The stereochemistry of the Sn2' reaction between 3- buten-2-YL-Z-4-d 2, 6-dichlorobenzoate and piperidine

The S_N2' mechanism has experienced a great deal of controversy since it was first proposed in the late 1930's. While the stereochemical consequences of other substitution reactions are well-known and understood those of the S_N2' have never been fully explored. This is due, in part, to the continuing controversy over its mechanism and, in part, to the observance of differing results from reactions presumed to occur by the same mechanism. Most stereochemical studies have involved either intramolecular reactions or intermolecular reactions on cyclic substrates. However, these systems introduce biases which may outweigh the stereoelectronic preference of the S_N2' mechanism. This dissertation outlines an intermolecular S_N2' reaction on a deuterium labelled, optically active, allylic, acyclic substrate. Reduction of the double bond of the products of this reaction provides a single compound whose optical activity, after correction for the optical activity of the substrate, for its %D labelling, and for the ratio of E and Z products, is equal to the % syn attack in the S_N2' reaction. This was checked by preparing the same compound from an alcohol of known optical activity. An impossible result was obtained. The optical activity of the final reduced compound was greater than its maximum as indicated by the alternate synthesis. A repetition of this synthesis provided identical results.