Enolates in 3-D: An Experimental and Computational Study of Deprotonated 2-Adamantanone

Abstract

Deprotonation of 2-adamantanone (1) in the gas phase affords the corresponding beta-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 (DeltaH degrees(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: beta > gamma > alpha > delta. An attempt to prepare the gamma-anion, however, resulted in the formation of its ring-opened isomer (i.e., deprotonated 7-methylenebicyclo[3.3.1]nonan-2-one).