Facile synthesis of 2-azaspiro[3.4]octane

Our annulation strategy utilized for the synthesis of 2-azaspiro[3.4]octane is explained. Three successful routes for the synthesis were developed. One of the approaches involved annulation of the cyclopentane ring and the remaining two approaches involved annulation of the four membered ring. All three approaches employ readily available starting materials with conventional chemical transformations and minimal chromatographic purifications to afford the title compound. The merits and limitations of the three approaches are also discussed. Synthesis of 2-azaspiro[3.4]octane was achieved by ring annulation of five-membered as well as four-membered rings. The merits and limitations of the three efficient synthetic methodologies developed are discussed.