| Abstract
| - Fragmentation of (S)-endo-5-norbornenyl-2-oxychlorocarbene [(S)-8] in cyclohexane-d12 gives ∼20%(S)-endo-2-chloro-5-norbornene [(S)-7] with ∼50% ee, 65−70% (R)-exo-2-chloro-5-norbornene [(R)-4] with >95% ee, and ∼12% (R)-3-nortricyclyl chloride [(R)-5] with ∼22% ee. (Analogousstereochemical results were also obtained starting with the enantiomeric carbene (R)-8.) The (S)-8to (S)-7 and (S)-8 to (R)-4 conversions are ascribed mainly to retention and inversion SNi transitionstates, respectively. These have been located by computational methods and are nearly isoenergetic.In more polar solvents (CDCl3 and CD3CN), the fragmentation of (S)-8 increasingly occurs viacompetitive ion pair pathways in which steroselectivity is diminished, and escape to thenorbornenyl−nortricyclyl cation directs the products away from endo-2-chloro-5-norbornene towardexo-chloride 4 and nortricyclyl chloride 5.
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