Reversible intramolecular photocycloaddition of a bis(9-anthrylbutadienyl)paracyclophane – an inverse photochromic system. (Photoactive cyclophanes 5)

• Henning Hopf,
• Christian Beck,
• Jean-Pierre Desvergne,
• Henri Bouas-Laurent,
• Peter G. Jones and
• Ludger Ernst

Beilstein J. Org. Chem. 2009, 5, No. 20, doi:10.3762/bjoc.5.20

• observed to occur under geometrical constraints [11][12][24] through a triplet state process [25]. [4+2]-Cycloadditions can take place in a hot ground state [26]. This result is reminiscent of the [4+2]-photocycloaddition between two naphthalene substrates for the anti-[2.2](1,4)-naphthalenophane leading