Naphthyl-Substituted Carbocations: From peri Interaction to Cyclization

The peri interaction of 1‐functionalized naphthalenes equipped with a triarylmethyl cation at the 8‐position has been studied because of the reversibility of the ring‐closing reaction, which was monitored closely by NMR spectroscopy in the case of the cyclic ammonium salt 5b. Carbocycle 4a and N‐heterocycle 5b did not exhibit any tendency for ring cleavage under various conditions, whereas the naphtho‐annulated furan 4c underwent reversible ring cleavage under strongly acidic conditions.(© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2008) The reversibility of the ring‐closing reaction has been studied for some 1,8‐difunctionalized naphthalenes, including carbocyclic as well as O‐ and N‐heterocyclic model compounds. A naphthofuran bearing a triarylmethyl moiety seemed to act as an indicator under strongly acidic conditions.