Enolates in 3-D: An experimental and computational study of deprotonated 2-adamantanone

Deprotonation of 2-adamantanone (1) in the gas phase affords the corresponding β-enolate anion. This ion was independently prepared by the fluoride-induced desilylation of 4-trimethylsilyl-2-adamantanone, and its reactivity and thermodynamic properties were measured (ΔH° _acid = 394.7 ± 1.4, EA = 16.8 ± 1.6, and BDE = 97.9 ± 2.1 kcal mol^-1). Density functional theory calculations with B3LYP and M06-2X, and G3 energies are also reported. The computed relative stabilities of the conjugate bases of 1 are as follows: β > γ > α > δ. An attempt to prepare the γ-anion, however, resulted in the formation of its ring-opened isomer (i.e., deprotonated 7-methylenebicyclo[3.3.1]nonan-2-one).