Angewandte Chemie International Edition
Copyright © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim
Cover Picture (Angew. Chem. Int. Ed. Engl. 12/1997)
The cover picture shows a ball-and-stick model of extremely strained, highly reactive o-benzyne (1,2-didehydrobenzene) (green) inside the protective inner phase of Cram's hemicarcerand (O atoms in red, C atoms in grey, and H atoms in white). The white, circular window in the lower right-hand corner represents the inner phase in which o-benzyne was photochemically generated from incarcerated benzocyclobutenedione in two steps via benzocyclopropenone and is stable for only a short time, even at −75°C. The other three windows highlight groups of signals in the 13C NMR spectrum of the fully 13C-labeled guest molecule. More about the NMR spectroscopic properties of this molecule is reported by R. Warmuth on page 1347 ff—one hundred years after the birth of Georg Wittig, who first postulated the existence of this “dehydrobenzene”. The graphic was generated by Jan Haller, University of California, Los Angeles, CA (USA) with the program POV-ray.