ABSTRACT
During the past four decades, radical chemistry has undergone a dramatic development. From being considered as mostly sluggish in the early times, although some clean and preparatively useful processes were known, nowadays, radical reactions are mechanistically well understood and therefore occupy an unquestionable position in the toolbox of synthetic methodology. e breakthrough from being a mostly useless to a synthetically highly valuable technology was closely linked to the development of easily controllable radical chain processes, which involve a suitable radical precursor (e.g., halides), a mediator (e.g., transition metal hydrides, such as tri-n-butyl tin hydride, nBu3SnH), and a radical initiator possessing a labile σ bond, which can undergo facile homolytic fragmentation (e.g., peroxides and azo compounds) [1]. Besides comparatively straightforward reactions, such as radical addition to π systems, speciƒcally domino radical processes consisting of two or more consecutive steps involving both intra-and intermolecular reactions are a powerful method to access complex structural frameworks in only few synthetic steps. Since the generally mild conditions for radical reactions are compatible with a large number of functional groups, time-consuming protection strategies can be minimized. In addition to this, the principles of stereocontrol, which were discovered and developed for ionic chemistry, can also be applied to free radical reactions, which have resulted in the development of highly stereoselective radical processes.
