Static and dynamic stereochemistry of ortho-bridged diarylsulphones

Ortho-bridged diarylsulphones I and II have been synthesized and their static and dynamic stereochemistry has been investigated by variable temperature 1H NMR spectroscopy. The results indicate that both compounds adopt a C2 propeller conformation in solution and the enantiomerization process occurs with ΔG≠ = 20.0 kcal mol-1 for I and ΔG≠ = 18.15 kcal mol-1 for II. The mechanism leading to the stereoisomerization process is believed to occur through a two-ring flip transition state. © 1990.