A novel phosphine-catalyzed [3+2] annulation of γ‑substituted allenoates with succinimides was developed, which was successfully applied to the synthesis of 2-azaspiro[4.4]nonenes-1,3-dione derivatives. The reaction afforded the desired products in moderate to high yields (up to 96%) with excellent regioselectivities and diastereoselectivities (up to >99 : 1 dr). A plausible reaction mechanism has