The heterocyclization reaction of oximes derived from aliphatic ketones with acetylene has been applied to piperidone oximes. Pyrrole[3,2-c]piperidines substituted on the six-membered ring have been prepared in this manner. Assumptions have been made concerning their conformational and configurational properties. These reactions have been demonstrated to lead to the formation of condensed systems containing a pyrrolenine fragment. © 1988 Plenum Publishing Corporation.