The reaction of piperidine with ethylene in the presence of Fe(CO)5, affords a mixture of N-ethyl- (minor product) and N-n-propylpiperidine (major product). Reactions conducted for 14 h at 170-degrees-C in the presence of Fe(CO)5 and water afford N-n-propylpiperidine with a turnover of 3.3 in the absence of an external source of carbon monoxide.