Aminomethylation of 2,4-Dioxo-3-azaspiro[5.5]undecane- 1,5-dicarbonitrile. Efficient Synthesis of New 3,7-Diazaspiro- [bicyclo[3.3.1]nonane-9,1′-cyclohexane] Derivatives

2,4-Dioxo-3-azaspiro[5.5]undecane-1,5-dicarbonitrile reacted with primary amines and formaldehyde on heating in boiling ethanol to give mixtures of 7-alkyl-2,4-dioxo-3,7-diazaspiro[bicyclo[3.3.1]nonane- 9,1′-cyclohexane]-1,5-dicarbonitriles and their ammonium salts. The former were isolated in 26–71% after acidification of the reaction mixture.