The Product of Homotropylium Cation Photolysis

Abstract

The product of homotropylium ion photolysis is the 1,2-dihydro-4H+-pentalenyl cation. CNDO/2 and analogies to cyclopentenyl cation rearrangements allow one to rationalize the formation of this product.

Carbocation

“…On irradiation in 5% sulfuric acid, the tropylium cation (71) yields the bicyclic alcohol (72) and the ether (73) (van Tamelen et al 9 1968, 1971). The homotropylium cation (75) is also cyclized photolytically (Hogeveen and Gaasbeek, 1970) and the photoproduct was recently identified as 76 (Christensen et al, 1974). In stronger acids, the cation (74) is not captured by a nucleophile but rearranges further to a 7-norbornadienyl cation (Childs and Taguchi, 1970;Hogeveen and Gaasbeek, 1970).…”