In an attempt to determine the preferred stereochemistry of the SN2' reaction of cyclohex-2-en-l-yl systems, it was desired to study the reactions of the cis and trans 6-alkyl cyclohex-2-en-l-yl 2,6-dichlorobenzoates (81, 82, 83; 39, 40, 41) with piperidine. Problems encountered in the preparation of these superficially simple compounds forced the curtailment of this exercise, however, and only the trans 6-isopropyl ester (40) was successfully obtained in a pure state. Attempt were made to find other 6-alkyl cyclohex-2-en-l-yl derivatives which would be suitable substrates for reaction with piperidine These were found in the cis and trans 3,5-dinitrobenzoates (84, 85), and the cis p-nitrobenzoate (87). Analysis of the reactions of these compounds with piperidine was complex - the esters reacted by substitution (SN2, SN2' ) and aminolysis, and were subject to isomerisation, by epimerisation and allylic rearrangement, during the course of reaction. However, it did eventually prove possible to establish that the SN2' reaction, when involved, proceeded only in syn fashion, regardless of the initial configuration of the substrate. The configuration of the SN2' products (229, 43) was confirmed by their comparison, after hydrosnation, with authentically prepared N-(4-alkyl cyclohexyl) piperidines (195, 196). The complexity of the reacting system precluded full kinetic analysis, but it was possible to determine approximate initial rates for the syn SN2 reactions of the cis and trans 3,5-dinitrobenzoates (84, 85) with piperidine. The implications of these findings are discussed
