Radical Reactions in Organic Synthesis

Abstract

Abstract The Oxford Chemistry Masters Series is designed to provide clear and concise accounts of important topics - both established and emergent - that may be encountered by chemistry students as they progress from the senior undergraduate stage through post-graduate study to leadership in research. These Masters assume little prior knowledge, other than the foundations provided by an undergraduate degree in chemistry, and lead the reader through to an appreciation of the state of the art in the topic whilst providing an entree to the primary literature in the field. Radical reactions exhibit many of the characteristics desired by synthetic organic chemists: mild, generally neutral experimental conditions; diminished susceptibility to eliminations and rearrangements; relative insensitivity to the nature of the solvent and to steric effects; a compatibility with functional groups that is often complementary to that of ionic and organometallic reactions, obviating in many situations the need for laborious and costly protection-deprotection steps. Yet elementary radical reactions are ultra-fast processes and their taming requires some knowledge of their kinetics and rate constants, which have only relatively recently become available. Not surprisingly, transformations involving radical intermediates have long harboured the reputation of beeing difficult to control, suitable only for the synthesis of polymers and tars. This book provides a description of radical reactions and their applications in organic synthesis. It attempts to show that armed with an elementary knowledge of kinetics and some common sense, it is possible to harness radicals into a tremendously powerful tool for solving synthetic problems. The book starts with a brief historical account and presentation of the basics. It then blends the discussion of the properties of radical processes with the now familiar chemistry of stannanes. Radicals being the same entities, whichever method is used to generate them, a study of the various processes for the creation and capture of radicals constitutes the remainder of the book. Silicon and mercury based techniques as well as the Barton and related decarboxylation procedures are discussed in detail, followed by the Kharasch type atom and group transfer reactions. The increasingly important persistent radical effect, also known as the Fischer-Ingold effect, is examined in the context of non-chain reactions. Both the Kharasch based methods and the persistent radical effect have recently been applied in the emerging field of controlled radical polymerisations. Finally, the vast domain of redox processes is presented in a unified manner with the aim of providing a simple rationale for the multitude of possible transformation. The book concludes with a brief overview and some general practical hints for conducting radical reactions. More than 700 references provide access to the primary literature.