advanced to the laboratory: the study of a new reactivity of a-cétohydrazones has expanded the knowledge of the properties of these compounds. In the second chapter, we discuss several radical reactions initiated by radical formation iminyles. These nitrogen radicals can be generated from various compounds such as hydrazones, xanthates and dithiocarbazones. We studied the behavior of the radicals thus formed on new substrates, including reactions of b-fragmentation. Finally, the third component of this work focuses on the use of isonitriles in multicomponent reactions. The study led to the development of a general method of synthesis of amidophosphonates.