Kinetic studies on the pyramidal inversion of optically active selenonium imides

Kinetic studies were carried out on the thermal epimerization by pyramidal inversion of optically active ( S )‐(−) Se ‐ and ( R )‐(+) Se ‐4‐[(‐)‐menthyloxycarbonyl]phenyl(2′,4′,6′‐triisopropylphenyl)selenonium‐ N ‐toluene‐4″‐sulphonimides (1). The first‐order rate constants for the pyramidal inversion of ( S )‐(−) Se ‐1 and ( R )‐(+) Se ‐1 were determined and the activation enthalpies and entropies were calculated. A fairly large difference was found in the activation parameters between optically active ( S )‐(−) Se ‐1 and ( R )‐(+) Se ‐1, i.e. a large negative activation entropy was obtained in the case of ( R )‐(+) Se ‐1.