GENERAL STEPS: To a stirred solution of 1,4-diazabicyclo[3.2.2]nonan-3-one (1.0 g, 7.2 mmol) in 1,4-dioxane (7.2 mL) was slowly added lithium aluminum hydride [2.0 M in THF] (4.1 mL, 8.2 mmol) at room temperature. Subsequently, the reaction mixture was heated to reflux, maintained for 6 h, and then cooled to room temperature. The reaction was quenched by stepwise addition of water (200 μL), 15% NaOH aqueous solution (200 μL) and water (600 μL). The mixture was filtered through a diatomaceous earth pad and washed with ethyl acetate (EtOAc). After combining the filtrates, they were concentrated under vacuum to afford 1,4-diazabicyclo[3.2.2]nonane (0.82 g, 90% yield), which was used for subsequent reactions without further purification. The 1H NMR (400 MHz, CDCl3) data of the product were as follows: δ 3.28-3.25 (m, 1H), 2.99-2.95 (m, 8H), 1.86-1.80 (m, 3H), 1.69-1.64 (m, 2H) ppm.