Pericyclic reactions - the third type of organic reaction mechanism along with ionic and radical reactions - include some of the most powerful synthetically useful reactions, like the Diels - Alder reaction, 1,3-dipolar cycloadditions, the Alder ene reaction, Claisen rearrangements, the 2,3-Wittig rearrangement, diimide reduction, sulfoxide elimination and many others. These reactions are characterised by having cyclic transition structures, and also have highly predictable stereochemical features. Every organic chemist must be able to recognise the various types of pericyclic reaction, and know something of their mechanism and the factors that affect how well they work in organic synthesis. This book will enable readers to recognise any pericyclic reaction and predict with confidence whether it is allowed, and with what stereochemistry, and to have a working knowledge of the range of pericyclic reactions available to the synthetic organic chemist.