Aminomethylation of Guareschi imides: synthesis of 2,4-dioxo-1H,5H-3,7-spiro[diazabicyclo[3.3.1]nonane-9,4'-piperidine]-1,5-dicarbonitriles

The aminomethylation reaction of 9-benzyl-2,4-dioxo-3,9-diazaspiro[5.5]undecane-1,5-dicarbonitrile hydrochloride in the presence of primary aliphatic amines and an excess of 37% aqueous formaldehyde led to the formation of 7-substituted 1'-benzyl-2,4-dioxo-1H,5Hspiro[3,7-diazabicyclo[3.3.1]nonane-9,4'-piperidine]-1,5-dicarbonitrile derivatives.