Reactions of benzeneselenyl and benzenesulfenyl chlorides with syn‐ and anti‐9,9′‐bibenzonorbornenylidenes

Reaction of syn‐9,9′‐bibenzonorbornenylidene (1a) with benzeneselenyl chloride produced vic‐dichloride (4) exclusively, which corresponds to the cis‐addition product of 1a with molecular chlorine, with retention of the original alkene configuration. Moreover, the reaction of anti‐9,9′‐bibenzonorbornenylidene (1b) with benzeneselenyl chloride gave the same vic‐dichloride (4) exclusively with inversion of the original alkene configuration. No expected benzeneselenyl chloride adducts were formed in both cases. On the other hand, reactions of 1a and 1b with benzenesulfenyl chloride only resulted in the syn–anti isomerization of the alkenes without any adduct formation. Mechanisms of these reactions are discussed in some detail. © 2001 John Wiley & Sons, Inc. Heteroatom Chem 12:625–629, 2001