Synthesis of substituted 3,9-diazaspiro[5.5]undecanes via spirocyclization of pyridine substrates

Construction of 3,9-diazaspiro[5.5]undecane derivatives can be easily achieved via intramolecular spirocyclization of 4-substituted pyridines. The reaction entails in situ activation of the pyridine ring with ethyl chloroformate followed by intramolecular addition of an attached β-dicarbonyl nucleophile in the presence of Ti(OiPr)4.