3-Bromo- and 3-chloro-hexahydroazocin-2(1H)-one undergo dehydrohalogenation rather than substitution reactions, even in the presence of weakly basic nucleophiles like iodide and cyanide ions. A mixture of two alkenes is formed, with the conjugated isomer, 5,6,7,8-tetrahydroazocin-2(1H)-one, predominating over the deconjugated isomer. Only thiolate nucleophiles, for example sodium benzenethiolate, gave substitution reactions and the resulting 3-phenylthiohexahydroazocin-2(1H)- one was oxidized to give a mixture of diastereoisomeric sulfoxides. On attempted Pummerer rearrangement, this mixture of sulfoxides afforded 3-phenylthio-5,6,7,8-tetrahydroazocin-2(lH)-one rather than the expected α-acyloxy sulfide.