Angewandte Chemie International Edition
Copyright © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim
Cover Picture (Angew. Chem. Int. Ed. Engl. 6/1992)
The cover picture shows the transition structures for six pericyclic reactions, provided by quantum chemical ab initio calculations, which are the subject of K. N. Houk's review on p. 682 ff. Common to these reactions are the changes in bonding involving six electrons. Examples are found among the most important reactions in preparative organic chemistry including sigmatropic rearrangements, elecrocyclizations, and the ene and Diels–Alder reactions. Calculations reveal interesting aspects—even now 25 years after the formulation of the Woodward–Hoffmann rules—for example, that these very different reactions have features in common and yet a variety of transition structures. Without these postulates organic chemistry would not have been as fruitful. Although by tradition we do not put portraits on the front cover, this issue breaks with editorial policy because Woodward (the right-hand photo) has become a legend and would have celebrated his 75th birthday this year.