Highly Enantioselective Construction of Azaspiro[4.5]decane via an <scp>NHC</scp> ‐catalyzed [5+1] Cycloaddition

Comprehensive Summary Azaspiro[4.5]decane scaffold represents a privileged structural motif that is widely found in natural products, bioactive molecules, and pharmaceuticals. Herein, we report the first N ‐heterocyclic carbene (NHC)‐catalyzed [5+1] annulation of α,β‐γ,δ‐unsaturated aldehydes with 3‐aminomaleimides for the efficient construction of azaspiro[4.5]decanes. This mechanistically distinct transformation proceeds under mild conditions to afford desired spirocyclic products in good yields (up to 85%) with excellent enantioselectivities (99% ee). Notably, this enantioselective catalysis demonstrates broad substrate compatibility, enabling efficient late‐stage functionalization of structurally diverse pharmaceuticals and bioactive molecules.