Bimolecular Nucleophilic Substitution with Anionotropic Rearrangement

Abstract

WE have been concerned to establish bimolecular substitution with rearrangement, S_N2′, in anionotropic, systems, for example, . This has proved somewhat difficult, though, as it now appears, not for the reason that the mechanism is particularly uncommon, but because, in most simple cases, it is obscured by an accompanying substitution without rearrangement, S_N2′. The one fully established and unambiguous case is that recently reported¹, in which an isotopic substituting agent was employed to destroy the power of a faster S_N2′ substitution to mask a slower S_N2′ reaction. This work confirmed a suggestion, which had been made on theoretical grounds earlier², that what was needed to make S_N2′ substitution observable without any necessity for such special measures was a suitable α-substituent in the allyl system, in order to retard selectively the S_N2′ process.