Stabilization in neutral bicyclic sulfoxide compounds

Density Functional Theory (DFT) calculations at the B3LYP/6-31+G* level hav e been performed on 5-thiabicyclo[2.1.1]hex-2-ene S-oxide derivatives. The geometrical and electronic properties of the compounds have been analyzed i n order to explain the favored stability of the exo configuration. Isodesmi c reactions at the Gaussian-G2 theory yielded the exo conformer as the most stable one. Moreover, the NMR chemical shift parameters (GIAO method) toge ther with the Atoms in Molecules theory reveal an stabilization of the S at om with the double bond for the exo configuration, in agreement with the ex perimental results. (C) 2000 John Wiley & Sons, Inc.