Electron transfer reactions have been at the heart of great advances in organic and inorganic chemistry and biology since the early work in 1954 by H. Taube (Nobel Chemistry Prize in 1983) and R. Marcus (Nobel Chemistry Prize in 1991). In organic chemistry, a new kind of chain substitution reaction with paramagnetic species was defined and identified as S(RN)1 (substitution, radial-nucleophilic, unimolecular). In our laboratory, choosing more or less complex molecules which possess electron-withdrawing groups and correctly disposed alkylation sites has enabled us to extend this concept to the heterocyclic (S(RN)1 HET) and quinonic (S(RN)1 QUI) series. These studies led us to prepare, under mild operating conditions, highly branched molecules hard to obtain via other pathways and which possess high pharmacological activity in various fields. We have discovered new reaction mechanisms such as LD-S(RN)1 (long-distance S(RN)1) E(RC)1 (elimination radical chain, unimolecular), bis-S(RN)1 and poly-S(RN)1. Moreover, we have developed a new technology using microwaves which increases the interest of electron transfer reactions in medicinal chemistry for drugs synthesis.