The Michael addition of diethyl malonate to 1-cyclohexene cyanide has been shown to give a mixture of the cis- and trans-diethyl 2-cyanocyclohexylmalonates in 72% and 28% yields respectively. The stereochemistry of the products was established by their unambiguous conversion to the respective cis- and trans-decahydroisoquinolines. Hydrogenation of a cyclohexane cyanide to the corresponding aminomethyl derivative takes place with retention of configuration. A number of substituted decahydroisoquinolines of known stereochemistry have been prepared. Decahydro-3,4-dioxoisoquinoline-4-phenylhydrazone underwent Fischer cyclization to a product assumed to be 2-oxo-octahydroindolo[2,3-d]isoquinoline indicating that the observation that 4-methyl-2,3-dioxopiperidine-3-phenylhydrazone did not undergo cyclization is not general for such 4-substituted piperidones.
