The synthesis of 3-diazo-2-nitromethylenepiperidine, in six steps from 2-piperidone, is reported. This is the first compound described which contains the 3-diazo-1-nitropropene function. The title compound is stable enough to be isolated and characterised in gram quantities using standard organic chemistry techniques and was used to prepare some 5- aza-spiro [2.5] octane and 4, 5, 6, 7-tetrahydro-1H-pyrazolo-[4, 3-b] pyridine derivatives.
