Effect of Dihydroaromatic Compounds on the Cation Radical Chain Oxygenation of Tetraalkyl Olefins

Article abstract of DOI:10.1021/jo00368a014

Ionic chain hydrogenation of syn-sesquinorbornene (7) to 13 by 1,4-cyclohexadiene (11) may be initiated by tris(2,4-dibromophenyl)aminium (9^.+) hexachloroantimonate at -78 deg C and is efficient enough to inhibit cation radical catalyzed oxygenation of 7 by oxygen.The chain-carrying steps appear not to involve radicals, and the reaction can be initiated by HBF4 at low temperature or TFA at above room temperature. anti-Sesquinorbornene (8) is considerably less reactive and requires HBF4 to initiate hydrogenation.Isopropylideneadamantane (16) requires FSO3H for initiation, but biadamantylidene (1) is not hydrogenated under our conditions.Nevertheless, addition of 5 equiv of 11 intercepts the kinetic chain for cation radical catalyzed oxygenation of 1 to dioxetane 2; the chain length for consumption of 1 drops from over 800 to less than 2, and epoxide 19 becomes a major product.It is proposed that the open peroxy carbocation B^.+ is trapped by 11 to lead to the observed results.