σ-Homoacenaphthylene and π-Homoacenaphthene (pages 683–686)
Dr. Roland Arnz, José Walkimar de M. Carneiro, Dr. Wolfgang Klug, Dr. Hans Schmickler, Prof. Dr. Emanuel Vogel, Rolf Breuckmann and Prof. Dr. Frank-Gerrit Klärner
Article first published online: 22 DEC 2003 | DOI: 10.1002/anie.199106831
“Freezing-in” as norcaradiene valence tautomer is possible in the case of 1,6-methanoannulene not only by acceptor substituents on the methylene carbon atom but also by suitable peri-bridges. The prognosis based on force field calculations that 2,10-etheno-1, 6-methanoannulene exists as valence tautomer 1, whereas 2,10-ethano-1,6-methanoannulene—the product of the diimine reduction of 1—retains the annulene structure, finds impressive experimental confirmation.