Solvolysis of 1-decenyl(phenyl)iodonium tetrafluoroborate: Mechanisms of nucleophilic substitution and elimination

Solvolysis of (E)-1-decenyl(phenyl)iodonium tetrafluoroborate 1 was carried out in some alcohols, acetic acid, and mixed aqueous alcoholic solvents at 50-60 degreesC and the effects of added carboxylates and other salts were also examined in methanol. Reaction products include enol derivatives (substitution) and 1-decyne (elimination) as well as iodobenzene. Rates for the solvolysis increase with increasing nucleophilicity of the solvent but have no correlation with the solvent ionizing power. The substitution occurs mostly via inversion of configuration, and is concluded to follow the in-plane S(N)2 mechanism with a minor concomitant out-of-plane S(N)2 pathway. The reactions with the deuterated substrates show that stronger bases of pK(a) of the conjugate acid > 3 induce exclusively alpha -elimination of 1 in methanol. However, both alpha- and beta -elimination occur in neutral methanol in a ratio of about 3/1 besides the substitution. Mechanisms for these reactions are proposed.