Substituent effects in selenoxide elimination chemistry

2α-(Arylseleno)cholestan-3-ones (3), 2α-(arylseleno)cholest-4-en-3-ones (4), and 4β-(arylseleno)-24-nor-5β-cholan-3-ones (5) were prepared and their stabilities toward oxidative elimination assessed. Simple competitive experiments demonstrate that electron-withdrawing substituents stabilize arylselenides toward oxidation, while electron-donating groups accelerate the oxidation process. In addition, ab initio and density functional calculations on model systems reveal that selenoxides are relatively insensitive to the nature of substituents on selenium toward elimination, suggesting that the oxidation step is rate-determining during oxidative elimination of selenides. Some results for sulfur and tellurium are also presented.