A Detailed Theoretical Analysis of the 1,7‐Sigmatropic Hydrogen Shift: The Möbius Character of the Eight‐Electron Transition Structure

Pronounced aromatic character is found in the helical transition structure 1 for the 1,7 H shift in (Z,Z)-1,3,5-heptatriene according to ab initio calculations. The CC bond lengths are similar to those in benzene, the 1H NMR shifts (IGLO calculations) indicate strong ring current effects, and the energy of concert (roughly 60 kcal mol −1) is the highest reported for any pericyclic reaction.